Low-temperature microwave-assisted pyrolysis of waste office paper and the application of bio-oil as an Al adhesive†
The conversion of waste office paper (printed or photocopied) to bio-oil via low temperature (<200 °C) microwave-assisted pyrolysis, and its utilisation as an adhesive for aluminium–aluminium bonding are reported. The yields for the organic and aqueous phase bio-oil are 19% and 23%, respectively. The pyrolysis products were characterized by ICP-MS, ATR-IR, GC-MS and NMR to reveal broad categories of compounds indicative of sugars (carbohydrates), aromatics and carbonyl-containing moieties. Application of the organic phase bio-oil (70 mg) to Al plates (50 mm × 50 mm) followed by curing at different temperatures and time periods revealed that a maximum tensile strength of approximately 2300 N could be attained at 160 °C for 8 h cure. Also, at a fixed temperature, the tensile strength increased with increasing curing time. To gain an in-depth understanding of the adhesive properties of bio-oil, a liquid–liquid fractionation of the organic phase bio-oil was conducted. The ‘acidic’ fraction showed far better adhesion properties than the ‘neutral’ fraction with no bonding achieved for the aqueous fraction. A combination of the ‘acidic’ and ‘neutral’ fraction gave better adhesion, thus suggesting a possible synergistic or co-operative effect.