| 摘要 |
<p>Impregnating compositions for the manufacture of preimpregnated mats are formulated by the addition to aqueous phenol-formaldehyde resins of resol type of a thickening agent consisting of zinc or manganese borates or of related products. The viscosity of these compositions, which are initially quite fluid, changes sufficiently rapidly for the preimpregnated mats to develop an appropriate consistency for their storage and their handling, while remaining suitable for the forming and the definitive curing by hot pressing.</p> |
