a process utilizing pet as a reactive constituent to manufacture other polymers containing the pre - condensed moieties by the rapid transesterification of the condensation polymer with a pre - made modifying polymer containing the desired mix of other monomers . the process involves as a first step the manufacture of a modifying polymer containing the desired mix of acids and alcohols to a specific molecular weight such molecular weight dependent on the desired final level of utilized condensation polymer and the finished molecular weight . the second step of the process involves the rapid buildup of molecular weight and / or polymer uniformity by the rapid transesterification of the condensation polymer with the modifying polymer . the second step can be performed in any suitable vessel including an extrusion line . the process has the advantage of greatly reduced cycle times over other condensation polymer utilization processes such as the recycling of pet into other materials .