加工温度对线型低密度聚乙烯/聚苯乙烯薄膜微观形态及光散射性能的影响

Effect of Processing Temperature on Morphology and Light-Scattering Properties of Linear Low Density Polyethylene /Polystyrene Films

采用微层共挤出制备了16层(线型低密度聚乙烯(LLDPE)/聚苯乙烯(PS))共混物/聚甲基丙烯酸甲酯(PMMA)交替层状材料,将PMMA层剥去后得到从皮层和芯层不同位置的LLDPE/PS薄膜。研究加工温度对皮层和芯层薄膜微观形态和光散射性能的影响。微观形态观察显示,对于200℃制备的皮层和芯层LLDPE/PS薄膜中PS均以球状分散,皮芯层差异较小。随着加工温度的升高,PS分散相开始沿挤出方向变形,特别在皮层薄膜中的变形尤为显著,皮芯层形态差异逐渐增大。光散射性能测试结果表明,加工温度升高后,试样的光散射各向异性程度增加,透光性降低,雾度均在93%左右,同时皮芯层的光学性能差异逐渐增大。说明较低的加工温度更有利于制得均匀结构和光散射性能优异的LLDPE/PS光散射材料。

The 16-layer materials consistintg of low density polyethylene （LLDPE）/polystyrene （PS） blend layers and polymethyl methacrylate （PMMA） layers were prepared through multilayered coextrusion. LLDPE/PS films located at skin and core layers of a multilaye：red material were obtained by peeling off PMMA layers. The effect of processing temperature on morphology and lilght-scattering properties of the LLDPE/PS films was investigated. The morphological observation shows that in the multilayered specimen extruded at 200 ℃ , the LLDPE/PS films located at skin and core layers have a similar morp＇hology and PS particles are dispersed as spheres in the matrix. With increasing the processing temperature, the dispersed phase located at the skin layer tends to be elongated along the extrusion direction, resulting in a distinct difference from the morphology of the core layer. Light scattering results display that with increasing processing temperature, the haze of each specimen is maintained around 93 % while the transmittance tends to decrease and the difference of the optical properties between skin and core layers is enlarged. This indicates that the films with uniform morphology and excellent light-scattering properties could be fabricated at a lower processing temperature in the melt processing.