Thermal and rheological characterization of semi-II interpenetrating polymer networks from poly(methyl methacrylate) and castor oil-based polyurethane

The synthesis and characterization of semi-II interpenetrating polymer networks (IPN) based on poly(methyl methacrylate) (PMMA) and on castor oil polyurethane (PU) of composition 70/30 are reported. Various degrees of crosslinking of the PU phase were obtained by varying the weight ratio of HDI/N-100 while maintaining the NCO/OH ratio fixed at 1.5. Thermal characterization was performed by thermomechanical analysis (TMA), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Two distinct glass transition temperatures were observed, indicating a two-phase morphology. This was also supported by scanning electron microscopy (SEM) observations. Rheological characterization was performed using a capillary rheometer. Shear thinning flow behaviour and reprocessing were confirmed for all semi-II IPN. All the results demonstrate that a higher crosslinking level leads to better overall properties.