Abstract: An improved polyformal is provided which has the formula:V-- R -- O -- CH.sub.2 -- O ] Wwherein R is the hydrocarbon portion of an .alpha.,.omega.-glycol, containing at least 4 carbon atoms in a single chain or a 4 carbon atom chain interrupted by a heteroatom which is oxygen or sulfur; wherein V is (a) --OCH.sub.2 OH or (b) --OCH.sub.2 ROH and W is (c) --ROCH.sub.2 OH or (d) ROH, R being as defined, wherein the ratio of the total of (b) and (d) to the total of (a) and (c) is not less than 9:1; and x is an integer representing the degree of polymerization of a magnitude sufficient to produce a molecular weight of at least 500. In addition, improved isocyanate terminated prepolymers and polyurethanes are also provided, as well as processes for preparing the improved polyformal.