سینتیک پلیمرشدن توده گرمایی دمازیاد متیل‌ استیرن

نوع مقاله: پژوهشی

نویسندگان

1 تهران، پژوهشگاه پلیمر و پتروشیمی ایران، پژوهشکده علوم، گروه علوم پلیمر، صندوق پستی 112-14975

2 تهران، دانشگاه تربیت مدرس، دانشکده علوم پایه، بخش شیمی، صندوق پستی 175-14115

چکیده

فرضیه: مونومر متیل ‌‌استیرن از مشتقات استیرن است که از قرارگرفتن گروه متیل روی گروه بنزنی یا وینیلی به‌وجود می‌آید. پلی(‌متیل ‌استیرن) افزون بر خواص مشابه پلی‌استیرن دارای خواصی ویژه از جمله چگالی کمتر و دمای انتقال شیشه‌ای بیشتر نسبت به پلی‌استیرن است که محدوده دمای عملکری آن را تحت تأثیر قرار می‌دهد. دانش سینتیک پلیمرشدن امکان ایجاد ساختار پیچیده با روش‌های مختلف پلیمرشدن را می‌دهد. هدف اصلی این مقاله بررسی سینتیک پلیمرشدن رایکالی آزاد متیل ‌استیرن (%64 ایزومر متا و %36 پارامتیل ‌استیرن) با استفاده از مدل‌های مرتبه دوم و سوم و معادله‌های ممان در محدوده دمایی 140-80 درجه سلسیوس است.
روش‌ها: پلیمرشدن توده گرمایی متیل ‌استیرن در محدوده‌ دمایی 140-80 درجه سلسیوس با روش آمپول انجام شد. درصد تبدیل نمونه‌ها با روش وزن‌سنجی و متوسط وزن مولکولی از آزمون سوانگاری ژل تراوشی (GPC) محاسبه شد. مدل‌سازی پلیمرشدن متیل ‌استیرن از حل معادله‌های ممان واکنش‌های موجود در پلیمرشدن با نرم‌افزار MATLAB، شبیه‌سازی شد. مدل‌های ارائه‌شده برای مرحله‌ آغاز پلیمرشدن شامل دو بخش شروع مرتبه سوم و دوم نسبت به مونومر بود.  
یافته‌ها: نتایج نظری به‌دست‌آمده از هر دو روش آغاز، با نتایج تجربی به‌دست آمده با روش وزن‌سنجی انطباق قابل قبولی نشان داد. همچنین مشخص شد، مدل مرتبه‌ سوم نسبت به مرتبه دوم انطباق‌پذیری بهتری دارد. نتایج مشابهی برای مدل‌سازی متوسط‌های وزن مولکولی به‌دست آمد. مشخص شد، اثر ژل نسبت به انتقال به مونومر مؤثرتر بوده و این اثر بر متوسط وزنی وزن مولکولی بیشتر از متوسط عددی وزن مولکولی بوده است. از سوی دیگر، مدل پلیمرشدن ایده‌آل که شامل حذف اثر ژل و ثابت درنظرگرفتن ثابت‌های سرعت است، انطباق خوبی با نتایج تجربی نشان نداد.

کلیدواژه‌ها


عنوان مقاله [English]

Kinetics of High-Temperature Bulk Thermal Polymerization of Methyl Styrene

نویسندگان [English]

  • Mohammad Reza Jozaghkar 1
  • farshid ziaee 1
  • Hamid Reza Heyran Ardakani 1
  • Samaneh Ashenagar 2
  • Mehrdad Jalilian 1
1 Iran Polymer and Petrochemical Institute, P.O. Box 14975-112, Tehran, Iran
2 Department of Chemistry, Faculty of Basic Sciences, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran
چکیده [English]

Hypothesis: Methyl styrene monomer is a styrene derivative, created by the methyl group(s) substituted on the benzene ring. Polymethyl styrene has similar properties as with polystyrene (PS) but a lower density and higher glass transition than PS. The knowledge of polymerization kinetics allows us to construct complex polymeric architectures with different polymerization techniques and controlling their polymerization conditions. The aim of this study is to study the kinetics of free radical polymerization of methyl styrene (64% meta- and 36% para-methyl styrene isomers) in the temperature range of 80-140°C, using second- and third-order thermal initiation models and moment equations.
Method: All polymerization runs were carried out through the ampoule method. Bulk thermal polymerization of methyl styrene was established in the range of 80-140°C and conversions were measured gravimetrically. Modeling of methyl styrene polymerization was simulated by MATLAB and moment equations. Moment equations were obtained by using the polymerization reaction. The assumed models for the initiation step of polymerization included second- and third-order in the monomer.
Finding: The theoretical results obtained from both initiation methods showed good agreement with the experimental results acquired from the gravimetric method. Also, it was demonstrated that the third-order model has better adaptation with experimental results of conversion than the second-order model. The similar results were obtained for modeling of average molecular weights. It was revealed that the gel effect had stronger effect on the average molecular weight than monomer transfer. This effect was more significant for weight average molecular weight than number average molecular weight. On the other hand, an ideal polymerization model, with no gel effect assumptions and having the same rate constants throughout, does not make good agreement with the experimental results.

کلیدواژه‌ها [English]

  • kinetic
  • methyl styrene
  • free radical polymerization
  • bulk thermal polymerization
  • modeling
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