Lead-acid battery: Polyvinyl chloride battery jars and covers

A detailed materials engineering evaluation of a low-cost, high impact, structurally modified rigid polyvinyl chloride (PVC) has demonstrated that battery jars and covers can be molded from PVC in conventional equipment. The battery jars are flame resistant, transparent, and sufficiently tough to withstand considerable abuse without cracking. Although mechanical properties indicate the material becomes slightly more brittle after exposure to 1.220 specific gravity H
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at 120°F, the behavior at all times exceeds the currently used styrene-acrylonitrile in toughness. PVC maintains its rigidity beyond 120°F and accelerated tests indicate it will creep less than 1 percent after 20 years at room temperature under all expected loads. Jars weighing 12 pounds and covers weighing 4.5 pounds were each molded in carefully designed molds in a five minute cycle at 400°F without difficulty. The molded parts show very little stress concentration even without expensive annealing treatments and are free of molding defects. The cover diameter is molded 0.005 in. larger than the jar to insure proper fit during assembly. This dimensional accuracy is maintained without requiring special cooling fixtures after molding to restrict uneven shrinkage.