The mold is then closed, and a low-viscosity reactive fluid is injected into the tool. The air is displaced and escapes from vent ports placed at the high points. Heat applied to the mold activates polymerization mechanisms that solidify the resin in the step known as cure. The resin cure begins during filling and continues after the filling process. Once the part develops sufficient green strength, it is moved or demolded.
Green strength refers to the strength of a part before it has completely cured.
When a part comes out of the mold it is still warm, and therefore still reacting. The green strength is an indication of how well it holds its shape until it is completely crosslinked. In reality, however, as shown by this schematic, it is much more complicated because processing is integrally coupled to performance. Each step of the process affects subsequent steps. Every decision made affects both processing of the part and the performance of the final part.