Examination of selected synthesis and room-temperature storage parameters for wood adhesive-type urea-formaldehyde resins by 13C-NMR spectroscopy. V

• Published in: Journal of applied polymer science Vol. 89; no. 7; pp. 1896 - 1917
• Main Authors: Kim, Moon G., Young No, B., Lee, Sang M., Nieh, World L.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 15-08-2003; Wiley
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polycondensation; Polymer industry, paints, wood; Preparation, kinetics, thermodynamics, mechanism and catalysts; resins; structure-property relations; thermosets; Wood-based materials; Wood. Paper. Non wovens; Stoichiometry; Heat treatment; resins; Solution polycondensation; Molecular structure; Gas release; Mechanical properties; Processing time; Experimental study; Property processing relationship; Formaldehyde; Aminoplast; Structure processing relationship; Urea; structure-property relations; Adhesive joint; thermosets; Reaction mechanism; Particleboard; Adhesive; Postpolymerization
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.12367

The effects of posttreatments of particleboard adhesive‐type urea–formaldehyde resins were studied. The resins were synthesized with formaldehyde/first urea (F/U1) mol ratios of 1.40, 1.60, 1.80, 2.10, and 2.40 and then the second urea was added to give a final formaldehyde/urea ratio of 1.15 in alkaline pH. The resins were posttreated at 60°C for up to 13.5 h and the 2.5‐h heat‐treated resin samples were stored at room temperature for up to 27 days. Resins sampled during the posttreatments were examined by 13C‐NMR and evaluated by bonding particleboards. In the posttreatments, hydroxymethyl groups on the polymeric resin components dissociated to formaldehyde and reacted with the second urea, and methylene and methylene–ether groups were formed from reactions involving the second urea. Methylene–diurea and urea groups bonded to UF polymers were identified. As a result, the viscosity of the resins initially decreased but later increased along with the cloudiness of the resins. Bond‐strength and formaldehyde‐emission values of particleboard varied with posttreatment variables as well as with the F/U1 mol ratios used in the resin syntheses. The results would be useful in optimizing resin synthesis and handling parameters. Various reaction mechanisms were considered. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1896–1917, 2003