聚乙烯熔体的离散松弛时间谱与熔融指数的关系

该文通过动态线性小振幅剪切震荡实验所得的聚乙烯熔体储能模量Ｇ′（ω）和耗能模量Ｇ″（ω）数据，采用最小二乘法线性回归、正则法和非线性回归法分别计算得到离散松弛时间谱，比较三种方法得到结果的差别，讨论计算参数、温度和材料对离散松驰时间谱影响．

THE RELATIONSHIP BETWEEN MELT INDEX AND DISCRETE RELAXATIOIN TIME SPECTRUM OF POLYETHYLENE MELTS

By using dynamic stress rheometer\|DSR\|200, linear viscolelasticity of four polyethylene melts has been characterized by small amplitude oscillatory shear test. From data of storage moduli G() and loss moduli G(), discrete relaxation spectra have been obtained for four polyethylene melts by means of linear regression method, regularization method and nonlinear regression method, respectively. Effects of the calculation methods, computing parameters, temperatures and materials on the spectrum have been discussed. It was found that computing parameters\|relaxation time numbers and relaxation time range have a strong effect on linear regression and regularization method, but less influence on nonlinear regression method. Three calculation methods can obtain nearly the same relaxation spectrum when choosing fewer relaxation time numbers, but quite different results when chossing more relaxation time numbers. Both temperature and materials have strong effects on discrete relaxation spectrum due to the s tructural characteristic of polymers. It is concluded that nonlinear regression method seems to be the best method for the calculation of the discrete relaxation spectrum.\=