مروری بر بازیافت مکانیکی پلی‌لاکتیک اسید: چالش‌ها و دستاوردهای اخیر
محورهای موضوعی : پلیمرهای بازیافتی و مدیریت زباله
1 - کارشناس ارشد واحد تحقیق و توسعه
کلید واژه: پلی‌لاکتیک اسید, بازیافت مکانیکی, تخریب حرارتی-مکانیکی, ارزشمندسازی پسماند, بسته‌بندی مواد غذایی, چاپ سه‌بعدی,
چکیده مقاله :
روند روبهرشد استفاده از پلی‌لاکتیک اسید (PLA)، فناوران را به تحقیق گسترده در زمینه‌ی ارزشمندسازی پسماندهای آن با بهترین کیفیت تشویق می‌کند. بهطورکلی، بازیافت مکانیکی PLA یکی از مقرونبه‌صرفه‌ترین روش‌های بازیابی این پلیمر است. اما مواد بازیافتی معمولاً برای کاربردهای کم‌اهمیت مصرف می‌شوند که علت آن تخریب حرارتی-مکانیکی ذاتی پلیمر در حین بازیافت بوده که عمدتاً باعث بریدگی زنجیرها و واکنش‌های ترنس استریفیکاسیون درونمولکولی و بین‌مولکولی میشود. از این رو، بازیافت مکانیکی بر توزیع جرم مولی و متعاقباً بر خواص مکانیکی، حرارتی و رئولوژیکی PLA بازیافتی تأثیر منفی میگذارد. در این مقاله، مروری بر پژوهش‌های دهه‌ی اخیر در زمینه‌ی اثرات بازیافت مکانیکی بر خواص PLA شامل تغییرات ساختاری، مورفولوژیکی، مکانیکی، رئولوژیکی و حرارتی انجام شد. همچنین مروری بر سه روش اصلی ارزشمندسازی PLA بازیافتی شامل اصلاح حرارتی، اصلاح‌های شیمیایی در حضور پایدارکننده‌ها، عوامل گسترش‌دهنده‌‌ی زنجیر و عوامل شاخه‌ای‌کننده و در انتها مخلوط کردن PLA بازیافتی با نانوافزودنی‌ها یا سایر پلیمرها برای ارتقای خواص انجام شد. در ادامه، به دلیل استفاده‌ی گسترده از الیاف طبیعی برای بهبود عملکرد PLA، قابلیت بازیافت زیست‌کامپوزیت‌های PLA تقویت‌شده با الیاف طبیعی مورد بررسی قرار گرفت. در انتها به دو کاربرد مهم PLA بازیافتی در صنایع بسته‌بندی مواد غذایی و چاپ سه‌بعدی پرداخته شد.
The growing use of polylactic acid (PLA) encourages technologists to conduct extensive research into valorization of PLA waste with best quality. In general, mechanical recycling of PLA is one of the most cost-effective recycling methods. However, recycled materials are commonly used for minor applications due to the inherent thermo-mechanical degradation of the polymer during recycling, which mainly results in chain scissions and intramolecular and intermolecular transesterification reactions. Therefore, it has a negative effect on the molar mass distribution and consequently on the mechanical, thermal and rheological properties of recycled PLA. In this article, a review of recent research on the effects of mechanical recycling on the properties of PLA including structural, morphological, mechanical, rheological and thermal changes was done. Furthermore, a review of three main ways of valorization of recycled PLA including thermal modification, chemical modifications in the presence of stabilizers, chain extenders, branching agents and finally mixing with nanoadditives or with other polymers was done in order to improve the properties of recycled PLA. Moreover, due to the widespread use of natural fibers to improve the performance of PLA, the recyclability of natural fiber-reinforced PLA biocomposites was investigated. Finally, two important applications of recycled PLA in the food packaging and the 3D printing industries were discussed.
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