T型口模气辅挤出中挤出胀大和挤出物变形的影响因素

摘要

The influence of relaxation time,gas-assisted extrusion length and slip time on die swell and warping was studied by means of numerical simulation for T-shape plastic profile. The results show that relaxation time,gas-assisted extrusion length and slip time have considerable influence on die swell and warping of the extrudate. When relaxation time is small,the slip time has little influence on die swell and can keep the die swell ratio below 1%. The gas-assisted extrusion length is the major factor to reduce warping of extrudate,so increasing relaxation time does not eliminate the generation of distortion. When relaxation time is longer,increasing slip time has greater effect on decrease of die swell and both gas-assisted extrusion length and slip time need to be increased for reducing warping of extrudate.%以T型截面异型材为对象，通过数值模拟研究气辅挤出成型中聚合物熔体的松弛时间、气辅挤出段长度和在气辅挤出段的停留时间对挤出物的变形和挤出胀大的影响。研究结果表明，气辅挤出时松弛时间、气辅挤出段长度和气辅挤出段停留时间对挤出胀大和挤出物的变形均有较大影响。在松弛时间较短时，停留时间对挤出胀大率的影响不大，均能使挤出胀大率小于1％，气辅挤出段长度是影响截面变形的主要因素，增加停留时间并不能消除变形的产生；当松弛时间较长时，增加停留时间对减小挤出胀大具有较大作用，而减小变形需要同时增加气辅段长度和停留时间。