Linear Coefficient of Thermal Expansion Test

When any material is heated, it begins to expand under the influence of increasing temperature. This causes significant changes in dimensions, part warpage, or internal stress. Linear (linear) coefficient of thermal expansion is a material property that characterizes the ability of a plastic to expand under the influence of temperature rise. The linear thermal expansion coefficient expresses how long the developed part will remain dimensionally stable under temperature changes.

The most common standards referenced for measuring the coefficient of linear thermal expansion in plastics are the following standards developed by the American Society for Testing and Materials (ASTM):

• ASTM D696-16 Standard test method for linear coefficient of thermal expansion of plastics from minus 30 degrees to plus 30 degrees with a vitreous silica dilatometer
• ASTM E831-19 Standard test method for linear thermal expansion of solid materials by thermomechanical analysis
• ASTM E228-06 Standard test method for linear thermal expansion of solid materials with a push-rod dilatometer

In addition, the ISO 11359 Plastics - Thermomechanical analysis (TMA) standard developed by the International Standards Organization (ISO) is based on.

The main techniques used in measurements in general are: dilatometry, interferometry and thermomechanical analysis.

The nature of most plastics and the nature of the dilatometer make minus 30 to plus 30 degrees Celsius a suitable temperature range for linear thermal expansion measurements of plastics. This range includes the temperatures at which plastics are most commonly used.

The thermal expansion of a plastic consists of a reversible component where length changes are superimposed due to changes in moisture content, curing, loss of plasticizers or solvents, release of stresses, phase changes, and other factors. Linear thermal expansion coefficient tests aim to determine the linear thermal expansion coefficient while excluding as many of these factors as possible. In fact, it is generally impossible to completely exclude the influence of these factors. Therefore, whichever test method is applied, it is expected to give an approximation of the actual thermal expansion.

Our organization also provides linear thermal expansion coefficient testing services with its trained and expert staff and advanced technological equipment, among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors.