A new analytical approach to investigate the influence of wood extracts on the curing properties of phenol-resorcinol–formaldehyde (PRF) adhesives

Abstract

In this study, the interactions between a phenol–formaldehyde resorcinol (PRF) adhesive and water-extractable wood constituents were investigated using combined in-situ FTIR spectroscopy and rheology analysis for a simultaneous examination of the progress of chemical reactions and coherent changes in rheological properties during adhesive curing. Complementary evolved gas analysis and pyrolysis gas chromatography/mass spectroscopy (Py-GC/MS) were performed to detect differences in the final crosslinking and chemical composition of the cured adhesive, respectively. The rheological and chemical analysis results correlated with the tensile shear strength of wood-PRF assemblies. The results showed that adhesive curing was significantly affected by the presence of acidic wood extractives. In particular, the acidic extractives of chestnut wood led to a delay in the resin curing and less final crosslinking of the cured adhesive. This was most likely caused by a reduction in the catalytic effect of the base-catalyzed curing of the adhesive rather than by direct chemical reactions between the extracts and adhesive. These findings can be useful for adapting the resin formulation to the chemistry of acidic wood species.

Torsional IR spectra of three conformers of the resorcinol molecule

“…were found by fitting calculated data using symmetry adopted basis functions (4-7). Using Euler's formulas, cosine polynomials were transformed into complex exponential polynomials (10). All transformations were carried out using the Mathematica package [68]:…”

“…Cu-doped organic RES-based aerogels, widely used as thermal insulators, light guides, and particle detectors, are studied in [9]. The properties of RES-based adhesives for joining wood are analyzed in [10].…”

Extractives in Douglas firs (Pseudotsuga menziesii (Mirb.) Franco) from three sites in south-west Germany and potential opportunities for valorization

“…For instance, some compounds generate additional costs in paper production as they act as pulping inhibitors or cause an excessive need of bleaching to obtain the aimed degree of whiteness (Gardner and Hillis 1962). Others affect acidity and wettability of wood, which are both important factors regulating natural durability (Windeisen and Wegener 2003) and bonding properties of wood (Özparpucu et al 2022;Roffael 2016).…”

How does ultrasound contribute to the migration of extractives inside Ailanthus altissima wood?

“…In the wood processing industry, extractives not only affect wood properties, such as color, odor, permeability, corrosion resistance, and acoustic performance, but also affect wood processing techniques, such as interfering with the formation of adhesive interfaces, hindering paint curing, and damaging cutting tools [11] , [12] , [13] , [14] , [15] , [16] . They can even have implications for the health of operators.…”