电子束辐照交联超高分子量聚乙烯等温结晶动力学

Isothermal crystallization kinetics of electron beam cross-linked ultra-high molecular weight polyethylene

研究了电子束辐照交联超高分子量聚乙烯的等温结晶行为与辐照剂量、交联度和结晶温度的关系.首先,用差示扫描量热技术(DSC)研究了以0,50,100 kGy电子束辐照的超高分子量聚乙烯分别在不同的温度下等温结晶过程,发现半结晶时间(t1/2)和Avrami指数(n值)与结晶温度有关.与未交联超高分子量聚乙烯相比,交联聚乙烯等温结晶动力学的t1/2和n值较小,证明交联网络可加速聚乙烯成核,且抑制晶体生长.在此基础上,采用阶梯式温度"跃变"方法,诱导交联聚乙烯分子链在不同温度下分别结晶,得到具有多个熔融温度的交联聚乙烯结晶,而未交联的超高分子量聚乙烯则只显示单一熔融温度,证实了在交联聚乙烯中存在的不均匀交联网络结构导致分子链结晶能力不同.

The isothermal crystallization of radiated cross - linked ultra - high molecular weight polyethylene （UHMWPE） was investigated as a function of irradiation dose and crystallization temperature by differential scanning calorimetry （DSC）. Isothermal crystallization of polyethylene irradiated with electron beam with 0, 50, and 100 kGy doses shows the dependences of half crystallization time （t1/2 ） and Avrami index （n value） on the crystallization temperature. Cross - linked UHMWPE shows lower t1/2 and n values, in comparison to non - irradiated UHMWPE, indicating that cross - linked network may accelerate the crystallization but hinder the crystal growth after nucleation. Furthermore, we crystallized cross - linked UHMWPE by sequentially quenching the polymer melted to different crystal temperatures to facilitate respective crystallization of polymer chains or segments, resulting in the crystal of cross - linked polyethylene with multiple melt temperatures, while non - cross - linked polyethylene shows just single melt temperature, which indicates that heterogeneous network within the cross- linked UHMWPE causes such unique crystallization behavior.