Research On Crosslinking Modification Of Ultra High Molecular Weight Polyethylene

UHMWPE is widely used since its high molecular weight,simple structure,non-toxic,harmless,and excellent comprehensive performance.UHMWPE can be made into pipes,plate materials,various films,fibers and other products.But there are also many deficiencies such as poor creep resistance,aging,poor hydrophilicity and poor heat resistance.Peroxide crosslinking can form a three-dimensional network structure and is proverbially used in ethylene propylene rubbers,cable cortexs,and polyethylene plates.Similarly,UHMWPE can get proficient properties and cover its imperfections by the accretion of Peroxide crosslinking.Therefore,in this paper,dicumyl peroxide(DCP)used as a cross-linking agent,mixed with the UHMWPE powder and then hot-pressed them to sheets.How the content of the cross-linking agent effects crosslinked UHMWPE sheet properties is discussed.In addition,the effects of the trans-cis ratio of decalin and the spinning temperature on the gel-spun UHMWPE fiber were studied,and the effect of DCP crosslinking modification on the properties of UHMWPE fiber was also studied.In this study,DCP/UHMWPE blends were mixed by the UHMWPE whose relative molecular mass was about one million and dicumyl peroxide(DCP),and the crosslinked UHMWPE sheets were prepared by hot-pressing.DSC and XRD test results showed:the DCP can indeed lead to crosslinking of UHMWPE,and the non-isothermal crosslinking reaction conformed to the first-order reaction was also proved.With the increase of DCP,the crystallinity and the recrystallization both decreased,while T_m and T_c decreased as the same.The grain sizes corresponding to the(110)and(200)crystal planes also decreased with the increasing of DCP.As the mechanical properties,when the DCP content was increased from 0.5%to 2%,although the crosslinked UHMWPE sheet reduced the strength to some extent,it also significantly reduced the elongation at break.After modified by DCP,the crosslinked structure of the UHMWPE greatly reduced the creep elongation.Among them,the creep elongation of uncrosslinked UHMWPE sheet was 33.75%,while the creep elongation of 2%DCP crosslinked UHMWPE sheet decreased to 7.09%,and the creep elongation was reduced by 78.99%.UHMWPE gel was prepared by using decalin as a solvent,and UHMWPE fiber was prepared by gel spinning-ultra drawing method.Mainly studied the effects of trans-cis ratio of decalin,UHMWPE dissolution temperature and DCP content on the changes in precipitation rate of decalin from gel over time.The results showed that the trans-cis ratio was 60:40 while the final amount of decalin precipitation was the least,and the final amount of decalin precipitation with a ratio of 90:10 was the most.As the dissolution temperature increased,the rate of precipitation increased.The precipitation rate of decalin in the modified gel was significantly higher than that unmodified gel.The process of gel-spinning UHMWPE fiber with decalin showed that the performance of UHMWPE fiber spun at 160°C and with a trans-cis ratio of 60:40 was excellent based on the analysis of mechanical properties.Finally,dissolving DCP into UHMWPE spinning mixture for the gel-spun modified UHMWPE fiber,the effects of the DCP content on the structural morphology,thermal properties,creep resistance and mechanical properties on the modified fiber were studied.The DSC indicated that the crystallinity and recrystallization of the modified dried gel-fiber were decreased,and the T_m also slightly decreased.The creep resistance of modified fiber showed that the creep resistance of the modified fiber can be obviously improved under the high temperature and low stress environment.The improvement of 20min creep resistance and 15min strain recovery of the 0.8%DCP modified UHMWPE fiber at 60?were 12.12%and 1.67%respectively,while the improvement of 20min creep resistance and 15min strain recovery at 100?were52.62%and 115.75%respectively.Obviously,the creep resistance and strain recovery improvement of modified fiber were more obvious when the higher temperature.At room temperature and high stress,the 20min creep elongation of the unmodified fiber was 2.83%,and the 1.2%DCP modified UHMWPE fiber had a 20min creep elongation of 2.06%.The creep elongation was reduced by 27.21%.