The influence of modification and the particle size of the montmorillonite on the hydrolytic stability of urea-formaldehyde composite

Abstract

Urea–formaldehyde (UF) resin adhesive is a polymeric condensation product of formaldehyde with urea and is considered as one of the most important wood adhesives. In spite of some advantages such as lower cost, fast curing, good performance in the panel, water solubility and being colorless, UF resin adhesives also possess a critical disadvantage: formaldehyde (FA) emission from the panels. Exposure to FA may occur by breathing contaminated indoor air, tobacco smoke, or ambient urban air. Furthermore, the FA emission from the panels used for interior applications is known as one of the main factors causing sick building syndrome in an indoor environment. Montmorillonite (MMT) clays are of great importance for processes such as adsorption and catalysis and polymer composites fabrication. The textural properties of this filler can be modified to increase its application. In this study, the hydrolytic stability of modified UF resins with modified and unmodified montmorillonites as scavengers of FA, with a different particle size (K10 and KSF), was studied. Five UF composite materials of F/U 0.8 ratio with MMT and Na-MMT were synthesized by the same method. The sensitivity to the hydrolysis of the crosslinked UF resin depends on its chemical nature and the degree of cross-linking. The hydrolytic stability of the investigated modified UF resin was determined by measuring the loss of weight and the concentration of released formaldehyde from the modified UF resin after acid hydrolysis. The obtained results showed improved hydrolytic stability of the modified resin containing unmodified KSF as a scavenger of FA.