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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]
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 and LLDPE have unique rheological or melt flow properties. LLDPE is less shear sensitive because of its narrower molecular weight distribution and shorter chain branching. During a shearing process, such as extrusion, LLDPE remains more viscous and, therefore, harder to process than an LDPE of equivalent melt index.
Low-density polyethylene (LDPE) is flexible and is used in the manufacture of squeeze bottles, milk jug caps, retail store bags and linear low-density polyethylene (LLDPE) as stretch wrap in transporting and handling boxes of durable goods, and as the common household food covering.
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).
Most polyolefin are made by treating the monomer with metal-containing catalysts. The reaction is highly exothermic. Traditionally, Ziegler-Natta catalysts are used. Named after the Nobelists Karl Ziegler and Giulio Natta, these catalysts are prepared by treating titanium chlorides with organoaluminium compounds, such as triethylaluminium.
Ethylene-vinyl acetate (EVA) foam, the copolymers of ethylene and vinyl acetate; also referred to as polyethylene-vinyl acetate (PEVA) Low-density polyethylene (LDPE) foam, first grade of polyethylene (PE) Nitrile rubber (NBR) foam, the copolymers of acrylonitrile (ACN) and butadiene; Polychloroprene foam or Neoprene; Polyimide foam
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.