Studies on Equivalent Viscosity of Particle-Reinforced Flexible Mold Materials Used in Soft Tooling Process

To reduce the cooling time in soft tooling process, one of the possible solutions is the use of composite mold materials, but that may affect melt mold flow properties. Therefore, a study on equivalent viscosity of melt mold material, which primarily influences the flow ability is essential. In this work, we have carried out an experimental study on equivalent viscosity of flexible mold materials (such as polyurethane and silicone rubber, which are of particular type) reinforced with highly thermal conductive filler particles, namely, aluminum and graphite powder. It has been observed that in addition to an increase of equivalent viscosity, different curing behaviors were noticed in mold materials reinforced with different fillers. By analyzing the performances of various equivalent viscosity models reported in literature, it has been observed that for higher particle size, the existing models deviate much from the experimental results. We have proposed an extension of the generalized model of Arefinia and Shojaei by including a factor that depends on particle size. It is found that the extension model provides better explanations compared to other models to the experimental results, especially for suspensions of flexible mold materials with higher particle sizes. Finally, a predictive approach is suggested for the equivalent viscosity of reinforced flexible mold materials, which may be useful to decide the amount of typical filler particles to be considered for mixing with a flexible mold material.