The effects of temperature and humidity on phenol-formaldehyde resin bonding

Abstract

onSummary The effects of temperature and relative humidity on phenol-formaldehyde resin bonding were evaluated. Two flakes in a lap-shear configuration were bonded under an environment of controlled temperature (110 ~ 120 ~ 130 ~ 140 ~ and relative humidity (41%, 75%, 90%) for a series of time periods (0.25 to 16 min). The lap-shear specimens were then shear-tested on a mechanical testing machine and the results were used to establish a family of bond strength development curves at each temperature and level of relative humidity. At 1 I0 ~ the higher relative humidity appeared to retard resin bonding. The effects of relative humidity diminished as temperature increased to 140 ~ Bond strength development was chemical ratecontrolled. The rate of bond strength development at each relative humidity follows a first order reaction mechanism. The activation energy of resin-wood bonding, determined by bonding kinetics, was higher than that of resin alone, determined by differential scanning calorimetry. This comparison indicates that to form a strong resin-wood bond, a higher energy level might be required. 253

Synthesis and Curing of Novel Phenol-Formaldehyde Resins Containing Pendant Citraconimides

“…1 HNMR spectra of the cured resins showed disappearance of the signal belong to phenolic OH proton and this is a clear proof which confirmed the success of estrification reaction. At the same time these NMR spectra revealed many characteristic signals including signals at δ(1.3-1.4) ppm for CH 3 protons, δ(3.1-3.8)ppm for methylene protons, δ(6.2-7.1)ppm for vinylic protons and signals at δ(7.3-8.1)ppm for aromatic protons.…”

“…1 HNMR spectra of the prepared resins [9][10][11][12] revealed many characteristic signals including signals at δ(1.25-1.9)ppm for CH 3 protons, δ(3.7-3.8)ppm for methylene protons, δ(6.7) ppm for vinylic proton, δ(6.9-7.1)ppm for aromatic protons and δ(9.8-9.9)ppm for phenolic OH proton.…”

“…Phenol-formaldehyde resins are the oldest commercial synthetic polymers, they exhibit excellent electrical and chemical resistance and retention of properties after long term exposure to high temperatures (1)(2)(3)(4) . These resins are used in a wide variety of applications including adhesives, surface coatings, binders and molding, therefore not surprisngly a number of synthetic strategies have been carried out to incorporate structural modifications in these resins to obtain new properties serving new applications (5)(6)(7)(8) .…”

Cure Kinetics, Bonding Performance, Thermal Degradation, and Biocidal Studies of Phenol-Formaldehyde Resins Modified with Crude Bio-oil Prepared from Ziziphus mauritiana Endocarps

“…The adhesive strength of the resins for wood-to-wood system was measured by a single lap-shear method according to the procedure reported by Wang et al (1995), with some modifications. In summary, 1.27 cm wide, 0.162 cm thick, and 10.61 cm long flakes were cut from a wood block of white pine (Pinus spp.)…”

Properties of Liquid and Polycondensed UF Resin Modified with pMDI

“…pMDI was used as a UF resin modifi er, introduced at 10 % in relation to the urea resin solution weight. In the case of liquid hybrid resin (UF/pMDI), its viscosity was determined by measuring fl ow time with a Ford's cup and gel times within the temperature range of 80, 90, 100 and 110 ºC, based on which relative activation energy of the cross-linking process was calculated (Wang et al, 1995). It was assumed that the curve illustrating the curing process in time, at specifi c temperatures of 80, 90, 100 and 110 ºC, was a linear function till the curing point was reached.…”