Effects of Esters and Resorcinol on Phenolic Resins as Adhesives in Medium-Density Fiberboard Manufacturing
Keywords:Phenolic resin, ester, resorcinol, formaldehyde emission, medium-density fiberboard
AbstractPhenol-formaldehyde (PF) resin-bonded composite wood panels exhibit very low formaldehyde emission levels, meeting the most stringent regulations. However, slow cure speed is a major limiting factor for its applications in the economical manufacturing of medium-density fiberboard (MDF) and particleboard. Commercial PF resins accelerated with esters or resorcinol and their applications in the manufacturing of MDF were investigated in this article. It was found that although ethylene carbonate, propylene carbonate, and triacetin were very effective in reducing the gel time of phenolic resins, these esters caused substantial loss of bonding strength, particularly in the case of phenolic resins with high alkalinity. The loss of bonding strength increased as the ester loading level in the PF resin was increased. On the other hand, resorcinol was not only an effective PF accelerator, but also preserved most of the bonding strength. Resorcinol-accelerated PF adhesives showed better performance in internal bond strength, bending strength, and water resistance of MDF in comparison with the ester-accelerated PF adhesive systems. The cure speed of the resorcinol-accelerated PF adhesive was evaluated against a urea-formaldehyde (E2 type) in the manufacturing of MDF.
ASTM (2002) E1333-96. Standard test method for determining formaldehyde concentrations in air and emission rates from wood products using a large chamber. American Society for Testing and Materials, West Conshohocken, PA.nASTM (2006) D6007-02. Standard test method for determining formaldehyde concentration in air from wood products using a small-scale chamber. American Society for Testing and Materials, West Conshohocken, PA.nCalve LR, Brunette GG (1984) Reducing formaldehyde emission from particleboard with urea-salt or sulfite liquor. Adhes Age 27(9):39-43.nCARB (2007) Airborne toxic control measure to reduce formaldehyde emissions from composite wood products. California Air Resources Board, Stationary Sources Division, Sacramento, CA. 59 pp.nJIS (2003) JIS A1901. Determination of the emission of volatile organic compounds and aldehydes for building products-Small chamber method. Japanese Industry Standard. Japanese Standards Association, Akasaka, Minatoku, Tokyo, Japan.nKamo N, Okamura H, Higuchi M, Morita M (2004) Condensation reactions of phenolic resins V: Cure-acceleration effects of propylene carbonate. J Wood Sci 50:236-241.nLemon PHRB (1990) An improved sand binder for steel castings. Int J Mater Prod Technol 5(1):25-55.nMeyer B (1983) Formaldehyde emission from particleboard post-cured by radio-frequency heating. Holzforschung 37 (1):41-45.nMyers GE (1985) Resin hydrolysis and mechanisms of formaldehyde release from bonded wood products. Wood Adhesives in 1985, Madison, WI. Pages 119-156.nPark B-D, Riedl B, Hsu EW, Shields J (1999) Differential scanning calorimetry of phenol-formaldehyde resins cure-accelerated by carbonates. Polymer (Guildf) 40: 689-699.nPizzi A (2003) Phenolic resin adhesives, Chapter 26, Part 3. Pages 541-572 in A Pizzi and KL Mittal, eds. Handbook of adhesive technology. Marcel Dekker Inc., New York, NY.nWang W, Zang X, Lu R (2004) Low formaldehyde emission particleboard bonded by UF-MDI mixture adhesive. For Prod J 54(9):36-39.nWu KT, Wuu YB (1987) Effect of nitric acid pretreatment on the properties of particleboard. Part II. Free formaldehyde emission. J Agric For 36(2):139-144.nZhao C, Pizzi A, Garnier S (1999) Fast advancement and hardening acceleration of low-condensation alkaline PF resins by ester and copolymized urea. J Appl Polym Sci 74:357-378.n
The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:
1. All proprietary rights other than copyright, such as patent rights.
2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.
3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.