Blending TPE elastomers with engineering plastics is an important way to improve the overall performance of materials, but this process faces many technical challenges, mainly in terms of compatibility, processing technology, mechanical property balance, thermal stability, interfacial bonding, cost and process complexity, and long-term performance stability.
The significant differences in molecular chain structures between TPE elastomers and engineering plastics lead to poor compatibility. TPE elastomers are typically composed of soft and hard segments, forming a microphase-separated structure, while engineering plastics such as polyamides (PA) and polycarbonates (PC) have highly crystalline or rigid segments. This structural difference makes it difficult to form a homogeneous system during blending, easily leading to phase separation, which in turn affects the mechanical properties and appearance quality of the blend. For example, when styrene-butadiene-styrene block copolymer (SBS) is blended with polypropylene (PP), the huge viscosity difference makes it difficult to reduce the dispersed phase size to the ideal range using traditional melt processing equipment, resulting in uneven blend performance.
Optimizing the processing technology is another major challenge in blending modification. The processing temperature and shear rate of TPE elastomers differ significantly from those of engineering plastics, necessitating adjustments to process conditions to achieve synergistic processing. For instance, when blending polyoxymethylene (POM) with thermoplastic polyurethane elastomer (TPU), the processing temperature must be controlled to prevent POM thermal degradation while ensuring sufficient plasticization of the TPU. Furthermore, shear heat generation during blending can lead to localized overheating, triggering thermal aging and further exacerbating performance degradation. Therefore, novel processing equipment or processes, such as specialized screw combinations in twin-screw extruders, are needed to achieve uniform mixing.
Balancing mechanical properties is the core objective of blend modification, but achieving it is challenging. TPE elastomers impart high elasticity and impact resistance to blends, while engineering plastics provide strength and rigidity. However, these properties often trade off, making simultaneous optimization difficult. For example, adding SBS to polypropylene (PP) can significantly improve its low-temperature impact strength, but may sacrifice some tensile strength and modulus. To address this issue, it is necessary to find the optimal balance between elasticity and rigidity by adjusting the blending ratio, introducing compatibilizers, or using core-shell structured particles.
Differences in thermal stability are also a challenge to overcome in blend modification. TPE elastomers typically have poor heat resistance, while engineering plastics such as polyphenylene oxide (PPO) exhibit excellent high-temperature stability. After blending, the low heat-resistant component may limit the overall material's operating temperature range. For example, SBS is prone to oxidative degradation at high temperatures, leading to performance deterioration in the blend. Therefore, it is necessary to add antioxidants, UV absorbers, or use TPE elastomers with better heat resistance, such as hydrogenated SBS (SEBS), to improve the thermal stability of the blend.
Interfacial bonding strength directly affects the mechanical properties and durability of the blend. Due to the polarity difference between TPE elastomers and engineering plastics, a weak boundary layer easily forms at their interface, leading to stress concentration and crack propagation. To enhance interfacial bonding, compatibilizers or surface treatments are required. For example, using maleic anhydride-grafted polypropylene (PP-g-MAH) as a compatibilizer can improve the compatibility of PP and TPU, and increase the tensile strength and impact toughness of the blend. Furthermore, modifying the surface of TPE elastomer through plasma treatment or chemical grafting can also effectively improve its interfacial adhesion with engineering plastics.
Cost and process complexity are key constraints to the commercial application of blend modification. The high cost of some high-performance TPE elastomers and engineering plastics leads to high blend costs. At the same time, blending processes require additional compatibilizers, additives, and other raw materials, and may involve multiple processing steps, further increasing production costs. For example, when preparing TPU/PA blends using reactive blending, strict control of reaction conditions is necessary to avoid side reactions, requiring high precision equipment and process control. Therefore, it is necessary to reduce the manufacturing cost of blends by optimizing formulation design, simplifying process flows, or developing low-cost alternative materials.
Long-term performance stability is a key focus that blend modification requires continuous attention. In practical applications, blends may face issues such as environmental aging and stress relaxation, leading to a gradual decline in performance. For example, outdoor TPE elastomer/engineering plastic blends need to withstand long-term exposure to environmental factors such as ultraviolet radiation and humid heat, making their weather resistance and aging resistance crucial. Therefore, accelerated aging tests and long-term performance tracking are necessary to evaluate the durability of blends and optimize formulations and process designs accordingly.
