A Designed Surface Modification to Disperse Silica Powder into Polyurethane

Nanoparticles of silica powder were modified by grafting polyurethane (PU) short chains or oligomers using surface-started condensation reactions of various di- or tri-ols and di-isocyanates in step-by-step. Surface density of NCO-groups, introduced by an autoclave method and ready for starting of subsequent reactions, was adjusted by amount of 3-isocyanatepropyltriethoxysilane (ICPTES). Length of grafted oligomers was determined by reaction steps. TG/DTA measurements demonstrated a gradual increase of NCO-groups density with the amount of modifier input. FTIR spectra and thermal weight loss analyses confirmed the occurrence of reaction in each step and the growth of grafted oligomer. SEM images of particles dispersed in N, N-dimethylacetamide or in prepolymer of PU indicated an improved dispersion. Moreover, when as-modified particles were incorporated in PU prepolymer, the resultant hybrid films displayed an enhanced optical property, thermal stability, and Vicker's hardness, suggesting a better dispersion of modified particles. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 000: 000000, 2012