• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Dynamic mechanical study of nanofilled polymers: Melt and glass transition behaviors.
【24h】

Dynamic mechanical study of nanofilled polymers: Melt and glass transition behaviors.

机译：纳米填充聚合物的动态力学研究：熔融和玻璃化转变行为。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Dynamic mechanical properties of fumed silica filled polymers are systematically studied at and above the glass transition temperatures, with highest filler concentration around 12 vol. percent.; Dramatic change in viscoelastic behavior is observed in filled melts, which includes high reinforcement at low strains and high nonlinearity in storage and loss moduli with strain. The reduction of dynamic modulus (nonlinearity) is recoverable with time if stress-free after large strain perturbations. The reinforcement, nonlinearity and the recovery behavior all show strong dependence on filler surface treatment, filler size and filler concentration, as well as the molecular weight of matrix polymers. The results suggest that filler-trapped entanglements and their release under applied strains, instead of filler structures and structure breakdown, are primarily responsible for the dynamic mechanical properties observed for the filled melts. Some substantial contributions to the reinforcement may also come from Langevin chain behavior, which becomes more important for nanocomposites because of the enhanced reference state bias of polymer chains. SEM pictures as well as small angle scattering data provide additional evidence that is also in favor of the entanglement-based mechanism.; Glass transition results show that all filled samples are thermo-rheologically simple just like most neat amorphous polymers, such as PVAc used in this study. The shift factors used for time-temperature-superposition of all samples form nearly identical curves versus temperature, regardless of filler concentration, with only one filled system (ST100L fumed silica) showing a little deviation at high filler concentrations. This filled system, which involves tethered silicone chains on the filler surface, is also the only exception to the universal dispersion of glass transition observed for other filled systems, i.e., identical normalized loss modulus peaks at Tg. The reinforcement in storage modulus agrees with conventional hydrodynamic models at several degrees below Tg, but increases substantially with temperature. Those results suggest that the filler-polymer energetic interactions are of a length scale of typical force fields, but far-field filler effects are also present through the long-range coupling of polymer chains, which agrees with the conclusions regarding the melt behavior.
机译：在玻璃化转变温度及以上的温度下，系统研究了气相二氧化硅填充聚合物的动态力学性能，其中最高填充剂浓度约为12 vol。百分。;在填充的熔体中观察到粘弹性行为的剧烈变化，包括低应变时的高补强和高非线性存储以及随应变的损耗模量。如果在较大的应变扰动后无应力，则动态模量（非线性）的降低可随时间恢复。补强，非线性和恢复行为都显示出对填料表面处理，填料尺寸和填料浓度以及基体聚合物分子量的强烈依赖性。结果表明，填料所缠结的缠结及其在施加的应变下的释放，而不是填料的结构和结构破坏，是造成填充熔体动态力学性能的主要原因。 Langevin链的行为也可能对增强做出了一些实质性贡献，由于聚合物链的参考态偏向性增强，这对于纳米复合材料而言变得更加重要。 SEM照片以及小角度散射数据提供了其他证据，这些证据也支持基于纠缠的机制。玻璃化转变结果表明，所有填充样品都是热流变简单的，就像大多数纯净的无定形聚合物一样，例如本研究中使用的PVAc。无论填料浓度如何，所有样品的时间-温度叠加所使用的位移因子均会形成几乎相同的温度曲线，其中只有一种填充系统（ST100L气相法二氧化硅）在高填料浓度下显示出很小的偏差。这种填充系统涉及在填充剂表面上的拴系硅酮链，也是唯一观察到的例外，即对于其他填充系统普遍存在的玻璃化转变的普遍分散，即在Tg处具有相同的归一化损耗模量峰。储能模量的增强在低于Tg几度时与常规流体力学模型一致，但随着温度的升高而大大增加。这些结果表明，填料-聚合物的能量相互作用具有典型力场的长度范围，但是远场填料效应也通过聚合物链的长距离偶联而存在，这与关于熔体行为的结论一致。

著录项

  • 作者

    Zhu, Ai-jun.;

  • 作者单位

    Rensselaer Polytechnic Institute.;

  • 授予单位 Rensselaer Polytechnic Institute.;
  • 学科 Engineering Materials Science.; Chemistry Polymer.
  • 学位 Ph.D.
  • 年度 2003
  • 页码 152 p.
  • 总页数 152
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;高分子化学（高聚物）;
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号