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Cross-linked polyacrylonitrile PAN granules were prepared at ambient temperature by γ-rays at a constant dose rate of 8.5 kGy/h. It was found that the rate of polymerization was linear with the radiation dose at the initial stage of polymerization, and then, at high conversion, it tends to level off above 35 kGy. Cross-linking of PAN is accompanied simultaneously with the polymerization process at high energy radiation. Characterizations of the cross-linked PAN prepared at different radiation doses were investigated by FT-IR, XRD, DSC, and TGA analysis. The appearance of an IR band at 1670 cm-1 confirmed the cross-linking of PAN via nitrile groups. The original crystal lattice and the entropy of melting ΔS m did not change significantly at high radiation doses.

Direct radiation‐induced grafting of aqueous acrylic acid (AAc) onto poly(tetrafluoroethylene‐ethylene) (ET) film has been studied. The effect of grafting conditions such as monomer concentration, exposure dose, dose rate, and film thickness on the grafting yield was investigated. The dependence of the grafting rate on monomer concentration was found to be 1.2 order. The dependence of the grafting rate on dose rate was found to be 0.6 order regardless of the film thickness. The relationship between the grafting rate and film thickness gave a negative first‐order dependence. The results suggest that the grafting process is mainly controlled by monomer diffusion, and it was concluded that this grafting system proceeded by the front mechanism. The swelling behavior increases linearly with degree of grafting. The electrical conductivity and mechanical properties for the trunk and grafted polymer were investigated at different irradiation doses in air and under vacuum irradiations. © 1992 John Wiley & Sons, Inc.

This work describes the immobilization of pullulanase onto two different polymers; agarose activated with epichlorohydrin and trichlorotriazine and casein activated with epichlorohydrin, in addition to a synthetic copolymer, butylacrylate±acrylic acid (BuA/AAc). Immobilization by covalent binding yields stable enzyme activity. The operational stability of the free and immobilized enzymes showed that the enzyme immobilized by a crosslinking technique using glutaric dialdehyde (GA) showed poor durability and the relative activity decreased sharply due to leakage after repeated washing, while the enzymes immobilized by covalent bonds resulted in a slight decrease in most cases in the relative activity (around 20%) after being used 10 times. Storage for 4±6 months showed that the free enzyme lost most of its activity, while the immobilized enzyme showed the opposite behavior. Subjecting the immobilized enzymes to doses of g-radiation (0.5±10 Mrad) resulted in complete loss in the activity of the free enzyme at a dose of 5 Mrad, while the immobilized enzymes showed relatively high resistance to g-radiation up to a dose of 5 Mrad. Nuclear Magnetic Resonance ( 1 H NMR) and FTIR measurements were carried out to con®rm the structure of the polymer as well as the immobilization process of the enzyme onto the polymeric carrier. The unique biochemical characteristics, mode of action and utility of the environmentally compatible pullulanase in starch conversion are well known. Using pullulanase with b-amylase in starch sacchari®cation processes can increase maltose yield by 20±25%.

Radiation-induced graft copolymerization of maize starch/acrylic acid has been performed. Also, natural byproduct wood pulp was used after chemical treatment for the removal of metal ions from the investigated wastewater. The surface and structure morphology of the wood pulp and starch/acrylic acid were investigated by scanning electron microscopy and infrared spectroscopy. The physical parameters, such as swelling, gel percentage, and grafting efficiency (%) of starch/acrylic acid copolymer, were studied. The factors affecting the abilities of the prepared materials for removing heavy metal ions and dyes from aqueous solutions were studied. It was found that the maximum metal uptake is in the following sequence: Fe 3ϩ Ͼ Cr 3ϩ Ͼ Pb 2ϩ Ͼ Cd 2ϩ . The adsorption capacity of such investigated metal ions increases with the increase of pH values.

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Activation enthalpy and entropy were measured to be 10.3 kcal mol"1 and -16 eu, respectively. In dioxane/water and acetonitrile/water mixtures the rate constants were found to be approximately proportional to the water content.It is concluded that the first step in the hydrolysis is the nucleophilic reaction of water with the unsubstituted ketene.

A kinetic study has been made on the preirradiation grafting of acrylic acid (AAc) onto poly(tetrafluoroethylene–hexafluoropropylene) (FEP) film. The effect of grafting conditions was investigated. The dependencies of the grafting rate on preirradiation dose and monomer concentration were found to be 0.58 and 1.25 order, respectively. The overall activation energy for the graft polymerization was 7.4 kcal/mol. The final degree of grafting increased with preirradiation dose and monomer concentration and slightly decreased as the grafting temperature was elevated. The relationship between the grafting rate and film thickness gave a negative first‐order dependency, which is in agreement with that obtained for polytetrafluoroethylene—AAc grafting system. It was reasonably concluded that this grafting proceeds from the surface to the center of film with progressive monomer diffusion through the grafted layer which swells in the monomer solution.