Visual inspection of surface mold growth on medium-density fiberboard bonded with oxidized starch adhesives

This study aims to visually inspect the effects of oxidized starch (OS) adhesives prepared with two cross-linkers namely citric acid (CA) and blocked-polymeric MDI (B-pMDI) on the extent of surface-inhabiting molds growth on the surface of medium-density fiberboard (MDF). Five surface-inhabiting molds namely Aspergillus niger (ASN), Penicillium funiculosum (PEC), Rhizopus oryzae (RHO), Aureobasidium pullulans (AUP), and Trichoderma virens (TRV) were inoculated onto MDF samples for four weeks at 26 ± 2°C and 70–80% relative humidity to enable them grow on the surface. The extent of mycelium growth on the MDF surface was assessed by visual inspection after incubation at four time intervals. The results showed that MDF samples bonded with OS adhesives were more susceptible to the surface-inhabiting molds than the control MDF samples bonded with urea-formaldehyde (UF) resins. The resistance of mold growth on MDF-OS/CA was comparable to MDF-control, particularly against AUP, which was around 0.7 after four weeks, indicating less mold growth on the surface of MDF. The susceptibility of MDF samples to mold increased in the order of MDF-control, MDF-OS/CA, and MDF-OS/B-pMDI.