The effect of tunable modification parameters on the structure and properties of polypropylene with cyclotrimerization surface of isocyanates

The cyclotrimerization of methylene diphenyl 4,4-diisocyanate (MDI) and 3-isopropenyl-,-dimethylbenzene isocyanate (TMI) was applied on the bead/membrane surfaces of a polypropylene (PP)-bearing isocyanate group to synthesize a protective networked polymer. Chemical structures of these molecules were characterized through attenuated total reflectance-Fourier transform infrared spectroscopy. Results showed that the absorption peak of isocyanate group at 2255 cm(-1) became negligible after the reaction was completed. The absorption peaks of the isocyanurate groups appeared simultaneously at 1600 cm(-1) and at 1510-1560 cm(-1); this result indicated that the grafted isocyanates were almost consumed, thereby forming isocyanurates. Energy X-ray dispersive spectroscopy revealed that oxygen content increased; indeed, isocyanurate was formed on the PP surface. Pure PP beads, PP-g-TMI, and cyclotrimerization products were also subjected to thermal property tests to investigate their corresponding thermal stabilities. Cyclotrimerization could result in the increase in PP-grafted decomposition temperature, even slightly higher than pure PP. Rheological behavior in oscillatory flow was also evaluated; the storage modulus, loss modulus, and complex viscosity of cyclotrimerization products were higher than those of the PP-grafted membranes. Surface morphology was further observed through field-emission scanning electron microscopy and atomic force microscopy. The cyclotrimerization products contained blocks and exhibited a rough surface. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43327.