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Abdel Moteleb, M. M., G. R. Saad, and R. I. Nessim, "The effects of preheating on the dielectric relaxation, and of temperature on the 'static' dielectric constant, of cellulose acetate fibers", Polymer Degradation and Stability, vol. 36, issue 3, pp. 217 - 224, 1992. AbstractWebsite

The effect of preheating at 140°C and 180°C on the dielectric relaxation of cellulose acetate of degree of substitution 1·90 has been investigated, together with the dependence on temperature over the range 80-200°C of the 'static' dielectric constant of variously acetylated cellulose samples. The results obtained are discussed in terms of progressive gain of compact structure, together with the initiation of crystallization at a temperature governed by the acetyl content in the fiber. Phase changes involving discontinuity in the first variation of the 'static' dielectric constant on heating, and irreversibility of the temperature dependence path on cooling are thus observed. © 1992.

Abdelrahman, N. A. G. S. H. S. R., Abdelgwad A. Fahmi, G. R. Saad, and M. M. Naoum, "Synthesis and mesophase behavior of four-ring azo-ester-azo compounds bearing two terminal alkoxy groups in different lengths and proportions", Liquid Crystals, vol. 47, issue 12, pp. 1772-1783, 2020.
Abou-Aiad, T. H., M. Z. El-Sabee, K. N. Abd-El-Nour, G. R. Saad, E. S. A. El-Sayed, and E. A. Gaafar, "Miscibility and the specific interaction of polyhydroxybutyrate blended with polyvinylacetate and poly(vinyl acetate-co-vinyl alcohol) with some biological applications", Journal of Applied Polymer Science, vol. 86, issue 9, pp. 2363 - 2374, 2002. AbstractWebsite

Bacterially produced polyhydroxybutyrate (PHB) polymer has a lot of potential as an application for environmentally degradable plastics. We aimed in this study to blend PHB with the semicrystalline polymers poly(vinyl acetate) (PVAc) and poly(vinyl acetate-co-vinyl alcohol) (PACA) to obtain material with better physical properties. We investigated compatibility over a wide composition range using different techniques. Viscosity measurements were used to study polymer-polymer miscibility in dilute solutions with chloroform as cosolvent. The data is discussed according to the viscosity interaction parameters, which are treated as excess properties by similarity with those of real solutions. Dielectric investigations were carried out at different frequencies ranging from 100 Hz to 50 kHz. The obtained data indicated that more than one relaxation mechanism was present, which were ascribed to the rotation of the main chain and its related motions. A glass-transition temperature composition diagram, IR spectroscopy, and a morphological investigation were also used to give more information about the compatibility of such blends. The results of this study indicate that PHB/PVAc is semicompatible, whereas PHB/PACA is compatible at least in the assayed composition range of hydrolysis. We also extended the study to carry out some biological activity investigations, which were tested against the representative number of pathogenic organisms with the disk diffusion method. The different compositions of the investigated blend were biologically active when compared with the individual polymers.

Abudonia, K. S., G. R. Saad, H. F. Naguib, M. Eweis, D. Zahran, and M. Z. Elsabee, "Surface modification of polypropylene film by grafting with vinyl monomers for the attachment of chitosan", Journal of Polymer Research, vol. 25, issue 5, 2018. AbstractWebsite

Polypropylene (PP) film activated by corona discharge treatment was grafted with methyl methacrylate (MMA) and acrylic acid (AA). The grafted PP was characterized by spectral, thermal analysis and swelling behavior which confirmed the occurrence of the grafting. The water vapor and oxygen permeability (OTR and WVTR) as well as the mechanical properties have been enhanced by grafting with both AA and MMA. The grafted PP was further immobilized with chitosan (CS) using ceric ammonium nitrate (CAN) as an initiator under ultraviolet radiation. The chitosan immobilized grafted film was characterized by FTIR, mechanical properties, thermal properties and swelling measurements. Scanning electron microscope (SEM) confirmed that the CS is bonded to the grafted PP film. The CS modified PP film has acquired enhanced antibacterial and antifungal properties. © 2018, Springer Science+Business Media B.V., part of Springer Nature.

Ahmed, H. A., M. M. Naoum, and G. R. Saad, "Effect of alkoxy-chain length proportionation on the mesophase behaviour of terminally di-substituted phenylazo phenyl benzoates", Liquid Crystals, vol. 40, issue 7, pp. 914 - 921, 2013. AbstractWebsite

A series of 4-alkoxyphenylazo-4′-phenyl-4′′-alkoxybenzoates bearing two terminal alkoxy groups (I m + n), where m and n denote the number of carbon atoms in the alkoxy groups attached to the phenylazo and benzoate moieties, respectively, was synthesised, and the molecular structures were established via elemental analyses, IR, NMR and mass spectroscopy. First, the thermal transitions and mesophase characteristics of any two isomeric molecules, having the same molecular length but with differently proportionated alkoxy groups, were investigated by differential scanning calorimetry and polarised-light microscopy. All compounds investigated proved to have a wide smectic C and nematic liquid crystalline ranges, except for the lower homologous (I 6 + 8 and I 8 + 6) where they are purely nematogenic. Mesophases were confirmed by the miscibility method, using dodecyloxybenzoic acid as the mesophase reference. Second, the mesophase behaviours of binary mixtures of isomeric compounds, bearing the same total alkoxy-chain length (m + n) but differ in the individual values of m and n, were studied and discussed. It was found that the smectic C and nematic phases behaved ideally in their binary mixture with the 4-alkoxy benzoic acid, independent of either n or m. © 2013 Copyright Taylor and Francis Group, LLC.

Ahmed, N. H. S., G. R. Saad, and M. M. Naoum, "Effect of position of the lateral fluoro substituent on the mesophase behaviour of aryl 4-alkoxyphenylazo benzoates in pure and binary mixtures", Liquid Crystals, vol. 45, issue 10, pp. 1487 - 1497, 2018. AbstractWebsite

Five groups of 4-substituted phenyl 4ʹ-(2ʺ- (or 3″-) substituted-4ʺ-alkoxyphenylazo) benzoates (Ina-c to Vna-c) were investigated in which, within each group, the length of the terminal alkoxy group varies between 8 and 16 carbons, while the other terminal substituent, X, is a polar group that alternatively changed between the electron-donating CH3O and the electron-withdrawing Br group, in addition to the un-substituted analogue (X = H). The lateral substituent (Y) in the five groups I–V varies, respectively, between H, 3-CH3, 2-CH3, 3-F and 2-F. Their mesophase stabilities were determined by differential scanning calorimetry and phases identified by polarised light microscopy. The two newly prepared groups of compounds (IVna-c and Vna-c) are structurally characterised by infrared, 1H-NMR, mass spectroscopy, thermogravimetric and elemental analyses. Binary phase diagrams were constructed for each pair of isomers from groups IV and V bearing the same wing substituents but the lateral F is attached to different positions (2ʺ or 3″). © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

Ahmed, N. H. S., A. M. Abdelrahman, G. R. Saad, and M. M. Naoum, "Effect of replacing an azo group with an azomethine one on the mesophase behavior of four-ring azo/ester/azomethine compounds bearing two terminal alkoxy groups", Liquid Crystals, vol. 47, issue 10, pp. 1409-1420, 2020.
Ahmed, N. H. S., G. R. Saad, and M. M. Naoum, "Effect of lateral bromo substituent on the phase behavior of four-ring azo/ester/azo liquid crystalline materials", https://www.tandfonline.com/loi/tlct20, 2019.
Ahmed, N. H. S., A. A. Fahmi, G. R. Saad, and A. M. Abdelfattah, "Synthesis and mesomorphic properties of laterally fluoro azo/ ester based on four ring compounds with a wide range mesophase thermal stability", Liquid Crystals, vol. 49, issue 5, pp. 666-678, 2022.
Ahmed, H. A., M. M. Naoum, and G. R. Saad, "Mesophase behaviour of 1:1 mixtures of 4-n-alkoxyphenylazo benzoic acids bearing terminal alkoxy groups of different chain lengths", Liquid Crystals, vol. 43, issue 9, pp. 1259 - 1267, 2016. AbstractWebsite

The thermal and mesophase behaviour of all possible 1:1 mixtures (In/Im) formed from any two homologues of 4-n-alkoxyphenylazo benzoic acids bearing different alkoxy chain lengths (n and m vary between 6 and 16 carbons), were investigated by differential scanning calorimetry (DSC) and phases identified by polarised light microscopy (PLM). Phase transitions were investigated as a function of the average alkoxy chain length (Formula presented) of the mixed acids. A comparison, made between the present series and previously investigated simpler analogues, 4-n-alkoxy benzoic acids, revealed that increasing the length of the mesogenic core increased the stabilities of both the smectic C and nematic phases. © 2016 Informa UK Limited, trading as Taylor & Francis Group.

Ahmed, N. H. S., G. R. Saad, H. A. Ahmed, and M. Hagar, "New widely stable four ring azo/ester/Schiff base liquid crystals: synthesis, mesomorphic, photophysical and DFT approaches", RSC Advances, vol. 10, issue 16, pp. 9643-9656, 2020.
Ahmed, H. A., and G. R. Saad, "Mesophase behaviour of laterally di-fluoro-substituted four-ring compounds", Liquid Crystals, vol. 42, issue 12, pp. 1765 - 1772, 2015. AbstractWebsite

Four new groups of the di-fluoro-substituted 4-(2′-(or 3′)-fluoro phenylazo)-2-(or 3-) fluoro phenyl-4″-alkoxyphenylazo benzoates (In–IVn) were prepared and investigated for their mesophase behaviour. An alkoxy group of variable chain length (n = 6, 10 and 14 carbons) is attached to the terminal phenylazo benzoate moiety, and two lateral fluoro substituents are attached individually with different orientations to the other two adjacent rings. The molecular structures of the prepared compounds were confirmed by Fourier transform infrared spectroscopy and 1H NMR spectroscopy. The study aims to investigate the steric effect of the spatial orientation and relative positions of the two lateral fluorine atoms on the mesomorphic properties in their pure states. The mesophase behaviour was investigated via differential scanning calorimetry and mesophases were identified by polarised light microscopy. The investigation shows that these compounds exhibit high enantiotropic mesophases (SmC and N) and broad mesophase temperature range. The type and stability of the mesophase depends on the length of the terminal alkoxy chain and the position the two fluoro substituents. A comparison between these investigated compounds with their corresponding three-ring analogues was discussed. © 2015 Taylor & Francis.

Al-Sabagh, A. M., T. M. Khalil, M. W. Sabaa, T. T. Khidr, and G. R. Saad, "Poly(n-Alkyl Itaconate-Co-Vinyl Acetate) as Pour Point Depressants for Lube Oil in Relation to Rheological Flow Properties", Journal of Dispersion Science and Technology, vol. 33, issue 11, pp. 1649 - 1660, 2012. AbstractWebsite

In the present work, poly(n-alkyl itaconate-co-vinyl acetate) comb-like polymers were synthesized by radical copolymerization of n-alkyl itaconates of various alkyl chain length and vinyl acetate monomers for use as pour point depressants in lubricant oil. Initially four n-alkyl itaconate monomers were synthesized by esterification of itaconic acid with a series of n-alkyl alcohol, having different alkyl chain length C 16/C 18/NAFOL 20 + A (C av = 20)/NAFOL 1822 B (C av = 22). The copolymerization of these monomers with vinyl acetate was then performed using dibenzoyl peroxide in toluene at 120°C up to high conversion, with molar ratios of 0.25:0.75, 0.50:0.50, and 0.75:0.25 for alkyl itaconate: vinyl acetate. All products were characterized by FTIR, 1H NMR and gel permeation chromatography (GPC). These copolymers were tested in terms of their suitability as pour point depressants and flow improvers for lube oil. The obtained data revealed that the prepared compounds depress the pour point of the lube oil successfully and the additive efficiency on the pour point reduction of the lube oil increases by increasing the concentration of these additives and by decreasing the alkyl chain length of n-alkyl itaconate. The rheological properties of lube oil (with and without copolymer additive) were studied in term of shear rate, shear stress and viscosity. The results indicated that the performance of flow improver was dependent on the copolymer compositions and the size of alkyl chain length of n-alkyl itaconate monomers. Poly(hexadecyl itaconate-co-vinyl acetate) with high content of vinyl acetate showed the best flow improver properties of lube oil. Comparison of morphologies and structures of wax crystals or aggregates in untreated and treated lube oil was also done by micro photographic studies which showed the modification in wax crystal morphology due to additives. © 2012 Copyright Taylor and Francis Group, LLC.

Al-Sabagh, A. M., M. W. Sabaa, G. R. Saad, T. T. Khidr, and T. M. Khalil, "Synthesis of polymeric additives based on itaconic acid and their evaluation as pour point depressants for lube oil in relation to rheological flow properties", Egyptian Journal of Petroleum, vol. 21, issue 1, pp. 19 - 30, 2012. AbstractWebsite

Modification of the wax crystal habit practical interest during transportation processing of lube oil at low temperature. Various pour point depressant (PPD) additives can facilitate this modification by different mechanisms. Comb shaped polymer additives are known to depress the pour point of lube oil by providing different nucleation sites for the precipitation of wax. This paper describes performance based design, synthesis, characterization and evaluation of comb shaped polymeric additives. Alkyl itaconates were prepared by the esterification of itaconic acid with different saturated alcohols C16/C18/NAFOL 20+A (Cav = 20)/NAFOL 1822 B (Cav = 22). The four synthesized monomers were characterized and copolymerized with styrene in different molar ratios. All the products were characterized by infra-red (FTIR), Nuclear Magnetic Resonance (NMR) Spectroscopy and Gel permeation chromatography (GPC). Rheological properties of lube oil (with and without additives) were studied by Brookfield viscometer. In this study the additives based on itaconic acid were evaluated as good PPD and rheology modifiers. © 2012 Egyptian Petroleum Research Institute

Alhaddad, O. A., H. A. Ahmed, M. Hagar, G. R. Saad, K. A. A. Al-Ola, and M. M. Naoum, "Thermal and photophysical studies of binary mixtures of liquid crystal with different geometrical mesogens", Crystals, vol. 10, issue 3, pp. 223, 2020.
Aziz, M. S. A., G. R. Saad, and H. F. Naguib, "Non-isothermal crystallization kinetics of poly(3-hydroxybutyrate) in copoly(ester-urethane) nanocomposites based on poly(3-hydroxybutyrate) and cloisite 30B", Thermochimica Acta, vol. 605, pp. 52 - 62, 2015. AbstractWebsite

The non-isothermal melt crystallization kinetics of PHB segment in copoly(ester-urethane)s based on poly(3-hydroxybutyrate) and poly(butylene adipate) and their nanocomposites with cloisite 30B (C30B) were investigated at different cooling rates (5, 10, 15, and 20 °C min-1) using DSC. Ozawa, Avrami, and the combined Avrami-Ozawa (Mo) methods were used for analyzing the non-isothermal crystallization behavior. The results showed that Avrami and Ozawa models provide a fair description of the non-isothermal crystallization process while Mo model was successful in describing it. The results indicated that C30B not only served as heterogeneous nucleating agents for PHB crystallization, at lower content (5 wt%), but also restricted the mobility and diffusion of PHB chains at higher content (10 wt%). Polarized optical microscope (POM) showed that the nucleation density of PHB segment was increased significantly in the case of nanocomposites. The isoconversional method of Friedman was used to determine the effective activation energy of crystallization of the PUs and the Lauritzen-Hoffman parameters (Kg and U∗) were calculated by applying the Vyazovkin method. © 2015 Published by Elsevier B.V.

Aziz, M. S. A., H. E. Salama, and G. R. Saad, "Diglycidyl ether of bisphenol A/chitosan-graft-polyaniline composites with electromagnetic interference shielding properties: Synthesis, characterization, and curing kinetics", Polymer Engineering and Science, vol. 59, issue 2, pp. 372 - 381, 2019. AbstractWebsite

Conducting filler based on chitosan and grafted polyaniline (Ch-g-PANI) was prepared with different grafting ratios and used as fillers for polyester powder coating system. Differential scanning calorimetry is applied to study the effect of Ch-g-PANI on the curing of the polyester powder coating. The activation energy calculated by isoconversional Kissinger method was increased by either increasing the Ch-g-PANI content or the content of polyaniline in the filler, suggesting the contribution of the filler in the curing reactions. The cured samples were characterized using FTIR and TG analyses. Thermogravimetric analysis showed that the total thermal stability was enhanced upon the filler addition as detected from the values of integral procedural decomposition temperature. Furthermore, a dielectric study showed that the dielectric constant and loss were increased upon increasing of the filler. Vogel–Fulcher–Tammann equation was well-fitted when used to examine the dependence of α-relaxation on the temperature and the dielectrically calculated Tg values were comparable to that measured by DSC. The shielding effectiveness toward microwaves was enhanced by increasing the filler content. POLYM. ENG. SCI., 59:372–381, 2019. © 2018 Society of Plastics Engineers. © 2018 Society of Plastics Engineers

Aziz, M. S. A., H. F. Naguib, and G. R. Saad, "Nanocomposites based on chitosan-graft-poly(N-Vinyl-2-Pyrrolidone): Synthesis, characterization, and biological activity", International Journal of Polymeric Materials and Polymeric Biomaterials, vol. 64, issue 11, pp. 578 - 586, 2015. AbstractWebsite

Organophilic montmorillonite (OMMT) was synthesized by cationic exchange between Na+-MMT and N-octyl-N-vinyl-2-pyrrolidonium bromide. Chitosan graft copolymer nanocomposites were synthesized by grafting N-vinyl-2-pyrrolidone onto chitosan in aqueous acetic acid in the presence of OMMT using free radical polymerization. The chemical structures were verified by FTIR. Scanning electron microscopy showed a surface roughness for chitosan graft nanocomposites. Wide-angle X-ray diffraction confirmed the intercalation of grafted chitosan chains between OMMT galleries. Thermogravimetric analysis indicated that the thermal stability of grafted chitosan was enhanced by OMMT incorporation. Preliminary studies showed that the nanocomposites exhibited antimicrobial activity compared with chitosan graft copolymer. © 2015 Taylor and Francis Group, LLC.

Aziz, M. S. A., M. G. Elsoholy, and G. R. Saad, "Preparation and characterization of bio-based polyurethanes obtained from castor oil and poly (3-hydroxybutyrate) and their nanocomposites", Polymer Composites, vol. 39, pp. E489 - E499, 2018. AbstractWebsite

Bio-based polyurethanes (PUs) were synthesized from castor oil (CO) and poly(3-hydroxybutyrate)-diol (PHB-diol) using 1,6-hexamethylene diisocyanate, as nontoxic connecting agent. The PHB content in the obtained PUs was adjusted from 0 to 60.0 wt%. The synthesis was carried out by one pot solution polymerization. PUs nanocomposites loaded with different contents of cloisite®25A (C25A) were prepared by means of in situ solution polymerization. The molecular structure of the obtained PUs was confirmed by FT-IR. The thermal properties of the neat PUs and the resulting nanocomposites were investigated using DSC and TGA. It was found that the cold crystallization of the PHB component was enhanced, while its melt crystallization was retarded with increasing its own content in the PUs. The incorporated C25A in the PU matrix shifted the cold crystallization peak to higher temperature. TGA studies reveal that neat PUs and nanocomposites exhibited three main decompositions steps. The thermal stability of the neat PUs decreased with increasing the PHB content and increased with increasing the C25A content. Tensile mechanical testing revealed that increasing the content of the PHB and C25A made the PUs rigid and strong. The elastic modulus and ultimate tensile strength of the neat PUs were found to increase with increasing the PHB content and enhanced with incorporation of C25A, while the elongation decreased with increasing the PHB and C25A content. The equilibrium swelling in 1,2-dichloroethane decreased with increasing both the PHB and C25A content in PU matrix. POLYM. COMPOS., 39:E489–E499, 2018. © 2017 Society of Plastics Engineers. © 2017 Society of Plastics Engineers

Aziz, M. S. A., H. F. Naguib, S. M. Sherif, and G. R. Saad, "Preparation and Characterization of Biodegradable Polyurethane Nanocomposites Based on Poly(3-hydroxybutyrate) and Poly(Butylene Adipate) Using Reactive Organoclay", Polymer - Plastics Technology and Engineering, vol. 53, issue 16, pp. 1671 - 1681, 2014. AbstractWebsite

Polyurethane nanocomposites were synthesized using one-step solution polymerization of poly(3-hydroxybutyrate)-diol, poly(butylene adipate)-diol using 1,6-hexamethylene diisocyanate. Nanocomposites were prepared using an in-situ polymerization method. The structure was verified using FTIR and 1HNMR. Morphology was examined by XRD and TEM methods. Thermal properties were examined using DSC and TG. DSC showed that all samples were semicrystalline. The Cloisite 30B enhanced the melt crystallization of PHB segments while hindering those of the PBA segments. Thermal stability was improved compared to the neat PUs samples. The Coats-Redfern model was used to calculate the activation energy. Mechanical properties were improved with incorporation of organoclays. © 2014, Copyright Taylor & Francis Group, LLC.

Aziz, M. S. A., H. F. Naguib, and G. R. Saad, "Non-isothermal crystallization kinetics of bacterial poly(3- hydroxybutyrate) in poly(3-hydroxybutyrate-co-butylene adipate) urethanes", Thermochimica Acta, vol. 591, pp. 130 - 139, 2014. AbstractWebsite

The non-isothermal melt crystallization kinetics of a series of copoly(ester-urethane)s, PUs, based on poly(3-hydroxybutyrate), PHB, and poly(butylene adipate), PBA, of different PHB content 20, 40, and 60 wt% were studied using DSC at different cooling rates. Various macrokinetic models, namely, Avrami, Tobin, Ozawa, and Mo models were applied to describe the crystallization process of PHB in the PU matrices. Avrami, Tobin, and Mo models could successfully describe the non-isothermal crystallization behavior of PHB segments in all samples, while Ozawa model provides a fair description of the non-isothermal crystallization process of PUs containing only 20 and 40 wt% PHB. The Avrami exponent was found to range from 3.6 to 4.0, while the Tobin exponent was found to range from 2.3 to 3.0. The spherulites shape and size were analyzed using polarized optical microscopy (POM). The results of kinetic parameters showed that the crystallization rate of PHB segments in the investigated PUs was increased with increasing the PHB content. The isoconversional method of Friedman was used to determine the effective activation energy of crystallization of the PUs and the Lauritzen-Hoffman parameters (Kg and U*) were calculated by applying the Vyazovkin method. © 2014 Elsevier B.V. All rights reserved.

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El Shafee, E., G. R. Saad, and M. Zaki, "Calorimetric and dielectric study on poly(trimethylene terephthalate)/ polycarbonate blends", Journal of Polymer Research, vol. 15, issue 1, pp. 47 - 58, 2008. AbstractWebsite

Poly(trimethylene terephthalate) (PTT)/polycarbonate (PC) blends with different compositions were prepared by melt blending. The miscibility and phase behavior of melt-quenched and cold-crystallized blends were studied using differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy. The blends of all compositions display only one glass transition (T g ) in both states. The melting temperature and the crystallinity of PTT in the blend decrease with increasing PC content. The dielectric results for the melt-quenched blends, for PC content up to 60 wt.%, exhibited two merged relaxation peaks during the heating scan; the lower temperature relaxation peak represent the normal glass-transition (α) relaxation of the mixed amorphous phase and the higher temperature relaxation due to the new-constrained mixed amorphous phase after crystallization. Cold-crystallized blends displayed only one glass transition α-relaxation whose temperatures varied with composition in manner similar to that observed by DSC. The dielectric α-relaxation of cold crystallized blends has been analyzed. Parameters relating to relaxation broadening, dielectric relaxation strength, and activation energy were quantified and were found to be composition dependent. The PTT/PC blends could be considered as two-phase system, a crystalline PTT phase and a mixed amorphous phase consisting of a miscible mixture of the two polymers. However, the crystallinity was only detected for blends containing greater than 40 wt.% PTT. © 2007 Springer Science+Business Media B.V.

El-Shafee, E., and G. R. Saad, "A dielectric study of the photodegradation of poly(vinyl chloride) in air", Polymer Degradation and Stability, vol. 43, issue 3, pp. 315 - 318, 1994. AbstractWebsite

The dielectric absorption caused by dipolar relaxation of poly(vinyl chloride) photolytically degraded in air, using ultraviolet radiation, was studied on samples in the form of cast thin films. It was found that with the progress of photodegradation over a period of 10 h at 35 ± 2°C, the change in the magnitude of the dielectric parameters ε{lunate}m′', ε{lunate}0-ε{lunate}∞, ΔHε{lunate}0 and α can be practically represented as a three-staged process. © 1994.

El-Shafee, E., and G. R. Saad, "Dielectric analysis of poly(vinyl chloride) films doped with cobalt(II) chloride", Polymer Degradation and Stability, vol. 41, issue 1, pp. 25 - 29, 1993. AbstractWebsite

The dielectric behaviour of solution-grown thin films of poly(vinyl chloride) containing cobalt(II) chloride as dopant was investigated within the temperature range 20-120°C and a 1-100 kHz frequency band. When correction was made for a conduction effect at low frequency, a high-temperature glass-transition relaxation process was observed in addition to the ordinary glass-transition process of pure PVC. The former was thus considered to be a cluster-ionic transition process which might be due to a phase-separation behaviour. The effect of moisture uptake by the doped films on the electrical properties is discussed. © 1993.

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