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A rotating mandrel in a tubing die produces multiaxial orientation in the extruded melt. If the polymer melt is quenched rapidly, some multiaxial orientation is retained in the resultant tubing. Multiaxially oriented tubing exhibits reduced crack propagation and some enhancement of yield and fracture strengths. During the processing of multiaxially oriented tubing, relaxation occurs after the melt leaves the die and gives rise to wall thickening and reduction in the lumen of the tubing; the magnitude of these effects is a function of the rate of mandrel rotation.

Polymerization rates a t 60 and 95 "C. and molecular weights have been measured for vinyl benzoate. Copolymerization and branch sites in the polymer involving the aromatic ring were h n d t o Le subtantially absent. The rate of polymerization was found tn-he proportional to the square root of the initiator concentration and to the reciprocal of the degree of polymerization. The slow polymerization rate is explained in terms of reversible complex formation between the vinyl radical and the aromatic ring. ZUSAMMENFASSUNG:Die Polymerisationsgeschwindigkeiten bei 60 und 95 "C sowie Molekulargewichte fiir die Polymerisation des Vinylbenzoats wurden bestimmt. Es wurde gefunden, daR der aromatische Ring weder zu Copolymerisation noch zu Kettenverzweigungen AnlaR gab. Die Polymerisationsgeschwindigkeit ergab sich proportional zur Quadratwurzel aus der Starterkonzentration und proportional zum reziproken Polymerisationsgrad. Die niederen Werte der Polymerisationsgeschwindigkeit wurden durch die Annahme einer reversiblen Komplexbildung zwischen dem Vinylradikal und dem aromatischen Ring erklart.

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A model dimer of acrylonitrile (2,4 dimethylglutaronitrile) was synthesized and separated into an isotactic (meso) isomer, m.p. = 8.8"C., and a syndiotactic (racemic) isomeg m.p. = 50°C. Infrared and NMR spectra of the dimers were measured. The methylene protons of the isotactic dimer resonate at a lower magnetic field strength and show a more complex spiu-spin splitting than the syndiotactic methylene protons. ZUSAMMENFASSUNG:Ein Modell eines dimeren Acrylnitrils (2,4.-Dimethylglutaronitril) wurde synthetisiert und in eine isotaktische (meso) Form, Schmp. = 8,8"C, und eine syndiotaktische (racem.) Form, Schmp. = 50 "C, aufgetrennt. Ultrarot-und Kernresonanzspektren der Dimeren wurden gemessen. Die Methylenprotonen des isotaktischen Dimeren zeigten Resonauz bei geringerer magnetischer Feldstiirke sowie eine kompliziertere Spin-Spin-Aufspaltung als die Methylenprotonen der syndiotaktischen Form.

Copolymers of sulfur dioxide and butadiene, isoprene, 2,3‐dimethylbutadiene, and chloroprene were prepared by irradiation at low temperatures with remarkably high efficiency. The polymers were all insoluble in the monomer mixtures and therefore only limited kinetic data could be obtained. However, the following conclusions could be reached from the data. Isoprene, butadiene, and 2,3‐dimethylbutadiene all produced 1:1 copolymers with sulfur dioxide across a wide range of temperature and composition. At high sulfur dioxide contents the cyclic sulfones began to form. Chloroprene behaved differently in that copolymers containing considerably more than 50 mole‐% of chloroprene were obtained. Also, the infrared spectra revealed a considerable proportion of pendant vinyl groups as compared with the predominately 1,4 addition in the case of the other dienes studied. The isoprene and 2,3‐dimethylbutadiene polymers were found to be soluble in highly polar solvents containing dissolved salts. At lower temperatures the radiation caused concurrent degradation of the polymer. The compositions of isoprene, 2,3‐dimethylbutadiene and sulfur dioxide terpolymers were found to be unusually sensitive to the polymerization temperature. Thermal gravimetric analysis of the various polymers showed thermal stabilities in the order, 2,3‐dimethylbutadiene > isoprene and butadiene > chloroprene. A sample of tetramethylene polysulfone prepared chemically showed greatly enhanced thermal stability, catastrophic degradation beginning about 100°C. higher than the corresponding butadiene copolymer. Attempts to hydrogenate the diene copolymers were unsuccessful although the corresponding cyclic sulfones were hydrogenated successfully. The highly efficient radiation polymerizations are believed to be free radical in nature and to proceed via monomer complex function. The difficulty of chain termination between sulfonyl radicals is suggested as a reason for the very high yields and molecular weights obtained at low temperatures.