Ultraviolet curing oligomers and liquid coating compositions based thereon are disclosed which cure with ultraviolet light in the presence of a photoinitiator. The coating compositions can provide either a single coating for optical glass fiber which resists microbending difficulties down to around -40° C., or a topcoat for overcoating softer buffer coatings which resist microbending down to around -60° C. The coating compositions consist essentially of the linear polyacrylate- terminated polyurethane polyurea oligomer in admixture with an ultraviolet curable liquid acrylate or polyacrylate to provide the liquidity needed for application and to adjust the hardness or softness of the cured coating for the selected single coat or topcoat utility. The linear polyacrylate-terminated polyurethane polyurea oligomer comprises a linear polyurethane terminated with an essentially monohydric adduct of low molecular weight diprimary amine with from about 1 to about 2.5 moles of monoepoxide per mole of diamine and reacted with a monohydric acrylate to leave about 1 hydroxy group per molecule. The several acrylate terminal groups increases the toughness and the cure speed.
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