The present invention relates to novel catalysts for use with a fiberglass non-woven binder. The catalyst can be a Lewis acid, an organic acid salt, a free-radical generator, or a mixture thereof. The catalyst provides stronger bonding, increased crosslinking density, reduced curing times, and reduced curing temperatures. Fiberglass mats made with polymer binder compositions containing the catalyst exhibit both flexibility and elasticity, allowing the mats to be compressed for storage, yet return to original thickness once the compressive forces are removed. Formaldehyde-free wood composites, such as plywood and fiberboard, may also be produced with polymer binder compositions containing the catalyst.