Silk grafting with methacrylic and epoxy monomers: Thermal process in comparison with ultraviolet curing

Abstract

AbstractSilk grafting with methacrylic and epoxy monomers was studied with the aim to obtain high graft yields. With both monomer types optimum operating conditions of thermal grafting in water bath were established. In particular, three epoxy monomers were tested at various concentrations, at different temperatures and reaction times, with sodium chloride or sodium thiosulphate as catalysts. Optimum yields (76–82%) were found with Araldite DY‐T for 2 h at 70°C with 3M sodium chloride. The results were compared with those obtained with the same monomers by UV curing, radical with methacrylates and cationic with the epoxy resin. The UV curing efficiency was tested by gel content determinations. Thermal and UV cured fibers were then subjected to measurements of fibroin solubility in ethanol–calcium chloride–water mixture to evaluate the crosslinking degree. Except in the case of methacrylamide, radical UV curing yielded fibers more crosslinked than thermal treatment, or crosslinked to the same extent, whereas cationic UV curing showed lower crosslinking effects. The grafted fibers were characterized through DSC measurements and FTIR‐ATR spectrometry. Finally, surface morphology of UV‐cured samples was investigated through SEM analyses which showed that the better products could be obtained with UV curing at low add‐on, mainly with dimethacrylates and Araldite DY‐T, whereas the thermal grafting seems to be preferable for high add‐on. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008