Polyethylene, High Density

Abstract

High density polyethylene (HDPE) is a product of ethylene polymerization with a density of 0.940 g/cm 3 or higher. HDPE resins include both homopolymers of ethylene and its copolymers with α‐olefins. HDPE resins include a large variety of products that differ in molecular weight, molecular weight distribution, and density; they are produced with several classes of catalysts: Phillips catalysts based on chromium oxides, catalysts containing chromium complexes, Ziegler catalysts based on titanium or vanadium compounds, and, in some special cases, metallocene catalysts. Two of the most important industrial processes for manufacturing HDPE are polymerization in a slurry and gas‐phase polymerization. HDPE is one of the largest volume commodity plastics produced in the world, with a worldwide capacity in 1994 of over \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${14\times 10^{6}{\hskip0.167em}{\hskip0.167em}{\rm{t}}/{\rm{yr}}}$\end{document} . Blow‐molded products represent the biggest use for HDPE resins. They also used for bottles, housewares, toys, pails, drums, tanks, and other similar products. Injection‐molding products are the second largest application; they include housewares, toys, food containers, pails, crates, and cases. HDPE is also used for film manufacture, pipes of various diameters, wire and cable coatings, and foam. Low molecular weight HDPE waxes are used for paper coatings, spray coatings, emulsions, and in printing inks. High molecular weight HDPE is a specialty plastic with a high impact strength and abrasion resistance; it is used in such industrial applications as chemical and mineral processing, electrical equipment, municipal plants, and medical implants. High strength fibers produced with this polymer are used in bullet‐proof jackets and armor.