Research Of Structure And Properties Of Functional EAA/NBR TPV

Thermoplastic vulcanizate(TPV)based on ethylene-acrylic acid copolymer(EAA)/nitrile butadiene rubber(NBR)were prepared via dynamic vulcanization,the mechanical properties,viscoelastic behaviors of Mullins effect under compression mode,Mullins effect under tearing mode,stress relaxation under compression mode,compression set and microstructure were investigated systematically.The shape memory properties of EAA/NBR TPV was researched,the microstructure,thermomechanical properties and shape memory behavior of TPV were studied,and the relationship between the shape memory effect and viscoelastic behavior was researched in depth;moreover the shape memory mechanism was expounded correspondingly.NBR/copper sulfate(CuSO₄)and NBR/CuSO₄/tetramethylthiuram monosulfide(TMTM)vulcanizates were successfully prepared by the metal-coordination cross-linking,the synergistic effect between CuSO₄and TMTM was analyzed.The curing characteristics,mechanical properties,Mullins effect under compression mode,mobility of macromolecular segment,morphology,swelling behaviors and dynamic features of the vulcanizates were investigated systematically.The main results were shown as below:(1)The research based on EAA/NBR and EAA/NBR/zinc dimethacrylate(ZDMA)TPV showed that increasing EAA dosage could lead to the increase of tear strength and hardness of TPV,the tensile strength and elongation at break of EAA/NBR TPV reached a maximum value at 40 phr EAA incorporation,and the tear strength of EAA/NBR TPV could be improved by introducing ZDMA into NBR;microstructure studies showed that EAA/NBR TPV had a typical“sea-island”structure,the cross-linked NBR particles were dispersed evenly in the EAA matrix with diameters of 5?8?m,the fracture surface of EAA/NBR/ZDMA TPV was rougher than that of EAA/NBR TPV,which significantly improved the interfacial compatibility.(2)The experimental results of Mullins effect and its reversibility under compression mode of EAA/NBR TPV indicated that increasing compression strain and EAA content in TPV could strengthen the Mullins effect,and the reversibility of Mullins effect could be significantly enhanced by increasing heat treatment temperature.The experimental results of Mullins effect and its reversibility under tearing mode of EAA/NBR and EAA/NBR/ZDMA TPV indicated that the Mullins effect of EAA/NBR TPV was enhanced with increasing EAA content,and the ZDMA reinforced EAA/NBR TPV showed the more obvious Mullins effect under tearing mode,while it was hardly to obverse in that of unfilled static NBR vulcanizate,the Mullins effect was recoverable and showed the obvious character of temperature-dependence relation,and the well deformation reversibility of the EAA/NBR TPV could be found at the elevated temperature.The experimental results of stress relaxation and its reversibility under compression mode of EAA/NBR TPV indicated that the stress relaxation of EAA/NBR TPV tended to be significant with increasing EAA content or strain,the reversibility of stress relaxation was improved with increasing heat-treatment temperature and heat-treatment time,the characteristics of stress and relaxation time in each stage of reversibility were quantitatively explained by data fitting.The experimental results of compression set and its reversibility of EAA/NBR TPV indicated that the reversible recovery speed of compression set was obviously accelerated,and the residual compression set was significantly reduced with increasing heat treatment temperature;when the heat treatment temperature was constant,the initial value of compression set and residual deformation showed a downward trend with increasing NBR content.(3)The shape memory behaviors of“sea-island”heat-triggered shape memory polymer(HSMP)based on EAA/NBR TPV was studied.Field emission scanning electron microscope(FE-SEM)studies showed that the high interfacial strength played an important role in the formation of sufficient physical entanglement between EAA and NBR,which significantly enhanced the shape memory effect(SME)of EAA/NBR TPV;the results of dynamic thermomechanical analysis(DMA)and shape memory research showed that the strong interface interaction between EAA phase and NBR particles provided critical assistance in keeping the temporary shape of deformed rubber particles and storing stronger elastic driving force;moreover,the optimal conditions for obtaining excellent SME were to set T_dand T_rat 95°C and EAA/NBR TPV weight ratio at 50/50;differential scanning calorimetry(DSC)and X-rad diffraction(XRD)results showed that the melting heat of TPV increased with increasing EAA content,and NBR particles promoted the crystallization of EAA phase,which made HSMP extremely tunability in terms of switching temperature and energy,as well as high fixation and recovery levels under high strain.(4)NBR/CuSO₄and NBR/CuSO₄/TMTM vulcanizates prepared by coordination cross-linking were systematically studied.The results of mechanical properties showed that the tensile strength of NBR/CuSO₄vulcanizates were improved significantly with increasing CuSO₄content,the coordination stability of NBR/CuSO₄vulcanizates was improved by the synergistic effect between CuSO₄and TMTM,and the tensile strength of NBR/CuSO₄/TMTM vulcanizates were also greatly improved.During the uniaxial cyclic compression of NBR/CuSO₄vulcanizates,the maximum compression stress under the same strain was decreased significantly with increasing the number of cycles,showing the phenomenon of stress softening,the instantaneous residual deformation was increased with increasing the strain and number of cycles,showing an obvious Mullins effect.With increasing CuSO₄dosage and compression strain,NBR/CuSO₄vulcanizates showed the phenomenon of“amplification effect”of Mullins effect;the results of fourier transform infrared spectroscopy(FTIR),DSC,X-ray photoelectron spectra(XPS),FE-SEM and cross-linking density experiment demonstrated that the three-dimensional cross-linking microstructure was held together by the metal-coordination bonds of nitrile groups(-CN)with copper ions(Cu²⁺),the torque during static vulcanization,tensile strength and cross-linking density of the obtained NBR/CuSO₄/TMTM vulcanizates were better than that of NBR/CuSO₄vulcanizates,which was attributed to the synergistic effect between the radicals formed by the splitting of TMTM under thermal activation and the Cu²⁺to form the complexes[Cu(S_nCNMe₂)]^·2+with highly reactive and high binding energy,which interacted strongly with-CN,and the XPS research further demonstrated that the synergistic coordination effect was significantly enhanced by the introduction of TMTM;moreover,the breakage of the coordination bonds during loading-unloading could be reformed under the later heat treatment condition,which contributed to the well reversibility of coordination cross-linking network in NBR/CuSO₄ and NBR/CuSO₄/TMTM vulcanizates.