Structural and Physical Changes in Phenol−Formaldehyde Resol Resin, as a Function of the Degree of Condensation of the Resol Solution

Abstract

The structural and physical differences of phenol-formaldehyde resol resins collected during a resin synthesis were studied, as a function of the degree of condensation of the resin. The structural and physical properties of the resins were analyzed using nuclear magnetic resonance (NMR) spectroscopy, viscosity and refractive index measurements, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), solids content analyses, and contact angle determinations on wood veneer. As a result of the condensation reactions, the amount of methylol groups and free reactive sites of phenolic species decreased, while the amount of methylene bridges increased, as a function of the degree of condensation. The changes in the resin structure resulted in an increase in the viscosity, refractive index, and average molar masses, and a decrease in reactivity, with increasing degrees of condensation. The wetting of the surface of the wood veneer was reduced as the viscosity and average molar masses of the resin solution each increased.

Surface Free Energy and Dynamic Wettability of Differently Machined Poplar Woods

“…The wettability of wood samples reduced with the increased viscosity of adhesives, consistent with the literature (Gavrilovic-Grmusa et al 2012;Monni et al 2007). Furthermore, the changes in surface tension of the three adhesives were not significant (from 66.87 mJ/m 2 to 68.23 mJ/m 2 , as shown in Table 1); therefore, the differences in contact angle were caused mainly by the change in viscosity.…”

“…The frictional heat generated by rotary machining can be expected to cause these materials to migrate to the surface and smear over the surface of the wood, and a hydrophobic wood surface can be caused. The tight side and loose side also had different behaviors of wettability (Vázquez et al 2003) because the wood surface was more dense on the tight side than on the loose side (Monni et al 2007). As is shown in Table 1, the standard deviations of the contact angles were small; therefore, it could be concluded that the calculation method for acquiring the contact angle values is suitable.…”

Lignin–phenol–formaldehyde resin adhesives prepared with biorefinery technical lignins

“…1 It is widely accepted that formaldehyde emissions from panels used in interior applications is a leading cause of sick building syndrome (SBS) in indoor environments. 2 However, formaldehyde emissions from PF resinbonded wood products are very limited.…”

Untitled

“…Di samping itu perekat UF dan air destilasi pada suhu yang sama memiliki viskositas sebesar 1,2 dan 0,008 poise. Keterbasahan permukaan bahan menurun seiring tingginya nilai viskositas cairan (Monni, et al, 2007;Gavrilovic-Grmusa, et al, 2012a, 2012bGavrilovic-Grmusa, et al, 2013). Berikutnya faktor lain yang berpengaruh terhadap proses pembasahan sangat kompleks, di antaranya adalah pH permukaan seperti yang dijelaskan oleh Gérardin, et al (2007).…”