热塑性聚氨酯弹性体改性聚甲醛的研究

Study on POM Modification by Thermoplastic Polyurethane Elastomer

聚甲醛(POM)是一种高结晶性工程塑料,存在缺口敏感,冲击强度低、热稳定性差等缺点。用热塑性聚氨酯(TPU)改性POM,对多种TPU进行了优选,发现聚己内酯共聚酯型TPU综合力学性能比其它TPU好,硬度为80HA时,与POM在熔融加工中粘度匹配,利于共混,增韧效果优于其它TPU。当TPU含量为40%时,共混物形成双连续相结构,冲击性能发生突变,达75 kJ/m2。共混物的断裂伸长率随TPU含量增加而增大,含40%TPU时,断裂伸长率达到400%。共混物的杨氏模量和拉伸强度随TPU含量的增加而减小。TPU的加入使POM中的添加剂部分迁移到TPU相中,影响了聚甲醛结晶过程。同时发现,TPU可显著提高聚甲醛的热稳定性。

Polyoxymethylene （POM） is an important plastic with pretty good properties. However, its poor impact strength and thermo-degradation limit its applications. In this paper, the polycaprolactone based thermoplastic polyurethane （ TPU - 1 ） with a Shore A hardness of 80 was selected to toughen POM, because this kind of TPU has the excellent mechanical properties and matchable viscosity with POM at the processing temperature around 190 ℃. The result shows that TPU - 1 can effectively enhance the notched impact strength of POM and when the content of TPU increases to 40%, the notched impact strength of POM/TPU - 1 blend abruptly increases and the co-continues phase structure forms. The elongation at break increases, while the tensile strength and modulus decrease with the increase of TPU - 1 content. TPU - 1 can extract some of the additives in POM, affect the crystallization process, and increase the thermo-degradation temperature of POM.