PA6材料尺寸稳定性的影响因素

通过双螺杆挤出机熔融共混制备PA6材料,分析了环境湿度、成核剂、热处理对PA6材料尺寸稳定性的影响。结果表明,吸湿膨胀和内应力释放收缩共同影响PA6材料的尺寸变化,前者是主导因素;环境湿度越高、时间越长,PA6材料尺寸变化率越大,且在垂直流动方向上的尺寸变化率大于流动方向上的;随着成核剂用量的增加,PA6材料的尺寸变化率降低,用量为0. 5份时,尺寸稳定性最佳,成核剂用量继续增加,PA6材料尺寸变化率下降较小;热处理促进PA6材料内应力释放收缩,与吸湿膨胀相反,PA6材料的尺寸变化率明显降低;在相对湿度为50%的环境试验180 d,未添加成核剂、添加0. 50份成核剂、添加0. 50份成核剂热处理后的PA6材料在流动方向上的尺寸变化率分别为0. 39%、0. 33%、0. 21%,垂直流动方向上的尺寸变化率分别为0. 53%、0. 43%、0. 38%。

Influencing Factors of Dimensional Stability of PA6 Materials

PA6 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 PA6 were analyzed. The results showed that hygroscopic expansion and internal stress release shrinkage affected the size change of PA6, the former was the dominant factor. The higher the ambient humidity and the longer the time was, the bigger the size of PA6, the size change of PA6 in the vertical flow direction was greater than in the flow direction. With the increase of nucleating agent content, the size of PA6 decreased slightly. When the content was 0. 5 phr, the size change was minimum value, while the content continued to increase, the size change decreased slightly. Heat treatment promoted the internal stress release shrinkage of PA6, and decreased the size change rate of PA6 materials by the opposite action with hygroscopic expansion. After 180 days of environmental test with relative humidity of 50%, the size change rates of PA6 in flow direction was 0. 39%, in vertical flow direction was 0. 53%, the size change rates of PA6 with 0. 50 phr nucleating agents in flow direction was 0. 33%, in vertical flow direction was 0.43%, the size change rates of the heat treated of PA6 with 0. 50 phr nucleating agent in flow direction was 0. 21%, in vertical flow direction was 0. 38%.