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SYNOPSISTwo unsaturated polyester resins based on poly ( 1,2 propylene-maleate-phthalate) ( P E 1 ) , and poly (oxy-diethylene-maleate-phthalate) ( PE2 ) were used for the impregnation of oven-dried white pine wood samples in admixture with styrene (S) . Curing was affected by the initiator-heat technique by either using 0.1-0.2% by weight of benzoyl peroxide (Bz,O,) , or 1% by weight of methyl ethyl ketone peroxide (MEK) . It was found that the use of PEl/S mixture resulted in the formation of wood-plastic combinations (wpc) with higher percent retention and higher percent polymer loadings than those obtained by the impregnation of wood samples with P E 2 / S mixtures. The use of different swelling solvents including ethanol, acetone or chloroform, did not influence the percent retention or polymer loadings of wpc for either P E l / S or P E 2 / S mixtures. Physical tests performed on wpc showed that compression, hardness, static bending were generally enhanced, water absorption was decreased, and dimensional change was retarded to different extents for both polyesters used, but no permanent stabilization was attained.

Low-density polyethylene-g-poly(acrylic acid) membranes were prepared by the direct radiation grafting of aqueous acrylic acid solutions (containing Mohr's salt) onto low-density polyethylene films and were irradiated at two different irradiation doses (2 and 3 Mrad) at a dose rate of 0.02 Mrad/h. Two series of polyethylene-g-poly(acrylic acid) membranes with 100 and 150% grafting were obtained. The free carboxylic acid groups in the grafted films were converted into the corresponding acrylates by reactions with different metal salts. The swelling (water uptake) and dialysis permeability of glucose and urea through the grafted membranes in different metal-ion forms were investigated. The prepared membranes showed good permeability to both solutes, which increased as the hydrophilicity of the membrane increased.

ABSTRACT:· 4-Vinyl pyridine was grafted on polyethylene films of different thicknesses by the direct irradiation method using a Co-60 y-irradiation source. Addition of different amounts of solvents such as methyl ethyl ketone and cyclohexanone was found to decrease the swelling and the grafting extent on polyethylene. The dependence of the rate of graft polymerization on the thickness of the films was studied. The rate of grafting was found to decrease with increasing film thickness and a first order dependence was obtained. The effect of radiation dose on some of the mechanical properties of the ungrafted and grafted polyethylene was examined. It was found that low doses cause an increase in elongation due to a degradation process of polyethylene chains. At high doses, elongation tends to decrease again due to crosslinking, while the tensile load is not affected. Low grafting percents of 4-vinylpyridine on polyethylene lead to a marked decrease in elongation of the grafted polymer, with almost no change in the tensile load. Increasing the extent of grafting causes a significant increase in the tensile load and almost the same decrease in elongation as for the low grafted polymer.KEY WORDS Grafting I Solvent Effect I Thickness Effect I Tensile Load ICo-60 I Y-Irradiation I Radiation-induced graft polymerization of vinylpyridine1 on preirradiated polyethylene using yradiation and accelerated electrons has been proved to proceed by radical mechanism with a considerable rate. The grafting rate was dependent on the concentration of the polymer radicals (up to 5 Mrad dose) and on the concentration of the monomer. It was reported also that diffusion plays a certain role on the grafting rate, as the latter is dependent on the thickness of the polyethylene films. Several authors2 -6 studied the radiation-induced graft polymerization of 4-vinylpyridine onto different polymeric substrates to improve their properties: such as dyeability, ion exchange capability, and capacity to prevent blood coagulation.(diffusion of monomer into the polymer) on the extent and rate of graft polymerization.Graft polymerization of 4-vinylpyridine on polyethylene, or other polymeric substrates, is not a fully studied system. Little attention has been given to studying the effect of solvents and film thickness The aim of the present work is to study the effect of the addition of different solvents, such as methyl ethyl ketone and cyclohexanone, on the swelling and the grafting extent of 4-vinylpyridine to polyethylene. The dependence of the graft polymerization rate on the film thickness was also examined by kinetic methods. We also tried to characterize mechanically the behaviour of the grafted and ungrafted polymers by investigating the effect of dose on the elongation and the tensile load of the grafted and the ungrafted polyethylene samples. The apparent and true grafting were also determined.

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