Functionalization of polypropylene in solution through grafting with monomethyl itaconate.

Polypropylene (PP) was functionalized in solution by grafting with monometh yl itaconate (MMI) by using xylene and decalin as solvents and 2,5-dimethyl -2,5-bis(tert-buthylperoxy)hexane (Lup. 101) as radical initiator. The exis tence of grafted MMI in PP was confirmed by FT-IR spectroscopy. Carbonyl ab sorption bands from MMI was observed in the FT-IR spectrum of the functiona lized polypropylene. These absorption bands are absent in the FT-IR spectru m of the unmodified polypropylene. The percentage of grafted MMI was estima ted by volumetric titration as well as FT-IR analysis. The amount of monome r incorporated in polypropylene by the latter method was determined from a FT-IR calibration curve established for this monomer. A systematic study of the reaction variables allowed the optimisation of th e grafting process where a maximum of nearly 0.4% of grafting was achieved when xylene was used as solvent. When decalin was used as solvent, the perc entage of grafting attained was lower. It was found that the percentage of grafting depends on the initial concentration of monomer and initiator as w ell as reaction time and reaction temperature. The grafted MMI was partiall y cyclized during the grafting reaction. This was attributed to the presenc e of the organic peroxide used as initiator for grafting reactions. It was also found that the molecular weight of the grafted polymer decreased with increasing initial concentration of the peroxide as was estimated by measur ing the melt flow index (MFI) of modified polypropylene samples.