冷却方式对聚乙烯管件性能的影响

Influence of Cooling Method on Performance of Polyethylene Fittings

通过模拟不同冷却方式对高密度聚乙烯(PE⁃HD)注塑管件性能的影响,发现在实际生产过程中,泡水冷却会使PE⁃HD管件冷却速率过快,使管件处在最大生长速率的时间大大缩短,很难形成较大的晶体,管件内部形成较多的微晶;同时,管件内部具有十分明显的体积松散性,管件内部结晶不均匀、内应力较大,性能不太理想。而自然冷却的PE⁃HD管件可克服以上缺陷,且其氧化诱导时间、密度值、结晶度和拉伸屈服应力等性能都优于泡水冷却的PE⁃HD管件。

In this paper,we simulated the influence of different cooling methods on the performance of injection⁃molded fittings based on high⁃density polyethylene.We found that in the actual production process,water⁃dipping cooling result⁃ed in a too fast cooling rate for the fittings and thus greatly shortened the period of the fittings staying at a maximum growth rate.This led to the formation of more microcrystals inside the fittings,which depressed the growth of larger crystals.As a result,an obviously loosen structure was generated inside the fittings with non⁃uniform crystals and large internal stress,thus resulting in poor performance.However,the natural cooling could avoid these defects and therefore led to better properties including oxidation induction time,density value,crystallinity,and tensile yield stress for the fit⁃tings in comparison with water cooling.