اثر نانوسلولوز بر رفتار فازی آمیخته PS/PVME در نواحی دور از ترکیب درصد بحرانی

نوع مقاله: پژوهشی

نویسندگان

1 تهران، دانشگاه صنعتی امیرکبیر، دانشکده مهندسی پلیمر، صندوق پستی4413-15875

2 قم، دانشگاه صنعتی قم، دانشکده فنی و مهندسی، گروه مهندسی پلیمر، صندوق پستی 1519-37195

چکیده

در این مطالعه، اثر نانوسلولوز آب‌گریز بر رفتار فازی آمیخته پلی‌استیرن (PS)-پلی‌وینیل متیل اتر (PVME) در ترکیب درصدهای دور از ناحیه بحرانی بررسی شده است. بدین منظور، آمیخته‌‌های خالص PS/PVME با ترکیب درصدهای 90/10 و 60/40 با %2 نانوذرات بررسی شدند. برای مطالعه اثر نانوذرات بر دمای جدایی فاز، از آزمون‌‌ پویش دمای مدول دخیره (از ناحیه تک‌فاز تا دماهای بیشتر از جدایی فاز) استفاده شد. برای مشاهده تغییرات شکل‌شناسی حین جدایی فاز نمونه‌ها از تصاویر میکروسکوپی نوری استفاده شد. تصاویر TEM نشان می‌دهد، حین جدایی فاز، نانوسلولوز آب‌گریز در فاز غنی از PS قرار گرفته که این موضوع با پیش‌بینی رابطه ترمودینامیکی پارامتر ترشدگی سازگار است. برای آمیخته 90/10 PS/PVME جدایی فاز گرانروکشسان کنترل‌کننده جدایی فاز است. وجود نانوذرات باعث شد تا در دماهای زیاد، شبکه ایجاد شده از فاز پلی‌استیرن پایدار باشد. جدایی فاز برای آمیخته 60/40 PS/PVME طبق سازوکار هسته‌گذاری و رشد است و با ادامه جدایی فاز اندازه قطره‌ها به‌‌طور شایان توجهی بزرگ‌تر شده و توزیع پهنی از اندازه قطره‌ها مشاهده می‌شود. افزایش دما موجب بیشترشدن بی‌تقارنی دینامیکی شده و در نتیجه در دماهای بیشتر تغییر سازوکار جدایی فاز از هسته‌گذاری و رشد به جدایی فاز گرانروکشسان مشاهده می‌شود. وجود نانوذرات در فاز پلی‌استیرن هم‌راستا با افزایش دما موجب افزایش بی‌تقارنی دینامیکی شده و در نتیجه از دماهای کمتر جدایی فاز طبق سازوکار گرانروکشسان مشاهده می‌شود.

کلیدواژه‌ها


عنوان مقاله [English]

Effect of Nanocellulose on Phase Behavior of off-Critical PS/PVME Blend

نویسندگان [English]

  • Mohamad Ali Sanjari Shahrezaei 1
  • Fatemeh Goharpey 1
  • Jafar Khademzadeh Yeganeh 2
1 Department of Polymer Engineering, Amirkabir University of Technology, P.O. Box: 15875-4413, Tehran, Iran
2 Polymer Engineering Group, Faculty of Engineering, Qom University of Technology, P.O. Box: 37195-1519, Qom, Iran
چکیده [English]

Hypothesis: The influence of hydrophobic nanocellulose on phase separation behavior of off-critical PS/PVME (polystyrene/polyvinyl methyl ether) blends was studied. While the effect of spherical nanoparticles (NPs) on the phase behavior of polymer blends has been previously explored, the impact of rod-like NPs on the phase behavior has not been well studied. Compared to nanospheres, nanorods are associated with much lower critical percolation concentration, due to the high aspect ratio of nanorods.
Methods: For this purpose, neat PS/PVME blends with compositions of 40/60 and 10/90 and in the presence of 2% nanocellulose were investigated. The temperature sweep of storage modulus, from the one-phase region temperature to those higher than the two-phase region temperature, was used to investigate the effect of nanoparticles on phase separation temperature. Phase-contrast optical microscopy (OM) was employed to investigate the morphological evolution of PS/PVME blends during the phase separation. TEM images indicated the localization of hydrophobic nanocellulose in the PS-rich phase which was consistent with the prediction of thermodynamic wetting parameter.
Findings: Viscoelastic phase separation (VPS) controlled the phase behavior of PS/PVME 10/90 blend which in the presence of nanoparticles increased the stability of the PS-rich network structure even at high temperatures. The PS/PVME 40/60 blend was phase separated under the nucleation and growth mechanism (NG), and there was a wide distribution of droplets size in the late stage of phase separation. With increasing the quench depth, the dynamic asymmetry increased, leading to transition of the phase separation mechanism from NG to VPS. The addition of nanoparticles enhanced the dynamic asymmetry which induced the VPS at lower temperatures.

کلیدواژه‌ها [English]

  • viscoelastic phase separation
  • nucleation and growth
  • Rheology
  • Nanocellulose
  • dynamic asymmetry

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