Low-density polyethylene (LDPE) filled with a small amount (1 to 10 wt.%) of titanium-dioxide (TiO/sub 2/) powder proves to be very suitable for studying the molecular motion of polyethylene by means of dielectric spectroscopy. The titanium dioxide acts as an oxidizing agent that induces a small concentration of polar carbonyl groups, which do not alter molecular motion, but couple it to the alternating electric field, The frequency and temperature dependences of molecular-motion processes in LDPE are determined. In particular, it is shown that the temperature dependence of the /spl beta/ process connected with the, glass-rubber transition in polyethylene obeys the Vogel-Fulcher-Tammann-Hesse law, which indicates co-operative behaviour. The dielectrically determined glass-transition temperatures are close to the literature value of about -30/spl deg/C. The unrelaxed permittivity increases with TiO/sub 2/ content by a factor of 1.45 at 35 wt.% TiO/sub 2/. This is lower than expected from models for the permittivity of heterogeneous mixtures. It points towards an inhomogencous TiO/sub 2/ -particle distribution.
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机译:填充有少量(1至10 wt。%)二氧化钛(TiO / sub 2 /)粉末的低密度聚乙烯(LDPE)被证明非常适合通过介电谱研究聚乙烯的分子运动。二氧化钛用作氧化剂,可诱导少量浓度的极性羰基,这些极性羰基不改变分子运动,但将其耦合到交变电场。确定了LDPE中分子运动过程的频率和温度依赖性。特别地,表明与聚乙烯中的玻璃-橡胶转变有关的/ spl beta /过程的温度依赖性服从Vogel-Fulcher-Tammann-Hesse定律,这表明了合作行为。介电确定的玻璃化转变温度接近约-30 / spl deg / C的文献值。在35 wt。%TiO / sub 2 /下,未松弛的介电常数随TiO / sub 2 /的含量增加1.45倍。这低于非均质混合物介电常数模型的预期值。它指向不均匀的TiO / sub 2 /-颗粒分布。
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