What ingredient is used to hold chopped strand mat together?

Chopped strand mat is a type of fiberglass reinforcement made from randomly oriented strands of glass fibers. The ingredient used to hold these strands together is known as a binder. The binder is crucial because it gives the mat its structural integrity, allowing it to maintain its shape while also facilitating easier handling during the composite manufacturing process.

In the context of composites, resin plays a different role; it is the matrix that saturates the mat and hardens upon curing to provide structural strength and durability. The hardener is an additive that is mixed with the resin to initiate the curing process, turning the resin from a liquid to a solid state. Plasticizers are substances added to materials to increase their flexibility and workability but are not relevant to the binding of the fibers in chopped strand mat. Therefore, the correct answer highlights the specific function of the binder in the context of composite materials.