Grafting of maleic anhydride onto polypropylene by reactive processing. II. Effect of rotor speed and reaction time

Grafting of maleic anhydride onto polypropylene was performed in a Haake to rque rheometer, according to a central composite experimental design, in wh ich four factors were varied: the maleic anhydride and peroxide concentrati ons, rotor speed, and reaction time. The current article investigates the e ffect of rotor speed and reaction time on the level of reacted maleic anhyd ride, obtained by infrared spectroscopy, and on the extent of degradation, by means of melt-flow index (MFI) measurements. The behavior of the variabl es studied depends on the levels of maleic anhydride and peroxide concentra tions. The increase in rotor speed results in an increase in the percentage of reacted maleic anhydride and a reduction in MFI when the initial maleic anhydride concentration is high, and in a reduction in the percentage of r eacted maleic anhydride and increase in MFI when the initial maleic anhydri de concentration is low (for the central levels of peroxide concentration a nd reaction time). The effect of the variable reaction time depends on the remaining parameters. (C) 1999 John Wiley & Sons, Inc.