Showing papers on "Polystyrene published in 1971"

Pressure‐Volume‐Temperature Properties and Transitions of Amorphous Polymers; Polystyrene and Poly (orthomethylstyrene)

Abstract: An apparatus based on Bridgman's bellows method, originally devised for fluids, has been constructed for use with solid samples. Mercury is employed as the confining liquid. The operating range is 0≤t≤200 °C and 1≤P≤2000 bar. Calibration with benzene and mercury shows an accuracy of ±2×10−4 cm3/g in the measurement of the specific volume change. A detailed investigation of two systems, polystyrene and poly(orthomethylstyrene) in the glassy and liquid states is undertaken. The P‐V‐T results in both states can be well represented by the Tait equation, with the single parameter B as an exponentially decreasing function of T. Similar to the earlier result for polystyrene, a β‐relaxation region is observed in terms of the isothermal compressibility of the methylated polymer with Tβ/Tg≃0.70 for both. The pressure coefficients for the two transition temperatures are discussed. For the glass transition, the Ehrenfest‐type equation appears to be obeyed by the low‐pressure glasses (formed by cooling the liquid at a...

Equation-of-state parameters for polystyrene

Abstract: The absolute density, thermal expansion coefficient α, and thermal pressure coefficient γ have been determined for atactic polystyrene in the non-glassy liquid (or amorphous) state. Dilatometric measurements on the pure polymer furnished α over the range 100° to 230°C. Thermal pressure coefficients were determined by extrapolation from measurements on concentrated solutions of the polymer in benzene, from 24° to 100°C. No evidence was found for a second order transition above 100°C. A small change in dα/dT was observed near 170°C. This and other observations suggest a minor departure from equilibrium below this temperature.

Colloidal and morphological behavior of block and graft copolymers : proceedings of an American Chemical Society symposium held at Chicago, Illinois, September 13-18, 1970

Abstract: Micromorphology-Property Relationships in Graft and Block Copolymers.- The Effect of Environment on the Morphology of Styrene-Butadiene Block Copolymers.- Light Scattering from Two-Phase Polymer System having Spherical Domain Structure.- Deformation Mechanism of Elastomeric Block Copolymers.- The Synthesis and Dilute Solution Properties of Styrene-Siloxane ABA Block Copolymers.- Properties of Polystyrene-Polydimethylsiloxane Block Copolymers.- Solvent Interactions of Poly(Diphenylsiloxane-Block-Dimethylsiloxane-Block-Diphenylsiloxane) Copolymers.- Structure and Function of Biological Membranes.- The Effect of an Oxidative-Caustic Environment on Graft Copolymer Membranes.- Microphase Separation in Organic Polymers Containing Ions.- Ionomer Graft Copolymers of Polystyrene-Polybutylacrylate.- Infrared Dichroism of Segmented Polyurethane Elastomers.- Emulsifying Effects of Block and Graft Copolymers-Oil in Oil Emulsions.- ABS Polymer as a Colloidal Dispersion.- Formation of High Impact Polystyrene from Blends of Polystyrene with Butadiene/Styrene Block Copolymers.- Morphology and Deformation Behavior of Crosslinked Butylacrylate Copolymer Gels, Prepared by Graft Reactions.- Microphase Separation in Mixtures of Block Copolymers with the Corresponding Homopolymers: Zeroth Approximation.- Dilute Solution Behavior of Copolymers.- The Adsorption Behavior of Polystyrene-Poly(Methyl Methacrylate) Mixtures Containing Block Copolymers.- Dilute Solution Behavior of Block Copolymers : Sytrene-Methyl Methacrylate and cx-Methyl Styrene-Methyl Methacrylate Systems.- Surface Morphologies of Styrene-Ethylene Oxide Block Copolymers.- Interfacial Morphology and Autohesion of A-B-A Triblock Copolymers.- Influence of Morphology on the Viscoelastic Behavior of a Solvent-Cast S-B-S Block Copolymer.

Pressure-sensitive hot melt adhesives

Abstract: A pressure-sensitive adhesive composition having instant room temperature tack, good cold flow resistance and good shear strength which comprises as a first component a resinous rubbery block copolymer of styrene and butadiene or isoprene, as a second component a rubber extending petroleum oil, as a third component a modified or unmodified rosin, a coumarone-indene resin, a polyterpene resin, a diene-olefin aliphatic hydrocarbon resin or a polystyrene resin, and as a fourth component a resinous atactic polypropylene.

Time‐dependent heat capacity in the glass transition region

Abstract: Time-dependent, apparent heat capacities of glucose, poly(vinyl chloride), polystyrene, selenium, poly(methyl methacrylate), and poly(2,6-dimethyl-1,4-phenylene ether) in the glass transition region were determined by differential thermal analysis. The thermal history was set by linear cooling at rates between 0.007 and 160°C/min. Linear heating for analysis was carried out at rates between 0.3 and 600°C/min. Average activation energies of 52, 81, 90, 54, 77, and 108 kcal/mole, respectively, were evaluated by using the hole theory of glasses previously developed. Within experimental limitations all data could be described quantitatively by the theoretical expressions using only one parameter, the number of frozen-in holes, to described the thermal history. Experimental and theoretical limitations are discussed.

The effect of molecular weight and orientation on the sorption of n-pentane by glassy polystyrene

Abstract: The effects of polymer molecular weight, molecular weight distribution, and orientation on the rate of relaxation-controlled sorption of n-pentane by glassy polystyrene were studied. The sorption follows Case II kinetics but for films which sorb slowly the sorption rate increases at relatively long times until sorption is sharply terminated. This rate increase may be explained by the development of dispersed microvoids within the unrelaxed film core. Overshoot of the equilibrium n-pentane content occurs in sorption experiments in which accelerated sorption is pronounced. The sorption rate is independent of polymer molecular weight and molecular weight distribution per se over a broad wrange of these parameters. Essentially identical vapor sorption kinetics were observed for well annealed polystyrene films of different molecular weights and distributions. Conversely, for vapor sorption by uniaxially oriented films and for liquid sorption by partially annealed films, high molecular weight film (1,880,000) exhibits greater sorption rates than low molecular weight film (ca. 200,000). These differences in rate are not due to molecular weight differences per se, but are a consequence of the dissimilar response of free volume and strain development for films of different molecular weight prepared with a given time-temperature-strain history. Crazing of carefully annealed polystyrene films occurs during desorption of n-pentane from partially saturated films. The depth of craze penetration reflects the point of advance of the discontinuous Case II sorption boundary.

Method for making imido-substituted aromatic polymers

Abstract: A FRIEDEL-CRAFTS'' ALKYLATION METHOD IS PROVIDED FOR INTRODUCING IMIDO-ALKYLENE SUBSTITUTION, SUCH AS MALEIMIDOMETHYLENE-SUBSTITUTION, INTO A VARIETY OF ORGANIC POLYMERS HAVING CHEMICALLY-COMBINED AROMATIC CARBOCYCLIC ORGANIC RADICATS, EITHER IN THE POLYMER BACKBONE SUCH AS POLYARYLENESULFONES, POLYARYLENEOXIDES, POLYARYLENECARBONATES, POLYARYLENE ESTERS, POLYPHENYLENE, ETC., OR AS PENDANT RADICALS ALONG THE POLYMER CHAIN, SUCH AS POLYSTYRENE, POLY (STYRENE-VINYLIC OR, DIENIC COPOLYMERS OR TERPOLYMERS) ETC. REACTION IS EFFECTED BETWEEN AN IMIDO-METHYLENE COMPOUND AND AN ORGANIC POLYMER HAVING CHEMICALLY-COMBINED AROMATIC CARBOCYCLIC ORGANIC RADICALS IN THE PRESENCE OF A FRIEDEL-CRAFTS'' CATALYST, SUCH AS BORON TRIFLUORIDE. THE IMIDO-ALKYLENE-SUBSTITUTED AROMATIC CARBOCYCLIC ORGANIC POLYMERS CAN BE EMPLOYED IN MAKING MOLDING COMPOUNDS, LAMINATES, VARNISHES, ETC.

Photochemical and thermal isomerization in polymer matrices: Azo compounds in polystyrene

Abstract: Photochemical and thermal geometrical isomerizations of monoazo compounds have been studied in polystyrene–n-butylbenzene compositions. Cis–trans isomer ratios established by light absorption were found to depend on matrix viscosity. Where the compositions were above their respective glass temperatures, all thermal isomerizations conformed to first-order kinetics. Where compositions were below their respective glass temperatures, the initial isomerization rates were abnormally fast, decaying to normal first-order processes after substantial amounts of reaction had taken place. These effects have been interpreted in terms of the vitreous properties of polystyrene.

Thermal conductivity of polymer melts

Abstract: A concentric cylinder conductivity cell with guard heaters was constructed and used to determine the thermal conductivity of polymer melts. Thermal conductivity was found to be a linear function of temperature for the melts studied, and the thermal conductivity decreased as the complexity of the polymer chain increased. The polymers studied were a linear polyethylene, branched polyethylene, polypropylene, polystyrene, nylon 6, and nylon 6,10. The measurements are precise to within ±6%.

Coordination catalysts for the selective hydrogenation of polymeric unsaturation

Abstract: The selective hydrogenation of poly-1,4-butadiene in the presence of poly-1,4-isoprene is described. Both of these polydienes are hydrogenated more easily than polystyrene. The catalysts which effect these selective hydrogenations are made by the reaction of organoaluminum or lithium compounds with transition metal salts of 2-ethylhexanoic acid.

Effect of matrix rigidity on the reactions of aromatic nitrenes in polymers

Abstract: The main products of the photolysis of aromatic azides in matrices of polystyrene, paraffin wax, polyisoprene and some other polymers are primary and secondary amines The yield of secondary amine in the matrix depends strongly on the rigidity of the polymeric system Matrix rigidity affects also the reaction kinetics of the nitrene intermediate, lifetimes of photogenerated triplet nitrenes being up to three orders of magnitude longer in rigid matrices than in plasticized materials From the results of flash photolysis experiments, it is concluded that in the rigid matrix the rate of interaction between a reactive species and the polymer is not controlled by the chemical reactivities of reactant and substrate, but by a steric rearrangement of the polymer chain in the vicinity of the reactive site

Steady flow and dynamic viscosity of branched butadiene–styrene block copolymers

Abstract: Steady flow and dynamic viscosities were determined for symmetrical linear and starbranched block copolymers of butadiene and styrene above their upper (polystyrene) glass transition. Block structures examined were B-S-B, (B-S-)3, S-B-S, (S-B-)3 and (S-B-)4. At constant molecular weight and total styrene content viscosities were greater for polymers terminating in styrene blocks, irrespective of branching. Branching decreased the viscosity of either polybutadiene-terminated or polystyrene-terminated block polymers, compared at equal Mw. However, comparisons at equal block lengths showed that the length of the terminal blocks, not the total molecular weight, governs the viscoelastic behavior of these polymers to a surprisingly good approximation. This unusual result is rationalized in terms of the two-phase domain structure of these polymers, which persists to a significant degree in the melt. Below the glass transition of the polystyrene blocks the effects of branching were masked by differences in the morphology of the domain structure unrelated to branching.

Pulpal Protection by a Cavity Liner Applied As a Thin Film Beneath Deep Silicate Restorations

Abstract: Before deep silicate restorations were placed in 40 contralateral pairs of permanent premolars, a thin film of a polystyrene liner was applied in one randomly chosen cavity of each pair. The observation periods were one and four weeks. In all but one of the 40 teeth, the liner gave satisfactory protection.

The production of rubber‐modified polystyrene. I. Rheological behavior of the polymerizing system

Abstract: The rheological behavior of the two-phase systems consisting of a polystyrene-in-styrene phase distributed in a rubber-in-styrene phase is shown to exhibit increasing non-Newtonian behavior up to the phase inversion point, as a consequence of its two phase nature. The equation is recommended for the prediction of the viscosity of the polymerizing mass up to phase inversion during the production of HIPS by the in situ bulk polymerization of styrene in the presence of dissolved rubber.

Effect of pressure in capillary flow of polystyrene

Abstract: Several corrections possibly required for capillary flow are based on the existence of a linear relationship between the pressure drop along the capillary and the length-to-diameter ratio at a given temperature and shear rate. Recently, the appearance of nonlinearities in this relationship has created some concern as to the cause of this behavior. The occurrence and an explanation of the nonlinearities for polystyrene form the basis of this study. A narrow-distribution, low molecular weight (20,400) polystyrene was tested in eight capillaries at temperatures of 140 and 160°C to initiate the discussion of the nonlinearity in a ΔP (pressure) versus L/D (length/diameter of capillary) plot. The sample exhibits negligible extrudate swelling at all pressures which reinforces the idea that pressure is influencing the flow. The pressure dependence of viscosity is determined using the equivalent expression of the WLF equation derived from free volume theory. Justification for its use is presented. A pressure correction, representing the increased shear stress necessary for flow of the higher viscosity material, is found to linearize the ΔP versus L/D data. A narrow-distribution, high molecular weight polystyrene (670,000) is subjected to a similar analysis at 165°C by using nine capillaries. The situation is quite different, as the high molecular weight sample is not nearly as ideal as the low molecular weight polystyrene.