拉伸速率对PLA/PUR–T材料拉伸行为与形态的影响

以聚乳酸(PLA)和热塑性聚氨酯(PUR–T)为基体,通过双螺杆挤出机进行熔融混合制备了一系列PLA/PUR–T(质量比分别为90/10,50/50,10/90)共混物,将共混物通过立式注塑机制备标准拉伸试样;再利用万能试验机制备了PLA/PUR–T材料的拉伸样条并对其进行了不同拉伸速率下的拉伸测试,选取不同拉伸状态下的试样分别进行扫描电子显微镜观察。结果表明,当PLA为基体相,PUR–T为分散相时,PLA/PUR–T材料的最大塑性应力较高,在较低的拉伸速率下,其材料的屈服平台区和断裂应力较大,断面形貌呈现液滴态–粗纤态–细纤态的演变,随着拉伸速率的升高,其材料的屈服平台区消失,断面形貌呈现粗纤态–细纤态的演变;当PUR–T为基体相,PLA为分散相时,PLA/PUR–T材料的最大塑性应力较低,其材料的表现出强烈的拉伸强化和极大的拉伸应变行为,断面形貌呈现连续的粗长纤态–细长纤态的演变。

Influences of Drawing Rate on Mechanical Behavior and Morphology of PLA/PUR-T Composites

Polylactic acid (PLA) and thermoplastic polyurethane (PUR-T) as the matrix phase,a series of PLA/PUR-T(mass ratio was 90 / 10,50 / 50,10 / 90) composites were prepared by melt compoumding with twin-screw extruder,and then,the blends were processed into standard spline by using injection molding machine.Universal testing machine and scanning electron microscope was used to test the mechanical behavior and morphology of PLA / PUR-T composites,respectively.The results show that PLA as a matrix phase,PUR-T as a dispersed phase,the yield point elongation and breaking stress of PLA / PUR-T samples are great at low drawing rate,and fractured surface morphology changes from droplets,thick fibers to thin fibers.With drawing rate increase,the yield point elongation of PLA / PUR-T samples vanish,and fractured surface morphology changes from thick fibers to thin fibers.PUR-T as a matrix phase,PLA as a dispersed phase,the plastics stress of PLA / PUR-T samples are low,showing intense tension stiffening and tensile strain behaviors.Fractured surface morphology changes from thick fibers to thin fibers.