Heat Deflection Temperature (HDT)

Heat Deflection Temperature (HDT) is a key indicator for measuring the heat resistance of materials, referring to the temperature at which a material undergoes a specified amount of deformation under a specific load. In foreign trade, it is commonly used in specifications for products such as plastics, resins, and composites, especially in industries like automotive, electronics, and home appliances that require heat resistance. Usage scenarios include: customers requesting HDT values in inquiries, specifying quality indicators in contracts, and marking material performance in technical documents. Note: HDT is affected by test load (e.g., 0.45MPa or 1.82MPa) and deformation amount; different standards (ASTM D648, ISO 75) may yield different results. When quoting or signing contracts, the test method and conditions must be clearly specified to avoid disputes caused by standard differences. Difference from 'Vicat Softening Temperature': HDT is the deformation temperature under load, while Vicat is the needle penetration temperature; their test principles and applicable materials differ. Difference from 'Continuous Use Temperature': HDT is a short-term heat resistance indicator and does not represent long-term thermal aging performance.