Abstract

The functionalization of isotactic poly(propylene) (iPP) through grafting with two itaconic acid derivatives, monomethyl and dimethyl itaconate (MMI and DMI, respectively), was performed in the melt using a Brabender plasticorder. The grafting reaction was carried out at 190°C using two different initial monomer concentrations and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane as radical initiator. Two samples of PP grafted with different amounts of either DMI or MMI (0.5 and 1.4 wt.-%) were used in this work. In order to evaluate the characteristics of these materials, different thermoplastic elastomers based on poly(propylene) and ethylene-propylene diene rubber blends (50/50) were processed and their properties were analyzed. A comparative study of materials prepared with unmodified PP is also reported. The flow properties analyzed by torque values, melt index and rheological studies showed that the blends prepared with modified PP have a better processability, showing a lower viscosity, with this effect being more significant DMI-modified PP. Dynamic mechanical analysis and tensile properties revealed that the grafting reaction promotes the interaction between both polymeric phases, giving rise to a more rigid structure. Furthermore, it was observed that the functional polar monomers not only act as compatibilizers but also behave as nucleating agents for PP crystallization, showing a substantial decrease of the half-time of crystallization, which could be attributed to the presence of a greater number of nuclei during the crystallization process. These results are in agreement with observations carried out by scanning electron microscopy (SEM), where a better interaction between both polymeric phases is observed when PP is functionalized with both itaconic acid derivatives.