SynopsisThis paper reports on the gas sorption and transport properties of poly(viny1idene fluoride) (PVF,) and on the effects uniaxial drawing and processing temperature have on these prop erties. Sorption and transport were first examined for "as-received" commercial Kynar PVF2 film at 35°C. This film was 54% crystalline by weight. Solubility, diffusion, and permeability coefficients were measured for He, H2, Ar, 0 2 , Nz, CH,, and COz. The solubility coefficient and the diffusion coefFicient D were correlated with the Lennard-Jones potential and mean molecular diameter of the gas, respectively. Uniaxial drawing of PVF, films was performed up to a draw ratio of 3.7 and over the temperature range 75-140°C. Transport properties were correlated with the extent of draw and drawing temperature. The permeability P and D were found to significantly decline with uniaxial drawing; the magnitude of this effect was dependent on both the drawing temperature and the molecular size of the penetrant considered. Reductions in P and D became progressively more pronounced with increasing molecular diameter and with decreasing drawing temperature (down to a limit of about 75"C), which reflects an increase in effectiveness of drawing at low temperatures. PVFz films annealed above 75°Cshowed a n increase in P and D as opposed to the effect of drawing. The solubility of various gases in PVF2 was not found to be sensitive to processing treatments such as drawing and annealing, in agreement with the relatively small changes observed in free volume. PVF2 films subjected to various treatments were characterized by DSC, density, birefringence, and dynamic mechanical measurements. Gas transport measurements appear to provide a more sensitive and hence more viable measure of the effectiveness of drawing than these other techniques. Drawing PVF2 in the melt state was found to increase P and D, in contrast with the effects observed for solid-state drawing. The results have been interpreted in terms of existing theories on morphology and microstructure in semicrystalline polymers. INTRODUCTIONIn an earlier paper' we reported a detailed study of the gas sorption and transport behavior of poly(viny1 chloride), a glassy and primarily amorphous material, and how these characteristics are influenced by uniaxial drawing and heat treatment. The latter processing steps were found to have substantial effects on the transport properties of PVC. In the present work, we focus on the effects of drawing and thermal treatments on gas transport in poly(viny1idene fluoride) (PVF,), which is a semicrystalline polymer whose amorphous fraction is rubbery at room temperature.PVF2 is a good barrier material, having gas permeabilities of the same order as those for PVC, and has excellent chemical resistance. PVFp is now finding some commercial uses in miscible blends with poly(methy1 methacrylate) for applications requiring good barrier performance and resistance to harsh chemical environments. These factors prompted us to examine the effects of uniaxially drawing...

SynopsisSorption and transport measurements for various gases in rigid poly(viny1 chloride) were made following uniaxial drawing and heat treatment. The permeabilities of He, Ar, N,, and CHI were found to be essentially independent of pressure in PVC while CO, showed a complex pressure dependence which varied with prior exposure and degassing history. Sorption is* therms were analyzed by the dual mode sorption model, and the parameters obtained were correlated with the Lennard-Jones potential-well depth of the gas. The Henry's law coefficient for CO, was found to be significantly larger than expected which is believed to be the result of a specific interaction with PVC. Uniaxial drawing of PVC above its glass transition caused significant reductions in gas permeabilities, of which roughly one-third is attributable to the accompanying heat treatment rather than molecular orientation per se. The physical state of the polymer was characterized by density, birefringence, and calorimetry. Changes in gas sorption and permeation behavior are discussed in terms of these results.

A new method for the formation of high molecular weight aromatic biphenylene polymers via the nickel coupling of aromatic dichlorides is described. Aromatic biphenylene polymers display a number of highly attractive features which are discussed. The novel reaction is performed in a dry aprotic solvent (e.g., in DMAC) using catalytic amounts of zero‐valent nickel, triphenylphosphine ligand and excess zinc metal. The reactions must be performed under an inert atmosphere and in the absence of water. In order to obtain high polymer, one must use low amounts of nickel, high triphenylphosphine/nickel ratios, excess zinc metal, and moderate temperatures (70 °C). Variables such as the choice of ligand or co‐ligand, salt addition, ligand and zinc concentration, etc … allow for optimization of the reaction efficiency. The method is general and allows for the preparation of an almost infinite variety of polymers. Polymerizations and copolymerizations involving aryl dichlorides possessing dissimilar chloro‐moieties are particularly intriguing since a number of sequence distributions are possible. The two prerequisites for a successful preparation of high molecular weight product are solubility of the monomer, and more particularly of the obtained polymer, in the reaction medium; and the necessity that any functional groups present in the monomer(s) (and in the resulting polymer) be inert toward the zinc/nickel system. Critical features of the polymerization mechanism are also reviewed.

SynopsisA study was conducted on the gas sorption and transport properties of a multiphase commercial acrylic polymer tradenamed Korad ACV before and after subjecting the polymer to mechanical drawing operations. The Korad system is a n emulsion-polymerized amorphous composite comprised of a glassy, predominantly PMMA matrix phase and a poly(buty1 acry1ateMispersed phase surrounded by a PMMA/PBA copolymer shell. Large increases (up to eightfold) in permeability P to several gases were observed upon drawing Korad. The observed changes in the permeability to He, Ar, Nz, and CH, on drawing were correlated with the draw ratio, drawing temperature, and molecular diameter of the gas penetrant. Most of the increase in permeability occurred at low draw ratios (1-2). The increases in P were most dramatic for drawing temperatures below or near the Tg of the matrix phase (about 90T) and were quite small for drawing temperatures 30°C or more above the matrix T,. The extent of the permeability increase also depended on the gas, being greatest for CHI and essentially imperceptible for He. The changes in permeability behavior were interpreted in terms of a morphological transformation in the phase of the drawn Korad, which causes the originally dispersed rubber particles to assume a more continuous character. The behavior of the composite was modeled by the Takayanagi and Nielson treatments of tw*phase composite systems. Volumetric, thermal, mechanical, and viscoelastic properties were measured for the as-received and processed Korad films to elucidate physical changes in the drawn polymer.

This article discusses the synthesis, properties, fabrication, and uses of aromatic polysulfones. These polymers are a class of high performance amorphous thermoplastics characterized by high glass‐transition temperatures, good mechanical strength and stiffness, and excellent thermal and oxidative resistance. They are used in a broad range of engineering applications and continue to find new uses as demands for high temperature plastic materials proliferate. The characteristic structural feature of these polymers is the presence of the para‐linked diphenylsulfone group as part of the backbone repeat unit. Emphasis of the discussion is placed on the three commercially available polysulfones, ie, those based on the polycondensation of 4,4′‐dihalodiphenylsulfone with bisphenol A, 4,4′‐dihydroxydiphenylsulfone, and 4,4′‐dihydroxydiphenyl, respectively. Polymerization techniques discussed include nucleophilic and electrophilic polycondensation routes. Property discussions touch on structure and property relations, thermal, physical, and mechanical properties, as well as other performance characteristics. Blendability of polysulfones with other polymers is also briefly discussed. Applications and uses for polysulfones are described as they pertain to specific resin performance features. Also included is information about commercial sources and costs for these materials.