-0.5 10-3 .r;O~g branch and 5 10-3 chloromethyl group permonomer uni t (m.u.) possibly originating from head-to-head monomer placement are f.ound in industrial PVC (fewer in low-temperature polymerized products). TertiarY chlorine atoms, if any, correspond to long branches ; internal double bonds (0.05 10-3 per m.u. and over) can start polydiene sequences. 1 H and 1 3c NMR spectroscopy shows that syndiotactic placement is slightly favored over isotactic, depending only on polymerization temperature (PT). The number of aggregates in solution is very sensitive to PT,increasing with syndiotacticity, and heating up gives molecular solutions. Crystallizability increases with syndiotacticity, and two types of crystals exist ;. crystallinity is higher in virgin powder, and fusion range covers 120o to 220°C • .Annealing over 110°C develops a lower order detectable by DSC. A zone of higher density disappearing at 210°C is seen at the center of virgin PVC "one micron granules"• The temperature of pseudofusion in plasticizers depends on heat treatment, and the kinetics of impregnation reveals morphological heterogeneities.

Currently, selection of screw configurations as well as the operating conditions for compounding polymer blends with desired morphology in a co-rotating twinscrew extruder is an art based on experience. In this paper a quenching section of a twin-screw extruder is described. The section may replace any segment of the extruder barrel. It allows, on the one hand, a regular operation of the machine, and on the other, a rapid quenching and removal of blend specimens for morphology analysis from any place along the extruder barrel and at any time of the blending. The experimental observation of development during compounding of polymer blends enables verification and improvement of the theoretical model, aimed at predicting and controlling the size and polydispersity of the minor phase. Development of the predictive model for blend morphology will provide a valuable guide to the polymer processing industry. The preliminary data were collected using polystyrene/high density polyethylene (PS/HDPE) blends at low concentration of the dispersed phase, 5 wt% of either PS or HDPE. It was observed that the viscosity ratio, blend composition, screw configuration, temperature, throughput, and screw speed significantly influence the blend morphology.

Dilute solution properties of twenty-five PVC fractions prepared from commercial and experimental bulk-polymerized PVC samples have been investigated by means of light-scattering, viscometry and exclusion-chromatography The following Mark-Houwink-Sakadura relationships: []2YC = 1,63 10-2 M°76° x 1.017 c.gs. I 125t -2 ir2 At 0.725 >< 1 02 Lflicyclohexanone -: ' c.g.s.have been found to be valid in a range of Mw-values between 6400 and 650000.The validity of various extrapolation procedures, proposed in order to calculate unperturbed dimensions and polymer-solvent interaction para meters from the empirical viscosity-molecular weight relationship, has been examined The Kurata-Stockmayer method applied to the measurements in tetrahydrofuran yields a Krvalue equal to 0.14 c.g.s. The polymer-solvent interaction parameter derived by the same method is not in agreement with the one deduced from second virial coefficient measurements.Molecular weight distributions determined in commercial PVC samples can be adequately represented, in a first approximation, by the usual exponential distribution function, first. proposed by Schulz. The chromatographic determination of MWD and its effect on the viscosity-molecular weight relationship are discussed.Finally, the possible occurrence of long chain branching in PVC has been investigated by means of an experimental study of the structure and properties of various polyethylene samples obtained by reduction with LiAIH4 of commercial PVC polymers. The melting temperatures and the intrinsic viscosity -molecular weight relationship for the polyethylene samples, so obtained, were found to be identical with those of High Density Polyethylene. It is concluded that most PVC polymers contain only very few long branches, if any

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