- Davis, Ethan
University of Maine Graduate School
A large amount of the waste material from the paper recycling process known as paper deinking sludge (PDS) is currently being disposed of in landfill facilities. This study explored the potential for making use of this material as an additive in the production of medium density fiberboard (MDF).
PDS was obtained from the Bowater-Great Northern recycling facility in Millinocket, ME. A treatment method was developed to reduce the moisture content and consistency of the PDS to within a raîge suitable for the production of MDF (6-9.5% MC). Treated material contained approximately l1% silicon, IïYo aluminum, 4o/o calcium, and2o/o titanium. 37Yo of the treated material passed a200 mesh screen (fine content). To investigate the effects of PDS on fiberboard, panels were produced using virgin MDF fiber (6% phenol formaldehyde resin) which included factors chosen based on PDS composition. These factors (by percent oven dry furnish weight) included fine content (0-35%), kaolin coating clay (0-20%) and calcium carbonate from (0-4Yo)
Response surface regression models were fit to describe several mechanical and physical panel properties.
Coating clay was the primary factor affecting mechanical properties, exhibiting linearly negative effects on modulus of elasticity (MOE), modulus of rupture (MOR) and internal bond strength (IB). The six model panels lacking coating clay yielded the highest values for MOE (avg. : 237,000 psi, standard deviation, SD : 28,000), MOR (avg. : 2593 psi, SD : 417), and IB strength (avg. : 59 psi, SD : 22), whlle the four panels containing the highest level of clay (20%) exhibited the lowest values for MOE (avg. : 136,000 psi, SD : 15,000), MOR (avg. : 798 psi, SD: 122), and IB (avg. : 13.50 psi, SD : 3.84). Moisture content, change in conditioned weight, and conditioned volume were found linearly increase along with clay content. By contrast, the equation for conditioned moisture content was dependent on fine and calcium carbonate content and included quadratic and linear terms. The model equation for the moisture content at RH 30o/o in the linear expansion test included a linear calcium carbonate term as well as quadratic terms for both clay and calcium carbonate. Flammability of the model panels was decreased by increasing clay content and was found to have a strong positive correlation with increased fiber content. Decay by the brown rot fungus G. trabeum increased with clay content and decreased with increased calcium carbonate content.
Comparison of actual results with values predicted using the model equations for mechanical properties (MOE, MOR, and IB strength) and the water absorption test were close to the experimental results at lower levels of PDS. As PDS content increased, deviation of actual from predicted increased. It was believed that this deviation was partially caused by the exclusion of greater than200 mesh degraded fiber from the model. Model equations for the MC at 30% RH, and the behavior of the panels under the influence of fire and decay were found to reasonably approximate the actual results.