Pipes manufactured with high density polyethylene (HDPE) have been widely used for gas and water supply because of their own processing ability and well-balanced mechanical properties such as ductility, impact strength and modulus etc. However, the HDPE pipes are often scratched or cracked by heavy machinery at road construction sites and so on, and the defects sometimes cause fatal destructions. Therefore, the pipe endowed high mechanical properties have been strongly requested. Under such circumstances, the aim of this study was research and development of high performance gas pipe products by means of the polymer blend technology combined with HDPE and a poly butylene terephthalate (PBT). The PBT domains with fibrous structure were formed and dispersed in the HDPE matrix during the profiled extrusion process. However, the effects of characteristic fibrous structure on the mechanical properties were insufficient, because the great majority of PBT domain was shaped as spherical or spheroid giving rise to the relaxation of fibrous domain while quenching. On the other hand, the PBT domain maintained the fibrous structure in thin and small diameter pipe due to high speed quenching, and efficiently made the HDPE matrix reinforced.

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