交联聚乙烯的结晶行为研究

本论文采用熔融共混法制备了高密度聚乙烯(HDPE)/光引发剂(BDK)/交联剂 (TAIC) 共混物，再用高压汞灯辐照制备一系列不同交联程度的样品。通过广角X射线衍射(XRD)与差示扫描量热法(DSC)等手段研究了紫外光交联对HDPE的晶体结构及非等温结晶动力学行为的影响。研究结果表明：紫外光交联不改变HDPE晶型；随着光交联时间的增加，结晶峰的强度下降；晶粒尺寸变小。随着降温速率的增加，HDPE与交联HDPE (XLPE)的结晶峰变宽，结晶温度(Tp)向低温方向移动，结晶速率变快，结晶度(Xc)下降。相比较而言，XLPE的Tp较低，F(T)较大，Xc较小，结晶活化能(?E)较高，表明紫外光交联抑制了HDPE的结晶。

Studies on Crystallization Behaviors of UV-photocrosslinked High-density Polyethylene

In the thesis, the blends of high-density polyethylene (HDPE), photoinitiator (Benzil dimethyl ketal, BDK), cross-linker (Triallyl isocyanurate,TAIC) were prepared by melt blending, and then a series of samples with different degree of crosslinking were prepared by UV photocrosslinking through a medium pressure mercury lamp (Philips HPM 15, operated at 2 kW), The effects of ultraviolet (UV) photocrosslinking on the Crystal structure and non-isothermal crystallization kinetics were characterized by means of X-ray Diffraction (XRD) and Different Scanning Calorimetry (DSC). The results show that: UV phtocrosslinking can not change the crystal type of HDPE. However, the intensity of crystallization peaks and the sizes of crystal decrease with increasing UV irradiation time. With increasing the cooling speed, for both neat HDPE and photocrosslinked HDPE (XLPE), the crystallization peaks become wider, the crystallization temperatures (Tp) move toward lower temperature, crystallization velocity becomes faster, and the degrees of crystallization (Xc) are reduced. In comparison with un-photocrosslinked HDPE, of XLPE possesses lower Tp, bigger F(T), smaller Xc and higher effective activation energy (?E), indicating that UV photocrosslinking suppresses the crystallization process of HDPE.