Influences of PP-g-MA on the surface free energy, morphologies and mechanical properties of thermoplastic polyurethane / polypropylene blends

Abstract

The effects of polypropylene-g-maleic anhydride (PP-g-MA) addition on the surface free energy (SFE), morphologies, and mechanical properties of thermoplastic polyurethane (TPU)/polypropylene (PP) blends were investigated in this study. Specifically, the SFEs of the unmodified and PP-g-MA-modified TPU/PP blends were studied through contact angle (CA) measurements; when PP-g-MA content was increased from 3 to 11 phr, the SFE of the blends decreased with different TPU/PP blending ratios while the corresponding CA increased. This decrease was attributed to the interaction between PP-g-MA and TPU. Wide-angle X-ray (WAXD) diffraction results indicated that the crystalline morphology of the blends was not significantly influenced by PP-g-MA. This morphology was observed through scanning electron microscopy (SEM), and the results showed that the TPU/PP blends exhibited an incompatible microstructure that improved with the addition of PP-g-MA. The partial disperse size curve indicated the changes in partial disperse phase size as observed through SEM. Moreover, the fine and mean partial dispersion of the TPU/PP blend was initiated by increasing PP-g-MA content. Specifically, the mechanical properties of the TPU/PP blend were optimized with the addition of 7 phr PP-g-MA. The thermogravimetric (TG) curves suggested that the addition of PP-g-MA could enhance the miscibility of TPU/PP blends.