高密度聚乙烯/乙烯-醋酸乙烯酯共混物的动态流变行为相形态及力学性能

Dynamic Rheological Behavior,Phase Morphology and Mechanical Properties of HDPE/EVA Blends

通过熔融共混制备了不同质量比的高密度聚乙烯(HDPE)/乙烯-醋酸乙烯酯(EVA)共混物,采用旋转流变仪、扫描电镜及电子万能试验机等研究了共混物的动态流变行为、相形态及力学性能。结果表明,HDPE/EVA为不相容共混物,HDPE质量分数较高的共混物界面相互作用高于EVA质量分数较高的共混物,这就导致了HDPE质量分数较高的共混物中分散相尺寸更小。在50/50共混物中发现了明显的共连续相结构。HDPE与EVA共混后降低了HDPE相的熔点,提高了EVA相的熔点,这归因于EVA相对HDPE相的稀释作用以及HDPE相对EVA相的成核作用。当HDPE质量分数较高时,共混物的拉伸强度呈现出正偏差,而对于50/50的共混物以及EVA质量分数较高的共混物则显示出负偏差。断裂伸长率与拉伸强度的变化趋势相同,除了80/20共混物有所例外,这可能是由于该组成下共晶度较高所致。

High density polyethylene（HDPE）/ethylene vinyl acetate copolymer（EVA）blends with different mass ratios were prepared by melt mixing.The dynamic rheological behavior,phase morphology and mechanical properties of the blends were investigated by rotational rheometer,SEM and electronic universal testing machine.The results show that HDPE/EVA is immiscible polymer blend.The interfacial interaction in HDPErich blends is higher than EVA-rich blends,which in turn leads to finer morphology in HDPE-rich blends.A clear co-continuous morphology for 50/50 blend was observed by morphological studies.The blending of HDPE and EVA decreases the melting temperature of HDPE phase and increases the melting temperature of EVA phase,which is due to the dilution effect of EVA phase for HDPE phase and nucleation effect of HDPE crystallites for EVA phase.For HDPE-rich blends the tensile strength shows positive deviation from mixing rule,while negative deviation is observed for 50/50 and EVA-rich blends.The elongation at break is found to follow the same trend as tensile strength except for 80/20 blend,which is attributed to the effect of higher co-crystallization in this composition.