STRUCTURAL-ANALYSIS OF POLY(4-HYDROXYBUTYL ACRYLATE)-GRAFTED SILK FIBERS

Poly(4-hydroxybutyl acrylate) poly(4-HBA) was graft-copolymerized onto silk fibres (bombyx mori) in aqueous medium with ammonium persulfate as initiator. The weight gain increased with increasing concentration of monomer in the grafting system. The gafting efficiency ranged from 45 to 65%. Equilibrium moisture regain decreased sharply beyond 10% we ight gain. The tensile properties of the silk fibres did not change si gnificantly as a function of the increasing weight gain. Birefringence and isotropic refractive index decreased until 35% weight gain and th en remained unchanged. The X-ray diffraction patterns showed that the crystalline structure was not affected by grafting. Differential scann ing calorimetry (DSC), thermomechanical (TMA), and thermogravimetric ( TG) measurements showed that poly(4-HBA)-grafted silk fibres underwent only slight changes in the thermal behaviour. The dynamic mechanical measurements (DMA) exhibited a downward shift of both the storage (E') and loss modulus peak (E '') with increasing weight gain. Scanning el ectron microscopy (SEM) observations showed the presence of some depos its adhering to the surface of silk fibres grafted at high monomer/sil k ratio (>50%).