Graft copolymerization onto rubber. VII. Graft copolymerization of methyl methacrylate onto rubber using potassium peroxydisulfate catalyzed by silver ion

The graft copolymerization of methyl methacrylate onto natural rubber (NR) was carried out varying the concentration of monomer, initiator, thiourea, and silver nitrate over a wide range. The grafting reaction was temperature-dependent. From the Arrhenius plot, the overall energy of activation was computed. A suitable reaction scheme and rate expression for the rate of polymerization was suggested.     

Swift and Selective Reduction of Nitroaromatics to Aromatic Amines with Ni–Boride–Silica Catalysts System at Low Temperature

Various nitroaromatics are successfully reduced to amines with 100% conversion and selectivity in methanol at low temperature (≈5 °C), by using versatile system of 5% Ni–SiO₂ catalyst and NaBH₄ and in situ generation of Ni boride. The catalytic efficiency of Ni loading (5%, 10% and 15%) with silica or titania as support materials is investigated for reduction of nitrobenzene. The Ni–titania/NaBH₄ system recorded lower conversion and selectivity. The IR studies indicate that silica support does not have free –OH group on its surface. Thus the nickel boride is anchored to the silica to facilitate the catalytic process.     

Plastic Limit, Liquid Limit and Undrained Shear Strength of Soil—Reappraisal

The concept that plasticity index of soils can be defined as a range of water contents producing a 100-fold variation in undrained shear strength has been experimentally verified with the help of a large number of tests on soils of diverse nature. This has led to the redefinition of the plastic limit as the water content at which undrained shear strength is around 170 kN/m2. Undrained shear strength of a soil at the liquid limit can be considered to be around 1.7 kN/m2. Accordingly, both the liquid limit and the plastic limit have been determined in the present work by a single consistent method, i.e., the Swedish fall cone method. The undrained shear strength-water content relationship has been found to be log-linear for a wide range of water contents beginning from lower than the plastic limit to higher than the liquid limit. This resulted in the formulation of an expression for predicting undrained shear strength of a remolded soil at any water content based solely on its liquid limit and plastic limit.     

Polymers from renewable resources. I. Castor oil-based interpenetrating polymer networks: Thermal and mechanical properties

A number of polyurethanes (PUs) were synthesized by reacting castor oil with toluene-2,4-diisocyanate and hexamethylene diisocyanate and varying the NCO/OH ratio. All these polyurethanes were reacted with some acrylic monomers like ethyl acrylate, n-butyl acrylate, ethyl methacrylate, and butyl methacrylate using a crosslinker ethylene glycol dimethyl-acrylate and benzoyl peroxide as the initiator. The physicochemical properties of interpenetrating polymer networks (IPNs) are reported. Thermogravimetric analysis was used to study the thermal behavior of IPNs and the evaluation of kinetic parameters. Degradation mechanism has also been investigated. Some of the mechanical properties viz. tensile strength, shore-A hardness, elongation at break, etc. are also reported. © 1993 John Wiley & Sons, Inc.     

Alkylation of Benzene with Isopropyl Alcohol over SAPO-5 Catalyst in an Integral Pressure Reactor

The alkylation of benzene with isopropyl alcohol was studied in an integral pressure reactor over silicon substituted aluminophosphate molecular sieves, SAPO-5. The influence of various process parameters such as temperature, pressure, time on stream, weight hourly space velocity, and mole ratio of reactants on cumene yield and selectivity were investigated. The activity of SAPO-5 was compared with that of Hbeta for this reaction under similar conditions and in the same reactor. At pressures higher than atmospheric, almost the theoretical maximum yields of cumene were achieved on this SAPO-5. Among the diisopropyl benzenes formed by the alkylation of cumene, the meta-isomer was found to form in a significant amount followed by the para-isomer. The ortho-isomer with relatively high strain energy of 4.26 kcal/mol was almost negligible. The cumene yield goes through a maximum in the temperature range 498-543 K studied. Cumene selectivity was found to decrease at higher temperatures, higher pressures and lower benzene to isopropanol mole ratios.     

Grafting vinyl monomers onto silk fibers. II. Graft copolymerization of methyl methacrylate onto silk by hexavalent chromium ion

The feasibility of chromium(VI) to induce graft polymerization of methyl methacrylate onto silk was investigated. The rate of grafting was determined by varying monomer concentration, chromium(VI) concentration, temperature, acidity of the medium, nature of the silk, reaction medium, and redox system. The graft yield increased with increasing monomer concentration up to 0.65M, and with further increase of monomer the graft yield decreased. The graft yield increased with increasing chromium(VI) concentration. The grafting is considerably influenced by chemical modification of silk prior to grafting. The graft yield is influenced by thiourea concentration, decreasing with increasing thiourea concentration. The effect of certain inorganic salts and anionic surfactants on the rate of grafting was investigated.     

Utilization of flyash as filler for polybutyleneterepthalate‐toughened epoxy resin

Flyash, a waste product generated in large quantities in thermal power plants, has been posing problems of disposal. The purpose of the present work was to make a meaningful utilization of flyash as filler in neat epoxy resin matrix and 2% Polybutyleneterepthalate (PBT)/epoxy blend matrix. For this purpose, the tensile, flexural, compression, impact, chemical resistance, and water absorption properties were studied. Composites were made with varying proportion of flyash in epoxy resin and 2% PBT/epoxy blend matrix. Tensile, flexural, and compression properties were measured on a computerized universal testing machine, according to ASTM procedures. Impact strength was determined using izod impact tester for un‐notched specimens. PBT (2%)/epoxy blend matrix composites showed improved mechanical properties over neat epoxy flyash composites. All the composites were found to have good chemical resistance toward acids, solvents, and alkalies. These composites showed better water resistance over neat epoxy flyash composites. POLYM. ENG. SCI. 46:946–953, 2006. © 2006 Society of Plastics Engineers     

Grafting vinyl monomers into nylon-6. II. Graft copolymerization of methyl methacrylate onto nylon-6 by hexavalent chromium ion

The feasibility of chromium(VI) to induce graft copolymerization of methyl methacrylate onto nylon-6 was investigated in the presence of nitrogen. The rate of grafting was determined by varying monomer concentration, chromium(VI) concentration, temperature, acidity of the medium, solvents, inorganic salts, and redox system. The graft yield increases significantly by increasing the monomer concentration. The graft yield increases with increase of [Cr(VI)] up to 0.025 mole/liter. With further increase of [Cr(VI)], the graft yield decreases. The increase of acid concentration up to 0.395 mole/liter results the increase in graft yield. Beyond this concentration the graft yield decreases. The graft yield increases with increase in temperature up to 55°C and thereafter it decreases. The graft yield is medium dependent. The graft yield increases with increasing thiourea concentration upto 0.0025 mole/liter but beyond this concentration, the percentage graft yield decreases. A suitable kinetic scheme has been proposed and the rate equation has been evaluated.     

Grafting of vinyl monomers onto natural rubber,II. Graft copolymerization of methyl methacrylate onto natural rubber using tetravalent ceric ions

The use of tetravalent ceric ions to initiate graft-copolymerization of methyl methacrylate onto natural rubber (NR) has been investigated. The rate of grafting has been determined by varying the concentration of monomer and cerium(IV), the temperature and the solvents. The graft yield increases with increasing monomer concentration up to 1.877 M, with further increase of the monomer, the graft yield decreases. The percentage of grafting increases with increasing cerium(IV) concentration up to 0.035 M, thereafter it decreases. With increasing temperature the graft yield increases. The effect of CuSO₄ on the rate of grafting has also been investigated. A plausible mechanism has been suggested and the kinetic rate expressions have been derived.