Flow enhanced high-filled polyamide composites without the strength-flowability trade-off

Polyamide (PA) composites exhibit excellent properties such as stiffness, impact resistance, chemical resistance, and thermal stability, making them widely used in automotive interiors, engine parts, and bodywork. To leverage these advantages, high-content composite materials that enhance the wettability and interfacial adhesion between polyamide 66 (PA66) and glass fiber are essential. In this study, we synthesized linear and hyperbranched amide-based flow modifiers to improve the flowability of PA66 composites. H-NMR and FT-IR analyses confirmed the successful preparation of these structures. FT-IR analysis confirmed the successful synthesis of flow modifiers, showing characteristic amide peaks at 1650 cm⁻¹ and the absence of -NH₂ peaks at 3300 cm⁻¹. Five flow modifiers were mixed with PA66 in various ratios using a micro-compounder, and viscosity reduction was confirmed by rotational rheometer measurements. Tensile strength and DMA indicated that PA66 composites with flow modifiers showed improved mechanical properties without significant reduction. Notably, PA66 composites with ACDA exhibited a superior viscosity reduction effect while maintaining mechanical strength. The DMA results indicated that the mechanical properties of PA66 composites with flow modifiers showed no significant reduction. The tensile strength of samples with flow modifiers ranged from 208 to 212 MPa, and the elongation at break was between 8.94 and 9.18%. These findings demonstrate that the synthesized flow modifiers improve the viscosity of PA66 composites while maintaining or enhancing mechanical properties.