Morphology, micromechanical, and thermal properties of undeformed and mechanically deformed poly(methyl methacrylate)/rubber blend

Poly(methyl methacrylate) (PMMA)/natural rubber (NR) blends prepared by the solution method and PMMA/core-shell particles (CSP) blends received commercially have been investigated, in both undeformed and deformed states, by means of microscopy, microindentation technique, and differential scanning calorimetry (DSC). Optical microscopy and transmission scanning microscopy clearly distinguish the morphology and the distribution of NR particles and CSP in the PMMA matrix. While NR particles exhibit a sharp phase boundary, CSP show no such boundary. The fall of microhardness by the inclusion of rubbery phase in the PMMA matrix clarifies a toughening behavior of the blends. The DSC reveals a decrease of glass transition temperature (T-g) for NR-modified blends and an increase of T-g for CSP-modified blends. Results are discussed based on the compatibility between the components of blends and their morphology along with the impact of both NR particles and CSP in the matrix. In the case of the drawn materials, the indentation anisotropy (Delta H) is shown to gradually increase with the draw ratio, where Delta H is found to be higher for the PMMA/NR blends than it is for the original PMMA and PMMA/CSP blends. This result is explained by the higher orientation of the PMMA molecules near the periphery of stretched rubber particles as well as the lower orientation of the network molecules in CSP.