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采用原位聚合法,制备了聚氨酯(PU)/聚甲基丙烯酸甲酯(PMMA)/层状双金属氢氧化物(LDH)纳米复合体系(PU/PMMA/LDH).通过广角X射线衍射(WXRD)、透射电子显微镜(TEM)对其结构和形貌进行了表征,并通过热失重(TGA)、动态力学分析(DMA)和宽频介电谱(BDRS)研究了LDH含量(φ)对PU/PMMA体系热稳定性和弛豫行为的影响.结果表明,当φ<1 wt%时,LDH在聚合物基体中以剥离结构为主,PU/PMMA/LDH体系的玻璃化温度(Tg)降低,最大损耗因子(tanδmax)增大;而当φ>1 wt%时,LDH在聚合物基体中以插层结构为主,插层结构对聚合物分子链的限制使复合体系的Tg升高、tanδmax降低.LDH表面与PU硬段间的氢键作用,使复合体系的α介电弛豫转变随φ增加而向高温方向移动,弛豫过程激活参数增大.
(PU) / polymethylmethacrylate (PMMA) / layered double metal hydroxide (LDH) nanocomposite system (PU / PMMA / LDH) was prepared by in-situ polymerization method.Using wide angle X-ray diffraction WXRD and TEM were used to characterize the structure and morphology of the films. The effects of LDH content (φ) on the structure and morphology of the PU were studied by means of thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and broadband dielectric spectroscopy / PMMA system.The results showed that when φ is less than 1 wt%, LDH is mainly stripped in the polymer matrix and the glass transition temperature (Tg) of the PU / PMMA / LDH system is decreased , And the maximum loss factor (tan δ max) increased. When φ> 1 wt%, LDH mainly intercalated in the polymer matrix, and the intercalation structure restricted the polymer chain to increase the Tg of the composite. The tanδmax decreases.The hydrogen bonding between the hard surface of LDH and the PU hard segment causes the α dielectric relaxation transformation of the composite system to move toward the high temperature with the increase of φ, and the activation parameter of the relaxation process increases.