挤出热历程对聚乳酸流变性能和热性能影响

以丙交酯法合成的聚乳酸为实验材料,在180～210℃间选用4个实验温度采用单螺杆挤出机进行挤出成型实验,研究了挤出成型对聚乳酸粘均分子量、熔融指数、流变性能和热性能的影响。结果表明：在挤出成型中聚乳酸主要发生力化学降解和热降解,以力化学降解形式为主。所发生的热降解随实验温度升高而加强。首次挤出成型使分子量下降明显。在180℃和210℃,聚乳酸分子量在首次挤出成型后分别下降了49.33%和60.80%。挤出成型使聚乳酸热分解温度和熔点略有升高。随着挤出成型次数增加,增加剪切应力可以更有效地增加熔体流动性。聚乳酸经3次以上挤出成型后基本没有再利用价值。

Influence of thermal progress of extrusion on the rheological properties and thermal properties of polylactic acid

With polylactic acid（PLA） synthesized by the lactide process as experimental materials, extrusion experiments were conducted in a single screw extruder at four experimental temperature between 180-210℃,then influence of the extrusion on viscosity-average molecular weight, melting index, rheological properties and thermal performance of PLA were studied. The results showed that stress chemical degradation and thermal degradation occurred mainly in the extrusion of PLA, and the former was primary molding.The thermal degradation was enhanced with experimental temperature going up. Molecular weight of PLA decreased obviously in the first extrusion. At 180 ℃ and 210℃, molecular weight of PLA respectively came down 49.33% and 60.80% in the first post-extrusion. Thermal decomposing temperature, and melting point went up slightly in the Extrusion. With the increase in the number of extrusion, increasing shear stress can be more effective to increase the melt flowability. PLA had no reuse value after more than 3 times extrusion progress.