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Effects of resin open time and melamine addition on cold pre-pressing performance of a urea–formaldehyde resin

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Abstract

The pre-pressing performance of urea formaldehyde resins has a significant impact on plywood production efficiency. This paper reports on the effects of the time elapsed after the addition of the hardener (“resin open time”) and of a melamine addition on the cold pre-pressing performance of UF resins. The changes in pH and viscosity, the thermal behaviour, and the structural composition as well as the performance during cold pre-pressing of veneers were investigated. Cold pre-pressing performance was measured by testing pre-pressed three-ply plywood stacks. The results showed that the cold pre-pressing performance is enhanced with longer time after preparation of the resin mix before application onto the veneers and also by longer pre-pressing times. All plywood stacks with at least 2 h pre-pressing time reached the so-called G1 grade (where the re-opened area of the cold pre-pressed plywood stack was 0), which meets the industrially accepted requirements for plywood fabrication. Further, the addition of melamine improved the cold pre-pressing behaviour compared to the investigated UF resin without melamine, showing an earlier start of the development of the pre-pressing shear strength and higher G grades at the various cold pressing times. There are two main reasons for the enhanced cold pre-pressing performance of the resin under the investigated conditions: (1) influence of the “resin open time”: a certain further condensation of the resin after preparing the glue mix (addition of hardener) leading to increased molar mass and viscosity ultimately transforming the resin from liquid-state to gel-state; (2) a higher methylol content in the resin after incorporation of melamine into the resin, which enhanced the formation of hydrogen bonds between the resin and the wood surface. These conclusions represent a feasible approach for the improvement of the cold pre-pressing properties and thus the practical applicability of UF resins with low molar ratios.

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References

  • Ayrilmis N, Lee YK, Kwon JH, Han TH, Kim HJ (2016) Formaldehyde emission and VOCs from LVLs produced with three grades of urea–formaldehyde resin modified with nanocellulose. Build Environ 97:82–87

    Article  Google Scholar 

  • Chen LO, Gao Q, Zhang JZ, Chen H, Zhang SF, Li JZ (2014) Effects of assembly time on wet shear strength and formaldehyde emission of plywood bonded by urea formaldehyde resin. BioResources 9:2975–2986

    CAS  Google Scholar 

  • Costa NA, Pereira J, Ferra J, Cruz P, Martins J, Magalhães FD, Mendes A, Carvalho LH (2013) Scavengers for achieving zero formaldehyde emission of wood-based panels. Wood Sci Technol 47:1261–1272

    Article  CAS  Google Scholar 

  • Ding R, Su CH, Yang YG, Li CF, Liu JC (2013) Effect of wheat flour on the viscosity of urea–formaldehyde adhesive. Int J Adhes Adhes 41:1–5

    Article  CAS  Google Scholar 

  • Dorner F, Zuckerstätter G, Müller U, Brüggemann O, Schwarzinger C, Panzer U (2011) Rapid melamine–formaldehyde resin characterization by means of quantitative 13C NMR with polarization transfer. Int J Polym Anal Charact 16:177–186

    Article  CAS  Google Scholar 

  • Gao Z, Wang XM, Wan H, Liu ZM (2009) DSC characterisation of urea–formaldehyde (UF) resin curing. Pigm Resin Technol 38:3–9

    Article  CAS  Google Scholar 

  • Gao Q, Qin ZY, Li CC, Zhang SF, Li JZ (2013) Preparation of wood adhesives based on soybean meal modified with PEGDA as a crosslinker and viscosity reducer. BioResources 8:5380–5391

    Google Scholar 

  • Kim MG (2000) Examination of selected synthesis parameters for typical wood adhesive-type urea–formaldehyde resins by 13C-NMR spectroscopy. II. J Appl Polym Sci 75:1243–1254

    Article  CAS  Google Scholar 

  • Kim MG (2001) Examination of selected synthesis parameters for wood adhesive-type urea–formaldehyde resins by 13C NMR spectroscopy. III. J Appl Polym Sci 80:2800–2814

    Article  CAS  Google Scholar 

  • Luo JL, Zhang JZ, Luo J, Li JZ, Gao Q (2015) Effect of melamine allocation proportion on chemical structures and properties of melamine–urea–formaldehyde resins. Bioresources 10:3265–3276

    CAS  Google Scholar 

  • Mao A, Kim MG (2013) The effects of adding melamine at different resin synthesis points of low mole ratio urea–melamine–formaldehyde (UMF) resins. BioResources 8:5733–5748

    Google Scholar 

  • Nuryawan A, Park BD, Singh AP (2014) Comparison of thermal curing behavior of liquid and solid urea–formaldehyde resins with different formaldehyde/urea mole ratios. J Therm Anal Calorim 118:397–404

    Article  CAS  Google Scholar 

  • Park BD, Jeong HW (2011a) Hydrolytic stability and crystallinity of cured urea–formaldehyde resin adhesives with different formaldehyde/urea mole ratios. Int J Adhes Adhes 31:524–529

    Article  CAS  Google Scholar 

  • Park BD, Jeong HW (2011b) Effects of acid hydrolysis on microstructure of cured urea–formaldehyde resins using atomic force microscopy. J Appl Polym Sci 122:3255–3262

    Article  CAS  Google Scholar 

  • Park BD, Kang EC, Park JY (2006a) Differential scanning calorimetry of urea–formaldehyde adhesive resins, synthesized under different pH conditions. J Appl Polym Sci 100:422–427

    Article  CAS  Google Scholar 

  • Park BD, Chang KE, Yong PJ (2006b) Effects of formaldehyde to urea mole ratio on thermal curing behavior of urea–formaldehyde resin and properties of particleboard. J Appl Polym Sci 101:1787–1792

    Article  CAS  Google Scholar 

  • Wang SM, Shi JY (2008) Performance of plywood made with low-toxicity urea–formaldehyde resin. China Wood Ind (in Chinese) 22:32–34

    Google Scholar 

  • Zhang SF, Li JZ, Zhang JZ, Li YH, Gao Q (2010) Study on properties of modified low molar ratio urea–formaldehyde resins (I). Adv Mater Res 113:2016–2020

    Article  CAS  Google Scholar 

  • Zhang JZ, Wang XM, Zhang SF, Gao Q, Li JZ (2013) Effects of melamine addition stage on the performance and curing behavior of melamine–urea–formaldehyde (MUF) resin. BioResources 8:5500–5514

    Google Scholar 

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Acknowledgements

This research was financially supported by National Natural Science Foundation of China (Project 31400501).

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Correspondence to Qiang Gao or Jianzhang Li.

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Gao, Q., Liu, C., Luo, J. et al. Effects of resin open time and melamine addition on cold pre-pressing performance of a urea–formaldehyde resin. Eur. J. Wood Prod. 76, 1253–1261 (2018). https://doi.org/10.1007/s00107-018-1307-y

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  • DOI: https://doi.org/10.1007/s00107-018-1307-y

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