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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.
These are sometimes called "very low density polyethylene" or "ultra low density polyethylene" . However, synthesis of LLDPE polymers with high levels of comonomers and a "common" Ziegler-Natta catalyst has also been able to yield polymers with a density below 0.91 cm 3. [1]
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]
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]
The Properties of Polyethylene Crystallized Under the Orientation and Pressure Effects of a Pressure Capillary Viscometer, Journal of Applied Polymer Science vol. 14, pp. 2305–2317 (1970). Kanamoto, On Ultra-High Tensile by Drawing Single Crystal Mats of High Molecular Weight Polyethylene, Polymer Journal vol. 15, No. 4, pp. 327–329 (1983).
Polyethylene terephthalate is produced largely from purified terephthalic acid (PTA), as well as to a lesser extent from (mono-)ethylene glycol (MEG) and dimethyl terephthalate (DMT). [ 41 ] [ 5 ] As of 2022, ethylene glycol is made from ethene found in natural gas , while terephthalic acid comes from p-xylene made from crude oil .
Low molecular weight poly-alpha-olefins are useful as synthetic lubricants such as synthetic motor oils for vehicles and can be used over a wide temperature range. [ 8 ] [ 10 ] Even polyethylenes copolymerized with a small amount of alpha-olefins (such as 1-hexene , 1-octene , or longer) are more flexible than simple straight-chain high-density ...
The synthesis and processing of polyacetylene films affects the properties. Increasing the catalyst ratio creates thicker films with a greater draw ratio, allowing them to be stretched further. [ 8 ] Lower catalyst loadings leads to the formation of dark red gels , which can be converted to films by cutting and pressing between glass plates. [ 20 ]