通过酰胺化合物(NA-BW)引导等规聚丙烯(iPP)制备高水平β晶型聚丙烯(β-iPP),借助广角X射线衍射(WAXD),差示扫描量热仪(DSC)及偏光显微镜(POM)研究其结晶形态及结晶行为,并研究了β型成核剂对iPP力学性能的影响。结果表明:加入β型成核剂NA-BW后,iPP的晶型和球晶形态均发生变化;等温结晶研究表明聚丙烯的半结晶时间(t1/2)明显降低,即结晶速度加快,非等温结晶研究表明iPP的结晶温度提高;iPP的冲击强度大大提高,拉伸和弯曲性能却略有下降。当成核剂用量为3 m g/g时,悬臂梁缺口冲击强度达到最大值,提高达3.5倍,由49.35J/m提高到176.23 J/m。热稳定性实验表明β型成核剂对聚丙烯成核效果的热稳定性良好。 相似文献
Linear regression models for interval-valued data have been widely studied. Most literatures are to split an interval into two real numbers, i.e., the left- and right-endpoints or the center and radius of this interval, and fit two separate real-valued or two dimension linear regression models. This paper is focused on the bias-corrected and heteroscedasticity-adjusted modeling by imposing order constraint to the endpoints of the response interval and weighted linear least squares with estimated covariance matrix, based on a generalized linear model for interval-valued data. A three step estimation method is proposed. Theoretical conclusions and numerical evaluations show that the proposed estimator has higher efficiency than previous estimators.
