Mesua Ferrea L Seed Oil Based Polyurethane and Melamine-formaldehyde Blends
Suvangshu Dutta and Niranjan Karak
Department of Chemical Sciences, Tezpur University, Napaam, Tezpur 784028, India
Two kinds of polyurethane resins with NCO/OH ratio of 0.5 were prepared from a renewable Mesua Ferrea L. seed oil and toluene diisocyanate (TDI) in the presence of dibutyl tin dilaurate (DBTDL) as the catalyst and xylene as the solvent as reported earlier. The polyurethane resins, namely polyurethane-ester (PE) and polyurethane-amide (PA), were blended with commercially available partially butylated melamine-formaldehyde (MF) resin at different compositions (40, 25 and 15 mass % loading of MF in PE or PA resin). All blends were obtained through solution blending technique by using xylene as the solvent in the presence of 0.5 mass % of p-toluene sulfonic acid (PTSA) as an acid catalyst. Films of blends were prepared by drawing the homogeneous solutions in the form of thin films over glass substrates using Doctor’s blade and were cured at 130°C for specified period of time. Both PE and PA based blends showed a gradual decrease in drying time with increase of MF resin content. Drying of films became faster in presence of the acid catalyst. The cross-linking between polyurethane and MF resins initiated by PTSA was confirmed by FT-IR spectroscopic analysis. The tensile strength, impact strength, adhesive strength, flexibility, hardness, elongation at break, swelling behavior and chemical resistance in different media of films for both blends were studied. Both blends were found to exhibit optimum properties at an intermediate blend ratio. The morphology of blends was investigated by scanning electron microscopy (SEM), which shows good compatibility between polyurethane and MF resins. The thermogravimetric analysis (TGA) of blends showed degradation above 200°C under the nitrogen atmosphere for both cases indicating their high thermostability.