As with all materials, Desmopan® expands when the temperature increases and contracts again when the temperature falls. This is expressed by the coefficient of linear thermal expansion, which is a function of the temperature at which the measurement is taken and the material’s Shore hardness.
Glass-fiber-reinforced grades of Desmopan® are interesting in this respect. Even with a glass fiber content of just 20 %, their coefficient of thermal expansion undergoes a considerable fall – down to the level of aluminum or steel, although the Young’s modulus does not increase beyond 2,000 MPa in the process.
The thermal conductivity is measured on the basis of DIN 52612 and sets out the quantity of heat that passes through a given specimen thickness in a unit of time.
At 20 °C, Desmopan® has a thermal conductivity of 0.20 to 0.25 W/(K m). At 80 °C, its thermal conductivity falls to 0.17 to 0.20 W/ (K m).
The specific heat is measured on the basis of DIN 51005 and expresses the amount of energy that is required to heat a specific mass of a material by 1 K.
At 20 °C, Desmopan® has a specific heat of 1.45 to 1.70 J/g K. At 80 °C, this increases to 1.70 to 1.90 J/g K.
Heating value from combustion
This value is determined on the basis of DIN 51900 and indicates the amount of energy released when one gram of the material undergoes combustion.
A distinction is drawn between the heating value and the calorific value. Desmopan® has a heating value of between 25,000 and 28,000 J/g. Desmopan® has a calorific value of between 26,000 and 29,000 J/g.
Heat distortion temperature
In the case of rigid thermoplastics, the heat distortion temperature is frequently specified as the Vicat
softening temperature (VST) to ISO 306 or the heat deflection temperature (HDT) to ISO 75.
These measurement methods are not suitable for thermoplastic polyurethanes such as Desmopan®,
since the measured values display a pronounced dependence on the Shore hardness and therefore
have no information value.