MYO ÖÄžRETÄ°M ÜYEMÄ°ZÄ°N Ä°KÄ° SCI MAKALESÄ° YAYIMLANDI

Meslek Yüksekokulu MüdürlüÄŸümüz Makine ve Metal Teknolojileri Bölümü ÖÄŸretim Üyesi Yrd. Doç. Dr. Fatma ÅžAHÄ°N DÄ°NÇ’in, SCI’de iki adet makalesi yayımlandı.
Hole Fraction Dependence on Linear Viscosity of PS, PP and ABS: PS (polistiren), PP (polipropilin) ve ABS'nin (poliakrilonitril butadien stiren) Lineer Viskozitesine BoÅŸluk Kesri BaÄŸlılığı” ve The Effect of Hole Fraction on Viscosity in Atactic and Syndiotactic Polystyrenes:  “Ataktik ve Sindiyotaktik Polistirendeki Viskoziteye BoÅŸluk Kesri Etkisi” baÅŸlıklı makale özetleri aÅŸağıda olup, yayımlandığı yerlere ilgili linklerden ulaÅŸabilirsiniz.
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1) Hole Fraction Dependence on Linear Viscosity of PS, PP and ABS: PS (polistiren), PP (polipropilin) ve ABS'nin (poliakrilonitril butadien stiren) Lineer Viskozitesine BoÅŸluk Kesri BaÄŸlılığı”

Abstract
A linear dependency of zero shear, constant shear-rate and constant shear-stress viscosities with temperature and hole fraction (“thermo-occupancy” function) was derived for polyacrylonitrile-butadiene-styrene (ABS), polypropylene (PP) and polystyrene (PS). The relation of viscosity parameters, such as transmission coefficient and a measure of activation energy coefficient, with shear-rate and shear-stress was also investigated and some conclusions on the differences for the studied polymers were discussed. In particular, it was found that, for all materials, the derivative of logarithm of viscosities at zero shear, constant shear-rate and constant shear-stress decreases with decreasing rate with the hole fraction.
Read More: http://www.hanser-elibrary.com/doi/abs/10.3139/217.3101


2)The Effect of Hole Fraction on Viscosity in Atactic and Syndiotactic
Polystyrenes:  “Ataktik ve Sindiyotaktik Polistirendeki Viskoziteye BoÅŸluk Kesri Etkisi”

Abstract
The non-Newtonian viscosity behavior of atactic and syndiotactic polystyrenes (aPS and sPS), at temperatures from 200∘C to 300∘C and pressures up to 30 MPa, was studied using the recently proposed Yahsi–Dinc–Tav model, in particular, the Cross-like model. Viscosity data with shear rates of 0.01s−1 to 5000s−1 were taken from literature at ambient pressure and were reproduced from the Cross-Vogel model at elevated pressures. The viscosities were predicted using the Yahsi–Dinc–Tav model with average absolute deviations of 4.37 % at ambient pressure and 9.63 % at high pressures for aPS and 2.54 % at ambient pressure and 4.79 % at high pressures for sPS. We extended this work to relate the zero shear and the constant shear rate viscosities in terms of the temperature- and pressure-dependent hole fraction using the thermo-occupancy function. The hole fraction (h) was computed from Simha–Somcynsky hole theory. Analytical relationships of specific density and hole fraction in terms of scaled temperature and pressure were constructed for practical purposes. The effects of tacticity of polystyrenes were discussed in terms of the thermo-occupancy function in detail. In particular, the derivative of the logarithm of the viscosities (viscoholibility) was found to decrease with an increasing hole fraction.
http://link.springer.com/article/10.1007%2Fs10765-015-1990-4