Study On Structure And Property Of High Grade HDPE Pipe Materials

High grade PE100 pipe resins have become more and more important in the pipe market.However,domestic unimodal PEI 00 showed worse performance than foreign bimodal PEI 00,and unimodalPE100 cannot meet the standard ofnew PE100 identification.In addition,PE 100-RC pipe resins have been studied for more than 10 years in foreign countries,but few in domestic research.The long-term property of PEI 00 pipe resins was determined by molecular chain structure and condensed state structure.Therefore,the systematic study of the polyethylene pipe resins was conducive to build relationship between the structure and property and provided technical guidance for the optimization of unimodal PEI 00 and the development of the PE100-RC.The MW and MWD,SCB and SCBD of the 9 bimodal and unimodal PE 100 have been investigated in this work.The results showed that when the SCBs were distributed in the high molecular weight of PE,the long-term property is improved.The lamella thickness and its distribution and melting recrystallization behavior also have been studied,the results showed that the lamella thickness was thicker and the crystal structure was more perfect with the improvement of the long-term property.In this work,the crystallization behavior of PE100-RC,bimodal and unimodal PE 100 and PE80 have been investigated for a comparsion.A correlation between the difference of the crystallization kinetics and the long-term property have been observed.The crystallization rate was faster with the improvement of the long-term property.Furthermore,the the rheological behavior and mechanical property of the PE pipe resins have been studied by the means of rheometer and the universal material testing machine.The results showed that the yield strength and the strain hardening modulus<Gp>were higher with the improvement of the long-term property.The results of SEM also proved that the lamella thickness was thicker and the crystal structure was more perfect.In the process of melting and recrystallization,the formed Shish-Kabab structure was larger and the number of cavitation and defects was less with the improvement of the long-term property.The results of the rheological property showed that the molecular weight distribution of the PE100-RC was wider.The high molecular weight fraction and the low molecular fraction had better microcompatibility,and the tie molecular and entanglement density were higher.