Short-Term Creep Tests on Phenol-Resorcinol-Formaldehyde (PRF) Resin Undergoing Moisture Content Changes
Publication Name: Wood and fiber science
Publication URL: https://wfs.swst.org/index.php/wfs/article/view/876
The objective of the study was to develop an experimental technique that would allow determination of the hygro-mechanical properties of thin uniform resin films undergoing moisture content changes; and to use the technique for assessment of the hygro-mechanical performance of phenol-resorcinol-formaldehyde (PRF) resin.
Creep tests on 6 small specimens of PRF film under constant stress (50% of the short-term ultimate stress level), at room temperature (23°C ± 2°C) and controlled relative humidity (RH) conditions (drying or wetting) were carried out. Digital images of the specimens were acquired using a CCD camera at discrete time intervals during the experiments. Displacements were then measured by comparing successive images using digital image correlation principles. Separation of strain components from total strain recorded during the creep tests was carried out by using data from two reference tests performed on the same material: 1) free deformations of unloaded specimens during drying or wetting conditions, and 2) creep under equilibrium conditions.
The experimental method developed for the study provided a tool to determine hygro-mechanical properties of thin resin films. Quantitative data on material properties of hygroscopic resins determined by means of the technique may be used for modeling the behavior of adhesive bonds as well as adhesive bonded materials in varying climate conditions. The PRF resin revealed a distinct mechano-sorptive behavior, though it seems to be less significant than that reported for wood in transverse directions.