Study On The Structure Design Of Elastomer And The Grafting And Toughening Mechanism Of Elastomer Copolymerization With Vinyl Chloride

P(nBA-co-St)/PVC composite resins were prepared via two-step seeded emulsion copolymerization. Firstly, P(nBA-co-St) copolymer latex was synthesized using n-butyl acrylate (nBA) and styrene (St) through semicontinuous seeded emulsion copolymerization, then the P(nBA-co-St) copolymer latexes were copolymerized with vinyl chloride monomer (VCM). Morphological structure of the composite particles and blending materials were characterized by Laser particle size analyzer (LPSA), scanning electron microscope (SEM), transmission electron microscope (TEM), differential scanning calorimeter (DSC), dynamic mechanical analyzer (DMA) and Charpy impact test machine. And the grafting situation of the P(nBA-co-St)/PVC composite particles was characterized by Soxhlet solvent extraction, Gel penetration chromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (1H-NMR). Effects of different monomer feed ratios on the particle morphology, grafting ratios (GR) of the composite particles, and the glass transition temperatures (Tgs), mechanical properties of the composite materials were investigated in detail.The LPSA result demonstrated that the PVC chains were successfully coated onto the surface of the P(nBA-co-St) latex particles, as growth in sizes of the composite particles after the P(nBA-co-St) grafted by PVC. The SEM graphs also corroborated this result, and the composite particles presented clearly core-shell morphology in TEM graphs. The P(nBA-co-St)-g-PVC was separated from the P(nBA-co-St)/PVC composite resins via Soxhlet solvent extraction technology. FTIR and 1H-NMR study results showed that the PVC reasonably grafted onto the P(nBA-co-St) chains. The phenomenon of retardation polymerization appeared in VC grafting P(nBA-co-St) copolymerization was well explained, the more the content of styrene in core layer, the greater the difficulty of VC grafting onto P(nBA-co-St) chain, and the graft ratio decreased along with it. Influence of PnBA to PSt feed ratios in the core layer on glass transition temperatures (Tgs) of the P(nBA-co-St) copolymers and the composite resins was investigated via DSC and DMA, respectively. DMA results showed that with an increasing content of the polystyrene segments in the core layer, the mechanical loss peak of the materials in low-temperature transition range gradually shift towards high-temperature transition region. Compared with the Tg value change before and after VC grafting, it was found that pure PnBA core greatly influences the Tg of the composite resin in the low-temperature transition region. With much incorporation of the PSt composition, the influence becomed little. This result should stem from different degree of the PnBA- and PSt-grafted-PVC to cause the change of the graft copolymer content in the composite resin. When nBA to St ratio in the P(nBA-co-St) was 75/25 (wt/wt), the Charpy notched impact strength of the material was 10 times as high as that of pure emulsion PVC materials. The SEM graphs of fractured surfaces for the P(nBA-co-St)/PVC samples showed a"root or beard"morphology, and confirmed that toughening mechanism in the P(nBA-co-St)/PVC materials derived from shear yielding of the matrix.