Advertisement

Effects of weight average molecular mass of phenol-formaldehyde adhesives on medium density fiberboard performance

  • Byung-Dae Park
  • Bernard Riedl
  • Ernest W. Hsu
  • Jack Shields
Original

Abstract

This study was conducted to investigate the effects of weight average molecular mass \((\bar M_W )\) of phenol-formaldehyde (PF) adhesives on the performance of medium density fiberboard (MDF). To obtain different \(\bar M_W \) PF resins, a series of PF resoles were prepared by blending low \(\bar M_W \) (LMW) and high \(\bar M_W \) (HMW) resins in different proportions. Six blending ratios of LMW:HMW were chosen: 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100. The prepared resins were characterized with size exclusion chromatography (SEC) for their \(\bar M_W \) determination and differential scanning calorimetery (DSC) for thermal cure kinetics. As the proportion of HMW was increased, \(\bar M_W \) and hence the viscosity of adhesives increased. The thermal curing kinetics of the blended resins obtained by DSC showed that total thermal energy (ΔH) and activation energy (Ea) of cure decreased with increasing resin \(\bar M_W \) as determined by SEC. Test result for a series of fiberboards prepared with the blended, resins showed that the LMW:HMW blending ratio of 40:60 gave the highest internal bond (IB) strength. The optimum viscosity of PF resin was approximately 300 mPa.s. The maximum values of MOR and MOE were found at a blending ratio of 80:20 (LMW:HMW). The density profile indicated that MOR and MOE were influenced by the maximum density of the board surfaces while the IB correlated to the minimum density in the core regions of the board.

Keywords

Size Exclusion Chromatography Internal Bond Medium Density Fiberboard Minimum Density Oriented Strand Board 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Einfluß des Gewichtsmittels der Molmasse von Phenol-Formaldehydharzen auf die Qualität von MDF-Platten

Zusammenfassung

In dieser Arbiet wird der Einfluß des Gewichtsmittels der Molmasse von PF-Harzen auf die Qualität von MDF-Platten untersucht. Eine Reihe von PF-Resolen wurde als Mischung von Harzen mit niedriger (LWM) and hoher Molmasse (HMW) hergestellt. Sechs Mischungsverhältnisse wurden ausgewählt: 100:0, 80:20: 60:40, 40:60, 20:80 und 0:100. Die Molmasse der Harze wurde durch Gelpermeations-Chromatographie (GPC) bestimmt, ihre Aushärtcharakteristik mittels DSC. Mit zunehmendem Anteil an HMW steigt die Molmasse und damit die Viskosität. Die thermische Analyse der Harze ergab, daß ihre Gesamtenthalpie (ΔH) und Aktivierungsenergie der Aushärtung (Ea) sich Verringern mit steigender Molmasse. Testversuche an MDF-Platten, die mit verschiedenen Harzmischungen hergestellt waren zeigten die höchsten Querzugfestigkeit (IB) bei einmen Verhältnis von 40:60 (LMW:HMW). Die optimale Viskosität der PF-Harze lar bei 300 mPa.s. Die höchsten Werte Für MOR und MOE ergaben sich bei einer Mischung von 80:20. Die Dichteprofile der Platten Zeigen, daß MOR und MOE von der maximalen Dichte der Plattenoberfläche abhängen, Während die Querzugfestigkeit mit der minimalen Dichte im Kern korreliert ist.

References

  1. Baker DE, Honeyford DE (1984) Adhesive requirements for overlaying plywood. In: Gillespie, R.M. (ed.) Adhesives for wood: research, application, and needs. Ed. R. H. Gillespie. Noyes Pub., New Jersey, pp. 79–84Google Scholar
  2. Chow S, Steiner PR, Troughton GE (1975) Thermal reactions of phenol-formaldehyde resins in relation to molar ratio and bond quality. Wood Sci. 8 (1): 343–349Google Scholar
  3. Chow S-Z, Steiner PR (1979) Comparison of curing and bonding properties of particleboard and waferboard-type phenolic resins. For. Prod. J. 29 (11): 49–55Google Scholar
  4. Chiu S-T (1984) U.S. Patent 4, 433, 120Google Scholar
  5. Christiansen AW, Gollob L (1985) Differential scanning calorimeter of phenol-formaldehyde resols. J. Appl. Polym. Sci. 30 (6): 2279–2289CrossRefGoogle Scholar
  6. Donaldon LA, Lornax TD (1989) Adhesive/fibre interaction in medium density fibreboard. Wood Sci. 23: 371–380CrossRefGoogle Scholar
  7. Ellis S (1993) The performance of waferboard bonded with powdered phenol-formaldehyde resins with selected MW distributions. For. Prod. J. 43 (2): 66–68Google Scholar
  8. Garn PD (1965) Thermoanalytical methods of investigation. Academic Press, New York, pp. 217–220Google Scholar
  9. Gollob L, Krahmer RL, Wellons JD (1984) Relationship between characteristics of phenol-formaldehyde resins and adhesive performance. For. Prod. J. 35 (3):42–48Google Scholar
  10. Gollob L (1989) The correlation between preparation and properties in phenolic resins. In: Pizzi, A. (ed.) Wood adhesives, chemistry and technology, vol 2. Marcel Dekker, New York, pp. 121–153Google Scholar
  11. Gupta MK, Salee G, Hoch DW (1986) Curing studies of phenolic resoles as a function of pH. Amer. Chem. Soc. (prep.). 27:309–310Google Scholar
  12. Hse C-Y (1972) Wettability of southern pine veneer by phenol-formaldehyde wood adhesives. For. Prod. J. 22(1): 51–56Google Scholar
  13. Hse C-Y (1972) Properties of phenolic adhesives as related to bond quality in Southern Pine plywood. For. Prod. J. 21(1):44–52Google Scholar
  14. Haupt RA, Sellers T Jr (1993) Phenolic resin-wood interaction. For. Prod. J. 44(2):169–173Google Scholar
  15. Johnson SE, Kamke FA (1994) Characteristics of phenol-formaldehyde adhesive bonds in steam injection pressed flakeboard. Wood and Fiber Sci. 26(2): 259–269Google Scholar
  16. Kelly SS, Gollob L, Wellons JD (1986) The effects of resin formulation variables on the dynamic mechanical properties of alkaline curing phenolic curing resins. Holzforschung 40(5): 303–308Google Scholar
  17. Kim MG, Nieh WL-S (1991) Study on the curing of phenol-formaldehyde resol resins by dynamic mechanical analysis. Ind. Eng. Chem. Res. 30(4): 798–803CrossRefGoogle Scholar
  18. Myers GE, Christiansen AW, Geimer RL, Follensbee RA, Koutsky JA (1991) Phenol-formaldehyde resin curing and bonding in steam-injection pressing. I. Resin synthesis, characterization, and cure behaviour. J. Appl. Polym. Sci. 43(2): 237–250CrossRefGoogle Scholar
  19. Nieh WL-S, Sellers T Jr (1991) Performance of flakeboard bonded with three PF resins of different mole ratios and MWs. For. Prod. J. 41(6): 49–53Google Scholar
  20. Pizzi A (1983) Phenolic resin wood adhesives. In: Pizzi A ( ed.) Wood adhesives, chemistry and Technology. Marcel Dekker, New York, pp. 105–176Google Scholar
  21. Pizzi A (1994) Advanced wood adhesives technology. Marcel Dekker, New York, pp. 89–147Google Scholar
  22. Riedl B, Calve L, Blanchette L (1988) Size-exclusion chromatography of spray-dried phenol-formaldehyde resins on different columns and solvent systems. Holzforschung 42(5): 315–318CrossRefGoogle Scholar
  23. Schulte M, Frühwald A (1996a) Shear modulus, internal bond and density profile of medium density fiberboard (MDF). Holz Roh-Werkstoff 54: 49–55CrossRefGoogle Scholar
  24. Schulte M, Frühwald A (1996b) Some investigations concerning density profile, internal bond and relating failure position of particleboard. Holz Roh-Werkstoff 54: 289–294CrossRefGoogle Scholar
  25. Stephens RS, Kutscha NP (1987) Effect of resin MW on bonding flakeboard. Wood and Fiber Sci. 9(4): 353–361Google Scholar
  26. Wellons JD, Gollob L (1988) GPC and light scattering of phenolic resins-problems in determining MWs. Wood Sci. 13(2): 26–30Google Scholar
  27. Willson G, Jay L, Krahmer RL (1979) Using resin properties to predict bond strength of oak particleboard. Adhesive Age 22(6): 26–30Google Scholar

Copyright information

© Springer-Verlag 1998

Authors and Affiliations

  • Byung-Dae Park
    • 1
  • Bernard Riedl
    • 1
  • Ernest W. Hsu
    • 2
  • Jack Shields
    • 2
  1. 1.Département des Sciences du Bois et de la Forêt, Centre de Recherche en Sciences et Ingénierie des Macromolécules, Faculté de Foresterie et GéomatiqueUniversité LavalSte-FoyCanada
  2. 2.Forintek Canada Corp.Ste-FoyCanada

Personalised recommendations