List of articles (by subject)
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Open Access Article
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Mohammad Azadi -
Open Access Article
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zahra daneshfar -
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امیر کرمی -
Open Access Article
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hamidreza heidari -
Open Access Article
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mina alizade -
Open Access Article
6 - Semi-Experimental Methods for Determination of Flory-Huggins Interaction Parameter in Polymeric Mixtures: A Review
Zahra Khoubi-AraniThe Flory-Huggins interaction parameter (χ) is a crucial factor affecting the miscibility and morphology of components in polymer mixtures and their final properties and applications. The reliable measurement of the interaction parameter is worthwhile in fundamental und MoreThe Flory-Huggins interaction parameter (χ) is a crucial factor affecting the miscibility and morphology of components in polymer mixtures and their final properties and applications. The reliable measurement of the interaction parameter is worthwhile in fundamental understanding and quantitative determination of structure-performance relation and finally in practical applications of polymers in different fields. Different methods are used for evaluation of this parameter. In this study, six semi-experimental methods are reviewed: measurement of melting point depression, equilibrium swelling, contact angle, phase separation points, vapor pressure, and inverse gas chromatography. In these methods, equilibrium melting temperatures of pure polymer and its mixtures, degree of equilibrium swelling of the cross-linked polymer in the presence of swelling agent, surface energy of components in the polymeric mixtures, equilibrium components composition in the two-phase system, the ratio of partial vapor pressure of solvent to its saturated one and retention volume are experimentally measured, respectively. Then a proper equation is fitted on the data and the interaction parameter is obtained. In some methods, such as measurement of contact angle, only a positive interaction parameter at temperature of the test is obtained. But in some others, such as measurement of melting point depression, there is no constraint for the sign of interaction parameter. In addition, some methods can determine the composition dependency of the interaction parameter, such as determination of phase separation points. Manuscript profile -
Open Access Article
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Amirhosein Yazdanbakhsh -
Open Access Article
8 - Crystallinity of polymers determined by differential scanning calorimetry (II)
Mina AlizadehaghdamDifferential scanning calorimetry (DSC) is widely used to determine the crystallinity of semicrystalline polymers. In the two-phase model, the measured heat of fusion is compared to the melting enthalpy of a completely crystalline polymer to get the crystallinity degree MoreDifferential scanning calorimetry (DSC) is widely used to determine the crystallinity of semicrystalline polymers. In the two-phase model, the measured heat of fusion is compared to the melting enthalpy of a completely crystalline polymer to get the crystallinity degree. Fusion heat of a polymeric sample is identified by area under the melting endotherm and a baseline. A correct baseline is heat capacity of the semicrystalline sample. It varies with both temperature and crystallinity and is difficult to evaluate. Enthalpy of a process is a state-function quantity and is independent of the process path. In polymer melting, temperature increase and fusion process occur simultaneously. This makes evaluation of the fusion heat challenging. Herein, alternative paths are supposed in which temperature increase and fusion process occur separately and sequentially. This leads to a convenient enthalpy evaluation. Two alternative paths can be defined: first, polymer melts at a constant temperature which is followed by temperature increase of the melt; second, polymer temperature increases without any change in crystallinity degree which is followed by polymer melting at a constant temperature. Lastly, an enthalpy deficiency due to the amorphous-crystalline interface and an excess enthalpy due to the defects present in crystalline regions are investigated how to affect the crystallinity. Manuscript profile