The radiation-induced solid phase graft copolymerization of NMA onto natural silk fabric

The radiation-induced solid phase graft copolymerization of N-methylolacrylamide (NMA) onto natural silk fabric has been studied using γ-irradiation at room temperature at dose rates from 0.326 to 18.01 kGyḣ^-1 on samples dried naturally and with drying oven at 37–105°C before irradiation. A good straight line which describes the relation between graft rates R_g and dose rates I, $\text{R}{}_{\mathrm{g}}\text{/I}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{− I}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, was obtained in γ-irradiation on the samples dried with drying oven at 50°C. Radical and ionic polymerization have taken place concurrently on the samples under these conditions. The add-on and the graft rate of NMA on the samples dried with drying oven at 37–50°C are much higher than that of the wet samples. The add-on increases with the dose up to 25 kGy. In certain ranges, the graft rates increase linearly proportionally with the content of NMA and the reciprocal of the moisture in samples. But when NMA content >17% and reciprocal of moisture >75.18, because of the increase of both radiation- and heat-homopolymerization of NMA, the graft rates would gradually decrease. When the room temperature =15–17°C in irradiation, dose rate = 0.326–18.01 kGyḣ^-1, NMA content <17% and moisture =0.93% in samples, the rate of the γ-radiation-induced solid phase graft copolymerization of NMA onto natural silk fabric may be approximately described as following equation: $\text{R}{}_{\mathrm{g}}\text{= 5.882 × 10}{}^{-3}\text{[}\text{M}\text{]}\text{I}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{+ 3.209 × 10}{}^{-4}\text{[}\text{M}\text{][}\text{X}\text{]}{}^{-1}\text{I}$.