Preparation And Characterization Of Polystyrene/Layered Double Hydroxide Nanocomposites

Polymer/inorganic layered materials nanocomposites have attracted great attention because of the obvious properties improvement (such as heat-resistance, barrier property et al) caused by the introduction of nanolayers. Layered double hydroxides (LDHs) are a new class of synthetic layered nano-materials, which can improve the heat-resistance, thermal stability (espically for chlorine-containing polymer), mechanical strength and weather-resistance of polymer materials as LDH incorporated into the base polymers in a nanoscale. Thus, polymer/LDH nanocomposites have a bright prospect in many fields. Concerning with the difficultity in preparing intercalated or exfoliated LDH/polymer nanocomposites, the new in-situ polymerization methods for preparation of polymer/LDH nanocomposites were investigated using PS as a representative in this thesis. The structure and properties of the resultant PS/LDH nanocomposites were characterized.In order to conduct in-situ intercalated polymerization of styrene/LDH, LDHs pillared with a monomer type anion-vinylbenzene sulfonate (VBS), a initator type anion- 4,4'-azobis(4-cyanovaleric acid)(ACP) group and VBS/ACP combination were prepared by the ion exchange reaction between nitrate anion pillared LDH (NO3-LDH) and VBS, ACP and VBS/ACP, respectively. The modified LDHs were characterized by using XRD, FTIR, DSC and EA. It was found that VBS, ACP or VBS/ACP can be intercalated into the interlayer of NO3-LDH by ion exchange reaction at pH=8 and at room temperature. The interlayer spacing increases from 0.9nm for NO3-LDH tol.83nm for VBS-LDH and to 1.61nm for ACP-LDH. The active groups of VBS and ACP still existed.PS/LDH nanocomposites were synthesized by in-situ intercalated suspension polymerization of St in the presence of VBS-LDH, ACP-LDH and VBS·ACP-LDH, respectively. It is found that the partially interclated LDH/PS nanocomposite can obtained by using VBS-LDH in polymerization. The intercalation degree was lowerwhen ACP-LDH was used. The best intercalation of PS in LDH was achieved when VBS'ACP-LDH was applied, and the thick of LDH layer was small as PS/LDH composite resins were melt-processed.Another method, named aging/in-situ polymerization, was also applied in the preparation of PS/LDH nanocomposites. In this method, the polymerization of styrene and the formation of LDH particles were conducted at the same time, which would simplify the production process and shorten the reaction time. It was found that small lamellas of exfoliated LDH were well-dispersed in the PS matrix at nanometer levelThe thermal and rheological properties of PS/LDH nanocomposite prepared by in-situ intercalated and aging/in-situ polymerizations were characterized. It was found that the thermal decomposition temperature of nanocomposites was remarkably higher than that of pure PS at the same mass loss, and increased as the weight fraction and dispersion degree of LDH increased. The melt flow index of the nanocomposites decreased, and the shearing stress and apparent viscosity increased as the content of the LDH increased.