The induction of preferred orientation in a liquid crystal co-polyester by extrusion and drawing

It is shown that liquid crystal polyester can be extruded and drawn from the melt into fine fibres which possess stiffnesses up to 68 GPa. Thicker fibres with smaller draw ratios have correspondingly lower stiffnesses, which are correlated with molecular alignments characterized by flat plate X-ray diffraction. Fibres with a range of diameters were heat-treated over a range of temperatures to determine the effect of annealing on preferred orientation and stiffness. Heat-treatment of as-spun fibres produced maxima in axial stiffness at 170° C, corresponding to an increase in preferred orientation, and 270° C, corresponding to the development of quasi-crystalline order which is analysed. Scanning electron microscopy showed the existence of needle-like domains of approximately circular cross section up to 0.8 m in diameter. These were aligned in the direction of drawing in contrast to being haphazardly arranged in a hot rolled specimen displaying no preferred orientation.     

Some mechanical properties of an epoxy resin system cured with multiple crosslinking agents

Arbitrary cure times and glass transition temperatures are reported for an epoxy resin cocrosslinked by various weight fractions of hexamethylenediamine (HMDA) and m-phenylenediamine (m-PLDA). The glass transition temperatures of the epoxy resin systems studied yielded an excellent fit to an empirical equation developed by Dyvik for copolymers. The cure time parameters were found to be a linear function of the weight fractions of each crosslinking agent present. The mechanical properties of the epoxy resins were measured by an in situ dynamic modulus technique which employed the use of a resin-coated metallic substrate.     

Chlorination of polystyrene

Chlorination of a low molecular weight polystyrene in the α position was studied by following changes in the infrared spectrum, glass transition temperature, and molecular weights of the polymer. The logarithm of the absorbance ratio at 2920 and 1500 cm^?1 as a function of mole per cent chlorination was linear. The glass transition temperatures, determined by use of a differential scanning calorimeter (DSC), were found to obey an equation developed by Dyvik for copolymers. The molecular weight of the chlorinated polystyrene decreased as a function of chlorination.     

Cure rates of some epoxy systems

The property changes of Epon 828 crosslinked by either diethylenetriamine or m-phenylenediamine at several temperatures have been studied by two in situ techniques. The mechanical property changes were followed by continuously monitoring the changes in the fundamental frequency of vibration during cure of a resin-coated substrate acting as a cantilever reed. The disappearance of the reactive epoxy group was followed in situ by continuously monitoring the absorbance of the infrared epoxide band at 915 cm.^?1. Correlation of the two techniques was accomplished by normalizing both the mechanical property and infrared data. The apparent energy of activation was calculated to be 10.4 and 11.4 kcal. /mole, respectively, for the m-phenylenediamine and diethylenetriamine systems by the mechanical technique, and 11.0 kcal./mole for the m-phenylenediamine crosslinked system by the infrared technique.     

An integrated behavioral medicine approach to improving care of patients with diabetes mellitus

A detailed approach to integrating behavioral techniques into patient education, case management, and treatment evaluation of persons with diabetes mellitus is offered. The author asks a series of "what if" questions to stimulate new thinking about ways to improve patient-physician relations in overcoming problems in managing the condition, citing recent research findings in the field. Adherence to regimens, self-management, goals of an integrated diabetes program and steps along the way to achieving it, psychophysiologic mechanisms in glucose metabolism, and the function of social support are among the topics covered.