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Thermal degradation studies of a stabilized HTPB based elastomer were conducted at temperatures from 50 °C to 110 °C. The concentration of extractable antioxidant (AO2246) in the polymer was quantified via AO extraction and a gas chromatography-based method using internal standards. The decrease in extractable AO levels as a function of time and temperature was evaluated and correlated with mechanical property changes. Most importantly, AO depletion features were found to be temperature dependent. At elevated temperatures (>80 °C) extractable AO levels decreased rapidly and faster than the concurrent loss in mechanical properties. While extractable AO concentrations decrease quickly, the material is able to maintain some useful mechanical properties, perhaps via non-extractable or grafted AO species formed during degradation providing additional protection. At lower aging temperatures extractable or free AO levels decreased more slowly than the mechanical properties. Therefore, for condition monitoring purposes a universal correlation between AO levels and aging state or material condition could not be established. Most importantly, however, loss of mechanical properties and oxidative degradation is observed at lower temperatures despite significant levels of free antioxidant in the material. The antioxidant appears to be limited in its effectiveness to completely prevent degradation reactions, or only fractions of the total AO available are actually involved in the inhibition process.  相似文献
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平行壁面间平衡聚合物吸附行为的自洽场分析   总被引:1,自引:0,他引:1       下载免费PDF全文
孙喆  岳新荣  刘川  章爱 《物理化学学报》2010,26(6):1629-1636
采用自洽场理论研究了平衡聚合物在平行壁面间的吸附规律. 结果表明, 平衡聚合物的吸附行为可根据壁面吸附强度划分为弱吸附和强吸附两个区间. 在强吸附区间, 平衡聚合物可以形成明确的吸附层, 增大吸附强度能够引起平均分子链长的陡增, 但不会改变链长分布的指数形式. 平衡聚合物的长链分子在强吸附条件下较短链分子更靠近吸附壁面, 在弱吸附条件下, 则更接近体系中心. 通过计算壁面压强发现: 在弱吸附作用下, 吸附壁面始终受到分子链的推斥作用; 在强吸附作用下, 分子链对壁面的作用随壁面间距的加大由推斥转变为吸引. 平衡聚合物的溶解性和排空效应以及壁面吸附作用之间存在竞争关系,加大排除体积作用参数会引起分子链密度分布的均一化和壁面承受压强的降低.  相似文献
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孙昭艳 《高分子科学》2016,34(9):1150-1157
We propose a simple and effective boundary model in a nonequilibrium molecular dynamics (NEMD) simulation to study the out-of-equilibrium dynamics of polymer fluids. The present boundary model can effectively weaken the depletion effect and the slip effect near the boundary, and remove the unwanted heat instantly. The validity of the boundary model is checked by investigating the flow behavior of dilute polymer solution driven by an external force. Reasonable density distributions of both polymer and solvent particles, velocity profiles of the solvent and temperature profiles of the system are obtained. Furthermore, the studied polymer chain shows a cross-streaming migration towards center of the tube, which is consistent with that predicted in previous literatures. These numerical results give powerful evidences for the validity of the present boundary model. Besides, the boundary model can also be used in other flows in addition to the Poiseuille flow.  相似文献
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