Which closed molding procedure is characterized by vacuum pressure only?

The procedure characterized by vacuum pressure only is infusion molding. In this technique, a dry fiber reinforcement is placed into a closed mold, and resin is drawn through the fibers by creating a vacuum. This process allows for a controlled flow of resin, ensuring that it fully saturates the fiber material, which contributes to a high-quality composite with reduced void content and improved mechanical properties.

Infusion molding is particularly advantageous for manufacturing large and complex components, as the vacuum pressure effectively manages the resin distribution without requiring additional pressure from other sources, such as pumps or mechanical means, that might be used in other molding techniques. The vacuum not only aids in drawing the resin into the mold but also helps eliminate air from the system, which is crucial for maintaining the integrity of the composite material.

In contrast, other methods, such as resin transfer molding and compression molding, typically employ combined methods of pressure application during the curing process, which means they do not rely on vacuum pressure alone like infusion molding does. Blow molding is a technique used for forming hollow plastic parts, which is different from the processes used for creating composite materials. Understanding these distinctions helps clarify why infusion molding stands out in this context.