فایل ورد کامل استفاده از یک بیوالاستومر جدید برای چقرمگی پلی لاکتید

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توجه : در صورت مشاهده بهم ریختگی احتمالی در متون زیر ،دلیل ان کپی کردن این مطالب از داخل فایل می باشد و در فایل اصلی فایل ورد کامل استفاده از یک بیوالاستومر جدید برای چقرمگی پلی لاکتید،به هیچ وجه بهم ریختگی وجود ندارد

تعداد صفحات این فایل: ۲۴ صفحه

پلی لاکتید PLA به شدت توسط الاستومر جدید تولید شده از منابع تجدید پذیر چقرمه شد. تحلیل حرارت مکانیکی دینامیکی، کالریمتر تفاضلی، میکروسگوپ الکترونی عبوری، و رویشی، و ازمایشات رئولوژیکی ، سازگاری بالا را برای PLA/BE نشان داد. DSC، ترکیبات نشان داد که فاز انتشار BE موجب بهبود قابلیت تبلور سرد PLA شد. مطالعات رئولوژیکی نشان داد که ویسکوزینه کمپلکس و مدول ذخیره ای ترکیبات بالاتر از PLA خالص در فرکانس پایین بود. انحراف مثبت از مقادیر نظری برای اثر متقابل فازی بین PLA و BE نشان داد که آن را می توان به تشابهات مولکولی نسبت داد زیرا دو جزء بر اساس پیوند استری هستند. BE موجب تغییر رفتار گسیخنگی PLA از انتقال شکنندگی به انعطاف پذیری بر اساس تست کششی و میکروگراف های سطح شکست شد. مقدار بهینه BE برای خواص جامع ۱۱۵ درصد حجمی بود که در آن ترکیب کاهش زیادی را در:
۱-ازیاد طول تا پارگی از ۷ تا ۱۷۹ درصد و
۲- مقاومت ضربه آیزود از ۲۵ کیلوژول بر متر مربع تا ۱۰۳ کیلوژول بر متر مربع شد.
میکروگراف های SEM نشان داد که بهبود چقرمگی ناشی از دفورماسیون ماتریکس بزرک مقیاس است که به دلیل حفره ای شدن ذرات لاستیک است. به علاوه، تست سیتوتوکسیتی درون شیشه ای نشان داد که این ترکیبات، برای فیبروبلاست های موش غیر سمی هستند. تحقیقات نشان می دهند که این ترکیبات PLA/BE پتانسیل زیادی برای کاربرد های مهندسی و زیست پزشکی دارند.

عنوان انگلیسی:Employing a novel bioelastomer to toughen polylactide~~en~~

Introduction Biobased polymers from renewable resources have received considerable interests from academia and industry in recent years, due to environmental concerns for ever-declining petroleum resources [1e3]. The use of biobased polymers is currently a major alternative to conventional petroleum-based polymers, and will provide a solution to the environment problem of plastic wastes [4]. Polylactide (PLA) is a polymer produced from renewable resources such as corn on a commercial scale [5]; it is a thermoplastic aliphatic polyester and has been proven viable in replacing petroleum-based plastics in some applications [6]. However, PLA is inherently brittle, which severely limits its application in industries. Toughening PLA has thus attracted great interests. Low-molecular weight plasticizers toughened PLA moderately but this was obtained at the cost of losing stiffness [7e11]. Inorganic fillers such as clay improved toughness little, although enhancing stiffness obviously [12e14]. The most practical and economic used methods for toughening PLA is to adopt flexible polymers or elastomers. Poly (-caprolactone) (PCL) was the earliest polymer used for toughening PLA [15e21]. Since PCL and PLA are not compatible, compatibilizers such as PLLA-PCL-PLLA triblock copolymer have been developed [18]; it produced an improvement in notched Charpy impact strength from 1.1 to 3.7 kJ/m2 at 30 wt% PCL. Compatible PLA/PCL blends were prepared through reactive processing induced by catalysts [19] or crosslinkers [20,21]. Jiang et al. [22] improved Izod impact strength by 170% via mixing PLA with 20 wt% poly (butylene adipate-coterephthalate) (PBAT). Li et al. [23] prepared PLA/poly(ether) urethane (PU) blends with improved impact strength from 64 kJ/m2 to 315 kJ/m2 . Zhang et al. [24] used polyamide elastomer (PAE) to toughen PLA, resulting in a increase in elongation at break from 5.1% to 194.6% at 10 wt% PAE. PLA was blended with four synthetic rubbers, including ethyleneepropylene copolymer (EPM), ethyleneeacrylic rubber (AEM), acrylonitrileebutadiene rubber (NBR), and isoprene rubber (IR), but toughening was only achieved by PLA/NBR blend with a 1.8 times higher value of Izod impact strength in comparison with PLA [25]. Even though these polymers toughened PLA effectively, unfortunately these polymers are either nonrenewable or nondegradable. A recent trend for toughening PLA is to adopt degradable, renewable polymers, including starch [26,27], poly (butylene succinate) (PBS) [28,29], poly (hydroxyalkanoates) [30,31], polymerized soybean oil [32] and polyamide11 (PA11) [33]; these are fabricated from renewable resources, and upon disposal are able to degrade completely in the environment within dozens of years. Shibata et al. [29] toughened PLLA by poly (butylene succinate-co-L-lactate) (PBSL) and poly (butylene succinate) (PBS); at 10 wt%, these two tougheners achieved 160% and 120% higher elongation at break, respectively. Robertson et al. [32] achieved 400% and 600% increase in elongation at break and tensile toughness by using polymerized soybean oil, respectively. However, most tougheners derived from renewable resources are less effective than those derived from petroleum resources in improving the PLA toughness. On the other hand, most studies used the improved elongation at break rather than the notched impact strength to gauge the toughening effects, while the impact testing is far more useful in practice. Therefore, the challenge is to develop biocompatible, highly toughened PLA blends which retain both completely renewable origins and ultimate degradability if necessary [34]. Considering the fact that elastomers have commonly been adopted as a second phase polymer for toughening many kinds of brittle polymer materials, such as epoxy [35,36], polypropylene [37], poly(methyl methacrylate) [38], and so on, it becomes very interesting and important to look for or design/synthesize the new biobased and biocompatible elastomers to toughen PLA. Recently we have developed novel bioelastomers from polymerizing commercial biobased monomersdsebacic acid, itaconic acid, succinic acid, propanediol and butanedioldall of which are derived from renewable resources [39]. While possessing complete biocompatibility, these elastomers exhibit satisfactory elasticity and good mechanical strength. It is noteworthy that the repeat units of these bioelastomers are based on ester groups, implying some compatibility with other ester bond-based polymers such as PLA [7,28]. Thus, a hypothesis made in this study is that our bioelastomers have great potential for toughening PLA. In this work, we will significantly toughen PLA by compounding with our synthetic bioelastomer. The morphology, thermal behaviors, rheological properties and mechanical properties of the blends will be extensively investigated. 2. Experimental section 2.1. Raw materials Itaconic acid (IA) (purity 99.0%), succinic acid (SA) (purity 99.0%), 1, 3-propanediol (PDO) (purity 99.0%) and 1, 4-butanediol (BDO) (purity 99.0%) were purchased from Alfa Aesar. Sebacic acid (SeA) (purity 99.0%) was obtained from Guangfu Fine Chemical Institute of Tianjin. Tetrabutyl orthotitanate (TBOT), hydroquinone and phosphorous acid were supplied by Fluka, Beijing Yili Fine Chenical Co. Ltd, and Sinopharm Chemical Reagent Co. Ltd, respectively. Polylactide (PLA, 5051x) was provided by Natureworks USA.

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