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| Polyester |
PolyesterFor the film, see the article Polyester (film)
Polyester (film)
Polyester (film) with a seven-lobed cross section]]
Polyester is a category of polymers, or, more specifically condensation polymers, which contain the ester functional group in their main chain.
Although polyesters do exist in nature, polyester generally refers to the large family of synthetic polyesters (plastics) which includes polycarbonate and above all polyethylene terephthalate (PET).
PET is one of the most important thermoplastic polyesters.
The first synthetic polyester, glycerine phthalate, was used in the First World War for waterproofing. Natural polyesters have been known since around 1830.
Applications
- Fibers (and microfibers) for fabric
- Bottles
- Films such as Mylar, often aluminized
- Photographic film (after cellulose triacetate, polyester is the most important substrate)
- A common matrix for glass-reinforced plastic (commonly called "fiberglass") and other composite materials.
- Liquid crystal displays
- Holograms
- Filters
Liquid crystalline polyesters are among the first industrially used liquid crystalline polymers. In general they have extremely good mechanical properties and are extremely heat resistant. For that reason, they can be used as an abradable seal in jet engines.
Thermosetting polyester resins are commonly used as casting materials, fiberglass laminating resins, and non-metallic auto-body fillers. In such applications, polymerization and cross-linking are initiated through an exothermic reaction involving an organic peroxide, such as methyl ethyl ketone peroxide or benzoyl peroxide.
Synthesis
Synthesis of polyesters is generally achieved by a polycondensation reaction.
In this classical method an alcohol and a carboxylic acid react to form a carboxylic ester.
To assemble a polymer, the water formed by the reaction must be continually removed by azeotrope distillation.
Alcoholic transesterification
See main article on transesterification.
Acylation (HCl method)
The acid begins as an acid chloride, and thus the polycondensation proceeds with emission of hydrochloric acid (HCl) instead of water. This method can be carried out in solution or as an enamel.
:Silyl method
:In this variant of the HCl method, the carboxylic acid chloride is converted with the trimethyl silyl ether of the alcohol component; trimethyl silyl chloride is produced.
Acetate method (esterification)
:Silyl acetate method
Ring-opening polymerization
Aliphatic polyesters can be assembled from lactones under very mild conditions, catalyzed anionically, cationically or metallorganically.
Common usage and culture
When the word polyester is used by the layman, it is usually in reference into the fiber; this is the most common general usage of the term. Polyester clothing is considered to have a "less natural" feeling to it in comparison to natural fibers. Quite frequently, polyester fibers are spun together with fibers of cotton, producing a cloth with some of the better properties of each.
Category:Esters
Category:Plastics
Category:Fibers
Category:Organic polymers
Category:Synthetic resins
ja:ポリエステル
Polyester (film)For the synthetic material, see the article polyester.
Polyester, a 1981 John Waters
Polyester, a 1981 John Waters movie starring Divine, Tab Hunter, Edith Massey, and Mink Stole.
The film, which was filmed in Waters' native Baltimore, Maryland, was a melodramatic satire dealing primarily with alcoholism, adultery, foot fetishes, abortion, and divorce.
----
Plot
Caution: May Contain Spoilers
Polyester tells the story of odor-aware housewife, Francine Fishpaw (Divine), whose life is crumbling around her in suburban Baltimore. Her husband, Elmer (Samson) is an unappreciative lout who is the owner of the Charles Art Theatre, an X-rated movie house. Their two children, Lulu (Garlington) and Dexter (King) are Francine and Elmer's terroristic children. The flirtatious Lulu turns tricks down at the golf course and dates bad-boy Bobo Belsinger (Bators); Dexter, a substance-abusing hooligan with a foot fetish, is the "Baltimore Foot Stomper", a local terror who stamps on womens feet for his own pleasure. In addition to her immediate family is her snobby mother, LaRue (White), who robs Francine blind and only cares about her "valuable shopping time".
Francine discovers that her husband is having an affair with his secretary, Sandra Sullivan (Stole), and later confronts them at a hotel, where Elmer asks Francine for a divorce. Promptly after, Francine falls face first into a bout of alcoholism. Dexter is apprehended at a supermarket after falling another victim, and Lulu becomes pregnant with Bobo's child (however, the mother-to-be plans on an abortion: "I'm getting an abortion, and I can't wait!").
After a disasterous evening in which Lulu tries to commit suicide by sticking her head in the oven, Francine's life begins to change. Dexter is released from jail, completely rehabilitated. Lulu suffers a miscarriage and sees the error of her ways, turning from a high school harlot to an artistic flower child. A beacon of light in the form of lounge-suit wearing Todd Tomorrow (Hunter) arrives, lifting her spirits. Soon, Todd proposes marriage to an elated Francine who agrees. However, the plot begins to twist as it conspires that Todd is acquainted with Francine's mother, LaRue, in more than friendly terms.
Francine soon finds out that LaRue and Todd are plotting to get Francine's divorce settlement ($2,000 and the house). Meanwhile, Elmer and Sandra break into the house in order to kill Francine, but are felled by Dexter and Lulu (Dexter steps on Sandra's foot, causing her to accidentally shoot the gun; the subsequent bullet kills Elmer; Lulu uses her macreme to strangle Sandra ("I never wanted to use macrame to kill").
- Incomplete
-
----
Dreamlanders
Waters' usual troupe of actors, the Dreamlanders, tend to play a minor role in this film. In opposition of Waters' last film, Desparate Living (which starred a majority of the Dreamlanders in major roles), only two: Divine and Edith Massey get top billing.
The film started a trend of introducing new talent, both undiscovered and the ludicrously placed (i.e. Sam Waterston, Patty Hearst, etc.). Mary Vivian Pearce, Sharon Niesp, Marina Melin, Susan Lowe, Jean Hill, along with others are given small roles; the roles, though, are still imperitive to the plot, but do not hold as much standing as their earlier roles.
Polyester was also the first of Waters' movies to become somewhat mainstream, even garnering an 'R' rating (his previous films were all rated NC-17). The film was well-received.
Trivia
This was the first, and to date, only, film to feature Odorama.
This was the last of Waters' movies that Edith Massey appeared in. She died in 1984.
External links
- [http://www.imdb.com/title/tt0082926/ IMDb entry on Polyester]
Category:1981 films
Category:Cult films
PolymerPolymer is a generic term used to describe a very long molecule consisting of structural units and repeating units connected by covalent chemical bonds. The key feature that distinguishes polymers from other molecules is the repetition of many identical, similar, or complementary molecular subunits in these chains. These subunits, the monomers, are small molecules of low to moderate molecular weight, and are linked to each other during a chemical reaction called polymerization.
Instead of being identical, similar monomers can have varying chemical substituents. The differences between monomers can affect properties such as solubility, flexibility, and strength. In proteins, these differences give the polymer the ability to adopt a biologically-active conformation in preference to others. (See self-assembly.) Identical monomers with nonreactive side groups result in a polymer chain that will tend to adopt a random coil conformation, as described by an ideal chain mathematical model. Although most polymers are organic, with carbon-based monomers, there are also inorganic polymers; for example, the silicones, with a backbone of alternating silicon and oxygen atoms.
Polymers are typically classified according to three main groups:
- thermoplastics (linear or branched chains)
- thermosets (crosslinked chains)
- elastomers
The term polymer covers a large, diverse group of molecules, including substances from proteins to stiff, high-strength Kevlar fibres. For example, the formation of polyethene (also called polyethylene) involves thousands of ethene molecules bonded together to form a straight (or branched) chain of repeating -CH2-CH2- units (with a -CH3 at each terminal):
image:example_polymerization.png
Polymers are often named in terms of the monomer from which they are made. Because it is synthesized from ethene in a process during which all the double bonds in the vinyl monomers are lost, polyethene has the unsaturated structure:
image:polyethene_monomer.png
If it were named according to its final structure, it would have the alkane designation "polyethane".
Because synthetic polymer formation is governed by random assembly from the constituent monomers, polymer chains within a solution or substance are generally not of equal length. This is unlike basic, smaller molecules in which every atom is stoichiometrically accounted for, and each molecule has a set molecular mass. An ensemble of differing chain lengths, often obeying a normal (Gaussian) distribution, occurs because polymer chains terminate during polymerization after random amounts of chain lengthening (propagation).
Proteins are polymers of amino acids. Typically, hundreds of the (nominally) twenty different amino acid monomers make up a protein chain, and the sequence of monomers determines its shape and biological function. (There are also shorter oligopeptides which function as hormones.) But there are active regions, surrounded by, as is believed now (Aug 2003), structural regions, whose sole role is to expose the active regions. (There may be more than one on a given protein.) So the exact sequence of amino acids in certain parts of the chains can vary from species to species, and even given mutations within a species, so long as the active sites are properly accessible. Also, whereas the formation of polyethylene occurs spontaneously under the right conditions, the synthesis of biopolymers such as proteins and nucleic acids requires the help of enzyme catalysts, substances that facilitate and accelerate reactions. Unlike synthetic polymers, these biopolymers have exact sequences and lengths. (This does not include the carbohydrates.) Since the 1950s, catalysts have also revolutionised the development of synthetic polymers. By allowing more careful control over polymerization reactions, polymers with new properties, such as the ability to emit coloured light, have been manufactured.
The characterization of a polymer requires several parameters which need to be specified. This is because a polymer actually consists of a statistical distribution of chains of varying lengths, and each chain consists of monomer residues which affect its properties. Some of these parameters are described below.
Physical properties of polymers
Physical properties of polymers include the degree of polymerization, molar mass distribution, crystallinity, as well as the thermal phase transitions:
- Tg, glass transition temperature
- Tm, melting point (for thermoplastics).
Branching
During the propagation of polymer chains, branching can occur. In free-radical polymerization, this occurs when a chain curls back and bonds to an earlier part of the chain. When this curl breaks, it leaves small chains sprouting from the main carbon backbone. Branched carbon chains cannot line up as close to each other as unbranched chains can. This causes less contact between atoms of different chains, and fewer opportunities for induced or permanent dipoles to occur. A low density results from the chains being further apart. Lower melting points and tensile strengths are evident, because the intermolecular bonds are weaker and require less energy to break.
Besides branching, polymers can have other topologies: linear, network (cross-linked 3D structure), IPN (integrated polymer network), comb, or star as well as dendrimer and hyperbranched structures.
Stereoregularity
Stereoregularity or tacticity describes the isomeric arrangement of functional groups on the backbone of carbon chains. Isotactic chains are defined as having substituent groups aligned in one direction. This enables them to line up close to each other, creating crystalline areas and resulting in highly rigid polymers.
In contrast, atactic chains have randomly aligned substituent groups. The chains do not fit together well and the intermolecular forces are low. This leads to a low density and tensile strength, but a high degree of flexibility.
Syndiotactic substituent groups alternate regularly in opposite directions. Because of this regularity, syndiotactic chains can position themselves close to each other, though not as close as isotactic polymers. Syndiotactic polymers have better impact strength than isotactic polymers because of the higher flexibility resulting from their weaker intermolecular forces.
Constitution of polymers
Copolymers
Copolymerization with two or more different monomers results in chains with varied properties. There are twenty amino acid monomers whose sequence results in different shapes and functions of protein chains. Copolymerising ethene with small amounts of 1-hexene (or 4-methyl-1-pentene) is one way to form linear low-density polyethene (LLDPE). (See polyethylene.) The C4 branches resulting from the hexene lower the density and prevent large crystalline regions from forming within the polymer, as they do in HDPE. This means that LLDPE can withstand strong tearing forces whilst remaining flexible.
A block copolymer is formed when the reaction is carried out in a stepwise manner, leading to a structure with long sequences or blocks of one monomer alternating with long sequences of the other. There are also graft copolymers, in which entire chains of one kind (e.g., polystyrene) are made to grow out of the sides of chains of another kind (e.g., polybutadiene), resulting in a product that is less brittle and more impact-resistant. Thus, block and graft copolymers can combine the useful properties of both constituents and often behave as quasi-two-phase systems.
The following is an example of step-growth polymerization, or condensation polymerization, in which a molecule of water is given off and nylon is formed. The properties of the nylon are determined by the R and R' groups in the monomers used.
nylon
The first commercially successful, completely synthetic polymer was nylon 6,6, with alkane chains R = 4C (adipic acid) and R' = 6C (hexamethylene diamine). Including the two carboxyl carbons, each monomer donates 6 carbons; hence the name. In naming nylons, the number of carbons from the diamine is given first and the number from the diacid second. Kevlar is an aromatic nylon in which both R and R' are benzene rings.
Copolymers illustrate the point that the repeating unit in a polymer, such as a nylon, polyester or polyurethane, is often made up of two (or more) monomers.
Chemical properties of polymers
Intermolecular forces
The attractive forces between polymer chains play a large part in determining a polymer's properties. Because polymer chains are so long, these interchain forces are amplified far beyond the attractions between conventional molecules. Also, longer chains are more amorphous (randomly oriented). Polymers can be visualised as tangled spaghetti chains - pulling any one spaghetti strand out is a lot harder the more tangled the chains are. These stronger forces typically result in high tensile strength and melting points.
The intermolecular forces in polymers are determined by dipoles in the monomer units. Polymers containing amide groups can form hydrogen bonds between adjacent chains; the positive hydrogen atoms in N-H groups of one chain are strongly attracted to the oxygen atoms in C=O groups on another. These strong hydrogen bonds result in, for example, the high tensile strength and melting point of kevlar. Polyesters have dipole-dipole bonding between the oxygen atoms in C=O groups and the hydrogen atoms in H-C groups. Dipole bonding is not as strong as hydrogen bonding, so ethene's melting point and strength are lower than kevlar's, but polyesters have greater flexibility.
Ethene, however, has no permanent dipole. The attractive forces between polyethene chains arise from weak van der Waals forces. Molecules can be thought of as being surrounded by a cloud of negative electrons. As two polymer chains approach, their electron clouds repel one another. This has the effect of lowering the electron density on one side of a polymer chain, creating a slight positive dipole on this side. This charge is enough to actually attract the second polymer chain. Van der Waals forces are quite weak, however, so polyethene melts at low temperatures.
Polymer characterization
A variety of lab techniques are used to determine the properties of polymers. Techniques such as wide angle X-ray scattering, small angle X-ray scattering, and small angle neutron scattering are used to determine the crystalline structure of polymers. Gel permeation chromatography is used to determine the number average molecular weight, weight average molecular weight, and polydispersity. FTIR is used to determine composition. Thermal properties such as the glass transition temperature and melting point can be determined by differential scanning calorimetry and dynamic mechanical analysis. Pyrolysis followed by analysis of the fragments is one more technique for determining the possible structure of the polymer.
Polymer known as polymer substrate is used for everyday banknotes in Australia and New Zealand, and is also used in commemorative notes in other countries.
See also: Polymerization -- Biopolymer -- Condensation polymer -- Addition polymer -- Synthetic polymer -- Glass transition temperature -- Polymer physics -- Important publications in polymer chemistry
External links
- [http://www.borealisgroup.com/public/dictionary/Dictionary.jsp Polymer dictionary]
- [http://www.vivamer.com/ Responsive Biopolymers for Drug Delivery and Imaging]
- [http://web.umr.edu/~wlf/ Polymer Chemistry Hypertext, Educational resource]
- [http://www.polychemistry.com/ Polymer Chemistry Innovations]
- [http://www.odcad.com/html/organicdevice_appearance1.HTM Materials for Organic devices]
- [http://www.pslc.ws/macrog/index.htm The Macrogalleria - a cyberwonderland of polymer fun!]
Category:Polymers
Category:Polymer chemistry
ko:중합체
ms:Polimer
ja:重合体
th:โพลีเมอร์
Ester
In chemistry, esters are organic compounds in which an organic group (symbolised by R' in this article) replaces a hydrogen atom (or more than one) in an oxygen acid. An oxygen acid is an acid whose molecule has an - group from which the hydrogen (H) can dissociate as an H+ ion.
The most common esters are the carboxylate esters, where the acid in question is a carboxylic acid. For example, if the acid is acetic acid, the ester is called an acetate. Esters may also be formed with inorganic acids; for example, dimethyl sulfate is an ester, and sometimes called "sulfuric acid, dimethyl ester".
Esters are named similarly to salts; although they don't really have cations and anions, the terminology follows the same pattern: a more electropositive part followed by a more electronegative part.
An ester can be thought of as a product of a condensation reaction of an acid (usually an organic acid) and an alcohol (or phenol compound), although there are other ways to form esters. Condensation is a type of chemical reaction in which two molecules with -OH groups are joined with eliminating a water molecule from their -OH groups. A condensation reaction to form an ester is called esterification. Esterification can be catalysed by the presence of H+ ions. Sulfuric acid is often used as a catalyst for this reaction. The name ester is derived from the German Essig-Äther, an old name for acetic acid ethyl ester (ethyl acetate).
Naming of esters
ethyl acetate
Esters can be produced by an equilibrium reaction between an alcohol and a carboxylic acid. The ester is named according to the alkyl group (the part from the alcohol) and then the alkanoate (the part from the carboxylic acid) which make it up. For example, the reaction between methanol and butyric acid yields the ester methyl butyrate C3H7-COO-CH3 (as well as water). The simplest ester is H-COO-CH3 (methyl formate, also called methyl methanoate).
For esters derived from the simplest carboxylic acids, the traditional names names are recommended by IUPAC, viz, formate, acetate, propionate, butyrate, though out of these only acetate may carry further substituents. For esters from higher acids, the alkane name with an -oate ending is generally preferred, e.g., hexanoate. Common esters of aromatic acids include benzoates such as methyl benzoate, and phthalates, with substitution allowed in the name.
Physical properties
Esters participate in hydrogen bonds as hydrogen-bond acceptors, but cannot act as hydrogen-bond donors, unlike their parent alcohols. This ability to participate in hydrogen bonding makes them more water soluble than their parent hydrocarbons. However, the limitations on their hydrogen bonding also make them more hydrophobic than either their parent alcohols or parent acids. Their lack of hydrogen bond donating ability means that ester molecules cannot hydrogen bond to each other, which makes esters generally more volatile than an carboxylic acid of similar molecular weight. This property makes them very useful in organic analytical chemistry: unknown organic acids with low volatility can often be esterified into a volatile ester which can then be analysed using gas chromatography, gas liquid chromatography, or mass spectrometry.
Many esters have distinctive odors, which has led to their widespread use as artificial flavorings and fragrances. For example:
:methyl butyrate smells of pineapple or apple
:methyl salicylate (oil of wintergreen) smells of the ointments called Germolene™ and Ralgex™ in the UK
:methyl benzoate smells of fruity-ylang ylang
:ethyl formate smells of rum
:ethyl butyrate smells of pineapple or strawberry
:ethyl salicylate smells of oil of wintergreen
:ethyl heptanoate smells of grape
:propyl isobutyrate (rum)
:isobutyl formate (raspberries)
:butyl butyrate (pineapple):pentyl acetate smells of banana
:pentyl pentanoate smells of apple
:pentyl butyrate smells of pear or apricot
:isopentyl acetate smells of pear or banana (it is used as the flavouring in the manufacturing of old fashioned Pear Drops)
:octyl acetate smells of fruity-orange
:benzyl acetate smells slightly of jasmine
Reactions
jasmine
Esters may undergo hydrolysis - the breakdown of an ester by water. This process can be catalyzed both by acids and bases. The base-catalyzed process is called saponification. The hydrolysis yields an alcohol and a carboxylic acid or its carboxylate salt.
Esters also react if heated with primary or secondary amines, producing amides.
Phenyl esters react to hydroxyarylketones in the Fries rearrangement.
External links
- [http://www.chm.bris.ac.uk/motm/ethylacetate/ethylh.htm Molecule of the month: Ethyl acetate and other esters]
References
# [http://www.acdlabs.com/iupac/nomenclature/93/r93_511.htm IUPAC naming of esters]
# [http://www.acdlabs.com/iupac/nomenclature/93/r93_705.htm IUPAC parent groups using traditional names]
Category:Functional groups
Category:Esters
Category:German loanwords
ja:エステル
SyntheticGenerally, synthetic means pertaining to synthesis, i.e., the putting-together of two or more parts into a coherent whole, whether by design or by natural processes.
- In philosophy, see synthetic proposition.
- In chemistry, see chemical synthesis.
- In linguistics, see synthetic language.
- In sociolinguistics, see synthetic personalisation.
- In fibers, see synthetic fiber
- See also synthesizer
Polycarbonate
kg
Polycarbonates are a particular group of thermoplastics. They are easily worked, molded, and thermoformed; as such, these plastics are very widely used in modern manufacturing. They are called polycarbonates because they are polymers having functional groups linked together by carbonate groups (-O-CO-O-) in a long molecular chain.
The most common type of polycarbonate plastic is one made from Bisphenol A, in which groups from Bisphenol A are linked together by carbonate groups in a polymer chain. This polycarbonate is a very durable material, and can be laminated to make bullet-proof "glass", though “bullet-resistant” would be more accurate. The characteristics of polycarbonate are quite like those of polymethyl methacrylate (PMMA; acrylic), but polycarbonate is stronger and more expensive. This polymer is highly transparent to visible light and has better light transmission characteristics than many kinds of glass.
Polycarbonate has :
- a density of 1.20 g/cm3
- a use range from -100°C to +135°C
- a melting point around 250°C
- a refractive index equal to 1.585 ± 0.001
- a light transmission index equal to 90% ± 1%
- poor weathering in an ultraviolet (UV) light environment
Polycarbonate is becoming more common in housewares as well as laboratories and in industry. It is often used to create protective features, for example in banks as well as vandal-proof windows and lighting lenses for many buildings. Other products made from polycarbonate include sunglass/eyeglass lenses, compact discs, DVDs, and automotive headlamp lenses. It is the major component of one variety of Nalgene bottles. It is also used for animal enclosures and cages used in research.
LEXAN® is the registered trademark for polycarbonate plastic manufactured (from Bisphenol A) by General Electric. MERLON® is the registered trademark used by the Mobay Chemical Company. MAKROLON® is the registered trademark for polycarbonate from Bayer, which is also referred to as "macrolon".
Synthesis
Polycarbonate can be synthesized from bisphenol A and phosgene (carbonyl dichloride, COCl2). The first step in the synthesis of polycarbonate from bisphenol A is treatment of bisphenol A with sodium hydroxide. This deprotonates the hydroxyl groups of the bisphenol A molecule.
Image:Bisphenol_A_plus_NaOH.PNG
The deprotonated oxygen reacts with phosgene through carbonyl addition to create a tetrahedral intermediate (not shown here), after which the negatively charged oxygen kicks off a chloride ion (Cl-) to form a chloroformate.
Image:Bisphenolate_A_plus_Phosgene.PNG
The chloroformate is then attacked by another deprotonated bisphenol A, eliminating the remaining chloride ion and forming a dimer of bisphenol A with a carbonate linkage in between.
Image:Adding_Bisphenolate_A_to_Chloroformate.PNG
Repetition of this process yields polycarbonate, a polymer with alternating carbonate groups and groups from bisphenol A. Density starts at about 1.20 g/cm3.
External link
- [http://www.apme.org/polycarbonate/ European polycarbonate industry]
Category:Plastics
Category:Optical materials
ja:ポリカーボネート
Polyethylene terephthalate
Polyethylene terephthalate (aka. PET, PETE, PETP) is a thermoplastic resin of the polyester family that is used to make beverage, food and other liquid containers, synthetic fibers, as well as for some other thermoforming applications. It is also one of the most important raw materials used in man-made fibers. Depending on its processing and thermal history, it may exist both as an amorphous (transparent) and as a semi-crystalline (opaque and white) material. It can be synthesized by a transesterification reaction between ethylene glycol and dimethyl terephthalate. It is manufactured under trade names Arnite, Impet and Rynite, Hostaphan, Melinex and Mylar films, and Dacron, Terylene and Trevira fibers. [http://www.goodfellow.com/csp/active/STATIC/E/Polyethylene_terephthalate.HTML]
Mylar
Uses
Mylar
The main virtue of PET is that it is fully recyclable. Unlike other plastics, its polymer chains can be recovered for additional use. PET has a resin identification code of 1.
resin identification code]]
PET can be semi-rigid to rigid, depending on its thickness, and is very lightweight. It makes a good gas and fair moisture barrier, as well as a good barrier to alcohol (requires additional "Barrier" treatment) and solvents. It is strong and impact-resistant. It is naturally colorless and transparent.
When produced as a thin film (often known by the tradename Mylar), PET is often coated with aluminium to reduce its permeability, and to make it reflective and opaque. PET bottles are excellent barrier materials and are widely used for soft drinks, (see carbonation). For certain specialty bottles, PET sandwiches an additional polyvinyl alcohol to further reduce its oxygen permeability.
When filled with glass particles or fibers, it becomes significantly stiffer and more durable. This glass-filled plastic, in a semi-crystalline formulation, is sold under the tradename Rynite.
PET was patented in 1941 by the Calico Printer's Association of Manchester. The PET bottle was patented in 1973.
Intrinsic viscosity
One of the most important characteristics of PET is refered to as I.V.(Intrinsic Viscosity)
The IV of the material is dependent upon the length of its polymer chains. The longer the chains, the stiffer the material, and therefore the higher the IV. The average chain length of a particular batch of resin can be controlled during polymerization.
An IV of about:
:0.6 - would be appropriate for fiber
:0.65 - film
:0.8 - bottles
:0.85 - tire cord
Drying
PET is hygroscopic, meaning that it naturally absorbs water from its surroundings. However, before the resin can be processed in a molding machine, all moisture must be removed from the resin. This is achieved through the use of a dryer.
Inside the dryer, the air is run through an after cooler, because it is easier to remove moisture from cold air than hot air. The air is then dispersed into a dessicant bed. The air leaving the dessicant bed is cool and dry. The air then flows through a process heater. After that hot dry air is pumped into the bottom of the hopper containing the resin and it flows up through the resin removing moisture on its way by. The air leaves the top of the hopper and is run back through the same processes in a closed loop.
This process takes less time per batch when the drier is run at a higher temperature.
:140 degrees Celsius air = 12 hours
:145 degrees Celsius air = 6.5 hours
:160 degrees Celsius air = 4 hours
Dryer residence time should not be shorter than 4 hours. This is because drying the material in less than 4 hours would require a temperature over 160 degrees Celsius. Exposure to such high temperatures will begin to degrade the outside of a pellet before its center is dry.
Copolymers
In addition to pure (homopolymer) PET, PET modified by copolymerization is also available.
In some cases, the modified properties of copolymer are more desirable for a particular application. For example, cyclohexane dimethanol (CHDM) can be added to the polymer backbone in place of ethylene glycol. Since this building block is much larger (6 additional carbon atoms) than the ethylene glycol unit it replaces, it does not fit in with the neighboring chains the way a ethylene glycol unit would. This interferes with crystallization and lowers the polymer's melting temperature.
melting temperature.]]
Another common modifier is isophthalic acid, replacing some of the para-linked terephthalate units. The 1,3- or meta-linkage produces an angle in the chain, which also disturbs crystallinity.
Such copolymers are advantageous for certain molding applications, such as thermoforming, which is used to make tray or blister packages from PET sheet (sometimes called APET, for "amorphous PET"). On the other hand, crystallization is important in other applications where mechanical and dimensional stability are important, such as seat belts. For PET bottles, the use of small amounts of CHDM or other comonomers can be useful: if only small amounts of comonomers are used, crystallization is slowed but not prevented entirely. As a result, bottles are obtainable via stretch blow molding ("SBM"), which are both clear and crystalline enough to be an adequate barrier to aromas and even gasses, such as the carbon dioxide in carbonated beverages.
Crystals
Crystallization occurs when polymer chains fold up on themselves in a repeating, symmetrical pattern. Long polymer chains tend to become entangled on themselves, which prevents full crystallization in all but the most carefully controlled circumstances. PET is no exception to this rule; 60% crystallization is the upper limit for commercial products, with the exception of polyester fibers.
PET in its natural state is a crystalline resin. We are able to produce clear products by rapidly cooling molten polymer to form an amorphous solid. Like glass, amorphous PET forms when its molecules are not given enough time to arrange themselves in an orderly fashion as the melt is cooled. At room temperature the molecules are frozen in place, but if enough heat energy is put back into them, they begin to move again, allowing crystals to nucleate and grow.
Like most materials, PET tends to produce many small crystallites when crystallized from an amorphous solid, rather than forming one large single crystal. Light tends to scatter as it crosses the boundaries between crystallites and the amorphous regions between them. This scattering means that crystalline PET is opaque and white in most cases. Fiber drawing is among the few industrial processes that produces a nearly single-crystal product.
Degradation
When PET degrades, several things happen, mainly the formation of acetaldehyde and cross-links ("gel" or "fish-eye" formation). Acetaldehyde is normally a colorless gas with a fruity smell. It forms naturally in fruit, but it can cause an off-taste in bottled water. Acetaldehyde forms in PET through the "abuse" of the material. High temperatures (PET decomposes above 300°C or 572°F), high pressures, extruder speeds (excessive shear flow raises temperature) and long barrel residence times all contribute to the production of acetaldehyde. When acetaldehyde is produced, some of it remains dissolved in the walls of a container and then diffuses into the product stored inside, altering the taste and aroma. This is not such a problem for non-consumables such as shampoo, for fruit juices, which already contain acetaldehyde or for strong-tasting drinks, such as sodas. For bottled water, low acetaldehyde content is quite important, because if nothing masks the aroma, even extremely low concentrations (10-20 ppb) of acetaldehyde can produce an off-taste.
One way to alleviate this is to use a copolymer. Comonomers such as CHDM or isophthalic acid lower the melting temperature of PET. Thus the resin can be plastically formed at lower temperatures and/or with lower force. This helps to prevent degradation, reducing the acetaldehyde content of the finished product to an acceptable (that is, unnoticeable) level. See copolymers, below.
Re-crystallization experiment
PET can be used to explore the crystallization of amorphous solids. The resin identification code can be used to verify the type of plastic is made of: many plastic beverage bottles have the letters PET or PETE and a code of 1 on the bottom, near the center. When a flame is held several inches below the bottle and slowly brought closer, part of the material will visibly change. This happens because high temperatures melt the PET. This releases the tension that was frozen in during the blow molding process and the polymer chains will shift to a more relaxed and disordered state, which results in shrinkage of the softened area. Because of the decreased order of the polymer chains, there are now fewer crystal nuclei. Consequently, when the crystallites re-form upon cooling they grow larger than the original crystallites in the bottle wall. Because the new crystallites are larger than the wave length of light, they will now cause light to scatter, giving the material an opaque white appearance.
Processing Equipment
There are two basic molding methods, one-step and two-step. In two-step molding, two separate machines are used, one for injection molding the preform, the second for stretch-blow molding it into the final container shape. In one-step machines, the entire process from raw material to finished container is conducted within one machine, making it especially suitable for molding non-standard shapes (custom molding), including jars, flat oval, flask shapes etc. Its greatest merit is the reduction in space, product handling and energy, and far higher visual quality than can be achieved by the two-step system.
Single Step Injection Stetch Blow Molding [http://www.nisseiasb.co.jp/index_e.html Nissei ASB Machine Co., Ltd.]
See also
- Recycling of PET Bottles
Category:Esters
Category:Plastics
Category:Household chemicals
Category:Organic polymers
ja:ポリエチレンテレフタラート
ThermoplasticA thermoplastic is a material that is plastic or deformable, melts to a liquid when heated, and freezes to a brittle, glassy state when cooled sufficiently. Most thermoplastics are high molecular weight polymers whose chains associate through weak van der Waals forces (polyethylene); stronger dipole-dipole interactions and hydrogen bonding (nylon); or even stacking of aromatic rings (polystyrene). Thermoplastic polymers are contrasted with thermosetting polymers (Bakelite; vulcanized rubber), which, once formed and cured, can never be remelted and remolded. Many thermoplastic materials are addition polymers; e.g., vinyl chain-growth polymers, such as polyethylene and polypropylene.
Temperature dependence
Thermoplastics are elastic and flexible above their glass transition temperature Tg, specific for each one. This is the midpoint of a temperature range, unlike the sharp freezing point of a pure crystalline substance like water. Below a second, higher melting temperature, Tm (also the midpoint of a range), most thermoplastics have crystalline regions, alternating with amorphous regions in which the chains approximate random coils. The amorphous regions contribute elasticity and the crystalline regions contribute strength and rigidity. Above Tm, all crystalline structure disappears and the chains become entirely random coils. As the temperature increases above this, the viscosity gradually decreases without any further phase change. Thermoplastics can go through both freezing and melting cycles repeatedly, but it is the fact that they can be reshaped upon reheating that gives them their name. Animal horn, made of the protein α-keratin, softens on heating and is somewhat reshapable, and may be regarded as a natural, quasi-thermoplastic material. Elasticity does not mean that a material is particularly stretchy; e.g., nylon rope, fishing line and guitar strings.
Thermoplastics are useful between Tg and Tm, a temperature range in which they are neither brittle nor liquid. If a plastic with useful properties has a Tg which is too high, it can often be lowered by adding a low-molecular-weight plasticizer to the melt before forming and cooling. A similar result can sometimes be achieved by adding non-reactive side chains to the monomers before polymerization. These methods make the polymer chains stand off a bit from one another. Plastic automobile parts often cracked in cold winter weather before the introduction of plasticizers. Another method of lowering Tg (or raising Tm) is to incorporate the original plastic into a copolymer or composite material. Modestly vulcanized natural and synthetic rubbers are elastomeric thermosets, but are not thermoplastic. Each has its own Tg, and will crack and shatter when cold enough so that the polymer chains can no longer move relative to one another; but they have no Tm, and will decompose at high temperatures rather than melt.
List of thermoplastics
- Acrylonitrile butadiene styrene (ABS)
- Acrylic
- Celluloid
- Cellulose acetate
- Ethylene vinyl alcohol (E/ VAL)
- Fluoroplastics (PTFEs, including FEP, PFA, CTFE, ECTFE, ETFE)
- Ionomers
- Liquid Crystal Polymer (LCP)
- Polyacetal (POM or Acetal)
- Polyacrylates (Acrylic)
- Polyacrylonitrile (PAN or Acrylonitrile)
- Polyamide (PA or Nylon)
- Polyamide-imide (PAI)
- Polyaryletherketone (PAEK or Ketone)
- Polybutadiene (PBD)
- Polybutylene (PB)
- Polybutylene teraphthalate (PBT)
- Polyethylene terephthalate (PET)
- Polycyclohexylene dimethylene terephthalate (PCT)
- Polycarbonate (PC)
- Polyketone (PK)
- Polyester
- Polyethylene/Polythene/Polyethene
- Polyetheretherketone (PEEK)
- Polyetherimide (PEI)
- Polyethersulfone (PES)
- Polyethylenechlorinates (PEC)
- Polyimide (PI)
- Polymethylpentene (PMP)
- Polyphenylene oxide (PPO)
- Polyphenylene sulfide (PPS)
- Polyphthalamide (PPA)
- Polypropylene (PP)
- Polystyrene (PS)
- Polysulfone (PSU)
- Polyvinyl chloride (PVC)
See also
- Thermosetting plastic
Category:Plastics
World War I
, and the use of new, devastating weapons - tanks, aircraft, machine guns, and poison gas.]]
World War I, also known as the First World War, the Great War, the War of the Nations and the War to End All Wars, was a world conflict lasting from 1914 to 1919, with the fighting lasting until 1918. The label World War I or First World War did not come into general use until after the outbreak of World War II in 1939, and until then it was known as the Great War or the World War. The war was fought by the Allied Powers on one side, and the Central Powers on the other. No previous conflict had mobilized so many soldiers or involved so many in the field of battle. By its end, the war had become the second bloodiest conflict in recorded history (behind the Taiping Rebellion), though it was surpassed within a generation by World War II.
World War I became infamous for trench warfare; this was especially true of the Western Front. The trenches went from the North Sea to the border of Switzerland in Europe. More than 9 million died on the war's battlefields, and nearly that many more on the home fronts because of food shortages, genocide, and ground combat. Among other notable events, the first large-scale bombing from the air was undertaken and some of the century's first large-scale civilian massacres took place, as one of the aspects of modern efficient, non-chivalrous warfare. In the First World War 5% of casualties were civilian. In the Second World War that was 50%.
World War I proved to be the decisive break with the old world order, marking the final demise of absolutist monarchy in Europe. Four empires were shattered: the German, the Austro-Hungarian, the Ottoman, and the Russian. Their four dynasties, the Hohenzollerns, the Habsburgs, the Ottomans, and the Romanovs, who had roots of power back to the days of the Crusades, all fell during or after the war.
The post-war failure to deal effectively with many of the causes and results of the War would lead to the rise of Fascism in Italy, Nazism in Germany and the outbreak of World War II within a generation. The War was the catalyst for the Bolshevik Russian Revolution, which would inspire later Communist revolutions in countries as diverse as China and Cuba, and would lay the basis for the Cold War standoff between the Soviet Union and the United States. In the east, the demise of the Ottoman Empire paved the way for a modern democratic successor state, Turkey. In Central Europe, new states such as Czechoslovakia and Yugoslavia were born and Poland was re-created.
__TOC__
Causes
Poland of Franz Ferdinand. The murder was the igniting torch of World War I.]]
:See also: Causes of World War I and Participants in World War I
On June 28, 1914, Franz Ferdinand, Archduke of Austria and heir to the Austro-Hungarian throne, was assassinated in Sarajevo by Gavrilo Princip, a Bosnian Serb student. He was part of a group of fifteen assassins, acting with support from the Black Hand, a secret society founded by pan-Serbian nationalists, with links to the Serbian military. The assassination sparked little initial concern in Europe. The Archduke himself was not popular, least of all in the Austro-Hungarian Empire. While there were riots in Sarajevo following the Archduke's death, these were largely aimed at the Serbian minority. Though this assassination has been linked as the direct trigger for World War I, the war's real origins lie further back, in the complex web of alliances and counterbalances that developed between the various European powers after the defeat of France and formation of the German state under the leadership of Otto von Bismarck in 1871.
Reasons & Responsibilities
- See also: Causes of World War I
There are many different hypotheses that try to explain who, or what, is to blame for the outbreak of the First World War. Early explanations, prominent in the 1920s and 1930s, stressed the official version of responsibility as described in the Treaty of Versailles and Treaty of Trianon, that Germany and its allies were solely responsible for the war. However, as time progressed, scholars began looking toward the rigidity of both German and Russian military planning, each of which stressed the importance of striking first and executing plans quickly.
The fact that for many decades the British had been accustomed to colonial wars which were won relatively easily against much weaker adversaries certainly helped build enthusiasm for the Great war. In addition, the fact that no major political force opposed the war meant that those who did not agree with it had little organisational power to build opposition, though small protests continued throughout the war.
Another cause of the war was the building of alliances and arms races. An example of the latter is the launch of HMS Dreadnought, a revolutionary battleship that rendered all previous ships obsolete as "pre-dreadnoughts", in 1906. This weakened Britain's power as a seafaring nation and sparked a major naval arms race in shipbuilding, particularly between Britain and Germany due to new imperialism. Overall, nations in the Triple Entente became fearful of the Triple Alliance and vice versa.
The civilian leaders of the European powers also found themselves facing a wave of nationalist zeal that had been building across Europe for years. This left governments with ever fewer options and little room to manoeuvre as the last weeks of July 1914 slipped away. Frantic diplomatic efforts to mediate the Austrian-Serbian quarrel simply became irrelevant, as the automatic military escalations between Germany and Russia reinforced one another.
Furthermore, the problem of communications in 1914 should not be underestimated; all nations still used telegraphy and ambassadors as the main form of communication, resulting in delays from hours to even days.
There is probably no single concise or conclusive assessment of the exact cause of the First World War.
Outbreak of war
ambassadors are depicted in green, the Central Powers in red, and neutral countries in yellow.]]
Austria–Hungary was created in the "Ausgleich of 1867" after Austria was defeated by Prussia. As agreed in 1867, the Habsburgs were the Emperors of the Austrian Empire. With the formation of the Dual Monarchy, Franz Josef became leader of a nation with sixteen ethnic groups and five major religions speaking no fewer than nine languages.
In large measure because of the vast disparities that existed within the Empire, Austrians and Hungarians always viewed growing Slavic nationalism with deep suspicion and concern. Thus the Austro-Hungarian government grew worried with the near-doubling in size of neighbouring Serbia's territory as a result of the Balkan Wars of 1912–1913. Serbia, for its part, made no qualms about the fact that it viewed all of Southern Austria–Hungary as part of a future Great South Slavic Union. This view had also garnered considerable support in Russia. Many in the Austrian leadership, not least Habsburg Emperor Franz Joseph, and Conrad von Hötzendorf, worried that Serbian nationalist agitation in the southern provinces of the Empire would lead to further unrest among the Austro-Hungarian Empire's other disparate ethnic groups. The Austro-Hungarian government worried that a nationalist Russia would back Serbia to annex Slavic areas of Austria–Hungary. The feeling was that it was better to destroy Serbia before they were given the opportunity to launch a campaign.
After the assassination of Franz Ferdinand by Gavrilo Princip and nearly a month of debate the government of Austria–Hungary sent a 10-point ultimatum to Serbia (July 23, 1914) — the so called July Ultimatum — to be unconditionally accepted within 48 hours. The ultimatum was the first of a series of diplomatic events known as the July Crisis which set off a chain reaction and a general war in Europe.
The Serbian government agreed to all but one of the demands in the ultimatum, noting that participation in its judicial proceedings by a foreign power would violate its constitution. Austria–Hungary nonetheless broke off diplomatic relations (July 25) and declared war (July 28) through a telegram sent to the Serbian government.
The Russian government, which had pledged in 1909 to uphold Serbian independence in return for Serbia's acceptance of the Bosnia annexation, mobilised its military reserves on 30 July following a breakdown in crucial telegram communications between Kaiser Wilhelm and Tsar Nicholas II (the famous "Willy and Nicky" correspondence), who was under pressure by his military staff to prepare for war. Germany demanded (31 July) that Russia stand down its forces, but the Russian government persisted, as demobilization would have made it impossible to re-activate its military schedule in the short term. Germany declared war against Russia on August 1 and, two days later, against the latter's ally France.
The outbreak of the conflict is often attributed to the alliances established over the previous decades — Germany-Austria-Italy vs France-Russia; Britain and Serbia being aligned with the latter. In fact, none of the alliances were activated in the initial outbreak, though Russian general mobilization and Germany's declaration of war against France were motivated by fear of the opposing alliance being brought into play.
Britain declared war against Germany on August 4. This was ostensibly provoked by Germany's invasion of Belgium on August 4 1914, whose independence Britain had guaranteed to uphold in the Treaty of London of 1839, and which stood astride the planned German route for invasion of Russia's ally France. Unofficially, it was already generally accepted in government that Britain could not remain neutral, since without the co-operation of France and Russia its colonies in Africa and India would be under threat, while German occupation of the French Atlantic ports would be an even larger threat to British trade as a whole.
The spread of war
;1914
- July 23: Austria-Hungary ultimatum to Serbia.
- July 28: Austria-Hungary declares war on Serbia.
- July 31: Russia begins mobilization.
- August 1: Germany declares war on Russia.
- August 2: German troops occupy Luxembourg.
- August 3: Germany declares war on France.
- August 4: Germany invades neutral Belgium; the United Kingdom declares war on Germany in response.
- August 6: Montenegro sides with its traditional ally, Serbia, and declares war on Austria-Hungary.
- August 10: Austria-Hungary declares war on Russia.
- August 12: The United Kingdom and France declare war on Austria-Hungary.
- August 23: Japan declares war on Germany.
- September: Unity Pact signed by France, Britain, and Russia.
- October 9: Belgium falls to German troops at the Siege of Antwerp.
- October 29: The Ottoman Empire enters the war on the side of Germany and Austria-Hungary.
- November 2: Russia declares war on the Ottoman sultanate.
- November 5: France and United Kingdom declare war on the Ottoman sultanate.
- December 25: Christmas Truce in the Trenches.
;1915
- April 25: Gallipoli campaign commences. Turks defeat Allies crushingly.
- April 26: Italy secretly signs the London Pact with the Triple Entente.
- May 23: Italy declares war on Austria-Hungary.
- October 14: Bulgaria declares war on Serbia and enters the war on the side of Germany and Austria-Hungary.
;1916
- March 9: Germany declares war on Portugal (see Portugal in the Great War).
- August 27: Romania declares war on Austria-Hungary.
- August 28: Italy declares war on Germany.
;1917
- January 16: Germany sends the Zimmermann Telegram to Mexico, proposing an alliance against the United States.
- April 6: The United States declares war on Germany.
- June 27: Greece enters the war on the side of the Entente.
- July 6: Arab Revolt troops under Lawrence Of Arabia capture Aqaba, a main sea port for the Ottoman Empire.
- August 14: The Republic of China declares war on Germany.
- October 26: Brazil declares war on Germany.
- November 7: The October Revolution takes place in Russia.
- December 7: United States declares war on Austria-Hungary.
;1918
- January 8: President Woodrow Wilson made his famous Fourteen Points address, introducing the idea of a League of Nations.
- 3 March: Russia and the Central Powers sign the Treaty of Brest-Litovsk, marking Russia's exit from World War I.
- October 30: Mudros/Turkish Armistice signed opening Turkish territory to Entente military operations.
- November 11: Armistice signed, end of World War I.
;1919
- 28 June: Treaty of Versailles, official end to World War I between the Entente and Germany.
;1920
- 4 June: Treaty of Trianon, partition of Austro-Hungarian Empire's Kingdom of Hungary.
;1923
- 24 July: Treaty of Lausanne, peace made with Turkey.
- 29 October: Turkey changes its government to republic.
Opening battles
republic
Some of the very first actions of the war occurred far from Europe, in Africa and in the Pacific Ocean. On August 8 1914 a combined French and British Empire force invaded the German protectorate of Togoland. On August 10 German forces based in South-West Africa attacked South Africa. New Zealand occupied German Samoa (30 August 1914) and on September 11 the Australian Naval and Military Expeditionary Force landed on the island of Neu Pommern, which formed part of German New Guinea. Within a few months the Entente forces had accepted the surrender of or driven out German forces in the Pacific. Sporadic and fierce fighting continued in Africa for the remainder of the war.
In Europe, Germany and Austria-Hungary suffered from miscommunication regarding each army's intentions. Germany had originally guaranteed to support Austria-Hungary's invasion of Serbia, but the interpretations of this idea differed. Austro-Hungarian leaders thought Germany would cover her northern flank against Russia, but Germany had planned for Austria-Hungary to focus the majority of its troops on Russia while Germany dealt with France on the Western Front. This confusion forced the Austro-Hungarian army to split its troop concentrations from the south in order to meet the Russians in the north. The Serb army, coming up from the south of the country, met the Austrian army at the Battle of Cer on 12 August 1914.
The Serbians occupied defensive positions against the Austrians. The first attack came on August 16th, between parts of the 21st Austro–Hungarian division and parts of the Serbian Combined division. In harsh night-time fighting the battle ebbed and flowed, until Stepa Stepanovic rallied the Serbian line. Three days later the Austrians retreated across the Danube, having suffered 21,000 casualties as against 16,000 Serbian. This marked the first major Allied victory of the war. The Austrians had not achieved their main goal of eliminating Serbia, and it became increasingly likely that Germany would have to maintain forces on two fronts.
Germany's plan (named the Schlieffen plan) to deal with the Franco-Russian alliance involved delivering a knock-out blow to the French and then turning to deal with the more slowly mobilized Russian army. Rather than invading eastern France directly, German planners deemed it prudent to attack France from the north. To do so, the German army had to march through Belgium. Germany demanded free passage from the Belgian government, promising to treat Belgium as Germany's firm ally if the Belgians agreed. When Belgium refused, Germany invaded and began marching through Belgium anyway, after first invading and securing Luxembourg. It soon encountered resistance before the forts of the Belgian city of Liège, although the army as a whole continued to make rapid progress into France. Britain sent an army to France (the British Expeditionary Force, or BEF), which advanced into Belgium. Initially the Germans had great successes in the Battle of the Frontiers (14–24 August 1914).
However, the delays brought about by the resistance of the Belgian, French and British forces; the unexpectedly rapid mobilization of the Russians; and the overly-ambitious objectives upset the German plans. Russia attacked in East Prussia, diverting German forces intended for the Western Front. Germany defeated Russia in a series of battles collectively known as the Second Battle of Tannenberg (17 August – 2 September). This diversion exacerbated problems of insufficient speed of advance from railheads, not allowed for by the German General Staff, and allowed French and British forces to finally halt the German advance on Paris at the First Battle of the Marne (September 1914) as the Entente forced the Central Powers into fighting a war on two fronts. The German army had fought its way into a good defensive position inside France and had permanently incapacitated 230,000 more French and British troops than it had lost itself in the months of August and September. Yet staff incompetence and leadership timidity, as Ludendorff had needlessly transferred troops from the right to protect Sedan, cost Germany the chance for an early knockout.
Early stages: from romanticism to the trenches
Sedan, 1917]]
The perception of war in 1914 was romanticized by many people, and its declaration was met with great enthusiasm by these people. The common view was that it would be a short war of manoeuvre with a few sharp actions (to "teach the enemy a lesson") and would end with a victorious entry into the enemy capital, then home for a victory parade or two and back to "normal" life. However, many people regarded the coming war with great pessimism and worry. Many military figures, such as Lord Kitchener and Erich Ludendorff, predicted the war would be a long one. Other political leaders, such as Bethmann Hollweg in Germany, were concerned by the potential social consequences of a war. International bond and financial markets entered severe crises in late July and early August reflecting worry about the financial consequences of war.
The perceived excitement of war captured the imagination of many in the warring nations. Spurred on by propaganda and nationalist fervor, many eagerly joined the ranks in search of adventure. Few were prepared for what they actually encountered at the front.
See also: Recruitment to the British Army during WW I
Trench warfare begins
:Main article: Western Front (World War I)
Advances in military technology meant that defensive firepower out-weighed offensive capabilities, making the war particularly murderous, as tactics had failed to keep up. Barbed wire was a significant hindrance to massed infantry advances; artillery, now vastly more lethal than in the 1870s, coupled with machineguns, made crossing open ground a nightmarish prospect. General Staffs of European armies had uniformly ignored the lessons of the U.S. Civil War and were often indifferent to massive loss of life (General Haig's diaries are particularly striking in this respect).
After their initial success on the Marne, Entente and German forces began a series of outflanking manoeuvres to try to force the other to retreat, in the so-called Race to the Sea. Britain and France soon found themselves facing entrenched German positions from Lorraine to Belgium's Flemish coast. Britain and France sought to take the offensive while Germany defended occupied territories. One consequence was that German trenches were much better constructed than those of their enemy: Anglo-French trenches were only intended to be 'temporary' before their forces broke through German defences. Some hoped to break the stalemate by utilizing science and technology. In April 1915, the Germans used mustard gas for the first time, opening a four mile wide hole in the Allied lines when French colonial troops retreated before it. This breach was closed by Canadian soldiers at Ypres, earning German respect. Neither side proved able to deliver a decisive blow for the next four years, though protracted German action at Verdun throughout 1916, and the Entente's failure at the Somme in the summer of 1916 brought the French army to the brink of collapse. Futile attempts at more frontal assaults, at terrible cost to the French poilu (infantry), led to mutinies which threatened the integrity of the front line after the Nivelle Offensive in spring of 1917. News of the Russian Revolution gave a new incentive to socialist sentiments. Red flags were hoisted and the Internationale was sung on several occasions. At the height of the mutiny, 30,000 to 40,000 French soldiers participated. Throughout 1915-17 the British Empire and France suffered many more casualties than Germany, but both sides lost millions of soldiers to injury and disease.
Around 800,000 soldiers from the British Empire were on the Western Front at any one time, 1,000 battalions each occupying a sector of the line from Belgium to the Arne and operating a month-long four stage system, unless an offensive was underway. The front contained over 6,000 miles of trenches. Each battalion held its sector for around a week before moving back to support lines and then the reserve lines before a week out-of-line, often in the Poperinge or Amiens areas.
Southern theatres
Entry of the Ottoman Empire
The Ottoman Empire joined the Central Powers in October–November 1914, due to the secret Turko-German Alliance signed on August 2, 1914, threatening Russia's Caucasian territories and Britain's communications with India and the East via the Suez canal. British Empire action opened another front in the South with the Gallipoli (1915) and Mesopotamian campaigns, though initially the Turks were successful in repelling enemy incursion. In Mesopotamia, by contrast, after the disastrous Siege of Kut (1915–16), British Empire forces reorganized and captured Baghdad in March 1917. Further to the west in the Sinai and Palestine Campaign, initial British failures were overcome with Jerusalem being captured in December 1917 and the Egyptian Expeditionary Force under Edmund Allenby going on to break the Ottoman forces at the Battle of Megiddo (September 1918).
Russian armies generally had the best of it in the Caucasus. Enver Pasha, supreme commander of the Turkish armed forces, was a very ambitious man, with a dream to conquer central Asia. He was not a practical soldier. He launched an offensive with 100,000 troops against the Russians in the Caucasus in December of 1914. Insisting on a frontal attack against Russian positions in the mountains in the heart of winter, Enver lost 86% of his force. A new Russian commander on the front in the fall of 1915, Grand Duke Nicholas, brought new vigour. A major offensive in 1916 drove the Turks out of much of present-day Armenia, and tragically provided a context for the deportation and genocide against the Armenian population in eastern Armenia. With control of part of the southern Black Sea coast, Nicholas pushed forward the construction of railway lines to bring up supplies. He was ready for an offensive in the spring of 1917. If it had gone ahead, there was a very good chance that Turkey would have been knocked out of the war in the summer of 1917. But, because of the Russian Revolution, Grand Duke Nicholas was recalled and the Russian armies soon fell apart.
Italian participation
:Main article: Italian Campaign (WWI)
Italy had been allied to the German and Austro-Hungarian Empires since 1882, but had its own designs against Austrian territory in the Trentino, Istria and Dalmatia, and a secret 1902 understanding with France effectively nullifying its alliance commitments. Italy refused to join Germany and Austria-Hungary at the beginning of the war, because the alliance was defensive, while Austria declared war on Serbia. The Austrian government started negotiations to obtain Italian neutrality in exchange for French territories (Tunisia), but Italy joined the Entente by signing the London Pact in April and declaring war on Austria-Hungary in May 1915; it declared war against Germany fifteen months later.
In general, the Italians enjoyed numerical superiority, but were poorly equipped; instead, the Austro-Hungarian defence took advantage of the elevation of their bases in the mostly mountainous terrain, which was anything but suitable for military offensives. For the most part the front remained unchanged during the war, while Austrian Kaiserschützen and Standschützen and Italian Alpini fought bitter close combat battles during summer and tried to survive during winter in the high mountains.
Beginning in 1915, the Italians mounted 17 major offensives on the Isonzo front (the part of the border nearest Trieste), all repelled by the Austro-Hungarians, who had the higher ground. The Austro-Hungarians counter-attacked from the Altopiano of Asiago towards Verona and Padua in the spring of 1916 (Strafexpedition), but they also made little progress. In the summer, the Italians took back the initiative, capturing the town of Gorizia. After this minor victory, the front remained practically stable for over one year, despite several Italian offensives, again all on the Isonzo front. In the fall of 1917, thanks to the improving situation on the Eastern front, the Austrians received large reinforcements, including German assault troops. On October 26, they launched a crushing offensive that resulted in the victory of Caporetto: the Italian army was routed, but after retreating more than 100km, it was able to reorganize and hold at the Battle of the Piave River. In 1918 the Austrians repeatedly failed to break the Italian line, and, decisively defeated in the Battle of Vittorio Veneto, surrendered to the Entente powers in November.
Throughout the war Austro-Hungarian Chief of Staff, Conrad von Hötzendorf had a deep hatred for the Italians because he had always perceived them to be the greatest threat to his state. Their betrayal in 1915 enraged him even further. His hatred for Italy blinded him in many ways, and he made many foolish tactical and strategic errors during the campaigns in Italy.
The War in the Balkans
After repelling three Austrian invasions in August-December 1914, Serbia fell to combined German, Austrian and Bulgarian invasion in October 1915. The Serbian army retreated into Albania and Greece. In late 1915, a Franco-British force landed at Salonica in Greece to offer assistance and to pressure the Greek government into war against the Central Powers. Unfortunately for the Allies, the pro-allied government of Eleftherios Venizelos fell before the allied expeditionary force even arrived, and the pro-German king, Constantine, prevented official Greek entry into the war for two years, until 1917. Meanwhile, the Salonica Front proved entirely immobile, so that it was joked that Salonica was the largest German prisoner of war camp. Only at the very end of the war, after most of the German and Austro-Hungarian troops had been removed and the front had to be held by the Bulgarians alone, were the Entente powers able to make a breakthrough, leading to Bulgaria's signing an armistice on September 29, 1918.
The Eastern Front
1918
:Main article: Eastern Front (World War I)
While the Western Front had reached stalemate in the trenches, the war continued in the east. The Russian initial plans for war had called for simultaneous invasions of Austrian Galicia and German East Prussia. Although Russia's initial advance into Galicia was largely successful, they were driven back from East Prussia by the victories of the German generals Hindenburg and Ludendorff at Tannenberg and the Masurian Lakes in August and September 1914. Russia's less-developed economic and military organization soon proved unequal to the combined might of the German and Austro-Hungarian Empires. In the spring of 1915 the Russians were driven back in Galicia, and in May the Central Powers achieved a remarkable breakthrough on Poland's southern fringes, capturing Warsaw on August 5 and forcing the Russians to withdraw from all of Poland, known as the "Great Retreat".
The Russian Revolution
Dissatisfaction with the Russian government's conduct of the war grew despite the success of the June 1916 Brusilov offensive in eastern Galicia against the Austrians, when Russian success was undermined by the reluctance of other generals to commit their forces in support of the victorious sector commander. Allied fortunes revived only temporarily with Romania's entry into the war on August 27: German forces came to the aid of embattled Austrian units in Transylvania, and Bucharest fell to the Central Powers on December 6. Meanwhile, internal unrest grew in Russia, as the Tsar remained out of touch at the front, while Empress Alexandra's increasingly incompetent rule drew protests from all segments of Russian political life, resulting in the murder | | |
