Modification of nanoclay with different methods and its application in urea-formaldehyde bonded plywood panels

The reinforcement of pristine nanoclay (PNC) and modified nanoclay (MNC) in urea-formaldehyde (UF) resins at the alkaline stage of synthesis was investigated in this work. The modification of PNC using copper (II) chloride (CuCl₂) as transition metal ions was carried by three different modification methods that were coded as Cu-MNC (25, 36), Cu-MNC (60, 6), and Cu-MNC (80, 3), respectively. The modification of PNC was characterized by X-ray diffraction, showing the increased d-spacing after the modification. The reinforcement of 5 wt% of PNC and Cu-MNC at the alkaline reaction of UF resins that were coded as UF/PNC, UF/MNC (25, 36), UF/MNC (60, 6), and UF/MNC (80, 3). The X-ray diffraction study showed that the addition of PNC and Cu-MNC into the UF resins decreased the crystallinity of resins from 48.1% to 45% for UF/PNC and 25% for all UF/MNC. The curing behavior exhibited that the activation energy of UF resins decreased with addition of PNC and Cu-MNC. The loading of PNC and Cu-MNC into UF resins improved the adhesion and reduced the formaldehyde emission of UF resins in plywood. Statistical analysis suggested that UF/MNC (80, 3) produced plywood with greater adhesion strength and lower formaldehyde emission over other modified resins.