Temperature of Deflection Under Load (HDT)
Determination of Temperature of Deflection Under Load (HDT) measures the temperature at which a plastic or composite specimen begins to deform under a constant flexural load. The test applies a specified stress while raising the temperature at a uniform rate until a defined deflection occurs. For medical manufacturers, HDT is essential to ensure housings, instrument components, tubing, and molded parts maintain dimensional stability during high-temperature sterilization, shipping, and clinical use.
Many medical plastics must endure autoclaving or other heat processes without softening or losing shape under load. A material with insufficient HDT can warp, affecting fit, function, or sterility. Applus+ Reliable Analysis already maintains accredited thermal testing capabilities, including HDT, along with our full suite of polymer characterization, mechanical, and environmental aging methods.
These evaluations support material qualification and regulatory requirements for medical devices and components. Manufacturers use HDT data to select appropriate resins, validate processing conditions, and document long-term thermal performance. Applus+ Reliable Analysis delivers accurate, reproducible results using equipment already operating daily under our ISO/IEC 17025 accreditation.
Temperature of Deflection Under Load (HDT) Medical Testing Standards
ASTM D648 Deflection Temperature of Plastics Under Flexural Load
ASTM D648 determines the temperature at which a plastic specimen deflects a specified amount under flexural load. The test applies a constant load (typically 0.455 MPa or 1.82 MPa) while increasing the temperature at a uniform rate until the specimen reaches a defined deflection. It is widely used for medical-grade plastics in housings, connectors, syringes, instrument components, and molded parts to ensure they maintain dimensional stability during high-temperature sterilization and use under load.
ISO 75-1 Plastics General Test Method
ISO 75-1 specifies the general procedures for determining the temperature of deflection under load for plastics and ebonite. The standard outlines specimen preparation, applied stress levels (Method A, B, or C), heating rate, and measurement of deflection. It is the primary international reference for evaluating heat resistance of medical polymers and components, particularly for products intended for European MDR compliance and high-temperature processing.
ASTM D648 / ISO 75 Autoclave and Sterilization Compatibility
The combined application of ASTM D648 and ISO 75 methods verifies that medical plastics and molded components can withstand steam autoclaving and other sterilization processes without excessive deflection or deformation under load. The standards simulate real-use conditions by applying flexural stress during temperature ramp-up. This testing is critical for ensuring dimensional accuracy and structural integrity of reusable medical instruments, trays, and device parts after repeated sterilization cycles.
USP <1031> Biocompatibility of Materials with Thermal Properties including HDT
USP <1031> addresses the biocompatibility of materials used in pharmaceutical and medical device applications and incorporates thermal characterization methods such as heat deflection temperature. The chapter helps ensure that plastics maintain mechanical performance and do not deform under load at elevated temperatures. It is commonly referenced for materials in drug-delivery devices, containers, and components where thermal stability directly impacts product safety and performance.
Your Partner for Expert Medical Plastic Laboratory Testing
Applus+ Reliable Analysis stands ready to support your medical polymer heat deflection temperature and thermal stability testing needs. Our ISO/IEC 17025 accredited laboratory already maintains the necessary HDT testers and supporting thermal chambers. This allows us to efficiently add these medical standards with only minor validation and training.
Whether you are qualifying new tubing and connectors, validating molded housings, or ensuring performance of rigid medical components, our team provides accurate and reliable data backed by decades of materials testing expertise. We invite you to Contact us to discuss how our expanded medical testing capabilities can support your next project or regulatory submission.
Additional Applus+ Reliable Analysis’ Commercial Medical Testing Capabilities
Whether it be material EMC, environmental, fabrication, or durability testing, Applus+ Reliable Analysis has a full lab of test equipment. This permits us to provide short lead times on scheduling. Our team strives to give our customers more time and energy on product development rather than testing.
Below is a list of common medical testing types that Reliable Analysis offers. Don’t see what you are looking for? Contact us, and we will determine the best course of action.
