Showing papers on "Surface modification published in 1976"

Polymer composites containing plasma‐treated mica. I. Flow and mechanical properties

Abstract: Suzorite mica has been surface modified by microwave plasma treatment in ethylene gas. The surface-treated mica was used as a filler in polyethylene, polystyrene, and a mixture of these two polymers. Significant changes in rheological behavior ensue. These indicate that adhesion between polyethylene and irradiated mica is superior to that of interfaces using unirradiated mica. In contrast, ethylene irradiation reduces the ability of filled polystyrene compounds to store elastic energy in melt flow, an effect consistent with impaired adhesion at interfaces involving these components. An intermediate situation exists in the case of the two-polymer blend. The tensile properties of these systems also reflect surface treatment, reinforcement occurring in polyethylene-containing compounds, while the tensile properties of polystyrene composites deteriorate. Plasma-induced surface modifications of fillers to produce desired property changes in specified polymer matrixes are implied by the present work, but a fuller understanding of the chemistry of surface modification reactions is needed to substantiate these implications.

Platelets, foreign surfaces, and heparin

Abstract: These studies clearly indicate that heparin has 2 antagonistic effects in this platelet-foreign surface interaction; it acts directly on platelets to increase retention, while acting on the foreign surface to reduce platelet retention, perhaps by competing for cationic sites. This study also suggests that it is unlikely that heparin bonding confers reduced surface thrombogenicity by virtue of the ability to leach off that surface and that further studies in heparin bonding or other surface modification should consider the antiplatelet effect which can easily be studied in vitro.

Surface modification of polyethylene by radiation-induced grafting for adhesive bonding. I. Relationship between adhesive bond strength and surface composition

Abstract: A number of vinyl monomers have been surface grafted onto a polyethylene sheet by the mutual irradiation in monomer vapor and by a trapped-radical technique. The surface composition of the grafted sheets has been determined by means of ATR infrared spectrophotometry and compared with the peel strength of the joints bonded with conventional structural adhesives. In the methyl acrylate grafts followed by a saponification treatment, only the surfaces having graft compositions of more than 80 mole-% methyl acrylate give a high peel strength. A similar relationship between peel strength and surface composition is found in the surface grafts of vinyl acetate, acrylic acid, acrylamide, and methylolacrylamide. It is concluded that the formation of a surface with such a high monomer content is a necessary condition for the strong adhesive bonding of grafted polyethylenes at bonding temperatures below the softening point. Moreover, the adhesive bondability of the highly modified surfaces with epoxy adhesives is significantly enhanced by the introduction of carboxy and carbamyl radicals.

Chemistry of Abietic Acid

Abstract: The study of the chemical conversion of l-abietic acid (1), main component of pine rosin, into optically active natural products with biological activity has been developed at the Institute of Physical and Chemical Research by the late Dr. Akira Tahara. This group's recent works are reviewd for his memory by his staffs.Various types of the acid rearrangements in phenacylidene derivatives of (1) were disclosed and applied to the syntheses of the A-ring substituted diterpenes and a possible intermediate to grayanotoxins. Selective functionalization at 11-, 13-and 14-positions of the aromatic C-ring were established. The 11-substitution reaction was applied to the synthesis of taxodione. Ozonolysis of the phenolic C-ring was proved to be a convenient method for the cleavage of the ring and used for the short-step synthesis of drimane-type sesquiterpenes. Modifications of the isopropyl group, including its methyl migration, made it possible to synthesize d-phyllocladene, d-kaurene, and the skeletons of pimaric acid and steroids. Finally, the synthesis of gibberellin A12 was completed by the combination of the skeletal transformation and the functionality modification of (1).

The effect of chemical modification of the surface of a filler on the behaviour of a polymer in boundary layers of different thickness

Abstract: Polymeric compositions on the surface of Aerosil modified with organic compounds, at different concentrations of the filler in the polymer systems, i.e. with interlayers of different thickness, have been investigated by the dielectric relaxation method. It was found that the variation in the properties of the surface layer of polymer as the thickness of the layer is changed, is not uniform. Modification of the surface does not affect the nature of the change in molecular mobility in the boundary layer.