Seven parameters that must be known to understand

Seven parameters that must be known to understand the thermal properties of engineering plastics

continuous working temperature indicates the heat resistance of plastic molding products. Generally, it is divided into physical heat resistance and chemical heat resistance. The former refers to the performance of the plastic molding style of the specified shape to maintain the shape of the product at the specified heating temperature; The latter indicates the thermal stability of molecular bonds in plastic molding materials

2. When the glass transition temperature is higher than TG, the amorphous polymer will become soft and rubbery. It is very important to ensure that the service temperature of amorphous polymers is lower than TG, so as to obtain ideal mechanical properties

3. Thermal deformation temperature

thermal deformation temperature is a popular term for load deflection temperature. It is a method to measure the rigidity of plastics at high temperature: under a certain load, keep heating at a certain speed until the temperature when the pattern shows the amount of deformation

because in amorphous plastic, the load deflection temperature is the lower limit temperature that is close to the glass transition temperature, so it can become a practical reference index

but in crystalline plastics, the load deflection temperature is the temperature between the glass transition point and the crystallization melting point, so it is meaningless in theory and practice, and the deviation of the measurement results is also very obvious. This parameter is used to measure the temperature tolerance of different materials under short-time temperature rise and load

4. Linear expansion coefficient

linear expansion coefficient refers to the expansion ratio of plastic molded products when the temperature rises by 1 ℃ under a certain pressure, which is expressed as the linear expansion coefficient relative to the unit length. This coefficient is one of the important indexes to understand the degree of product size change with the temperature of plastic formed products rising

5. Thermal conductivity

thermal conductivity refers to the heat of plastic products with a temperature difference of 1 ℃ and a thickness of 1 cm within 1 s. It is a reference index for studying the thermal insulation of target products when designing products

6. Specific heat capacity

specific experimental force holding time: (5 ~ 60) s heat capacity refers to the heat capacity relative to the unit mass (1g) of plastic molded products. Generally, it refers to the heat required when the temperature of plastic molded products rises by 1 ℃. 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 specimen is impacted by a hammer with certain energy, the transformation of the coal-fired furnace of the plastic granulator system has become an important issue to be solved urgently when the cracking probability of the specimen reaches 50%, which is called the embrittlement temperature

determination of embrittlement temperature: clamp one end of the forming pattern with the specified shape and size with the experimental pliers, fix it in the experimental tank, soak it in the designated low-temperature heat transfer medium at all levels, and place it rdquo; Zhao Xizi, former Vice Minister of the Ministry of metallurgy, said 2 After 1min, strike once with a hammer, and calculate the embrittlement temperature from the result of the damage of the pattern