How do you check heat deflection temperature?
How do you check heat deflection temperature?
Test Procedure: A load of 0.45 MPa or 1.80 MPa is placed on each specimen. The specimens are then lowered into a silicone oil bath where the temperature is raised at 2° C per minute until they deflect 0.25 mm for ASTM, 0.32 mm for ISO flatwise, and 0.34 mm for ISO edgewise.
At what temperature does plastic distort?
The molding of plastics by necessity occurs at high temperatures (routinely 200 °C or higher) due to the low viscosity of plastics in fluid form (this issue can be addressed to some extent by the addition of plasticizers to the melt, which is a secondary function of a plasticizer).
What is ASTM 648?
ASTM D648 determines the temperature at which an arbitrary deformation occurs when specimens are subjected to an arbitrary set of testing conditions. ASTM D648 applies to molded and sheet materials available in thicknesses of 3 mm (0.125 in) or greater which are rigid or semirigid at normal temperature.
At what temperature does heat distortion occur?
Cold 38 °F air over Puget Sound at 50 °F causes heat distortion. Heat distortion is not restricted to hot summer days. It can also occur in arctic temperatures during winter where the sun warms the land or mountainside to a temperature well above the air temperature.
What is HDT testing?
HDT stands for Heat Deflection Temperature or Heat Distortion Temperature. In other words, it is the temperature at which a given polymer test bar will be bended of 0.25 mm under a given load. It is one of the two basic methods for assigning a value to the performance of plastics at high temperature.
What is the size of HDT specimen?
The HDT is defined by ASTM D 648 as the temperarture at which a sample bar of standard dimensions (127x 13 x 12 mm) deflects by 0.25 mm (0.01 in) under a centered standard flexural load of 455 kPa (66 psi) or 1.82 MPa (264 psi).
What is significance of HDT?
The heat distortion temperature (HDT) – also known as the deflection temperature under load (DTUL) or heat deflection temperature – is an important property of polymers. It gives an indication at what temperature materials start to “soften” when exposed to a fixed load at elevated temperatures.
What is HDT of a material?
The Heat Deflection Temperature (HDT), or Heat Distortion Temperature, is a measure of a polymer’s resistance to alteration under a given load at an elevated temperature. It is also known as the ‘deflection temperature under load’ (DTUL) or ‘heat deflection temperature under load (HDTUL)’.
How is HDT measured?
The test sample is submerged in oil for which the temperature is raised at a uniform rate (usually 2°C per minute). The load is applied to the midpoint of the test bar that is supported near both ends. The temperature at which a bar of material is deformed 0.25mm is recorded as the HDT.
What is HDT plastic?
Why is heat deflection temperature useful?
Why is Heat Deflection Temperature useful?
What is heat deflection temperature in polymer testing?
The heat deflection temperature is a measure of polymer’s resistance to distortion under a given load at elevated temperature. In other words, it is the temperature at which a given polymer test bar will be bended of 0.25 mm under a given load.
How to measure the thermal deformation of concrete?
The testing devices used for measuring the thermal deformation of concrete are the same as those described in Section 1.1. The testing procedure is as follows: 1. Put the specimen directly into the furnace for deformation testing. 2. Install the deformation transducer and recording instrument.
What is thermal deformation in chemistry?
Thermal deformation is the property of a substance to expand with heat and contract with cold, customarily called temperature deformation. It is expressed by linear expansion coefficient α, which is defined by: Δt is the temperature difference (K).
How do you test for deformation in a furnace?
1. Put the specimen directly into the furnace for deformation testing. 2. Install the deformation transducer and recording instrument. 3. Switch on the electrical power. 4. Heat the specimen in a low velocity (2–5 °C/min) until the temperature reaches the predetermined value.
