Let me dispel one myth about sizings. Many glass reinforcement products are multi-compatible. This does not mean the product is a compromise between polyester and epoxy or between vinyl ester and polyester. In fact, the chemistry used to make it multi-compatible often has a synergistic effect enhancing the performance in one or the other resin matrix. Reinforcement suppliers are well-versed in recommending the appropriate sizing once they know the resin matrix in which the product will be used.

Binder is often referred to as the chemistry applied after the glass fibers are manufactured to stick the bundles of glass fibers together to create mats. Binders fall into two general categories – soluble and insoluble. Soluble binders are intended to dissolve very quickly, allowing the glass to lie down nicely. They are commonly used in hand layup operations. Insoluble binders are very slow to dissolve, allowing the wetted mats to maintain their integrity and permit resin flow within their architecture. Pultrusion and infusion processes use insoluble binder mats.

This is only the tip of the iceberg with respect to glass fiber reinforcements. An understanding of the composition of glass reinforcements and their product forms is a good place to start. Physical, mechanical, dimensional, thermal and durability properties will be covered in a future column.