【Basic Knowledge of Glossary Definitions for “Polymers and Materials”-020】Glossary definitions related to polymers
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1. Viscous flow temperature: the transition temperature between the elastomeric state and the viscous flow state. 2. Glassy state: Amorphous polymers are in a state of pseudo-elasticity. 3. Heat distortion temperature: It refers to the temperature at which, with a heating rate of 2°C per minute and a load of 18.5 Kg/cm2 or 4.6 Kg/cm2 applied to the surface of the plastic (with the sample being 120 mm long and 15 mm wide), the sample undergoes bending deformation; this temperature is reached when the bending deflection at the midpoint of the sample reaches 0.21 mm. 4. Shear-thinning: The viscosity of pseudoplastic fluids decreases as the shear rate increases. 5. Mechanical relaxation: The mechanical properties of polymers change over time.
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Could you explain what effects the level of thermal deformation temperature has on the material?
The heat distortion temperature is a parameter that expresses the relationship between heating and deformation of the material being tested. The test for heat distortion temperature involves recording the temperature under specified loads and deformations. It is the temperature corresponding to a specified deformation when a certain load is applied to a polymer material or polymer and the temperature is increased at a certain rate. It is a measure used to assess the heat resistance of polymers or high-molecular materials. The heat deformation temperature has a significant impact on the range of applications for materials. Taking polymer materials as an example, the fourth-generation stealth fighter jets use a large amount of polymer composite materials to reduce weight and to absorb radar waves, thereby enabling stealth capabilities. An important capability of the fourth-generation stealth fighters is supersonic cruising. When flying at supersonic speeds, the airframe experiences friction with the air, which causes its temperature to rise to over 200 degrees. If the materials used do not have a heat deformation temperature of at least 200 degrees, then the aircraft will melt to a large extent even before it reaches its target. Therefore, the heat deformation temperature of the polymer composite materials used in fourth-generation stealth fighters is much higher than 200 degrees.