PROPERTIES OF POLY(STYRENE) - GRAFTED SILK FIBERS AND MOLECULAR-WEIGHT OF POLY(STYRENE)

Poly(styrene) was grafted onto silk fibers in an aqueous medium, using ammonium persulphate initiator. Add-ons of up to 100% were achieved. The add-on increased linearly with the monomer concentration of the gr afting system, all other factors remaining constant. The yield of the reaction attained about 80% and the extent of homopolymerization was n egligible. The equilibrium moisture regain decreased noticeably with i ncreasing add-on. Breaking load showed a tendency to increase in the 0 -55% range of poly(St) content, while elongation at break and work of rupture decreased. The DSC endothermal peak at 315 degrees C slightly shifted towards higher temperature by graft-copolymerization, and a ne w endothermal transition appeared beyond 400 degrees C. TG measurement s showed an increase of weight retention beyond 300 degrees C for poly (St)-''grafted' silk fibers. The dynamic mechanical behavior was chara cterized by a shift to lower temperature of the loss modulus peak. The transverse dimension of the fibers increased with increasing add-on. The polymeric residue remaining after alkaline dissolution of silk fib roin showed a porous texture with a sponge-like morphology. The molecu lar weight of poly(St) removed from silk increased up to 120 kDa in th e 0-55% add on range and then remained constant. The ''Poly(St)/Silk'' molar ratio increased linearly over the add-on range examined. (C) 19 96 John Wiley & Sons, Inc.