• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Applied Polymer Science >Calculating molecular weight distributions in emulsion polymerization under conditions of diffusion limited chain transfer
【24h】

Calculating molecular weight distributions in emulsion polymerization under conditions of diffusion limited chain transfer

机译：扩散受限链转移条件下乳液聚合的分子量分布计算

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

When highly reactive chain transfer agents with low water solubilities (e.g., long chain thiols) are used in emulsion polymerizations, transport of the chain transfer agent (CTA) from the monomer droplets to the polymer particles can become diffusion limited. Consequently, the concentration of CTA in the particles is lower than expected, resulting in apparent transfer constants that can be much lower than the actual transfer constants obtained from studies with homogeneous systems such as bulk or solution. Furthermore, molecular weights will be greater than those obtained in homogeneous systems with the same overall concentration of CTA. There are currently no techniques or methodologies available for predicting molecular weight distributions when the transport of CTA is diffusion limited. Apparent transfer constants may be used but they are typically restricted to a given system and operating conditions. In this work, we describe how the actual CTA concentration in the polymer particles can be estimated through analysis of instantaneous molecular weight distributions. This information is then used to calculate the cumulative molecular weight distribution during the polymerization. Comparisons with experimental molecular weight distributions validate the essential correctness of the approach, but also highlight potential problems. The extension of the approach to online applications is discussed. (C) 2000 John Wiley & Sons, Inc. [References: 27]
机译：当在乳液聚合中使用具有低水溶性的高反应性链转移剂（例如，长链硫醇）时，链转移剂（CTA）从单体液滴到聚合物颗粒的传输会受到扩散的限制。因此，颗粒中CTA的浓度比预期的要低，导致表观的传递常数可能远低于从均相系统（例如本体或溶液）中获得的实际传递常数。此外，分子量将大于在相同总CTA浓度下均质系统中获得的分子量。当CTA的运输受到扩散限制时，目前尚无可用于预测分子量分布的技术或方法。可以使用视在传输常数，但它们通常限于给定的系统和操作条件。在这项工作中，我们描述了如何通过分析瞬时分子量分布来估算聚合物颗粒中的实际CTA浓度。然后，该信息用于计算聚合过程中的累积分子量分布。与实验分子量分布的比较证实了该方法的基本正确性，但也突出了潜在的问题。讨论了将方法扩展到在线应用程序的问题。 （C）2000 John Wiley＆Sons，Inc. [参考：27]

著录项

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