R. D. Patel

Adsorption of cellulose triacetate on calcium silicate

Abstract Adsorption of cellulose triacetate from its chloroform solution on calcium silicate has been studied. The adsorption follows first order kinetics. The adsorption data are adequately described by the Langmuir isotherm indicating that the adsorbed polymer molecules behave as rigid molecules in the adsorbed state. An attempt has been made to fractionate cellulose triacetate employing the adsorption technique.

Synthesis and Characterization of the Poly-(2-Methoxycyanurate) of 1,1′-Bis-(4-Hydroxyphenyl)-cyclohexane

Abstract The poly-(2-methoxycyanurate) of l, l′-bis-(4-hydroxyphenyl)-cyclohexane (PMCBC) was synthesized by the interfacial poly-condensation technique. The polymer was fractionated by preparative gel permeation chromatography (GPC). The fractions were characterized by viscometry, osmometry, and GPC techniques. The viscosity-molecular weight relationship was established in pure solvent and in different binary solvent mixtures. The unperturbed dimensions, (〈R2〉0/M)1/2, and the solvent-polymer interaction parameter, B, were computed by applying the two-parameter theories of the excluded-volume effect.

Investigation of kinetics of curing of triglycidyl-p-aminophenol with aromatic diamines by differential scanning calorimetry

The kinetics of curing of triglycidyl-p-aminophenol with four different diamines in stoichiometric amounts were investigated by means of differential scanning calorimetry. The results indicated that the curing reaction follows first-order Arrhenius kinetics with an activation energy in the range 40–70 kJ · mol−1. The effect of the structure of the curing agent on the curing characteristics is discussed on the basis of the curing characteristics and the kinetic parameters. An epoxy fortifier was observed to lower the curing temperature of an epoxy-amine system when incorporated prior to curing.ZusammenfassungMittels Differential-Scanning-Kalorimetrie wurde die Kinetik der Vernetzung von Triglycidyl-p-aminophenol mit stöchiometrischen Mengen vier verschiedener Amine untersucht. Laut den Ergebnissen verläuft die Vernetzungsreaktion mit einer Arrhenius-Kinetik erster Ordnung, wobei die Aktivierungsenergie im Bereich von 40–70 kJ/mol liegt. Auf Grundlage der Vernetzungscharakteristika und der kinetischen Parameter wird der Einfluss der Struktur des Vernetzungsreagenz auf die Vernetzungskenndaten beschrieben. Mit einem vor der Vernetzung eingebrachten Epoxyfortifyers konnte die Vernetzungstemperatur eines Epoxy-Amin-Systemes heruntergesetzt werden.РЕжУМЕМЕтОДОМ Дск ИсслЕДОВ АНА кИНЕтИкА ОтВЕРжД ЕНИь тРИглИцИДИл-п-АМИНОФ ЕНОлА с ЧЕтыРьМь РАжлИЧНыМИ ДИАМИНАМИ, Вжьтых В стЕхИОМЕтРИЧЕскИх к ОлИЧЕстВАх. РЕжУльтА ты пОкАжАлИ, ЧтО РЕАкцИь ОтВЕРжДЕНИь пОДЧИНь Етсь АРРЕНИУсОВскОИ кИНЕ тИкЕ пЕРВОгО пОРьДкА с ЁНЕРгИЕИ АктИВАцИИ В ИНтЕРВАлЕ 40–70 кДж·МОль−1. НА ОсНОВЕ кИНЕтИЧЕскИх пАРАМЕтРОВ ОБсУжДЕНО ВлИьНИЕ ст РУктУРы ВУлкАНИжИРУ УЩЕгО АгЕНтА НА хАРАктЕРИстИкИ РЕ АкцИИ ОтВЕРжДЕНИь. УстАНОВлЕНО, ЧтО ЁпОк сИжАкРЕпИтЕль, ВВЕДЕ ННыИ РАНьшЕ ВУлкАНИжИРУУЩЕгО Аг ЕНтА, пОНИжАЕт тЕМпЕРАтУР У ОтВЕРжДЕНИь.

Glass-reinforced Vinyl Ester Resin Composites:

The curing behaviour of vinyl ester resin, the condensation product of acrylic acid with diglycidyl ether of bisphenol-A, was studied by differential scanning calorimetry. The glass-fibre-reinforced composites of the vinyl ester resin were prepared and evaluated for their chemical, electrical and mechanical properties. The incorporation of styrene during the curing of the vinyl ester resin showed significant improvements in tensile strength and dielectric properties.

Co-ordination polymers of bis(8-hydroxy-5-quinolylmethylene) sulphide (BHQS)

Abstract Co-ordination polymers of bis(8-hydroxy-5-quinolylmethylene)sulphide have been prepared with Zn2+, Cu2+, Ni2+, Co2+ and Mn2+ ions and characterized by elemental analyses, by i.r. and diffuse reflectance spectral studies and by magnetic moment. The metal contents in all polymers are found to be consistent with 1:1 (metal:ligand) stoichiometry. The thermal behaviour of each of the co-ordination polymer has been studied by TGA in air up to 700°C.

Solution properties of cellulose triacetate—I. Method of fractionation and light scattering, osmometry, viscometry on dilute solutions

Abstract Cellulose triacetate prepared from Egyptian cotton was fractionated by the adsorption technique using porous adsorbent calcium silicate. Chloroform-acetone mixture is suitable for preferential adsorption of CTA on calcium silicate while chloroform-ethanol is adequate for desorption of the polymer from the adsorbent. Light scattering and osmotic pressure measurements for various fractions reveal that fractions are monodisperse. The viscosity measurements along with light scattering give the Mark-Houwink constants in chloroform at 30° as v = 0.800 and K′ = 1.396 × 10−4. Studies showed negligible partial draining character and therefore the higher value of v seems to be mainly due to solvent-polymer interaction, which is common for many stiff chain polymers like cellulose and amylose derivatives. Other parameters, e.g. second virial coefficient, radius of gyration and unperturbed dimension, have also been evaluated.

Crystallization of polyacrylonitrile: Growth mechanisms for various growth features

SummaryCrystallization of polyacrylonitrile has been carried out at different temperatures from fractionated sample, and different morphological growth features obtained are compared with those observed previously from unfractionated sample. Several new growth features like rectangular single crystals, twinned crystals, ovals and spherulites have been observed. The role of different typical growth features for the development of spherulites has been studied. It seems that the proposed growth mechanism for the development of spherulite grown either from the melt or concentrated solution is the same for different polymers. From the observed growth features of dendritic nature in different conditions, a mechanism of development of dendritic spherulite is discussed.ZusammenfassungDie Kristallisation von Polyacrylnitril und anderen Polymeren wird nach der Methode der Filmbildung ausgeführt. Das Polyacrylnitril war hergestellt durch Polymerisation von Acrylnitril initiiert mit einem Cer-Ionen-Redoxsystem. Die Fraktionierung des Polyacrylnitrils wurde mit der Methode, dieKobayashi undFujisaki beschrieben haben, durchgeführt. Die vorliegende Studie für die Untersuchung der wachsenden Kristalle wurde an einer Probe mit dem mittleren Molekulargewicht

Crystallization kinetics of polyacrylonitrile: single crystal growth rate and thermodynamic considerations

\bar M_w = 1,2 \times 10^5