Showing papers on "Polystyrene published in 1973"

The preparation and characterisation of polymer latices formed in the absence of surface active agents

Abstract: Methods have been devised for the formation of monodisperse polystyrene latices in the absence of added surface active agents. The particles are stabilised, as a colloidal dispersion, by surface groupings which are an integral part of the particle and are not removed by dialysis. By suitable variation of the ionic strength of the aqueous phase, the initiator concentration and the polymerisation temperature, the final particle size obtained in single-stage reactions was varied between c. 0.15 and 1.0 μm. The coefficient of variation on particle diameters was usually less than 5%. The ionic strength of the aqueous phase was found to play an important part in determining particle size; this was explained in terms of a limited coagulation process occurring at the stage involving the nucleation of polymer particles. Conductometric titration experiments revealed the presence of sulphate, carboxyl and hydroxyl groups on the particle surfaces. Molecular weight determination of the polystyrene formed showed that this was lower than that formed in conventional emulsion polymerisation.

Acrylate and methacrylate terminated polystyrene macromolecular monomers having a substantially uniform molecular weight distribution

Abstract: This application discloses a copolymerizable macromolecular monomer having a substantially uniform molecular weight distribution such that its ratio of Mw/Mn is not substantially above about 1.1, wherein Mw is the weight average molecular weight of the macromolecular monomer, and Mn is the number average molecular weight of the macromolecular monomer, said macromolecular monomer being represented by the structural formula:

Solvent crazing of “dry” polystyrene and “dry” crazing of plasticized polystyrene

Abstract: The critical strain ec for crazing of polystyrene in each of a variety of organic liquids has been measured along with the degree of swelling of the polymer by the liquid and the attendant reduction in the glass transition temperature Tg of the polymer. The critical strain for the crazing in air and the Tg of each of a set of specimens molded from mixtures of o-dichlorobenzene and polystyrene have also been determined. Correlations of ec with Tg in the two cases are identical within experimental error for the first 40°C of Tg reduction; these results imply (1) that organic liquids do not exercise a significant surface energy role in solvent crazing and (2) that their only roles are associated with flow processes. Correlation of solvent crazing ec with solubility parameter of the crazing fluid is very poor for several reasons that are discussed.

A deformational mechanism in particulate‐filled glassy polymers

Abstract: : The stress-strain behavior of glass bead filled polystyrene, styrene- acrylonitrile, ABS, and PPO composites is studied at various temperatures below their glass transition temperature. Earlier studies of bead filled composites indicated that the addition of filler decreases toughness and ultimate elongation. Results show this is true for certain conditions; however, it is also possible for such composites to have higher toughness and ultimate elongation than the unfilled matrices. A deformational mechanism, involving crazing of the matrix, is proposed which explains this behavior.

A study of bicomponent coextrusion of molten polymers

Abstract: An experimental study has been carried out of coextruding polystyrene with lowdensity polyethylene and polystyrene with high-density polyethylene, using both slit and circular dies. Two melt streams were separately fed to the die entrance and forced to flow side by side through a die. When using the slit die, wall normal stresses were measured with three melt pressure transducers flush-mounted on each of the rectangle's long sides, directly opposite each other. When using the capillary die, three different capillary length-to-diameter (L/D) ratios were employed: 4, 11, and 18. Wall normal stresses were measured for dies having L/D ratioes of 11 and 18 only. The measurements of wall normal stresses permitted one to determine the pressure gradient, and hence the viscous property. For each set of extrusion conditions (L/D ratio, flow rate, and component ratio), extrudate samples were collected. These were later carefully cross sectioned and photographed in order to examine the shape of the interface between the two components. At the phase interface of the polystyrene/low-density polyethylene system, it has been observed that the polystyrene, which is more viscous and yet less elastic than the low-density polyethylene, has a convex surface. However, at the phase interface of the polystyrene/high-density polyethylene system, the high-density polyethylene, which is more viscous and also more elastic than polystyrene, is seen to be convex. This then appears to indicate that the viscosity ratio of two components is primarily responsible for the final shape of the interface.

Deposition of latex particles on to a planar surface

Abstract: The theory of the mass transport of a negatively charged colloid onto a negatively charged substrate in a rotating disc system may be modified to take into account the energy barrier arising from electrostatic forces at low electrolyte concentrations and the deposition of aggregates at higher electrolyte concentrations. The deposition of polystyrene latex particles onto a smooth polystyrene surface has been studied as a function of electrolyte concentration and the results are consistent with the theoretical predictions. The stability ratio for deposition is found to be very sensitive to the potential on the deposition surface, which is considerably smaller than the potential of the latex particles.

Laminate for refrigeration apparatus, refrigerator and method of forming same

Abstract: A laminate especially useful in refrigeration applications which includes a sheet of rubber-modified polystyrene, a film of rubber-modified copolymer of styrene and acrylonitrile acting as a buffer and in contact with a sheet of polyurethane foam. A refrigeration cabinet and method of forming same utilizing such laminate are likewise disclosed.

Dynamic thermogravimetric analysis of polystyrene: Effect of molecular weight on thermal decomposition

Abstract: A dynamic TGA method was used to study the effect of the molecular weight of well-defined polystyrene samples as well as the effect of heating rate and sample weight on the kinetic parameters of the thermal decomposition. It is shown that the maximum rate, the average specific rate, and the activation energy of the decomposition increase up to molecular weights of about 360,000 and then level off. The activation energy for the first part of the decomposition was 33 ± 5 kcal/mole and 50 ± 5 kcal/mole for the second part. An activation energy of 42 ± 5 kcal/mole was determined for the overall decomposition of polystyrene.

Well-Characterized Monodisperse Latexes as Model Colloids

Abstract: Monodisperse polystyrene latexes prepared with persulfate-ion initiator can be ion exchanged to remove the adsorbed emulsifier and solute electrolyte. Rigorous purification of the ion-exchange'resi...

Graft copolymer modification of polyethylene–polystyrene blends. I. Graft preparation and characterization

Abstract: The preparation and characterization of styrene–low-density polyethylene graft copolymers for addition to blends of polyethylene and polystyrene to improve blend mechanical properties is described. The direct method of grafting with 60Co radiation was employed using the polyethylene in pellet form. This approach gave good grafting efficiency with maximum yields limited to about 1 g of styrene reacted per gram of polyethylene. Excessive crosslinking at radiation doses beyond about 1 mrad was detrimental to the melt processibility of the graft. Crystallinity, dynamic mechanical properties, morphology, and stress–strain behavior of the grafts were examined and compared with melt blends of similar composition in order to better characterize the material produced.

Photodecomposition of polystyrene on long-wave ultraviolet irradiation: A possible mechanism of initiation of photooxidation

Abstract: The long-wave (λ < 3000 A) photo-oxidation of polystyrene in solution at 25°C has been studied osmometrically. Two types of chain scission have been observed: a purely photo process which occurs completely independently of oxygen and which is attributed to fission of photolabile groups in the polymer, and another process associated with random photolyses of the products of oxidation Scavenger experiments with 131I2 have shown that approximately two iodine atoms are incorporated per chain scission when photolysis is carried out in solution (benzene, hexafluorobenzene, methylene chloride) under high vacuum conditions in the presence of 131I2. No iodine incorporation or chain scission occurs when ionically prepared polystyrenes are treated similarly. The nature of the photolabile bond has been discussed, and there is some evidence for a peroxidic linkage arising from oxygen copolymerization in the chains. It is suggested that fission of the photolabile groups contributes to the initiation of the long-wave photooxidation of the polymer.

Method of preventing corrosion in connection with extrusion of mixtures containing polyvinyl chloride and wood flour or similar cellulosic material, and analogous mixtures containing polystyrene or acrylonitrile-butadiene-styrene resin, respectively

Abstract: The invention provides a method of preventing corrosion and wear caused by corrosion in connection with extrusion of a mixture containing polyvinyl chloride and wood flour or similar cellulosic material and analogous mixtures with polystyrene or acrylonitrile-butadiene-styrene resin, respectively. In order to neutralize acidic gaseous matter originating from the cellulosic material contained in the mixture, the extrusion is effected in the presence of at least one gaseous alkaline compound.

Graft copolymer modification of polyethylene--polystyrene blends. II. Properties of modified blends

Abstract: The use of graft copolymers of styrene onto polyethylene as additives to improve the mechanical properties of polyethylene–polystyrene blends is described. Blends containing equal proportions of low-density polyethylene and polystyrene were selected for this study since this composition represents the poorest balance of properties in this system. Graft addition generally increased both the yield strength and the elongation at break of the blend. Of the grafts employed, those prepared at an irradiation dose near 0.5 megarad appear optimal for this purpose. These conditions apparently balance the beneficial effects of grafting extent and the detrimental effects of crosslinking, both of which increase with irradiation dose.

Alpha-olefin terminated polystyrene macromolecular monomers having a substantially uniform molecular weight distribution

Abstract: This application discloses a copolymerizable macromolecular monomer having a substantially uniform molecular weight distribution such that its ratio of Mw/Mn is not substantially above about 11, wherein Mw is the weight average molecular weight of the macromolecular monomer, and Mn is the number average molecular weight of the macromolecular monomer, said macaromolecular monomer being represented by the structural formula:

Vapor sorption and liquid interactions with glassy polyblends of polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)

Abstract: Polystyrene, poly(phenylene oxide), and solution-cast blends of the parent homopolymers were exposed to normal hexane in the liquid and vapor phase. The kinetics of absorption and desorption, the sorption equilibria, and the kinetics of morphological changes were studied as a function of temperature and blend composition. Absorption kinetics of n-hexane vapor in all blends were largely controlled by polymer relaxations. The sorption rates from the vapor phase varied monotonically with blend composition and increased over a range of four orders of magnitude with increasing poly(phenylene oxide) content. The equilibrium n-hexane content similarly increased monotonically with poly(phenylene oxide) content although the increase was only by a factor of two over the entire range of compositions. These results were interpreted in light of and were completely consistent with earlier findings with pure polystyrene homopolymer. Films immersed in liquid n-hexane produced a white, opaque outer shell surrounding an essentially unaffected central core. The kinetics of this whitening process were much more rapid for each of the homopolymers than the kinetics characterizing morphological changes in the blends. These data suggest that film whitening is caused by crazing in the polystyrene-rich samples and that solvent-induced crystallization is involved in the whitening of the poly (phenylene oxide) rich material.

Composition of a polyphenylene ether and a block copolymer of a vinyl aromatic compound and a conjugated diene

Abstract: There are provided compositions comprising (a) a polyphenylene ether, (b) an elastomeric block copolymer and (c) a high impact rubber modified polystyrene resin or a blend of a high impact rubber modified polystyrene resin and a homopolystyrene resin.

Modulus reinforcement in elastomer composites. II. Polymeric fillers

Abstract: Blends were prepared with high-modulus “filler polymers,” polystyrene, polyamide, and poly(methyl methacrylate) dispersed in a low modulus matrix of ethylene/vinyl acetate copolymer. The modified Kerner equation was applied to dynamic mechanical data obtained on these blends, which may be considered to be model systems for thermoplastic elastomer block polymers. The implication of the interaction parameter, B, in terms of the reinforcing capability of each polymer as well as its optimum volume fraction in the blend, is discussed.