This article deals with the characterization of blend films obtained by mixing silk fibroin (SF) and polyacrylamide (PAAm). The DSC curves of SF/PAAm blend films showed overlapping of the main thermal transitions characteristic of the individual polymers. The exothermic peak at 218°C, assigned to the ␤-sheet crystallization of silk fibroin, slightly shifted to a lower temperature by blending. The weightretention properties (TG) of the blend films were intermediate between those of the two constituents. The TMA response was indicative of a higher thermal stability of the blend films, even at low PAAm content (Յ25%), the final breaking occurring at about 300°C (100°C higher than pure SF film). The peak of dynamic loss modulus of silk fibroin at 193°C gradually shifted to lower temperature in the blend films, suggesting an enhancement of the molecular motion of the fibroin chains induced by the presence of PAAm. Changes in the NH stretching region of silk fibroin were detected by FTIR analysis of blend films. These are attributable to disturbance of the hydrogen bond pattern of silk fibroin and formation of new hydrogen bonds with PAAm. The values of strength and elongation at break of blend films slightly improved at 20 -25% PAAm content. A sea-island structure was observed by examining the air surface of the blend films by scanning electron microscopy.

expanded to other applications, such as power plants, the foodindustry,petrochemicalplants,refineries,heatexchangers,marinestructuresandmedicalprostheses(4,5). Commercially available titanium is classified depending on its purity and elemental composition. The main classification for titanium is provided by the American Society forTestingandMaterials(ASTM).Thefirst4ASTMgradesof titanium are referred to as "commercially pure" and are not alloyed but only present differences in terms of contents of impurities, especially oxygen (6): grade 1 contains a maxi-mumof0.18% oxygen whilegrade4hasamaximumof0.40%.

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SYNOPSISSilk fibers were graft-copolymerized with methacrylamide (MAA) and 2-hydroxyethyl methacrylate (HEMA) in aqueous media, using a chemical redox system as an initiator. High weight gains (300%) were obtained with both monomers, the weight gain being linearly related to the amount of monomer contained in the reaction system. The reaction efficiency attained 95-100%. The extent of homopolymerization was negligible for the MAA grafting system, while large amounts of poly-HEMA covered the surface of silk fibers beyond 70% weight gain. The fiber size increased linearly with the weight gain. The moisture content of MAA-grafted silk fibers was highly enhanced by grafting. The severe grafting conditions caused a partial degradation of the tensile properties of silk fibers, as well as of the degree of fiber whiteness. Following grafting, the breaking load slightly increased, while elongation at break and energy decreased. The decomposition temperature of grafted silk fibers shifted upwards. The Raman spectra of untreated silk fibers showed strong lines at 1667 (amide I), 1451, 1227 (amide 111), 1172 and 1083 cm-'. Overlapping of the lines characteristic of both silk fibroin and grafted polymer was observed in the spectra of grafted silk samples.The vibrational mode of the amide I11 lines of silk fibroin was significantly modified by grafting.

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