低缠结超高分子量聚乙烯的制备及其对线性低密度聚乙烯的增强作用∗

摘要

利用单活性位点前过渡金属 FI 催化剂(Fenokishi-Imin catalyst)进行乙烯的聚合反应，在较低的温度下，制备出具有低链缠结度的超高分子量聚乙烯。经高温凝胶色谱(PL-GPC)测定，产物分子量达到了(2~5)×106；差示扫描量热仪(DSC)检测表明其结晶度达到了70%；流变学研究表明，相对于商业超高分子量聚乙烯，产物链缠结密度大大降低。进一步的力学性能测试显示添加少量的低缠结超高分子量聚乙烯对线性低密度聚乙烯的增强作用非常明显，可使拉伸强度和断裂伸长率大大提高。%The present research applied a type of single-active-site transition metal catalyst named Fenokishi-Imin catalyst (FI catalyst)to the polymerization of ethylene at a relatively lower temperature.With the controlled chain growth rate,we successfully synthesized ultra-high molecular weight polyethylene (UHMWPE)with low entan-glement density and much improved processing characteristics.Detected by gel permeation chromatography (GPC),it has a molecular weight range of 2-5 million.Differential scanning calorimeter (DSC)test showed that the crystallini-ty reaches above 70%.Rheological characterization indicated that the synthesized ultra-high molecular weight polyeth-ylene has a much lower entanglement density than commercial UHMWPE.To explore its potential application,a very small amount of this disentangled UHMWPE was blended with linear low-density polyethylene (LLDPE),obtaining significant improvement of tensile strength and elongation at break confirmed by mechanical tests.