Silane grafting and moisture crosslinking of polypropylene

Peroxide initiated vinylsilane grafting of polypropylene in an intensive mi xer, and the subsequent water crosslinking process were studied. Different concentrations of vinyl trimethoxysilane and dicumyl peroxide were used. Th e materials obtained after mixing in the rheocord were hot pressed at 190 d egrees C. The melt viscosity of the obtained sheets, the melting enthalpy a nd melting temperature (DSC, differential scanning calorimetry), the mechan ical properties and the thermal decomposition behavior (TG, thermogravimetr ic analysis) were studied, No evidence of grafting during the rheocord proc essing was observed. Nevertheless, for the hot pressed sheets with concentr ations higher than 4 phr of vinyl silane an important increase in the melt viscosity was observed. This increase agrees with the change observed in th e mechanical properties, which show a maximum for the water crosslinked sam ples containing 4 phr of vinyl silane. The modulus increases by 39% at 90 d egrees C and 33% at 130 degrees C, while the tensile strength rises by simi lar to 22% at both temperatures. The silane grafted water crosslinked sampl es show a more stable thermal behavior than both the silane grafted samples and the unmodified polypropylene.