Understanding variables that affect production of unsaturated polyester polyols based on dimer fatty acids Unidyme®14 and Unidyme®18 with ethylene glycol and 1,4-butane diol that were synthesized via the polycondensation reaction mechanism. We studied a fast way to determine molecular weight, which usually takes a lot of time and is not very economical and ecological. Among the experimental controlled parameters for each polyol synthesis a special attention was paid to these products viscosity, color, molecular weight, acid and hydroxyl value parameters of extremely commercial importance. The Unidyme®14 dimer fatty acid, having a dimer acid percentage of 94%, induces the polyols based on them to be products of relatively commercial relevance. As for the Unidyme® 18 dimmer fatty acid, its dimer percentage is 81,8%. Unidyme®18 its based polyols commercial interest is specially relevant not only when a lower cost is a relevant factor, but also when its trimmer content is important to confer non-crystallinity properties to the final end product. Also, flexible polyurethane foams were developed (1250-2000 molecular weight) polyol polyester and tested regarding oil absorption capacity.