Zinc borate is a non-halogenated flame retardant. Zinc borate is useful as a flame retardant in polyethylene and PVC. The boron functions as a flame retardant by forming trihalides which are effective Lewis acids. The boron trihalides promote cross-linking which minimizes flammable gasses forming from the polymer. In addition to the hydrate, zinc borate can be offered as the metaborate.