Investigations On The Structure And Properties Of Polyamide 6/polyvinylidene Fluoride Blends

In this study, solution polymerization was used to synthesize the copolymer of methyl methacrylate and glycidyl methacrylate(MMA-co-GMA), which could be used as compatibilizer for the blends of polyamide 6 and polyvinylidene fluoride(PVDF/PA6).The influence of MMA and GMA composition on the compatibilization effect was investigated. On the other hand, the effect of PA6 on the crystalliztion phase transformation of PVDF phase was studied. The main parts are as follows:1 In this part, the methyl methacrylate-co-glycidyl methacrylate copolymers(MMA-co-GMA) with different GMA content were prepared to compatibilize the polyamide 6(PA6) and poly(vinylidene fluoride)(PVDF) blend. DMA result showed the glass transition peaks of PVDF phase almost disappeared in the PA6/PVDF/MMA-co-GMA blends which proved the suppressed thermal transition due to the restricted movement of PVDF chains. MMA-co-GMA copolymers decreased the phase domain size of the PA6/PVDF blends significantly. PVDF dispersed in the PA6 matrix uniformly and the interface between the two phases was obscure due to the compatibilization effect. The addition of MMA-co-GMA into the PA6/PVDF blend decreased the crystallization temperature of the PVDF phase which proved the enhanced interaction between the PVDF and PA6 and retarded the crystallization. Mechanical tests indicated that the elongation at break of the PA6/PVDF blends increased with the addition of MMA-co-GMA.The increase of the fracture toughness was due to the compatibilization effect of MMA-co-GMA copolymers which induced a delay of debonding of the PA6 and PVDF phases at the interface and inhibited the initiation and propagation of cracks.2 In this part, the influence of PVDF/PA6 composition on the properties of the blends were studied. MMA-co-GMA copolymer in which GMA was 10wt%(MMA-co-GMA10)was used as compatilizer of PVDF/PA6 blends. The tensile test results indicated that the yield stress decreased and elongation at break increased with the increase of PA6 content.Due to the compatibilization effect of MMA-co-GMA, the interfacical debonding was delayed and the interfacial strength was improved which enhanced the toughness of the blends. Scanning electron microscope(SEM) results showed the dispersed phase domain size decreased due to the compatibilization effect and the contact area between the two phase was improved which induce the inhibited crystallization of PVDF due to the PA6 phase. The polarizing microscope(POM) test indicated that the addition of PA6 decreased the spherulite size and the number of spherulite was also decreased. When MMA-co-GMA was introduced into the PVDF/PA6 blends, PVDF showed much lower crystallization ratecompared with the PVDF in the PVDF/PA6 blends. At the same time, PVDF showed much smaller spherulite size and number. Fourier transform infrared spectroscopy(FTIR)indicated that, for PVDF/PA6 blends, PA6 could not promote PVDF crystal transformation.While PA6 could promote crystal transformation of PVDF from α to β when MMA-co-GMA was introduced into the PVDF/PA6 blends.