Synthesis and properties of resol-type phenol-formaldehyde resins prepared from H2SO4- and HCl-catalyzed phenol-liquefied Cryptomeria japonica wood

Abstract

Wood of Cryptomeria japonica (Japanese cedar) was liquefied in phenol with H2SO4 or HCl as catalysts and used as raw materials to prepare phenol-formaldehyde (PF) resins. The curing behavior and adhesion properties of resins prepared were investigated. Wood liquefied with H2SO4 as a catalyst had better liquefaction effect than that with HCl; however, the reaction of resin synthesis was hard to control due to its quickly increasing viscosity. Differential scanning calorimetry analysis shows that PF resins prepared from HCl-catalyzed liquefied wood had higher reactivity than those of H2SO4-catalyzed wood. These PF resins were employed for manufacturing three-layer plywood. The wet bonding strength of plywood prepared with resins from HCl-catalyzed liquefied wood exceeded 0.7 MPa and fulfilled the requirement of the CNS 1349 standard

Microwave-assisted synthesis and characterization of resole-type phenolic resins

“…1 The common catalysts of phenol-formaldehyde resole synthesis are sodium, potassium, lithium hydroxides and rarely hydroxides of divalent metals such as magnesium, calcium, or barium. [1][2][3] At the start of the resol synthesis, highly exothermic methylolation reactions between phenol and formaldehyde yield methylol phenols. The methylolation stage of the synthesis is followed by the condensation stage, in which the methylol groups react with the free sites of other phenolic species yielding methylene bridge structures between the phenolic rings.…”

“…1,2 The formation of dibenzyl ether bridges resulting from the reactions of two methylol groups is not favored under highly alkaline conditions. [1][2][3] The resole resin synthesis is halted when the appropriate degree of condensation in the resin (viscosity) has been achieved. These resole resins are generally provided under conventional heating in batch reactors for a couple of hours.…”

“…These resole resins are generally provided under conventional heating in batch reactors for a couple of hours. 1,3 Microwave-assisted organic synthesis [4][5][6] has attracted attention in recent years due to enhanced reaction rates, high yields, improved purity, ease of work up after the reaction, and eco-friendly reaction conditions compared with the conventional methods. Microwave irradiation can interact with the polar substance because of the inability to instant reorientation of dipole according to the changes in the electromagnetic field.…”

Synthesis of alcohol-soluble phenol-formaldehyde resins from pyrolysis oil of Cunninghamia lanceolata wood and properties of molding plates made of resin-impregnated materials

“…Žilnik and Jazbinšek (2012) described a recovery process for the phenolic fraction from various Py-oils. There are ambitious efforts to substitute phenol (Ph) in phenol-formaldehyde (PF) resins by phenolics from renewable resources (Geng et al 2007;Derkyi et al 2011;Lee et al 2011, Lee et al 2012cSahaf et al 2012;Lu and Wu 2013), and experiments with phenolic Py-oils could be promising in this context. Amen-Chen et al (2002a,b) prepared resol-type PF resins, in which 50% of the Ph was replaced with Py-oil, and the product was suited as a binder in manufacturing OSB.…”

Properties of molding plates made with various matrices impregnated with PF and liquefied wood-based PF resins

“…PF resins prepared with a formaldehyde/phenol molar ratio of about 2.0 or above have a significant bonding strength even after boiling in water. Lee et al (2012b) liquefied Japanese cedar wood in phenol with H 2 SO 4 or HCl as catalysts, while the latter proved to be better in terms of reactivity of the resin and wet bonding strength of the product. Hassan et al (2009) showed that LW-based resins have low viscosity and sufficient stability for storage and thus are suited for manufacturing particleboards.…”