Synthesis of functional polypropylene via solid-phase grafting soft vinyl monomer and its mechanism



Solid-phase grafting of a soft vinyl monomer, butyl methylacrylate (BMA), onto polypropylene (PP) matrixes with 2,2′-azobisisobutyronitrile (AIBN) as initiator was carried out to enhance the polarity of polymer. Soft vinyl monomer was a novel notion in grafting modification of PP. Effects of swell time, BMA concentration, AIBN concentration, grafting reaction time, and temperature on grafting percentage (Gp) and grafting efficiency (Ge) were examined. The optimal conditions of grafting reaction were obtained: swell time of 60 min, BMA concentration of 6 wt %, AIBN concentration of 0.05 wt %, reaction temperature of 85°C, and reaction time of 2 h. The grafting samples were investigated by such characterization techniques as Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and scanning electron microscope (SEM) analysis. FTIR results indicated that BMA was actually grafted onto PP backbone. TGA results showed that the decomposition temperature increases with addition of BMA into PP backbone. SEM results indicated that the surfaces of PP-g-BMA had a markedly bumpy texture, whereas the pure PP surface was very smooth. Water contact angle results showed that the polarity and hydrophilicity of PP were improved effectively. Compared with the traditional monomer MAH, Gp, and Ge, melt flow rate and mechanical property results all indicated that the soft vinyl monomer had a many advantages in the modification of PP. In the end, the mechanism of solid grafting was discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009