Embodiments generally relate to preparation of polyamide-imide resins using N-Formyl Morpholine:3-Methoxy N,N-Dimethylpropanamide. An embodiment of a method includes generating a polymer solution using a polymerization process, the polymerization process including preparing a solvent including at least N-formylmorpholine (NFM) or a combination of NFM with 3-methoxy N,N-dimethylpropanamide (MDP) as a cosolvent, mixing methylene diphenyl diisocyanate (MDI) and trimellitic anhydride (TMA) with the solvent to generate the polymer solution, and diluting the polymer solution by adding an NFM:MDP solvent mixture or MDP into the generated polymer solution. The method further includes processing the diluted polymer solution to generate polyamideimide polymer or a polyamide-amic acid resin polymer.