PPI - The Plastics Pipe Institute, Inc. https://yse.yabesh.ir/std/handle/yse/111 Wed, 06 May 2026 18:42:08 GMT 2026-05-06T18:42:08Z PPI TR-21 https://yse.yabesh.ir/std/handle/yse/60702 PPI TR-21; Thermal Expansion and Contraction in Plastics Piping Systems PPI - The Plastics Pipe Institute, Inc. Mon, 01 Jan 2001 00:00:00 GMT https://yse.yabesh.ir/std/handle/yse/60702 2001-01-01T00:00:00Z