甲基丙烯酸镁增强氢化丁腈橡胶的结构与形态和性能

用不同份量的甲基丙烯酸镁(MgMA)作增强剂,过氧化二异丙苯(DCP)作硫化剂,通过混炼和硫化过程的原位聚合制备了氢化丁腈橡胶/聚甲基丙烯酸镁(HNBR/PMgMA)纳米复合材料,用XRD、FTIR1、3C-NMR、SEM、TEM、DMA和交联密度分析等方法研究了其结构、形态和性能,并阐述了MgMA改性HNBR的相关机理.结果表明,MgMA在混炼过程中粒径明显变小,部分达到纳米级.硫化过程中发生原位自由基聚合,并部分接枝到HNBR分子链上,HNBR硫化胶和PMgMA有可能形成接枝互穿聚合物网络(接枝IPN).随着MgMA用量的增加,纳米复合材料硫化胶的定伸应力、拉伸强度、扯断伸长率、撕裂强度和热氧老化性能逐渐提高.当MgMA含量为30份时,体系的拉伸强度和扯断伸长率分别为38.5MPa和545%,并具有优异的热空气老化性能.MgMA能明显增加HNBR复合材料的储能模量,并降低其损耗因子.随着MgMA用量的增加,纳米复合材料硫化胶的总交联密度(Ve)和离子键交联密度(Ve2)增加,而共价键交联密度(Ve1)下降,表明离子键对HNBR/PMgMA纳米复合材料的力学性能起重要作用.

STRUCTURE,MORPHOLOGY AND PROPERTIES OF HYDROGENATED NITRILE RUBBER REINFORCED BY MAGNESIUM METHACRYLATE

The nanocomposites of hydrogenated nitrile rubber(HNBR)/poly(magnesium methacrylate)(PMgMA) were prepared by compounding and in situ polymerizing in the curing process by using different contents of MgMA as a reinforcing agent and dicumyl peroxide(DCP) as a curing agent.The structure,morphology and properties of the nanocomposites were investigated by means of XRD,FTIR,()~(13)C-NMR,SEM,TEM,DMA and crosslinking density analysis,and the interrelated modification mechanism was expounded.The results showed that the diameter of MgMA particles decreased obviously during the mixing,and a part of MgMA monomers graft-copolymerized onto HNBR chains while MgMA monomers in situ polymerized during vulcanization,and hence grafted interpenetrating polymer networks were formed(grafted IPN).With increasing MgMA content the stress at 100% elongation,tensile strength,elongation at break,tear strength and heat air ageing properties of the nanocomposites were improved.The tensile strength and elongation at break of the nanocomposites with 30 phr MgMA contents are 38.5 MPa and 545%,respectively,at the same time they exhibit the excellent air-oven ageing properties.MgMA can increase markedly the storage modulus(E′) and decrease the loss factor(tanδ).When the contents of MgMA were increased,the total crosslinking density and ionic crosslinking density of HNBR nanocomposites were increased,but covalent bonds crosslinking density were decreased,indicating the ionic crosslinking bonds exert a significant effect on the mechanical properties of HNBR nanocomposites.HNBR having 36% acrylonitrile content was provided by Zeon Chemical,Japan.The Mooney viscosity ML(1+4) 100℃ of the rubber is 135.The compounds were mixed on a two-roll mill(friction ratio 1∶1.12) below 60℃ for 15 min.Accelerating agent,anti-ageing agent,activating agent,and MgMA were added into HNBR rubber matrix in sequence.The curing agent DCP was added at last.The optimum cure time(t_c=90 min) was determined by U-CAN UR-2030 vulcameter,Taiwan.The samples for tensile testing were then prepared in an electrically heated press at 178℃ for t_c=90 min.Tensile tests were conducted following ISO standard 37-2005 at room temperature.The structure and morphology of HNBR/PMgMA nanocomposites were characterized by FTIR,XRD,()~(13)C-NMR,SEM,TEM and DMA.The crosslinking density analysis was based on Flory-Rehner equation.Magnesium methacrylate is a very effective reinforcing agent for hydrogenated nitrile rubber.The MgMA monomer in situ polymerized and graft-copolymerized onto HNBR chains during vulcanization,and hence formed the grafted interpenetrating polymer networks(grafted IPN).The ionic crosslinking bonds have important effects on the properties of nanocomposites.The excellent general mechanical and ageing properties of HNBR/PMgMA nanocomposites can be achieved when the content of MgMA is between 20 and 40 phr.