gamma-radiation induced effects on the physical and chemical properties of natural lignocellulose (jute) polymer were investigated. Samples were irradiated to required total doses at a particular dose rate. The changes in the parameters such as the tensile strength, elongation at break, and work done at rupture for the lignocellulose samples on irradiation with the gamma-rays from a cobalt-60 source were measured. The mechanical properties were found to have nonlinear relations with the radiation doses. The chemical stability of irradiated fibers was found to degrade progressively with the increase of radiation dose. Additionally, other chemical changes of the samples due to exposure to high-energy radiation were also investigated using fluorescence and infrared spectroscopic analysis. Differential scanning calorimetry and thermogravimetric studies showed a significant reduction in thermal stability. The wide-angle X-ray diffraction study showed that structural changes of cellulose appeared due to the radiation-induced chemical reaction of lignocellulose.

Graft copolymerization of methyl methacrylate (MMA) onto jute substrate was carried out using gamma radiation ( 60 Co) both by the preirradiation and "simultaneous irradiation and grafting" methods in an aqueous emulsion system. The variation of graft weight with radiation dose, intensity of radiation, and irradiation environment was investigated. In the case of the preirradiation method, irradiation in air produced up to 30% graft weight compared to only 20% obtained when the irradiation was conducted in nitrogen environment. In this method the graft copolymerization reaction was initiated by reactive species having different life times, some of which were very long. In simultaneous irradiation and grafting method, the graft weight passes through a maximum value (∼15%) with radiation dose and graft weight limited due to excessive homopolymerization. A comparative study on the mechanical properties of samples grafted by both preirradiation and simultaneous irradiation and grafting methods was carried out. The results showed that the method of grafting has significant influence on the mechanical properties of grafted jute.

ABSTRACT:The preirradiation method of grafting has been established by ultraviolet radiation. Methyl methacrylate (MMA) was grafted onto jute fiber in an aqueous medium. The variation of graft weight with UV-radiation time, monomer concentration, and reaction time was investigated. The conversion of monomer into homopolymer and graft copolymer was evaluated. The graft weight passes through a maximum value (ϳ 122%) with UV-radiation time. The optimum value of the monomer concentration was evaluated for maximum degree of grafting. Graft copolymerization of MMA onto lignocellulose fiber significantly increases the elongation at break (ϳ 65%) compared to that of the "as-received" sample. However, a linear decrease on breaking load was observed with the increase of graft weight. The estimation of degree of grafting was achieved using an IR technique by correlating band intensities with the degree of grafting. Considering the water-absorption property, the grafted sample showed a maximum up to 61% decrease in hydrophilicity compared to that of the as-received sample.

No abstract