A process which comprises reacting a glycol-digested polyethylene terephthalate (PET) or glycol-modified polyethylene terephthalate (PETG) with a glycol selected from the group consisting of propylene glycol, diethylene glycol, 2-methyl-1,3-propanediol, sorbitol, neopentyl glycol, glycerol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, bisphenol A ethoxylates, 1,6-hexanediol, block or random copolymers of ethylene oxide and propylene oxide, and mixture thereof, and an unsaturated dimer fatty acid to produce the polyol, wherein the molar ratio of dimer fatty acid to PET or PETG is within the range of 0.1 to 0.5, the molar ratio of glycol to PET or PETG is within the range of 2.5 to 4.5, and the polyol has a hydroxyl number within the range of 40 to 400 mg KOH/g.