GB/T 1634.1-2019

This part of GB/T 1634 specifies the method for determining the deformation temperature of plastics under load (bending stress under three-point loading). To adapt to different types of materials, it stipulates different types of specimens and different constant test loads. GB/T 1634.2 specifies specific requirements for plastics (including filled plastics and fiber-reinforced plastics with fiber length not exceeding 7.5 mm) and hard rubber. GB/T 1634.3 specifies specific requirements for high-strength thermoset laminates. This part is applicable to evaluating the relative performance of different types of materials under load when heated to high temperatures at a specified heating rate. The results obtained may not necessarily represent the maximum applicable temperature. Because major factors in actual use, such as time, loading conditions, and nominal surface stress, may differ from the test conditions. Only data obtained from materials with the same bending modulus at room temperature are truly comparable. This part specifies the preferred dimensions of the specimens used. This part is commonly referred to as HDT (Heat Distortion Test), although no official document uses this identifier.