کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5191640 | 1381236 | 2005 | 10 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Miscibility and viscoelastic properties of acrylic polyhedral oligomeric silsesquioxane-poly(methyl methacrylate) blends
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موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی آلی
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
We investigate the miscibility of acrylic polyhedral oligomeric silsesquioxanes (POSS) [characteristic size dâ2 nm] and poly(methyl methacrylate)(PMMA) in order to determine the effect of well-dispersed POSS nanoparticles on the thermomechanical properties of PMMA. Two different acrylic POSS species (unmodified and hydrogenated) were blended separately with PMMA at volume fractions up to Ï=0.30. Both POSS species have a plasticizing effect on PMMA by lowering the glass transition temperature Tg and decreasing the melt-state linear viscoelastic moduli measured in small amplitude oscillatory shear flow. The unmodified acrylic-POSS has better miscibility with PMMA than the hydrogenated form, approaching complete miscibility for loadings Ï<0.10. At a loading Ï=0.05, the unmodified acrylic POSS induces a 4.9 °C decrease in the Tg of PMMA, far less than the 17.4 °C decrease in the glass transition temperature observed in a blend of 5 vol% dioctyl phthalate (DOP) in PMMA; however, the decrease in the glass transition temperature per added plasticizer molecule is nearly the same in the unmodified acrylic-POSS-PMMA blend compared with the DOP-PMMA blend. Time-temperature superposition (TTS) was applied successfully to the storage and loss moduli data and the resulting shift factors were correlated with a significant increase in free volume of the blends. The fractional free volume f0=0.046 for PMMA at T0=170 °C while for a blend of 5 vol% unmodified acrylic-POSS in PMMA f0=0.057, which corresponds to an addition of 0.47 nm3 per added POSS molecule at Ï=0.05. The degree of dispersion was characterized using both wide-angle X-ray diffraction (WAXD) and dynamic mechanical analysis (DMA). Diffraction patterns for both blend systems show clear evidence of phase separation at Ï=0.20 and higher, but no significant phase separation is evident at Ï=0.10 and lower. The storage modulus measured in DMA indicates appreciable phase separation for unmodified acrylic POSS loadings Ïâ¥0.10, while no evidence of phase separation is present in the Ï=0.05 blend in DMA.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polymer - Volume 46, Issue 13, 17 June 2005, Pages 4743-4752
Journal: Polymer - Volume 46, Issue 13, 17 June 2005, Pages 4743-4752
نویسندگان
Edward T. Kopesky, Timothy S. Haddad, Gareth H. McKinley, Robert E. Cohen,