Effects of Si/Al, Na/Al, and H2O/Na2O molar ratios on formaldehyde barrier properties of inorganic aluminosilicate coatings
27 July 2020
Revised: 17 September 2020
Accepted: 18 September 2020
Available online: 19 September 2020
Abstract: Wood-based panels containing urea-formaldehyde resin result in the long-term release of formaldehyde and threaten human health. To obstruct formaldehyde release, inorganic aluminosilicate coatings prepared by combining metakaolin, silica fume, NaOH and H2O, were applied to the surfaces of wood-based panels. The Si/Al, Na/Al, and H2O/Na2O molar ratios of the coatings were regulated to investigate their effects on the structure and formaldehyde-resistant barrier properties of coatings. The results showed that as the Si/Al molar ratio increased from 1.6 to 2.2, the cracks present in the coatings gradually disappeared and the formaldehyde-resistance rates of the barrier increased. This value also increased as the Na/Al molar ratio increased from 0.9 to 1.2 due to the improvement of the degree of polymerization. As the H2O/Na2O molar ratio increased from 12 to 15, the thickness of the dry film decreased gradually and led to the reduction in the formaldehyde-resistance rate. When the Si/Al, Na/Al and H2O/Na2O molar ratio were 2.2, 1.2, and 12 respectively, the inorganic aluminosilicate coating showed the good performance as a formaldehyde-resistant barrier and its formaldehyde-resistance rate could reach up to 83.2%.