مطالعه ساختارهای بلورمایع در پلیمرها و اثر آن‌ها بر خواص نهایی الیاف نساجی

نوع مقاله: تالیفی

نویسنده

دانشگاه سمنان

چکیده

ساختار پلیمرهای نیمه‌بلوری اغلب با مدل سه‌فازی بررسی می‌شود. برخی از زنجیرهای پلیمری بین فازهای بلور و بی‌نظم قرار می‌گیرند که به آن‌ها ساختارهای بلورمایع گفته می‌شود. پلیمرهای بلورمایع اغلب دارای گروه‌های میله‌ای‌شکل تک‌بعدی در زنجیر اصلی یا جانبی هستند. حالت‌های بلورمایع متعددی گزارش شده‌اند که از نظم جهت‌یافته بلنددامنه (فازهای نماتیک و کلستریک) تا نظم جهت‌یافته بلنددامنه جهتی و موقعیتی (فازهای اسمکتیک) طبقه‌بندی می‌شوند. حالت‌های بلورمایع را می‌توان به سه دسته حلالیت‌افزا، گرماگرا و ترکیبات گروه جانبی میان‌زا طبقه‌بندی کرد. با توجه به این نکته که ساختارهای بلورمایع از زنجیرهای پلیمری با نظم پارابلوری تشکیل شده‌اند و این ساختارها نقش کلیدی در خواص نهایی الیاف نساجی ایفا می‌کنند، شناسایی و تغییرات ایجاد شده در آن‌ها بر اثر عملیات بعدی از قبیل کشش و تثبیت گرمایی، دارای اهمیت است. طراحی فرایندهای پلیمری جدید یا بهبود انواع موجود، تنها با شناخت کامل سازوکارهای توسعه ریزساختار و انتقالات میان‌شکلی در الیاف نساجی امکان‌پذیر است که رفـتار بلورمایع نشان می‌دهند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Study of Liquid-crystalline Structures in Polymers and their Effects on the Properties of Textile Fibers

چکیده [English]

A three-phase model is often used to investigate the structure of semicrystalline polymers. Some of the polymeric chains lay in-between crystalline and amorphous phases so-called liquid-crystal structures. Liquid-crystalline polymers consist mainly of one-dimensional rod-like groups placed in the main chain or side chain. A great number of liquid-crystalline states have been reported, ranging from those exhibiting only long-range orientational order, nematic and cholesteric phases, to those exhibiting both long-range orientational and positional order, the smectic phases. Liquid crystalline structures can be organized into three classes, lyotropic, thermotropic, and mesogenic side group compositions. As the liquid-crystalline structures consist of polymeric chains with para-crystalline order and has a key role on the ultimate properties of textile fibers, it will be important to learn about this structure and the post-treatment changes such as drawing and thermal annealing that occur in this structure. Designing new polymer processes or improving upon old ones can only be achieved by exactly knowing the mechanisms of microstructure development and the mesomorphic transitions in the textile fibers exhibiting liquid-crystalline behaviour.

کلیدواژه‌ها [English]

  • liqiud-crystalline structure
  • high performance fibers
  • mechanical properties
  • glass transition temperature
  • Crystallinity
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