Surface functionalization of polypropylene-bearing isocyanate groups in solid state and their cyclotrimerization with diisocyanates

Solid-state graft polymerization of 3-isopropenyl-,-dimethylbenzene isocyanate (TMI) onto the surface of polypropylene beads was carried out in a triethylborane/oxygen redox system. Chemical structures were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy. Results showed that TMI was successfully grafted because of the appearance of an NCO absorption peak at 2255 cm(-1). The emergence of oxygen and nitrogen elements detected by EDS and XPS also demonstrated the existence of isocyanate group on PP-grafted. The grafting ratio of TMI to polypropylene was examined using 9-(methylamino-methyl)anthracene (MAMA) as an intermediate substance. The fluorescent property of MAMA before and after reaction was characterized to guarantee interaction between MAMA and isocyanate. Thermal properties were examined using differential scanning calorimetry-thermogravimetric analysis. Results indicated that melting temperature (T-m) of pure PP was 168(o)C, while the PP-grafted decreased to 164(o)C. Meanwhile, decomposition temperature (T-d) decreased with increased grafting ratio for about 8 to 15(o)C; however, when styrene was introduced, T-m increased probably because of the stabilizing effect on macromolecular radicals and the suppression effect on chain degradation. Besides, the cyclotrimerization of isocyanates on the grafted polymer chain was further conducted to prepare thermally stable isocyanurate composite materials, remedying the T-d loss of PP-g-TMI by improving for 10(o)C appropriately. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42186.