It is important to consider material characteristics when selecting a thermoset material grade.
Material data used in Reactive Molding analyses include the following:
- Melt temperature and recommended range.
- Mold temperature and recommended range.
- Ejection conversion-the lowest conversion value (degree of cure) at which a part can be ejected from the mold without causing defects.
- Reactive viscosity-calculated as a function of temperature, shear rate, and conversion (extent of cure).
- Gelation conversion-the level of conversion at which the resin stops flowing. It is also coupled with the reactive polymer viscosity models to determine the instant when viscosity becomes infinite.
- Melt density.
- Solid density.
- Specific heat.
- Thermal conductivity.
- N-th order kinetics with induction time-the reaction in the resin is described by the curing kinetics model during the conversion period and by the induction model during the induction period. Many fast-curing resins, such as epoxy or polyurethane, do not exhibit an induction period. This model is a general form and has been applied to various reactive resins.
The definition of conversion (degree of cure) is extended to include the induction period, if one exists. Under this model, conversion is described by a numerical value between 0 and 1, as indicated below:
| Conversion value |
Means |
|---|
| 0 |
At the beginning of the reaction or induction period |
| 0 < conversion < 1 |
During the induction or reaction (conversion) period |
| 1 |
At the end of reaction (conversion) |
If filler material is used, the following data must be specified:
- Density.
- Specific heat.
- Thermal conductivity.
- Mechanical data.
- Coefficient of thermal expansion (CTE) data.
- Tensile strength data.
- Aspect ratio.