PPI - The Plastics Pipe Institute, Inc. https://yse.yabesh.ir/std/handle/yse/111 2026-05-06T20:34:05Z 2026-05-06T20:34:05Z PPI TR-21 PPI - The Plastics Pipe Institute, Inc. https://yse.yabesh.ir/std/handle/yse/60702 2017-09-04T15:57:23Z 2001-01-01T00:00:00Z PPI TR-21; Thermal Expansion and Contraction in Plastics Piping Systems PPI - The Plastics Pipe Institute, Inc. 2001-01-01T00:00:00Z