Effects of compatibilizers on microstructural and viscoelastic properties of polypropylene/polybutadiene thermoplastics vulcanizates

Compatibilized thermoplastic vulcanizates (TPVs) based on polypropylene (PP) and polybutadiene rubber (PBR) were developed through the melt-mixing method, and their morphological, rheological, and dynamic mechanical properties were investigated. The composition of PBR/PP blends (30/70 and 40/60) was designed in a way to study the interrelationship between the compatibilizer content and blend composition. In this study, a hydrocarbon resin (MS 40) was employed as the compatibilizer. Based on morphological analysis, the addition of compatibilizer in both blend compositions led to a finer and more uniform distribution of rubber domains; however, only for 40/60 composition, the higher content of compatibilizer caused the formation of a co-continuous morphology. Both dynamic and static rheology results were highly susceptible to the compatibilizer content and blend composition. According to the storage and loss modulus curves, the incorporation of PBR into PP resulted in a significantly enhanced elastic response with 30/70 composition showing lower elasticity. The viscosity upturn in complex viscosity curves indicated the formation of a three-dimensional network of dispersed rubber domains within the matrix, which led to the appearance of a highly elastic response. Based on the dynamic mechanical analysis, the highly restricted macromolecular motions upon the addition of a compatibilizer confirmed the enhanced compatibility of TPVs.

Automated summary

Compatibilized thermoplastic vulcanizates (TPVs) based on polypropylene (PP) and polybutadiene rubber (PBR) were studied in terms of their morphology, rheology, and dynamic mechanical properties. The addition of compatibilizer led to finer and more uniform distribution of rubber domains in both 30/70 and 40/60 blends, with only the 40/60 composition showing a co-continuous morphology. Rheology results were highly influenced by the content of compatibilizer, and the incorporation of PBR into PP resulted in enhanced elastic response, particularly in the 30/70 composition. Dynamic mechanical analysis confirmed the enhanced compatibility of TPVs with the addition of a compatibilizer.