Selecting high-temperature resistant plastics requires a comprehensive evaluation based on multiple core criteria-including thermal, mechanical, and environmental compatibility-to prevent product failure caused by relying on a single parameter.
Core Thermal Performance Indicators
- Heat Deflection Temperature (HDT): The temperature at which a material undergoes a specified deformation under a defined load; a key indicator of short-term heat resistance (tested per ASTM D648). Higher values indicate superior structural stability at high temperatures.
- Continuous Use Temperature (CUT/RTI): The maximum temperature at which the material operates stably over the long term. Evaluation should consider a service life of 1,000 to 10,000 hours; this is the primary basis for selection in long-term high-temperature applications.
- Vicat Softening Temperature (VST): The critical temperature at which the material begins to soften under heat (tested per ASTM D1525); it helps determine processing limits and short-term heat resistance thresholds.
- Thermo-oxidative Aging Stability: Thermal decomposition temperature (Td) is determined via Thermogravimetric Analysis (TGA); typically, Td ≥ 300°C is required, along with a mass loss of less than 5% after 1,000 hours at 150°C, to ensure performance does not degrade during prolonged high-temperature exposure.
Key Mechanical Performance Indicators
- High-Temperature Mechanical Property Retention: The rate of decline in tensile and impact strength at elevated temperatures. High-quality materials typically retain ≥70% of tensile strength and ≥60% of impact strength at 120°C.
- Creep and Fatigue Resistance: The ability to resist deformation under sustained stress at high temperatures. Glass fiber-reinforced grades significantly enhance rigidity and creep resistance, making them suitable for structural and transmission components.
- Flexural Modulus: Reflects the material's rigidity at high temperatures; a crucial reference factor when selecting materials for precision structural components and load-bearing parts.