Push rods may be of the vitreous silica type, the high-purity alumina type, or the isotropic graphite type.ĪSTM D696 – This test method covers determination of the coefficient of linear thermal expansion for plastic materials having coefficients of expansion greater than 1 µm/(m.☌) by use of a vitreous silica dilatometer. It is the widely used technique in which specimen is heated in a furnace and displacement of the ends of the specimen are transmitted to a sensor by means of push rod. (ofcourse there exist several other methods as well, but they are not discussed here). The main techniques used for CTE measurements are: Most widely used standards to measure coefficient of linear thermal expansion in plastics ( thermoplastics and thermosetting materials, filled or unfilled, in the form of sheet or molded parts) are ASTM D696, ASTM E831, ASTM E228 and ISO 11359. How to Measure Coefficient of Linear Thermal Expansion? » Factors Affecting Thermal Expansion Coefficient Measurements » Main Techniques Used to Measure CTE, Linear
It also determines thermal stresses that can occur, and cause failure of a solid artifact composed of different materials when it is subjected to a temperature excursion (specially to predict efficient material bonding or while using plastics with metals)Ĭheck out more on Linear Coefficient of Thermal Expansion:. It helps determine dimensional behavior of structures subject to temperature changes. » Find out the top 3 roots causes to avoid plastic quality crashes efficiently Thermal expansion is often used to predict shrinkage in injection molded parts. Hence, CLTE is important for the economics of production as well as the quality and functioning of products. The thermal expansion difference develops internal stresses and stress concentrations in the polymer, which allows premature failure to occur. When reporting the mean coefficient of thermal expansion, the temperature ranges must be specified. Therefore, α is obtained by dividing the linear expansion per unit length by the change in temperature. ΔT is temperature change, ☌, during test. L 0 is the original length of specimen at room temperature. ΔL is change in length of test specimen due to heating or to cooling. 
α is coefficient of linear thermal expansion per degree Celsius.
0 kommentar(er)
