An improved polyisocyanurate comprising polymethylene polyphenylisocyanate having a functionality of 2.1 to 3.2 and having an equivalent weight between 120 and 180; a polyol having an equivalent weight between 30 and 100; certain tertiary amino phenols; an alkali metal carboxylate, and a blowing agent.These compositions exhibit an advantageous cream time, firm time, tack free time, and a low friability.