Viscosity Minimum

Heating Influence

Faster temperature ramps generally lead to a lower absolute value at the trough of the curve. This happens because the resin reaches higher temperatures before the chemical cross linking has time to heavily increase the molecular weight. A lower viscosity minimum allows for better wetting of tight geometries but increases the risk of excessive resin squeeze out.

If the value is too high, the resin will not flow sufficiently to remove air bubbles from the stackup. Press operators must balance the ramp rate to hit a target range that ensures both wet out and structural integrity.

Material Aging

The shelf life of the prepreg also affects this property. As the material ages, the baseline polymerization level rises, which typically increases the viscosity minimum and shortens the time the resin remains fluid. This shift requires adjustments to the press parameters to maintain consistent results.