Synthesis of carbohydrate biomass-based furanic compounds bearing epoxide end group(s) and evaluation of their feasibility as adhesives

Current issues of energy and environment prompt us to replace fossil-based resources with renewable and sustainable ones. In this regard, carbohydrate biomass photosynthesized from atmospheric carbon dioxide attracts much attention due to its abundance and availability. Recently, furanic compounds that can be derived from carbohydrate biomass are highlighted as promising substitutes for aromatic compounds that are totally dependent on petroleum reforming processes. In this article, we report on several carbohydrate biomass-based furanic compounds as alternatives to petroleum-based adhesives. Furanic compounds bearing epoxide end group(s) were synthesized from renewable and sustainable carbohydrate biomass-based compounds (>70% yields). Another bis-epoxy furanic compound with a mimetic structure of bisphenol A (BPA) was also synthesized from xylose-derived 2-furan carboxylic acid and acetone (39% overall yield). In particular, epoxy groups were efficiently introduced to the hydroxymethyl functionality attached by furanic cores under the bi-phasic solvent system using phase transfer catalysis. Cationic photo-curing kinetic profiles of synthetic compounds were investigated in terms of heat flow integrals using photo-DSC. It was found that their halftime values (t(1/2)), representing curing rates, ranged from 0.54 to 1.15min when irradiated with 40mW/cm(2) UV light. When synthetic furanic compounds functionalized by epoxide group(s) were used for bonding polycarbonate by cationic photo-curing, we noted that tensile-shear strength of PC joints bonded with biomass-based furan mono-epoxide having furan ring was greater (4.7MPa) than that of joints bonded with petrochemical-based phenyl glycidyl ether having phenyl ring (2.6MPa). When bonded with di-epoxide functionalized furan di-epoxide, tensile-shear strength of PC joint was 3.5MPa after photo-curing for 3min at 40 degrees C. However, bis-furan di-epoxide (bFdE), the mimetic compound of BPA showed lower tensile-shear strength (approximately 1MPa) due to structural features of bFdE, such as rigidity and hydrophobic property.