Structure And Properties Of Functional EAA/CR TPVs

Thermoplastic vulcanizates(TPVs)based on ethylene-acrylic acid copolymer(EAA)/chloroprene rubber(CR)were prepared by dynamic vulcanization.The mechanical properties,microstructure,Mullins effect under compression mode and its reversibility behavior were systematically studied;the heat-induced shape memory polymer(HSMP)material based on EAA/CR TPV was prepared,and the effects of deformation temperature,recovery temperature,rubber/plastic ratio on the shape memory performance of TPV were also studied,and the SME mechanism of the TPV-based HSMP materials was proposed and a method of tuning the shape memory performance was obtained;HSMP material was prepared by EAA,and its mechanical behavior,orientation structure and shape memory behavior were systematically studied.For the non-isothermal crystallization process of EAA and EAA/CR TPV by using differential thermal scanning calorimeter(DSC)method under different cooling rates were systematically studied.Avrami,Ozawa and Mo methods are used to further study the non-isothermal crystallization kinetics.The main results were shown as below:(1)The microscopic phase structure study showed that the particles size of CR vulcanizates in EAA/CR TPV was 3?6 ?m,which was evenly dispersed in the surface of etched samples.Compared with that of the CR static vulcanizates,the tensile strength and elongation at break of EAA/CR TPV were significantly enhanced,and with the increasing of EAA dosage,the tensile strength and tear strength were increased obviously.In addition,there was significant Mullins effect in the uniaxial cyclic compression of EAA/CR TPVs,and the Mullins effect could be enhanced by increasing the dosage of EAA in TPV or increasing the compression strain.The reversible recovery of compression Mullins effect in the TPV could be significantly improved by increasing the heat treatment temperature,and when the heat treatment temperature was 100?,the degree of recovery was the best.(2)Chloroprene rubber(CR)vulcanizate was reinforced by carbon black(CB),and its mechanical properties and the dosage of CB on the "Amplification Effect" of Mullins effect of the system were studied.The existence of CB could improve obviously the strength of CR vulcanized adhesive,and there was an obvious Mullins effect during the process of uniaxial cyclic compression of CR vulcanizate was reinforced by CB;under the same compression strain,the maximum compression stress reached a maximum value at the first load-unloading cycle while was decreased at the later loading-unloading cycles.The instantaneous residual strain increased obviously with the increasing of compression times;With the increasing of CB dosage and compression strain,Mullins effect was enhanced obviously.(3)The HSMP materials based on EAA/CR TPV were prepared.The test results of mechanical properties showed that EAA/CR TPVs belonged to the category of TPE.The FE-SEM showed that an obvious banded micro-oriented structure could be clearly observed on the surface,when the EAA/CR TPV sample was longitudinally stretched.The results of shape memory performance test showed that the shape fixation ability of EAA/CR TPV was determined by the crystal region in EAA resin phase,while the shape recovery ability was determined by the cross-linked CR dispersed phase and the non-crystal region in EAA resin phase,and the shape recovery can be realized in a variety of modes(such as stretching,helix and crimp).When the deformation temperature was close to the melting point of EAA phase,shape fixed rate and shape recovery rate of the EAA/CR(weight ratio=40/60)TPV samples were greater,and the sample had an excellent shape memory behavior.The results of DSC test showed that the melting peak value of EAA gradually decreased and the melting temperature range gradually widened with the decreasing of EAA phase dosage,indicating that the crystallization of EAA phase was disturbed by CR phase and led to the increase of crystal defects.The results of DMA test and stress relaxation under temperature scanning mode showed that the tan? value of EAA decreased while the value of E' increased with the increase of EAA content in EAA/CR TPVs;Meanwhile,the shape memory effect of TPV was affected by the deformation temperature.When the deformation temperature was close to the melting point of EAA,the SME of TPV was the best.(4)The HSMP material based on EAA was prepared,and its microstructure,crystallization behavior and shape memory properties were studied systematically.The results of FE-SEM showed that there were obvious orientation microstructures on the longitudinal tensile surface of EAA samples.DSC results showed that the EAA sample had a more perfect crystallization melting peaks of shape-recovered sample in the DSC curve.The results of SMP tests showed that the when the deformation temperature was close to the melting point of EAA,the shape memory performance was the best,and the excellent shape fixation rate and shape recovery rate were obtained.Heating treatment of EAA samples under tensile and crimp modes had an excellent recovery ability and a rapid speed of recovery.When the recovery temperature was increased,the shape recovery rate increased gradually and the recovery time continuous decreased.According to the research of EAA shape memory behavior,a formation mechanism of shape memory effect for EAA was proposed.(5)The non-isothermal crystallization of EAA/CR TPV were studied systematically by DSC method.Avrami,Ozawa and Mo methods were used to describe the non-isothermal crystallization kinetics.The results showed that the Avrami analysis and Mo method improved by Jeziorny could well describe the non-isothermal crystallization processes of pure EAA and EAA/CR TPV.However,the Ozawa method could not be adequately applied.The crystallization of pure EAA and EAA/CR TPV could be accelerated by increasing the cooling rate.The initial crystallization temperature(To)and crystallization termination temperature(Tc)of EAA/CR TPV were higher than the corresponding values of pure EAA at the same cooling rate,indicating that CR had an obvious heterogeneous nucleation effect on TPV;the semi-crystallization time(t1/2)of EAA/CR TPV was higher than that of pure EAA(t1/2),which meaned that CR could delay the crystallization process of TPV due to steric hindrance effect.