滚塑成型用LLDPE加工性能的实验室评价

Laboratory evaluation of processability of rotational moulding grade LLDPE

通过滚塑成型实验发现,密度、熔体流动速率、相对分子质量分布等常规性能相似的两种线型低密度聚乙烯(LLDPE)(试样1和试样2),在滚塑成型过程中存在一定差异;采用相同加热温度和加热时间,试样2成型快,所得制品内部气泡少,低温缺口冲击强度高。通常的动态流变性能实验无法解释这种加工性能上的差异,而低剪切条件下的应力流变实验发现:试样2的零切黏度、弹性形变以及特性松弛时间分别比试样1低25%,26%,46%,差异较为明显,可以此初步评价LLDPE树脂的加工性能。

It was found in the rotational moulding experiment that there were some differences in the rota- tional moulding process between two linear low density polyethylene （LLDPE） resins （sample No. 1 and No.2） with similar density, melt flow rate, relative molecular mass distribution, etc. It took less time for the sample No.2 to finish the rotational moulding, and the products so obtained had less bubbles inside and higher notched impact strength at low temperature under the conditions of same heating temperature and time. The differences in processability between the two samples could not be explained by conventional dynamic rheology. The stress rheological experiment at low shear stress showed that the sample No.2 had zero shear viscosity, elastic deforma- tion and characteristic relaxation time lower than those of sample No. 1 by 25%, 26%, 46%, respectively. These significant differences can be used to preliminarily evaluate the processability of LLDPE resin.