Extrusion & Post
4 조회수
Bamboo-node pattern/melt fracture appears on the surface of heat-resistant polyethylene extruded products
문제 현상
Periodic coarse ripples or bamboo-node-like undulations appear on the extrudate surface, and in severe cases the extrudate shape is distorted.
Melt fracture is a serious defect in the extrusion process and directly leads to product scrapping.
원인 분석
(1) Extrusion speed exceeds critical shear rate, melt flow unstable
(2) Die temperature too low, melt viscosity high
(3) Die sizing section length insufficient, melt not fully relaxed
(4) Resin molecular weight too high or molecular weight distribution too wide
(5) Improper die entrance angle, melt entrance flow unstable
해결 방법
(1) Reduce extrusion speed below the critical shear rate
(2) Increase die temperature to the higher value within 190-230°C to reduce melt viscosity
(3) Increase die sizing section length, generally 10-20 times the die diameter
(4) Select grades with moderate molecular weight distribution
(5) Optimize die entrance design, entrance angle 30-60°
(6) Add a small amount of processing aid (fluoroelastomer) to improve fluidity if necessary
핵심 요약
Melt fracture is flow instability caused by extrusion speed exceeding the critical value, and the speed needs to be reduced, the temperature increased and the die design optimized.
이 정보가 도움이 되었나요?
0 명이 도움이 되었다고 합니다
의견 주셔서 감사합니다!