Preparation, Structure And Properties Of Poly(Vinylidene Fluoride), Fluororubber, And Silicone Rubber Blends

Dynamic vulcanization technology and its theory for the preparation of thermoplastic vulcanizates(TPV) has been developed very well, especially for PP/EPDM system, however, little attention has been paid in the field of special plastic/special rubber thermoplastic elastomer. Due to the special structure and properties of special plastic and special rubber, which was different from PP/EPDM system, special plastic/special rubber thermoplastic elastomer was prepared by dynamic vulcanization. It was very important to investigate the morphology and properties of the thermoplastic elastomer.Blends based on poly(vinylidene fluoride)(PVDF), fluororubber(FKM), silicone rubber(MVQ) blends were prepared by dynamic vulcanization or through melt blending. The structure and properties of PVDF/MVQ blends prepared by melt blending, dynamically cured PVDF/MVQ blends, and dynamically cured PVDF/FKM/MVQ blends were studied using the mixing torque, scanning electron microscopy(SEM), transmission electron microscopy(TEM), flourier transform infrared(FT-IR) spectroscopy, dynamic mechanical analysis(DMA), differential scanning calorimetry(DSC), thermal gravimetric analysis(TGA), contact angle measurement, rubber process analyzer(RPA), dynamic rheological characterization, polarized optical microscopy(POM), X-ray diffraction(XRD), X-ray spectra(EDS), and mechanical properties test, etc. In addition, PVDF/MVQ blend loaded with zinc dimethacrylate(ZDMA) was successfully prepared by dynamic vulcanization, using dicumyl peroxide(DCP) as curing agent.PVDF/MVQ blends with different compositions were prepared through melt mixing progress. Typical “sea-island” structure was formed in PVDF/MVQ blend. The blend(90/10) with low MVQ content showed spherical shape of disperse phase whereas the blend(70/30) with high MVQ content resulted in irregular shape of rubber phase. The mechanical properties of blends reduced with increasing MVQ content, which was attributed to the bad compatibility between PVDF and MVQ. The complex viscosity and complex storage of blends showed a significant decrease as the MVQ content increased in the blends, which still demonstrated pseudoplastic behavior. The onset of crystallization temperature of the blends was higher than the pure PVDF, suggesting that the incorporation of MVQ promoted the crystallization process of PVDF phase. The incorporation of MVQ improved the thermal stability of PVDF/MVQ blend. The mass of residual char in experiment of the blends was lower than that obtained in theory.PVDF/MVQ blends with different compositions were prepared via dynamic vulcanization. A “network” morphology was observed, which was formed by the crosslinked MVQ particles. The blends retained the pseudoplastic nature after dynamic vulcanization, with some increase in viscosity with MVQ content increased. All the results of isothermal and non-isothermal crystallizations indicated that MVQ enhanced the crystallization rate of PVDF in the blends. MVQ might play a heterogeneous nucleating role in PVDF/MVQ blends, accelerating the crystallization of PVDF in the blends. The average diameters of spherulites decreased with increasing MVQ content. More MVQ retarded the growth of the crystal, generating some incomplete crystallization in the blends. The addition of MVQ did not change the crystal morphology and crystalline structure, retaining the spherelitic structure and the α-phase of PVDF. Compared with the PVDF/MVQ blend prepared by melt blending, the dynamic vulcanization significantly improved the mechanical properties.PVDF/MVQ blends with different amounts of ZDMA were prepared via peroxide dynamic vulcanization. Some rubber particles with different diameters were aggregated and distributed in the PVDF matrix. The average diameters of rubber particles increased when ZDMA was incorporated into the PVDF/MVQ blend. ZDMA preferentially located at the interface between the PVDF and MVQ phases. Complex chemical reactions of PVDF, ZDMA and MVQ at the interface between PVDF and MVQ phase occurred during dynamic vulcanization. The interface adhesion and interfacial interaction was significantly improved as the ZDMA content increased. A large number of fibrils were observed on the fracture surfaces, which contributed to the improvement of Izod impact strength. The tensile strength and total crosslink density of MVQ/ZDMA composites decreased with increasing the ZDMA loading, resulting in tensile strength, flexural strength, and flexural modulus of PVDF/MVQ/ZDMA composites decreased. The complex viscosity of the blends remarkably decreased when ZDMA was added, but still retained the pseudoplastic behavior.The rubber-rich PVDF/FKM/MVQ thermoplastic elastomers were prepared via dynamic vulcanization. MVQ phase was encapsulated by the FKM phase in the PVDF matrix, MVQ was core and FKM was shell. A core-shell structure was formed in the PVDF/MVQ/FKM thermoplastic elastomers. Dynamically vulcanized PVDF/FKM/MVQ blend with cross-linked MVQ/FKM core-shell particles had excellent mechanical properties.The PVDF-rich PVDF/FKM/MVQ blends were prepared via dynamic vulcanization. MVQ phase was encapsulated by the FKM phase in the PVDF matrix. A core-shell structure was formed. The rubber particle diameter was almost unchanged with increase of FKM content. More interactions between PVDF and rubber phase significantly increased when raising fluororubber content, and obviously restricted the crystallization of PVDF in tertiary elastomeric blends, which reflected reduced growth dimension and slower crystallization rate of PVDF crystallizing in tertiary blends. The addition of FKM did not change the crystal morphology and crystalline structure, retaining the spherelitic structure and the α-phase of PVDF. The PVDF/FKM/MVQ blends had better mechanical properties, which was attributed to the formation of core-shell structure.