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The influence of beta-crystal content in PP-RCT materials and calculations of the test pressure of pipe

 

Tu Xiang-qun, Wang Chao, Cheng Zhong-lin, Dong Bo-bo

Papers # 2016 Berlin

This paper is to verify the impact of different contents of nucleating agent and annealing processes on the content of β-crystal. By using four-parameter equation of PP-RCT with requirements in different application conditions, different temperature coefficients and Miner's rules the design stress of PP-RCT materials under different applications and the calculation process of test pressure of the PP-RCT pipes have been deduced, which can facilitate the better understanding and learning of relevant standards for plastic piping engineers. Moreover, it provides reference for the research and development of plastic pipe materials and quality control method.

As the third generation of polypropylene material, random copolymer polypropylene (PP-R), with good mechanical properties, non-toxic, good heat resistance and long-term creep resistance etc., has been widely used as the hot & cold water pipe system in construction buildings. However, when the installation is taken under at low ambient temperature, the brittle fracture could happen. In order to increase the low temperature impact resistance and heat resistance of PP-R pipes, the improvement of crystal structure of PP-R pipe by adding the nucleating agents has been proposed by many researches. The PP-R with modified crystalline structure is called PP-RCT. It is found from the longterm hydrostatic pressure test curve of PP-RCT, obtained by material modification, no knee point is observed before 8760h at any temperature, including 110 ℃, which indicates there is no brittle failure.

Related keywords : β crystalline polypropylene; PP-RCT; design stress; test pressure.
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