SynopsisThe initial stage of the suspension polymerization of poly(viny1 chloride) (PVC) is characterized I>y the formation of colloidally stahle micron-sized grains of PVC inside the polymerizing ca. 150 pm vinyl chloride droplets. The fate of these micron-sized PVC grains depends upon the agitation conditions. If no agitation is employed, they serve as growth centers for further polymerimtion to give a final particle possessing a uniform internal head morphology. In agitated systems, these grains coagulate early in the conversion to give a more irregular structure in the interior of the PVC particle. The formation of these stable growth centers appears to he unique to PVC. The polymerization of' acrylonitrile. also insoluhle in its monomer. is characterized hy rapid agglomeration of t.he precipitated Fblymer throughout the polymerization. In PVC. the colloidal stability of the polymerizing grains is demonstrated to he electrical in nature. A pericellular membrane or skin formed by polymerization in hot.h the water and vinyl phase completely surrounds the polymerizing droplet after nhorit (I-.'L)% conversion. This skin is responsil)le for the charge retention of the PVC grains inside the polymerizing monomer droplets.

Polarized infrared measurements were made on polymer samples to obtain the structural changes occurring during the orientation process. The absorbances of the infrared bands were measured by determining the three components of the absorbance. Two components were obtained directly with plane‐polarized light while the third is obtained by tilting the sample and extrapolating. Corrections were made for machine optics polarization, sample birefringence, polarizer inefficiency, anisotropy of the index of refraction, and scattering from the film surface. Data are reported for polyethylene obtained from cold‐drawn specimens as a function of draw temperature. Polyethylene exhibits no strain‐induced crystallization as a result of the chain‐alignment process. Annealing of the drawn samples reperfects the distorted crystals.

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Vinyl chloride polymerizations are known to be autoaccelerating. The reaction rate increases with conversion. Because of this phenomenon, substantial reactor productivity at early conversion can be lost because the heat‐removal capacity of the reactor is not fully utilized until near the end of the polymerization. For this reason it is desirable to speed up the polymerization at the beginning and slow it down near the end. This rate adjustment can be achieved by running the polymerization hotter in the beginning and then cooling. We have written a scientifically based computer model of the polymerization designed specifically to simulate such temperature‐programmed reactions. The model does a complete heat balance on the polymerization, has a molecular weight predictor, and will be described and demonstrated for a polymerization at 50°C using sec‐butyl peroxydicarbonate (SBP) as initiator. By using this single initiator and a very simple straight‐line temperature‐programmed reaction, the time to 80% conversion can be reduced from 335 minutes to 240 minutes. This is a substantial increase in productivity.

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