MICROWAVE IRRADIATION TECHNIQUE TO ENHANCE PROTEIN FIBRE PROPERTIES

Microwave irradiation technique was used for the chemical modification and grafting of protein fibrous materials, such as domestic silk (Bombyx mori), tussah silk (Antheraea pernyi), and wool fibres. Epoxide compounds Denacol EX810 and EX313 reacted effectively with the protein substrates. As alkali catalysts, sodium hydroxide was more effective than sodium thiocyanate. The optimum concentration was 0.25 w%. Weight gain values up to 8% were attained with 10-15 min irradiation time at 200W power. Graftcopolymerisation of vinyl monomers onto protein fibres resulted in variable weight gains, depending on the kind of fibre, the grafting monomer used, and the concentration of the padding solution. For example, after grafting with iso-propyl methacrylate (IPMA), the weight gain of fibrous proteins took place in the following order: Bombyx mori silk > tussah silk > wool. Bombyx mori silk gained more weight with IPMA than with 2hydroxyethyl methacrylate (HEMA) or methacrylamide (MAA). The weight gain of Bombyx mori silk with HEMA significantly increased when the initial monomer concentration was raised to 400% owf, reaching a maximum value of 40%. The tensile properties of the protein fibres grafted with IPMA, MAA, and HEMA remained unchanged or slightly improved compared to the reference fibres. Fibres modified with epoxides showed a drop in tensile performance. The surface morphology of fibres treated with epoxide compounds or graft-copolymerised with vinyl monomers was almost unaffected, with the exception of HEMA-grafted fibres, which showed the presence of homopolymer deposited onto the surface at a weight gain exceeding 20%.