Structure And Performance Of Functional EMA/NBR TPV

Thermoplastic vulcanizate(TPV)based on ethylene-methylacrylate copolymer(EMA)/nitrile-butadiene rubber(NBR)blends were prepared by dynamic vulcanization.The mechanical properties,morphology and dynamic viscoelastic behavior,including Mullins effect and compression set,were studied systematically.The influences of dosage of ZDMA and weight ratio of EMA/NBR blends on the properties of TPV were investigated;furthermore,the shape memory properties of pure EMA and series EMA/NBR TPVs were researched systematically,and the effects of rubber plastic ratio,deformation temperature and recovery temperature on the shape memory properties were investigated.The non-isothermal crystallization kinetics of pure EMA and EMA/NBR TPV at different cooling rates were studied by DSC.The NBR was reinforced by CB and its Mullins amplification effect was studied.(1)The mechanical properties of pure EMA,NBR static vulcanizate and EMA/NBR TPV were studied systematically.The effects of weight ratio of TPV and ZDMA content on the properties of TPV were studied.The results showed that the elongation at break,tensile strength and tear strength of TPV were decreased by increasing the weight ratio of EMA/NBR.The irregular NBR rubber particles of TPV were distributed evenly in TPV with a diameter of3?5?m.Mullins effect could be observed in the compression stress-strain curves of the TPV during the uniaxial loading-unloading cycles and the maximum stress at specific strain were decreased obviously after the first loading-unloading while only decreased slightly at the later loading-unloading cycles.The maximum compression stress reversibility of the compressed sample during the secondary compressing were improved with the increase of the heat treatment temperature,and the best performance was achieved when the temperature was 80?.For the compression set and its recovery,the generalized Maxwell model was fitted the compression set behavior of TPV well,And it could be found that the NBR content in TPV and increasing heat-treatment temperature could lead to the fast recovery of compression set and improve the degree of recovery obviously;moreover,the TPV which weight ratio is 30/70had best reversible deformation ability when the temperature of heat-treatment was 60 ?.The different dosages of ZDMA were adapted to reinforce the EMA/NBR TPV.The results showed that ZDMA can greatly increase the strength of TPV,and the elongation at break of TPV was decreased slightly with the increase of ZDMA dosage while the ZDMA dosage in TPV was less than 9 phr.When ZDMA reached 9 phr,the TPV had the best comprehensive performance.(2)The crystallinity and shape memory effect of pure EMA and EMA/NBR TPVs with typical sea-island structure were studied.The results showed that the melting temperature of EMA obtained by DSC is about 98?,the shape memory behavior of TPVs and pure EMA performed well.Compared with TPV,pure EMA has higher shape fixation rate(SF)and lower shape recovery rate(SR).Increasing the heat treatment temperature,which is below 95?,would lead to increase of SF and SR of EMA and TPV.In addition,SF of TPVs would increased and SR of TPV would decreased with the increase of EMA content.It can be seen that the shape fixity of TPVs was achieved mainly through ethylene crystallization as the result of XRD analysis.The switching temperature is largely determined by melting temperature of EMA.(3)The non-isothermal crystallization kinetic behavior of EMA and EMA/NBR TPV were investigated,and the Jeziorny equation and Mo equation were employed to analyze isothermal crystallization kinetics of EMA and EMA/NBR TPV.The results showed that Jeziorny equation and Mo equation was satisfied for describing the crystallization behavior well.The crystallization of pure EMA and EMA/NBR TPV could be accelerated by increasing the cooling rate.In addition,compared with that of EMA,TPV has a higher initial crystallization temperature,the slower crystallization rate and stable crystallinity at the same cooling rate,indicating that NBR had heterogeneous nucleation effect on TPV,while the crystallization enthalpy of TPV does not change with the cooling rate,indicating that NBR had a certain inhibition on the crystallization of EMA.(4)The NBR vulcanizate,which was reinforced by CB,studied its strength and Mullins effect affected by various CB dosage,Mullins effect were studied.The results showed that the strength and elongation at break of NBR vulcanizates would increased significantly with the increase of CB dosage,and would also increased the heterogeneity of static vulcanizate,leading to the enhancement of stress softening phenomenon(Mullins effect).