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Polyethylene was first synthesized by the German chemist Hans von Pechmann, who prepared it by accident in 1898 while investigating diazomethane. [12] [a] [13] [b] When his colleagues Eugen Bamberger and Friedrich Tschirner characterized the white, waxy substance that he had created, they recognized that it contained long −CH 2 − chains and termed it polymethylene.
LDPE has SPI resin ID code 4 Schematic of LDPE branching structure. Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene.It was the first grade of polyethylene, produced in 1933 by John C. Swallow and M.W Perrin who were working for Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization. [1]
The degradation of polyethylene occurs by random scission—a random breakage of the bonds that hold the atoms of the polymer together. When heated above 450 °C, polyethylene degrades to form a mixture of hydrocarbons. In the case of chain-end scission, monomers are released and this process is referred to as unzipping or depolymerization ...
Polyethylene glycol (PEG; / ˌ p ɒ l i ˈ ɛ θ əl ˌ iː n ˈ ɡ l aɪ ˌ k ɒ l,-ˈ ɛ θ ɪ l-,-ˌ k ɔː l /) is a polyether compound derived from petroleum with many applications, from industrial manufacturing to medicine. PEG is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular weight.
HDPE is known for its high strength-to-density ratio. [4] The density of HDPE ranges from 930 to 970 kg/m 3. [5] Although the density of HDPE is only marginally higher than that of low-density polyethylene, HDPE has little branching, giving it stronger intermolecular forces and tensile strength (38 MPa versus 21 MPa) than LDPE. [6]
Ultra-high-molecular-weight polyethylene (UHMWPE, UHMW) is a subset of the thermoplastic polyethylene. Also known as high-modulus polyethylene ( HMPE ), it has extremely long chains, with a molecular mass usually between 3.5 and 7.5 million amu . [ 1 ]
Epoxide monomers may be cross linked with themselves, or with the addition of a co-reactant, to form epoxy; BPA is the monomer precursor for polycarbonate; Terephthalic acid is a comonomer that, with ethylene glycol, forms polyethylene terephthalate. Dimethylsilicon dichloride is a monomer that, upon hydrolysis, gives polydimethylsiloxane.
For example, in polyethylene terephthalate (PET or "polyester"), the repeat unit is -CO-C 6 H 4-CO-O-CH 2-CH 2-O-. The polymer is formed by the condensation reaction of the two monomers terephthalic acid (HOOC-C 6 H 4-COOH) and ethylene glycol (HO-CH 2-CH 2-OH), or their chemical derivatives. The condensation involves loss of water, as an H is ...