Ultrahigh Flowability and Excellent Mechanical Performance of Glass Fiber/PA6 Composites Prepared by Hyperbranched Polymers

Lightweighting of automotives is crucial for the decrease of fuel and energy consumption, as well as CO2 emission and environmental pollution. Polymer composites, especially the high strength glass fiber/polyamide (GF/PA) composites, have great potential in lightweight; however, they have not been universally accepted due to their insufficient performance. Here, a stearate‐ended hyperbranched polyester (HBP‐12‐n) is designed and high‐performance GF/PA6 composites with high GF content are prepared. The flowability of the composites can be further increased by combining carboxyl‐ended hyperbranched polymer (HyPer C181) with HBP‐12‐n. Compared with unmodified GF/PA6 composites, the melt flow index (MFI) can be increased remarkably to 587% by adding a 0.7 wt% mixture of HBP‐12‐75 and HyPer C181, and the strength and toughness remain competitive. The simultaneous improvement in MFI and impact strength of GF/PA6 composites is the first discovery of this kind, and a synergistic mechanism of amphiphilic bridging‐deformation slipping‐interfacial strengthening of hyperbranched polymers is proposed to account for this phenomenon. This work provides a simple strategy to fabricate GF/PA6 composites with the extensive application for automotive parts and has great prospects in making automotives lightweight and reduction of CO2 emissions. A series of stearate‐ended hyperbranched polyester (HBP‐12‐n) by the esterification reaction between the hydroxyl groups of HBP‐12 and stearic acid is synthesized. The melt flow inde of the glass fiber/polyamide 6 (GF/PA6) blends can be increased approximately 5.87 times upon the mixed use of HBP‐12‐75 and carboxyl‐ended hyperbranched polymer (HyPer C181), without sacrificing the strength and toughness of the composites.