POTENTIAL OF PULP AND PAPER SECONDARY SLUDGE AS CO-ADHESIVE FOR PARTICLEBOARD MANUFACTURING

摘要

The most common sludge disposal methods are landfilling, incineration for power production, and land application for soil amendment. Current disposal alternatives are affected by shrinking space, public opposition, increasing regulatory pressure, and poor economics. Valuing sludge as a commercial product would be a beneficial way to recycle this residue. Secondary sludge (SS) is rich in protein and lignin and has some binding potential. This study investigated the potential of SS as urea-formaldehyde (UF) co-adhesive for particleboard manufacturing. Three proportions of SS from three conventional pulping processes (thermomechanical pulp (TMP), chemical-thermomechanical pulp (CTMP) and Kraft pulp (Kraft)) were added in the formulation of particleboard manufacturing. A 3~3 factorial design was used where the factors were urea-formaldehyde (UF) content (5%, 7%, and 9%), pulping process (TMP, CTMP and Kraft) and secondary sludge percentage (75%, 100%, and 125%), with three replicates. Three control panels were made for each UF's content also (3x3 = 9). A total of 90 panels were produced. All panels were tested for thickness swell (TS), linear expansion (LE), internal bond strength (IB), flexural modulus of elasticity (MOE), flexural modulus of rupture (MOR) and formaldehyde emission (FE). Results indicated that particleboards made with SS from TMP and Kraft pulping processes met the ANSI standards for LE, IB, MOE and MOR (with 7% and 9% UF). However, the thickness swell of panels made with SS was higher than that of control panels and adding SS to the formulation affected negatively this property. Particleboards from made with CTMP SS failed to meet most standards. SS sludge reduced FE, especially for particleboards made with CTMP SS. It was concluded that TMP and Kraft SS can be used as a co-adhesive for particleboard manufacturing. The main advantage of using SS as co-adhesive is environmental in nature due to the important reduction of formaldehyde emission.