Factors influencing the formation of elongated morphologies in immiscible polymer blends during melt processing

The morphology of the dispersed phase in immiscible polymer blends plays an important role in the determination of the final physical properties. This paper considers factors that influence the final state of deformation of the dispersed phase, and in particular, the formation of fibers and lamellae. Blends of polyethylene and nylon-6 were extruded by ribbon extrusion at different draw ratios. Prior to single-screw extrusion the materials were blended in a co-rotating twin-screw extruder, and the size of the dispersed phase was studied as a function of the viscosity ratio. As the blends are extruded into ribbons and drawn through the calender rolls, the morphology of the dispersed phase undergoes drastic transformations. The fiber formation is enhanced by increasing the draw ratio. At high draw ratios, long thin fibers are observed. Some biaxial deformation is obtained for the noncompatibilized systems when the extruded materials enter the calender with the maximum closing pressure applied to the rolls. The same effect is observed for the compatibilized systems with lower values of the viscosity ratio. As a general rule, it has been observed that the final dispersed phase deformation is diminished in interfacially compatibilized systems.     

Coupling of polystyrene to a silane-treated mica

This paper deals with the coupling of polystyrene to a closely packed and highly ordered cationic vinylbenzyl silane (CVBS) on mica. It is shown that a thermal treatment is required for maximum retention of polystyrene on treated mica. Moreover, a thermal treatment at 250°C is much more effective than one at 170°C. The effect of the number of silane monolayers on mica was investigated. In general, one monolayer of CVBS gave optimum retention of polystyrene. The addition of peroxides further improved this retention and at the same time allowed the use of lower treatment temperatures. Some data are presented which consider the importance of the silane solution concentration and silane functional groups.     

Simulation d'un réacteur catalytique à lit fixe (Oxydation du propène)

A bidimensional pseudo homogeneous model is developed to explain the behaviour of a fixed bed catalytic reactor for oxydation of propene to acrolein. The rate of the main reaction and of side reaction are expressed as power fonctions of partial pressures of oxygene and propene. Heat transfer parameter (Pe_hr et Bi) necessary for simulation are obtained by the help of temperature profiles in the absence of reaction. The integration of the model has been done by orthogonal collocation and the results i.e. temperature profiles and outlet concentration are compared with experimental data.     

Mechanical properties of certain oriented crystalline polymers

The yield stress is a simple function of the deformation ratio in the direction of testing for specimens oriented by uniaxial or biaxial stretching or rolling. Unless the yield stress increases more rapidly than in proportion to the deformation ratio, there will be instability during tensile creep under high loads. The relative merit of various polymers differs for creep and stress relaxation. Fatigue and bend recovery are also related to the molecular structure.     

Calculated effect of pulsed pheromone release on range of attraction

In order to assess the possible function of pulsed release of windborne pheromones, calculations were performed to predict the concentration pattern downwind of the source. Two patterns of pulsed releases (sinusoidal and instantaneous) were compared to a constant release pattern. In all three cases, the average rate of release was the same. Assuming the receiving animal needs only a momentary exposure to concentrations above threshold to respond, it is clear that sinusoidal release has a greater distance of detection than constant release and that instantaneous release is even better. The relative magnitude of the increase in range of detection depends on the ratio of average release rate to threshold concentration. Pulsed releases have a greater advantage when the threshold is high and the range of attraction is inherently short. Under these conditions, sinusoidal release can double the range of attraction and instantaneous release can increase it 10-fold. In contrast, with a low threshold and consequent long range of attraction, the pulsed patterns are lost and the increase in range is insignificant. Several testable predictions are derived from the hypothesis that the primary function of pulsed release is to extend the range and time over which a given quantity of pheromone can act.     

A Multi-Channel Pulse-Coded Multiplexing and Demodulating Telemetry System

A multiplexing, demodulating, and recording telemetry system designed to process multiple pulse-coded temperature channels is described. The system provides complete control of recording and multiplexing sequences and timing, and gives a single analog signal in response to each sample of pulse-coded data. It identifies all channels and indicates to a computer when a new data sample is to be processed. The system is self-calibrating to maintain accuracy over extended data collection periods, and is inexpensive.