Practical properties and formaldehyde emission of medium density fiberboards (MDFs) recycled by electrical method

In this study, the performance of the electrical method in MDF wastes recycling was determined. For investigating the practical aspect of the electrical method, the hydrothermal method as a known recycling method was studied too. The recycling process by electrical method conducted for two different time durations (2 and 4 min) at a temperature of 100 °C and recycling using the hydrothermal method was done at a temperature of 105 °C for 150 min under 4 bar pressure with subsequent refining step. Recycled fibers were analyzed by determination of the chemical composition of fibers and fiber classification. After that, laboratory MDF boards with dimensions of 35 × 35 × 12 mm³ and density of 0.7 g/cm³ were manufactured. Practical properties of MDF boards including thickness swelling, modulus of rupture, modulus of elasticity and internal bonding were studied according to EN standard. Formaldehyde emission of boards was measured using the desiccator method. The results showed that some changes in the chemical composition of recycled fibers had occurred as compared to the original fibers, especially for the hydrothermal method where lignin content was significantly reduced. Fiber classification test showed significant reduction in the length of the fibers recycled by hydrothermal method as compared to other fibers. Investigations of the quality of manufactured MDF boards showed that the electrical method performed better in comparison with the hydrothermal method. The results of this study confirmed the positive effect of recycled fibers on reducing the formaldehyde emission from MDF boards which can be considered as an excellent benefit for the recycling process due to the importance of environmental and human health issues.