Hydrogen bonding-based self-assembly technology for high-performance melt blending TPU/PA6 polymers

Toughness and tensile strength are important mechanical properties of polymers. However, it is generally very challenging to improve the toughness without an obvious decrease in the tensile strength, and vice versa, which greatly limits the applications of polymers. Here we developed a novel hydrogen bonding-based self-assembly technology for melt blending polymers to achieve a notable improvement in toughness without an obvious decrease in the tensile strength. Thermoplastic polyurethane (TPU)/polyamide 6 (PA6) blend was selected a model composite and its elongation at break increased significantly from 1150% (0 wt% PA6) to 1350% (7.5 wt% PA6) and 1375% (10 wt% PA6), without an obvious decrease in the tensile strength. We deeply investigated the relationship between microcosmic self-assembly and macroscopic mechanical properties in polymer melt blends. It was found that the hard and soft segment groups (urethane and ester) of TPU form new hydrogen bonds with the amide group of PA6 through hydrogen-bonded self-assembly during the melt blending process, while the intrinsic hydrogen bonding structure of TPU was obviously shielded and weakened. As a result, the TPU/PA6 melt blends showed a notable improvement in toughness without an obvious decrease in the tensile strength. Since most previous self-assembly studies were carried out in solution and there was little work focused on the industrial convenient melt blending method, our study paves the way for further studies on both theoretical studies and practical applications of polymer blends.