含氟聚合物对茂金属聚乙烯加工性能的影响

采用4种不同种类含氟聚合物（PPA）分别按照0.04 %、0.08 %、0.12 %（质量分数，下同）的添加量加入茂金属聚乙烯树脂，有效降低了双螺杆挤出机或吹膜机在挤出时主机负荷、模头压力；同时，讨论了4种PPA对茂金属聚乙烯薄膜力学、光学以及流变特性的影响。结果表明，PPA的作用效果不仅仅与含氟聚合物含量有关，也与分散剂含量及种类有一定关系；在加入PPA之后，茂金属聚乙烯粉料树脂的临界剪切速率从281 s-1上升到1 400 s-1，茂金属聚乙烯粉料在加入了PPA加工稳定性得到显著提升；而PPA添加量与茂金属聚乙烯薄膜的拉伸性能、落镖冲击强度、光学性能有一定关系，在使用PPA-4时，薄膜雾度可降低到12.4 %，使用PPA-3时，落镖冲击强度可达到716 g，具体应用时应根据性能需求寻找最合适添加量。

Effect of Fluoropolymer on Processing Properties of Metallocene Polyethylene

Four types of polyphthalamide (PPA) resins were incorporated into metallocene polyethylene (mPE) at four different weight fractions to modify its processing properties. As a result, the main engine load and die pressure of twin-screw extruder or film blower were reduced effectively during the extrusion process. The effect of PPA on the mechanical, optical and rheological properties of mPE was investigated. The results indicated that the modification effect of PPA was not only related to the weight fraction of PPA resins but also related to the content and type of dispersant. The critical shear rate of mPE powders was found to increase from 281 s-1 to 1 400 s-1 with addition of PPA, suggesting a significant improvement in processability. Moreover, the introduction of PPA affected the tensile properties, dart impact strength and optical properties of mPE films. The haze of the film decreased to 12.4 % in the presence of PPA-4, whereas the mPE achieved the dart impact strength of 71 g due to the addition of PPA-3. The optimum additive amount of PPA is strongly dependent on the practical requirements.