What is the thermal performance of engineering plastics?

1, continuous working temperature

The continuous working temperature indicates the heat resistance of the plastic molded article. Generally, it is classified into physical heat resistance and chemical heat resistance. The former refers to the performance of a plastic molding pattern of a prescribed shape to maintain the shape of the product at a specified heating temperature; the latter is a thermal stability of a molecular bond in a plastic molding material. Mainly refers to the heat resistance of plastic molding patterns under no load conditions. Common engineering plastics such as PEEK have a long-term operating temperature of 260 °C.

2, glass transition temperature

When the temperature is higher than Tg, the amorphous polymer will become soft and rubbery.

It is important to ensure that the temperature of the amorphous polymer is below Tg in order to achieve the desired mechanical properties.

3, heat distortion temperature

The heat distortion temperature is a popular saying of the deflection temperature of the load. It is a method of determining the rigidity of a plastic at a high temperature: under a certain load, it is continuously heated at a certain speed until the pattern shows the temperature indicating the amount of deformation.

Since the deflection temperature under load in the amorphous plastic is a lower limit temperature which is close to the glass transition temperature, it can be a practical reference. However, in the crystalline plastic, the deflection temperature under load is a temperature between the glass transition point and the melting point of the crystal, so that it is meaningless temperature both theoretically and practically, and the deviation of the measurement result is also remarkable. This parameter is used to correspondingly measure the ability of different materials to withstand temperature rise in a short period of time and under load.

4, coefficient of linear expansion

The coefficient of linear expansion refers to the expansion ratio of a plastic molded article at a temperature rise of 1 ° C under a certain pressure, and is expressed as a coefficient of linear expansion with respect to a unit length. This coefficient is one of the important indicators for understanding the degree of change in product size as the temperature of plastic molded articles increases.

5, thermal conductivity

The thermal conductivity indicates the heat of a finished plastic product having a temperature difference of 1 ° C and a thickness of 1 cm in 1 s. It is a reference indicator for studying the thermal insulation of target products when designing products.

6, specific heat capacity

The specific heat capacity refers to the heat capacity per unit mass (1 g) of the plastic molded article. It is generally the amount of heat required to increase the temperature of a plastic molded article by 1 °C. The specific heat capacity is the same as the thermal conductivity, which is the reference data for studying the temperature rise of the target product during product design.

7, embrittlement temperature

A measure of the low temperature mechanical behavior of plastics. When the sample is impacted by a hammer having a certain energy, the temperature at which the cracking probability of the sample reaches 50% is called the embrittlement temperature. Determination of embrittlement temperature: clamp one end of the molding pattern of the specified shape and size with an experimental clamp, fix it in the experimental tank, immerse it in the specified low temperature heat transfer medium, place it for 2.9-3.1 min, and knock with a hammer One shot is used to determine the embrittlement temperature from the result of the pattern being destroyed.