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The less the polymer chains are branched, and the lower the molecular weight, the higher the crystallinity of polyethylene. Crystallinity ranges from 35% (PE-LD/PE-LLD) to 80% (PE-HD). Polyethylene has a density of 1.0 g/cm 3 in crystalline regions and 0.86 g/cm 3 in amorphous regions. An almost linear relationship exists between density and ...
Ethylene gas (H 2 C=CH 2) is the monomer for polyethylene. Other modified ethylene derivatives include: tetrafluoroethylene (F 2 C=CF 2) which leads to Teflon; vinyl chloride (H 2 C=CHCl) which leads to PVC; styrene (C 6 H 5 CH=CH 2) which leads to polystyrene; Epoxide monomers may be cross linked with themselves, or with the addition of a co ...
Ethylene vinyl alcohol (EVOH) is a formal copolymer of ethylene and vinyl alcohol. Because the latter monomer mainly exists as its tautomer acetaldehyde , the copolymer is prepared by polymerization of ethylene and vinyl acetate to give the ethylene vinyl acetate (EVA) copolymer followed by hydrolysis.
Two broad classes of monomers are susceptible to anionic polymerization. [3] Vinyl monomers have the formula CH 2 =CHR, the most important are styrene (R = C 6 H 5), butadiene (R = CH=CH 2), and isoprene (R = C(Me)=CH 2). A second major class of monomers are acrylate esters, such as acrylonitrile, methacrylate, cyanoacrylate, and acrolein.
Alpha-olefins such as 1-hexene may be used as co-monomers to give an alkyl branched polymer (see chemical structure below), although 1-decene is most commonly used for lubricant base stocks. [8] 1-hexene, an example of an alpha-olefin. Many poly-alpha-olefins have flexible alkyl branching groups on every other carbon of their polymer backbone ...
The newly formed nucleophile will then attack the atom X in another monomer molecule, and the sequence would repeat until the polymer is formed. [20] Anionic ring-opening polymerizations (AROP) involve nucleophilic reagents as initiators. Monomers with a three-member ring structure - such as epoxides, aziridines, and episulfides - undergo ...
In polymer chemistry, emulsion polymerization is a type of radical polymerization that usually starts with an emulsion incorporating water, monomers, and surfactants.The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer (the oil) are emulsified (with surfactants) in a continuous phase of water.
PAN is soluble in polar solvents, such as dimethylformamide, dimethylacetamide, ethylene and propylene carbonates, and in aqueous solutions of sodium thiocyanate, zinc chloride or nitric acid. [13] Solubility parameters: 26.09 MPa 1/2 (25 °C) are 25.6 to 31.5 J 1/2 cm −3/2. Dielectric constants: 5.5 (1 kHz, 25 °C), 4.2 (1 MHz, 25 °C).Can ...