Preparation And Properties Of Thermoplastic Elastermer Based On PVDF/PTW Blends

Thermoplastic elastomer(TPE)is defined as a polymeric material with great functional performance and it can be processed in molten state as thermoplastic polymer,but it still exhibit toughness and elasticity as conventional vulcanized rubber.Thermoplastic vulcanizate(TPV)is a very special type of TPE produced via dynamic vulcanization of blends consisting of a rubber and a thermoplastic polymer.In recent years,most researches focused on TPV based on common plastic/rubber blends.However,these thermoplastic material are difficult to meet the requirements of harsh environment.Therefore,the high performance plastic/rubber blends have gradually attracted more attention.In this study,poly(vinylidene fluoride)(PVDF),which can be processed by conventional melt blending,was selected as plastic phase.Poly(ethylenebutylacrylate-glycidylmethacrylate)(PTW),which has excellent low temperature resistance and great adhesion,was chosen as rubber phase.A novel TPV based on PVDF/PTW blends has been successfully fabricated by dynamic vulcanization.The research content mainly included the following three parts:1.Understanding of intermolecular interaction and miscibility between PVDF and PTWPVDF/PTW blends were directly prepared by melt blending and the interaction and properties of PVDF/PTW blends were explored systematically.The crystallization behavior,thermal stability,dynamic mechanical property,and morphological features of PVDF/PTW blends with different ratios have been studied by XRD,ATR-FTIR,DSC,TGA,DMA,POM and miscibility between PVDF and PTW was explored by using the dynamic rheology.The results showed that the crystalline structure of neat PVDF was dominantly ?-phase crystalline and the incorporation of PTW had no effect on the crystalline structure of PVDF in the PVDF/PTW blends.And the glass transition temperature(Tg)of PVDF in PVDF/PTW blends shifted to higher temperature compared with that of neat PVDF,indicating the weak interaction between PVDF and PTW.An increase in the coarseness and ring-band spacing observed from POM further substantiated the weak interaction between PVDF and PTW.From the rheological analysis,time-temperature superposition(tTS)principle works well for PVDF/PTW blends in homogeneous region.On the other hand,in the phase-separated region,the viscoelastic properties of PVDF/PTW blends were different from characteristic thermorheological responses,especially for the characteristic deviations of the storage modulus at low frequencies,and the Han plots and vGP plots also showed the different shapes corresponding to the homogeneous system.These results showed that PVDF/PTW(PVDF/PTW=90/10 w/w)blend had better miscibility than the others(100/0?90/10?70/30?50/50?30/70?10/90?0/100 w/w)and it was also confirmed by SEM.2.Estimation of interfacial adhesion between PVDF and PTW by PBS through reactive compatibilizationPoor miscibility between PVDF and PTW has been occurred with increasing amount of PTW in PVDF/PTW blends.Therefore,it is necessary to use a functionalized compatibilizer to enhance the interfacial properties between PVDF and PTW.The compatibility between PVDF and PTW could be improved by the addition of poly(butylene succinate)(PBS),which was used as a reactive compatibilizer.In order to clarify the interfacial adhesion of PVDF/PTW blends,the effect of PBS content on the interfacial adhesion was studied,also the morphological structures,the rheological behavior,and mechanical properties were studied.The results suggested that the interfacial adhesion of PVDF and PTW was enhanced by the addition of PBS into PVDF/PTW system via reactive compatibilization during melting process.A very beneficial effect was observed as PBS content increased up to 7 wt %.Furthermore,these observations were consistent with the interfacial activity of PBS at the PVDF/PTW interphase,accounting for the interfacial activity of the in-situ formed PTW-g-PBS at the PVDF/PTW interface in PVDF/PTW blends and strong dipole-dipole interacton between carbonyl group of PBS and fluorines of PVDF.Overall,understanding and estimating PVDF-PTW interfacial adhesion is a critical issue for designing high performance TPV based on PVDF/PTW blends.3.Preparation and properties of dynamically vulcanized thermoplastic blends based on PVDF and PTWA novel TPV based on PVDF/PTW(30/70 w/w)blends has been successfully fabricated by dynamic vulcanization due to selective cross-linking of PTW by adding small amount of 3-(2-Aminoethylamino)propyldimethoxymethylsilane(KH602)and reactive compatibilizer PBS.The morphological structures,rheological,thermal,mechanical properties as well as melting behavior of the resulted TPVs were investigated systematically.Rheological probing of the structures revealed the blends with KH602 had the solid-like behavior at low frequency and enhanced viscosities and dynamic modulus in oscillatory experiments.The morphological investigation indicated that the TPV exhibited a co-continuous morphology with 2 % KH602,which was different from the “sea-island” structure of PVDF/PTW blend.It was interesting to find that the cross-linking of PTW not only induced the depression of the crystallization and melting temperature of PVDF and PTW,but also induced the decrease in the crystallinity of PVDF and PTW.It was showed from dynamic mechanical analysis(DMA)results that the addition of a small amount of KH602 not only shifted Tg to higher temperature,but also increased the storage modulus of the blend markedly.The resulted TPVs displayed excellent mechanical properties,namely,high tensile strength,large elongation at break,and excellent strain recovery.