Synthesis and Characterization of Bio- Based Thermosetting Resins from Lactic Acid and Glycerol

A bio-based thermoset resin has been synthesized from glycerol reacted with lactic acid oligomers of three different chain lengths (n): 3, 7, and 10. Lactic acid was first reacted with glycerol by direct condensation and the resulting branched molecule was then end-functionalized with methacrylic anhydride. The resins were characterized by Fourier-transform infrared spectroscopy (FT-IR), by C-13-NMR spectroscopy to confirm the chemical structure of the resin, and by differential scanning calorimetry and dynamic mechanical thermal analysis (DMTA) to obtain the thermal properties. The resin flow viscosities were also measured using a rheometer with different stress levels for each temperature used, as this is an important characteristic of resins that are intended to be used as a matrix in composite applications. The resin with a chain length of three had better mechanical, thermal, and rheological properties than the resins with chain lengths of seven and 10. Also, its bio-based content of 78% and glass transition temperature of 97 degrees C makes this resin comparable to commercial unsaturated polyester resins. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40488.