| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4513331 | Industrial Crops and Products | 2014 | 8 Pages |
•Improved utilization of switchgrass through liquefaction thermal conversion.•An environmentally friendly organic solvent (diethylene glycol) was utilized for liquefaction.•Optimization of liquefaction time and temperature and blending ratio (epoxy:bio-oil) for maximum polymer performance.
The goal of this study was to determine the optimum liquefaction time and temperature needed to produce a bio oil such that the thermal and mechanical properties of the bio oil based epoxy thermosets would be optimized. Switchgrass was liquefied at temperatures between 200 and 260 °C for 1–3 h to produce bio oil with varying amounts of functional groups such as hydroxyl groups (OH). The bisphenol A/epichlorohydrin derived liquid epoxy resin was then blended with bio-oil at ratios between 1:1 to 1:4 and cured for mechanical and thermal testing. The optimal recipe for liquefaction was 250 °C for 2 h and the optimal ratio for most properties was a 1:1 (epoxy:oil) ratio. The storage modulus of the bio-modified polymer performed best at this ratio for temperatures greater than 70 °C. Likewise, higher degradation temperatures and lower weight loss upon exposure to acetone solvents also demonstrated the highest crosslinking efficiency at a 1:1 ratio. Vibration spectroscopy confirmed a nearly complete consumption of OH functional groups at this ratio based on the disappearance of the peak absorbance at 3336 cm−1. It was concluded that the severity of liquefaction coupled with precise tuning of epoxy:oil ratio was an effective method to control cross linking while ensuring the highest thermal and mechanical properties of the bio-modified polymer. Furthermore, there was excess diethylene glycol in the bio-oil after liquefaction resulting in a plasticizing effect on the epoxy as indicated by the lower glass transition at lower residence times during liquefaction.
