热塑性聚氨酯微孔发泡材料的表观密度与其力学性能的关系

用高压CO2流体通过升温发泡法制备了一系列不同表观密度的热塑性聚氨酯(TPU)微孔发泡材料,探究了TPU发泡材料的表观密度与其力学性能的关系.微孔发泡材料的泡孔结构和表皮结构由扫描电子显微镜表征;不同表观密度材料的力学性能利用万能材料试验机和旋转流变仪表征.研究发现:TPU微孔发泡材料的表观密度主要是由材料皮层厚度占比和泡孔层密度决定的,皮层厚度占比越小和泡孔面积占有率越高,泡沫的表观密度越小;微孔发泡材料在线性应变区的压缩模量E与材料表观密度ρ的关系为:E∝ρ1.7,符合泡沫材料压缩模量与表观密度呈指数关系的基本结论;循环压缩实验中,随微孔发泡材料表观密度减小,损耗百分比增大,残余应变减小;流变实验中,微孔发泡材料的模量随表观密度变化没有明显的变化,阻尼因子tanδ随泡沫表观密度变化不呈单一的规律性.同时,阐明了微孔发泡材料的压缩模量E和损耗百分比随表观密度变化的机理.

Relationship between Apparent Density and Mechanical Properties of Microcellular Thermoplastic Polyurethane Foam

A series of microcellular thermoplastic polyurethane foams with different apparent densities were prepared by temperature-increasing foaming method with high-pressure CO2 as blowing agent,and the relationship between the apparent density and mechanical properties was investigated.The structure of microcellular thermoplastic foam was characterized by scanning electron microscopy.The mechanical properties of the materials with different apparent densities were characterized by universal material testing machine and rotational rheometer.The results show that the apparent density of the microcellular thermoplastic polyurethane foam is mainly determined by the thickness ratio of the skin layer and the area occupation of cell.The smaller the ratio of the thickness of the skin layer and the higher the area occupation of cell,the smaller the foam density;the relationship between compression modulus E and apparent densityρof the samples in the linear strain region is as follows:E∝ρ1.7,which is consistent with the basic conclusion that the relationship between modulus and density of foam materials is exponential;in the cyclic compression experiment,as the density of the foam material decreases,the residual strain decreases,and the hysteresis increase;in the rheological experiment,the modulus of the foamed material does not change significantly with the density,and the damping factor tanδdoes not vary monotonically with the foam density.At the same time,the dependence of compression modulus E and hysteresis with foam density was also explained.