Abstract:

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.

Key words: high-density polyethylene, ultraviolet photocrosslinking, crystal structure, different scanning calorimetry, nonisothermal crystallization kinetics