7 parameters that must be known about the thermal properties of engineering plastics
1. heat resistance
The continuous working temperature indicates the heat resistance of plastic molding products. Generally divided into physical heat resistance and chemical resistance, the former refers to the provisions of the shape of the plastic molding style when the heating temperature is specified, the performance to maintain the shape of the product; the latter is that the thermal stability of plastic molding materials in molecular bond.
2. Glass transition temperature
The temperature is higher than Tg, non crystalline polymers will become soft and rubbery. It is very important to ensure that the use temperature of amorphous polymers is lower than Tg, so that the ideal mechanical properties can be obtained.
3. Hot deformation temperature
Hot deformation temperature is a popular term for load deflection temperature. It is a method of measuring the rigidity of plastics at high temperature: heated at a certain speed under a certain load until the temperature of the pattern indicating the amount of deformation is indicated.
Because in non crystalline plastics, the load deflection temperature is the lower limit temperature which is close to the glass transition temperature, so how much can be used as a practical reference index.
But the crystalline plastic, load deflection temperature is between the glass transition and crystallization melting temperature, so it is no significance either in theory or in the temperature of the utility, and the deviation of the measurement result is obvious. This parameter is used to measure the temperature tolerance of different materials under short time heating and load conditions.
4. Coefficient of linear expansion
Linear expansion coefficient refers to the expansion ratio of plastic molding products at a temperature of 1 degrees under certain pressure, which is expressed as linear expansion coefficient relative to the unit length. This coefficient is one of the important indexes to understand the change degree of product size with the increase of plastic forming temperature.
5. thermal conductivity
The thermal conductivity of said through the temperature of 1 DEG C, the thickness of 1 cm of the plastic products of heat in 1s. It is a reference index to study the heat insulation of the target product in the design of the product.
6. specific heat capacity
Specific heat capacity refers to the heat capacity relative to the plastic unit mass (1g). Generally refers to the amount of heat required for plastic molding to increase by 1 degrees centigrade. The specific heat is the same as the thermal conductivity, and it is the reference data for studying the temperature rise of the target product in the product design.
7. Embrittlement temperature
A measure of mechanical behavior of plastics at low temperature. When the impact rate of the sample reaches 50%, the brittleness temperature is determined by the impact hammer with a certain energy.
Determination of embrittlement temperature: experimental clamp end provisions molding pattern shape and size, fixed on the groove, soaked in low temperature heat transfer media at all levels specified in place after 2.9-3.1min, with a hammer blow, destroyed from the style of results to calculate the brittle temperature.