Polyamides are widely used engineering plastics, but their performance often needs to be further adjusted by blending with other polymers. Due to polarity differences, most PA-based blends require compatibilizers to ensure stable morphology and mechanical integrity. Recent studies on PA/PP and PA/PC blends have provided new insights into compatibilization mechanisms and material optimization. In PA/PP blends, poor interfacial adhesion caused by large polarity differences leads to severe phase separation. Maleic anhydride-grafted polypropylene (PP-g-MAH) remains the most widely used compatibilizer. Its anhydride groups react with amine end groups of PA, forming stable chemical bonds that strengthen the interface. With deeper research, it has become clear that grafting efficiency, MAH content, and molecular weight distribution significantly influence the final toughness and processability of the blend. Block copolymer compatibilizers represent a newer direction, enabling finer phase dispersion and better toughness. Nanoparticle-assisted compatibilization has also emerged, improving long-term thermal resistance and fatigue behavior of the blends. For PA/PC blends, the challenge lies in mismatched processing temperatures and complex interfacial chemistry. Epoxy-functional compatibilizers have proven highly effective, forming chemical linkages with both PA and PC end groups. As a result, thermal stability, impact strength, and dimensional stability at elevated temperatures have greatly improved. Recent developments focus on reaction rate control, ensuring that compatibilization occurs at lower temperatures to prevent PC degradation. Additives containing silicon or flexible chain segments further enhance transparency, weather resistance, and chemical durability. Compatibilization strategies are becoming increasingly sophisticated, enabling nylon blends to meet the stringent requirements of automotive, electrical, and structural applications.

Carbon fiber reinforced nylon has become an important lightweight structural material due to its high specific strength, stiffness, and good processability. As mechanical systems move toward lightweight designs, accurately evaluating the fatigue life of this composite under complex loading conditions is essential. Classical metal fatigue theories do not fully apply to polymer composites, so dedicated methodologies must be developed. Fatigue evaluation begins with understanding the composite’s microstructure. Fiber orientation, distribution, and interfacial adhesion significantly influence load transfer. Under cyclic loads, carbon fibers bear most of the tensile and bending stresses, while the nylon matrix provides toughness and delays crack propagation. Microstructural characterization tools such as SEM and micro-CT help analyze fiber orientation patterns and their effects on fatigue behavior. In practice, stress-controlled S-N curve testing is commonly used. Since nylon is sensitive to moisture and temperature, specimens must be conditioned before testing. However, carbon fiber reinforced nylon exhibits multiple damage mechanisms—fiber breakage, interfacial debonding, and matrix yielding—which limits the predictive power of S-N curves alone. Therefore, fracture mechanics-based crack growth models are increasingly applied. Measuring fatigue crack growth rate under various stress intensity factors helps establish a ΔK–da/dN model that reflects real crack propagation behavior. Finite element simulations incorporating fiber orientation and complex geometry further enhance prediction accuracy. In applications such as gears, pulleys, brackets, and couplings, additional factors—including contact stress, lubrication, and frictional heating—must be considered. Realistic test conditions help bridge the gap between laboratory results and field performance. A comprehensive evaluation combining microstructural analysis, S-N testing, crack growth modeling, and numerical simulation provides the most reliable prediction of service life.  

尼龙因其强度、耐磨性和成本的平衡性而被广泛应用于汽车零部件、户外设备、电气连接器和工业机械等领域。在常温下，PA6 和 PA66 保持稳定的韧性，但在零度以下的环境中，其性能会显著下降。当温度降至 -20°C 或更低时，分子运动性急剧降低，导致脆性增加、冲击强度降低和尺寸稳定性下降。因此，用于长期户外暴露或寒冷气候环境的部件需要采用特殊改性的尼龙材料以确保可靠性。韧性的损失源于玻璃化转变温度附近的分子冻结效应。随着温度下降，链段运动受限，材料由韧性转变为脆性。冲击载荷无法再通过塑性变形耗散，导致裂纹快速扩展。如果部件包含薄肋、尖角、卡扣配合或孔洞，这些几何形状会加剧应力集中，加速脆性断裂。对于无人机、雪地工具、寒冷气候汽车零部件和极地监测设备等，其后果十分严重。低温韧性增强通常涉及橡胶增韧、嵌段共聚物结构、纳米填料改性和分子链端调整。 POE、EPDM-g-MA 和 ABS-g-MA 等橡胶增韧体系将微小的橡胶畴分散在尼龙基体中。冲击过程中，这些橡胶畴会引发剪切带形成和局部屈服，从而有助于耗散能量。这种方法必须平衡刚度、流动性和热稳定性，以避免过度软化。嵌段共聚物提供了一种更本质的改性途径。 通过将柔性链段引入聚合物主链，尼龙即使在低温下也能保持链段的运动性。这种方法最大限度地减少了相分离，并保持了结构的均匀性，从而提高了对可靠性要求高的应用中的耐久性。纳米填料技术进一步增强了低温性能。 石墨烯、纳米二氧化硅和纳米弹性体等材料能够提高抗裂纹扩展能力和界面强度，且不会显著降低刚度。此外，纳米级增强材料还能降低低温下不均匀收缩引起的内应力，从而提高尺寸稳定性。设计策略同样重要。圆角过渡、均匀壁厚、纤维取向控制和合理的浇口位置都发挥着作用。在纤维增强尼龙中，纤维取向对低温冲击性能有显著影响。过度取向会导致方向性脆性。优化熔体流动路径或改变零件几何形状有助于减轻这些影响。低温韧性尼龙 广泛应用于汽车前端模块、传感器支架、外置摄像头外壳、无人机起落架和滑雪设备连接器。 这些部件必须在-30°C或-40°C的温度下保持完整性，而不会发生脆性断裂。未来的发展将聚焦于高效增韧体系、精细的分子工程以及多尺度复合结构。新兴趋势包括纳米弹性体增强、高结晶度可控结构以及生物基耐寒尼龙。随着极端环境应用需求的日益增长，低温韧性不仅是一种材料特性，更成为影响设计、工装和长期可靠性评估的关键工程能力。