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采用恒速型双毛细管流变仪对比研究了LDPE/LLDPE不同组分含量共混物在较宽速率范围内的流变行为,通过研究共混物的黏度、弹性、挤出压力振荡、流动曲线、挤出畸变的差异,分析讨论了共混组成对黏弹性,进而对挤出压力振荡、鲨鱼皮等不稳定流动现象的影响。结果表明,共混使熔体的非线性黏性、弹性均增加,挤出畸变现象加重;少量LDPE的混入可消除LLDPE的挤出压力振荡现象,但鲨鱼皮畸变加重;而少量LLDPE的混入却不能消除LDPE熔体在毛细管入口处的压力振荡现象。
The rheological behavior of blends with different components of LDPE / LLDPE in a wide range of velocity was studied by constant-speed double-capillary rheometer. The viscosity, elasticity, , The difference of extrusion distortion was analyzed. The influence of blending composition on viscoelasticity, and then on the phenomena of extrusion pressure oscillation and shark skin instability was analyzed and discussed. The results showed that the blend increased the non-linear viscosity and elasticity of the melt and increased the extrusion distortion. The extrusion pressure oscillations of the LLDPE were abated by the addition of a small amount of LDPE, but the shark skin distortion was aggravated. However, the incorporation of a small amount of LLDPE The pressure oscillation of the LDPE melt at the capillary inlet can not be eliminated.