Preparation And Dynamic Properties Analysis Of Rubber Composites With Hybrid Network Structure

In the rubber industry,the overall performances of rubber composites are controlled by the interfacial structure strongly.In this paper,the interface interaction networks,such as hydrogen-bonded network or carboxylate network,between rubber matrix and filler were designed precisely,and the effects on the properties of rubber composites were investigated thoroughly.(1)In this work,two types of clays,halloysite nanotube(HNT)and montmorillonite(MMT),were chosen to reinforce carboxylated nitrile rubber(XNBR).Based on the low surface polarity of HNTs and the intercalability of MMT,flexible macromolecule,poly(ethylene oxide)(PEO),was introduced to prepare organic modified halloysite(PHNT)and montmorillonite(PMMT),respectively.Results showed that the nitrile groups and carboxyl groups of XNBR could form hydrogen bonds with PEO chains distributed on the outer surface of PHNT,however,interactions between XNBR molecular chains and the PEO chains intercalated MMT were found to be very weak.The difference between these two interactions among XNBR,PHNT and PMMT leads to different dynamic mechanical properties of XNBR/PHNT and XNBR/PMMT composites.The tan ?~T curve of XNBR/PHNT composite showed an obvious loss peak around 50 °C due to the hydrogen bonds between XNBR chains and PHNT,which could lead to an extra energy dissipation through the model of dissociation-complexation-dissociation.In comparison,the loss factor of XNBR/PMMT composite is smaller than the unmodified one at high temperature.Though the presence of PEO reduced the modulus and tensile strength of XNBR/HNT and XNBR/MMT composites slightly,PHNT or PMMT could provide considerable reinforcement for XNBR matrix.In addition,the plasticization of flexible molecular chains weakened the reduction in maximum loss factor of HNT or MMT for XNBR,which is of great significant importance for filler to reinforce rubber while maintains its high loss factor.(2)The reinforcing effect of silica is lower than carbon black for rubber matrix due to the relatively high surface energy and poor dispersion in the rubber matrix.In this work,N-?-(aminoethyl)-?-aminopropyl-methyl-dimethoxysilane(KH602)was utilized to modify silica as filler,and sorbic acid(SA)was grafted to the molecular chains of styrenebutadiene rubber(SBR)with the aid of peroxide,which resulted in the carboxylate network in the SBR/silica composites through the interaction between KH602 and SA.Thereby,the effect of carboxylate network on the properties of SBR composites was studied in details.Results showed that KH602 could improve the dispersibility of silica in the SBR matrix,and then improved the modulus and tensile strength of SBR/silica composites.But,when KH602 continued to increase,the tensile strength of composites decreased.Meanwhile,silica could disperse more homogenous in the SBR matrix when SA is introduced into SBR composite,resulting in stronger interfacial adhesion between SBR matrix and silica.As a consequence,the 300 % modulus and tensile strength of SBR composite increased by 46 % and 20 %,respectively,compared to the one without SA.Moreover,the tan ? value of 60 °C of the SA grafted SBR composite was 14 % lower than the ungrafted one,suggesting that the carboxylate network could reduce the rolling resistance of SBR/silica composites markedly,.