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

Abstract

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.