Specific Heat
Sensitivity | Availability | Datasheet Category | Cool Time Relationship |
|---|
Low | High | Physical Properties | Direct Variation |
The Specific Heat of a material is the energy required to raise the temperature of one kilogram of the material by one degree Celsius. Materials with lower Specific Heat require less energy to heat up and cool down, so cool time decreases as Specific Heat decreases.
Specific Heat appears in the Physical Properties category in the material specification. Accuracy of values for this property is less important than accuracy of values for
Eject Deflection Temp,
Mold Temp, and
Melting Temp.
Estimating Specific Heat
If you want to add a new material to your Digital Factory, and you cannot obtain Specific Heat from a material’s specification, you may be able to estimate the value based on the Specific Heat for a similar base polymer. The following considerations may help you formulate your estimate:
• Specific Heat of a polymer decreases as the volume of glass fiber in it increases.
• Typically, semi-crystalline polymers have higher
Specific Heat values than amorphous polymers. (For information on which materials are semi-crystaline and which are amorphous, see
https://www.iapd.org/Documents/Members%20Only/iapd_rectangle.pdf. Note that URLs may change.)
If you know the Specific Heat for the raw polymer, you may be able to calculate composite Specific Heat as a weighted sum:
1 For each component of the mixture, find the density, D1, D2, …, Dn. For the density of glass, use 2500kg/m3.
2 Find the fraction, F1, F2, …, Fn, of the volume of the mixture accounted for by each component. For example, if a compound contains 30% glass fiber and 70% polymer resin, the fractions are 0.3 and 0.7.
3 Find the specific heat, Cp1, Cp2, …, Cpn, of each component of the mixture. For the specific heat of glass, use 0.84J/g°C.
4 Estimate Sepcific Heat for the mixture as the weighted sum (F1 * D1 * Cp1) + (F2 * D2 * Cp) + … + (Fn * Dn * Cpn).