【作者】 董伏强；

【导师】 潘明旺；

【作者基本信息】 河北工业大学 ， 高分子化学与物理， 2011， 硕士

【摘要】 采用丙烯酸正丁酯(nBA)与苯乙烯(St)为核层单体、氯乙烯(VC)为壳层单体,通过两步乳液聚合法合成了PnBA、P(nBA-co-St)和PSt三类具有窄粒径分布的共聚或均聚乳液,并以该乳液为种子与氯乙烯(VC)单体进行乳液接枝共聚,制备了P(nBA-co-St)/PVC系列不同形态的复合粒子。通过激光粒度分析仪(LPSA)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、动态热机械分析仪(DMA)、差示扫描量热分析法(DSC)与简支梁冲击试验机等测试手段对复合粒子的微观形态结构、材料冲击性能、冲击断面形貌等进行了测试和表征。通过索氏抽提、凝胶渗透色谱仪(GPC)、傅里叶红外光谱仪(FTIR)、核磁共振波谱仪(1H-NMR)等表征了复合粒子的接枝情况。着重考查了不同核层单体配比对复合树脂的粒子形态、接枝情况、玻璃化转变温度、冲击性能等的影响。研究结果表明:P(nBA-co-St)/PVC复合粒子具有与接枝前相似的粒径分布,乳液粒径在接枝前后有明显增长,证明了PVC已成功地包覆在P(nBA-co-St)乳胶粒上;SEM照片与TEM照片显示,复合粒子粒径大小均匀,与粒径分析结果相吻合。并且从TEM照片能清楚分辨出,复合粒子具有明显的核壳结构;采用索氏抽提的方法分离出了复合树脂中的接枝共聚物P(nBA-co-St)-g-PVC,通过FTIR与1H-NMR对该接枝共聚物的结构进行了表征;并很好地解释了在VC接枝P(nBA-co-St)过程中显现的缓聚现象:核层共聚单体中苯乙烯含量的增加,使得接枝VC过程变得困难,并且PVC的接枝率也随之降低,索氏抽提结果与GPC结果也证实了这一观点;DSC和DMA结果表明,随着核层共聚物中聚苯乙烯组分含量的增加,复合材料在低温区的力学损耗峰逐渐移向高温方向。比较PSt组分,因纯PnBA核更易于接枝VC,从而显著地影响了复合树脂低温转变区的Tg值;当核层单体投料比nBA/PSt为75/25(wt/wt)时,所制材料缺口冲击强度为纯乳液PVC材料的10倍。从材料缺口冲击断面的扫描电镜照片分析可知:该材料断裂为典型的的韧性断裂,P(nBA-co-St)原位增韧PVC机理源于基体的剪切屈服。更多还原

【Abstract】 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.更多还原