PA66产品尺寸稳定性的影响因素

Influencing Factors on Dimensional Stability of PA66 Products

通过双螺杆挤出机熔融共混制备尼龙66 (PA66),模拟长期使用环境,研究环境湿度、吸水率、成核剂、热处理对PA66产品尺寸稳定性的影响。结果表明,PA66产品的尺寸稳定性受吸湿溶胀和内应力释放收缩共同作用,吸湿溶胀作用是主导因素;环境湿度越高、时间越长,PA66产品尺寸变化越大;PA66产品在垂直流动方向上的尺寸变化大于流动方向;环境湿度越低,达到相同吸水率需要的时间越长,吸湿溶胀作用越明显,PA66产品尺寸越大;添加成核剂影响PA66产品的尺寸变化和吸水率,随着成核剂用量的增加,PA66产品的尺寸变化和吸水率减小;成核剂用量为0.5份时PA66产品尺寸变化率和吸水率较小;继续增加成核剂用量,PA66产品的尺寸变化和吸水率变化不大;热处理能有效地消除内应力,使PA66产品的尺寸变小,成核剂有促进作用;热处理使内应力释放收缩和吸湿溶胀作用相互抵消,有利于降低PA66产品的尺寸变化。

Nylon 66 (PA66) was prepared by melt blending in twin-screw extruder. The effects of humidity,water absorption, nucleating agent and heat treatment on the dimensional stability of PA66 product were studied by simulating long-term service environment. The results show that,hygroscopic swelling and internal stress release shrinkage affect the dimensional stability of PA66, and the former is the dominant factor. The higher the ambient humidity is and the longer the time is, the greater the size change of PA66 product is. The size change of PA66 product in the across flow direction’s greater than in the flow direction. The lower the environmental humidity is,the longer the time required to achieve the same water absorption rate is,the bigger the size of the PA66 product is. The addition of nucleating agent has an effect on the size change and water absorption of PA66. With the increase of nucleating agent content,the size change and water absorption decrease of PA66 product. When the content of nucleating agent is 0.5 phr,the size change and water absorption are smaller,while the content of nucleating agent continues to increase,the size change and water absorption decrease little. Heat treatment can effectively eliminate internal stress,and makes PA66 product smaller in size,and nucleating agent has an advancing effect. The opposite effects of heat treatment and hygroscopic swelling are mutually exclusive,which is beneficial to reducing the size change of PA66 product.