On the other hand, most polymer blends are thermodynamically incompatible due to the absence of interactions of the blend components. This incompatibility leads to weak interfacial adhesion which results in poor mechanical and thermal properties. In order to improve the interfacial adhesion between NR and PP, chemical modification may contribute to enhancing the interactions between the two polymers. The chemical modification of NR has already been achieved through different means. These include epoxydation [12,13], the grafting of a vinyl monomer such as methyl methacrylate or styrene [14], or the grafting of maleic anhydride (MAH) [15]. The chemical modification not only improves the interactions between the blend components but can also compensate some of NR drawbacks such as its resistance to
ageing and to solvents or its gas impermeability. The grafting of MAH can be carried out in the molten state using
a peroxide in an internal mixer at high temperature [15,16]. It can also be performed in solution [14].