SynopsisDeuterated analogs of polyvinyl chloride (PVC) have been prepared and their infrared spectra analyzed as an aid to the more detailed assignment of bands in the spectrum of PVC. The following deuterated polymcrs were studied: PVC-adl, PVC-fldl, PVC-mod2, and PVCd,. These, as well as PVC, were polymerized in urea-complex, at -78"C., and a t +50°C. in order to determine which bands are of crystalline origin and whi-h of noncrystalline origin. Polarized spectra of oriented samples were obtained in each case to assist in the analysis. As a result of this study several of the previously uncertain assignments have been clarified. With the help of other studies on model chlorinecontaining compounds i t has been possible to identify the various conformations present in the polymer and to associate these with isotactic and syndiotactic pair configurations in the chain. A method is suggested for determining the proportion of each type of pair configuration in PVC. \ 2632 KRIMM, FOLT, SHIPMAN, BERENS r -
Poly(vinyl chloride) Single Crystals 235 of these lines are 1.9, 3.0, and -1.6 kcal per mol (±0.1) for PS-PVK, PMMA-MVK, and PPVK, respectively. Although the number of values of the quantum yield are too small for exact determination, the activation energies obtained are reasonable for the barriers to rotation about carbon-carbon bonds. ConclusionsAt room temperature and above, photochemical reactions may compete with very efficient radiationless processes. Below the glass transition temperature in PMMA-MVK, PS-PVK, and PPVK a temperature dependence exists for the Norrish type II reaction which can be attributed to the changes in the segment mobility of the polymeric molecule. In the case of PMMA-MVK and PS-MVK, higher type II quantum yields are obtained at higher temperatures in the glassy region. In the case of PPVK, the type II quantum yield decreases slightly with increas-ing temperature. The apparent activation energies obtained from the temperature dependences are 2-3 kcal/mol which are of the same order of magnitude as the energy barriers to rotation around C-C bonds.In the glass transition region the type II quantum yield increases greatly in all the polymers studied due to the great increase in polymer segment mobility which occurs at this temperature. Above the glass transition region, the type II quantum yields in all polymers studied seem to be constant and, within experimental error, equal to the quantum yields obtained in solution for the same polymer and/or analogous low molecular weight model compounds.Acknowledgment. The authors acknowledged the able assistance of Mr. B. McAneney in the molecular weight determinations, Dr. J. Slivinskas for the computer program calculating scission and cross-linking yields, and the National Research Council of Canada for generous financial support.
The melt flow behavior of straight emulsion-polymerized PVC in a capillary extrusion rheometer has been found to depend upon both the molecular weight and the particle size of the sample. Observations of flow-rate, post-extrusion swell, and extrudate appearance, as functions of extrusion temperature and pressure, suggest that both molecular deformation and particle slippage are involved in the flow mechanism. The relative importance of these two modes of flow varies with extrusion conditions and with the PVC molecular weight and particle size. Particle slippage is favored by large particle size, high molecular weight, and low temperature and by a shear stress above a critical yield value. Apparent melt viscosity, swelling, and roughness are minimized under conditions corresponding to the maximum contribution of particle slippage. In the proper range of temperature and shear rate, straight emulsion PVC yields smooth, low-swell extrudates of excellent physical properties.
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