The article discusses two types of Hi-fax to the wire and cable industry. The 1600 type is recommended for use in all applications not requiring the ultimate in stress-crack resistance. This type has moderate stress-crack resistance, somewhat better than the stress-crack resistance of 1-2 melt index low molecular weight polyethylene which has found wide acceptance in this market. The heat-shock resistance of 1600 Hi-fax at normal operating temperatures is at least comparable to the heat-shock resistance of 1-2 melt index low density polyethylene. Extended exposure to high temperatures is not recommended for either low density polyethylene or Hi-fax because of the susceptibility to oxidation. However, even at 90C., the heat-shock resistance of 1600 type Hi-fax is very good. Applications such as cable sheaths, where the ultimate in stress-crack resistance is required, require use of 1800 type Hi-fax. Although this is a higher molecular weight resin than the 1600 type, it has similar physical and electrical properties, but has a substantially higher level of stress-crack and heat-shock resistance. The higher molecular weight resin will withstand more than 1,000 hours exposure without failure in the Bell Laboratories stress-cracking test. Therefore, in stress-crack resistance, it is equivalent to the low melt index, low density polyethylene now used for sheaths.
Annual Wire and Cable Symposium (6th) on Technical Progress in Communication Wires and Cables, Asbury Park, N. J., 3-5 Dec 57.