Molecular Weight Phenol Formaldehyde Resin Research Articles

Effects of Compression Ratio and Phenolic Resin Concentration on the Properties of Laminated Compreg Inner Oil Palm and Sesenduk Wood Composites

Due to its inferior properties, oil palm wood (OPW) extracted from the inner layer of the oil palm (Elaeis guineensis) trunk, referred as inner OPW in this study, is frequently regarded as a waste. Phenolic resin treatment and lamination of inner OPW with other hardwoods may be an excellent way to improve the properties of the inner OPW. In this study, inner OPW were treated with two different concentrations (15% and 20%) of low molecular weight phenol formaldehyde resin (LmwPF) and compressed at different compression ratios (10%, 20%, and 30%). The physical and mechanical properties of the modified inner OPW’s were evaluated according to British Standards (BS) 373: 1957. The results revealed that inner OPW treated with the highest compression ratio (30%) and resin concentration (20%) exhibited the highest weight percent gain, polymer retention and density. In the following phase of the research, the treated inner OPW was used as the core layer in the fabrication of a three-layer laminated compreg hybrid composites, with untreated and treated sesenduk (Endospermum diadenum) wood serving as the face and back layers. The compression ratios of 10% and 20% and resin concentrations of 10% and 20% were used in this phase of study as laminated boards made with 30% compression ratio failed. The findings showed that resin concentration had a significant impact on both the inner OPW and the laminated compreg hybrid panels. Markedly, higher resin concentrations (20%) resulted in improved physical properties, i.e., thickness swelling and water absorption, as well as enhanced mechanical properties (modulus of rupture and modulus of elasticity). Although compression ratios had no significant effect on the properties of the laminated products, those compressed at higher compression ratios (20%) performed slightly better than the panels compressed at lower compression ratios (10%).

Review paper: properties of low molecular weight phenol formaldehyde – treated bamboo composite

Impregnation of bamboo in phenol formaldehyde (PF) solution is one of the promising solutions to overcome the drawback of the material. The use of low molecular weight PF resin (LMW PF) in the production of bamboo composite materials not only improves the dimensional stability but also increases the mechanical strength of the material. The bonding interface between bamboo elements and adhesives is presumed to be significantly influenced by the degree of adhesive penetration into the porous network of interconnected cells of bamboo surfaces. The permeation of PF resins in bamboo is closely related to their molecular weight. LMW PF resin will overpenetrate and lead to an undesirable starved bondline while high-MW PF resins only remain in the bondline and it is difficult to form mechanical interlocking. This paper discusses the research results on the bonding quality of bamboo strips when impregnated in LMW PF solution with different ratios and different pressing technology parameters; at the same time, physical and mechanical properties of bamboo composite materials treated with PF PTLT such as: water absorption resistance, dimensional stability, bonding strength, modulus of rupture (MOR), modulus of elasticity (MOE) are also significantly improved. This is a scientific basis that can serve as a premise for the research on technology to produce composite materials from bamboo and LMW PF in Vietnam.

Properties Enhancement of Oil Palm Trunk Plywood against Decay and Termite for Marine Applications.

Oil palm trunk (OPT) veneers have the potential to be used in the production of plywood for marine applications. However, OPT is not resistant to fungal decay and termites, limiting its use in the production of marine plywood. As a result, in this study, phenolic resin treatment was used to improve the biological durability of OPT and produce marine grade equivalent (MGE) plywood. The OPT veneer was treated with medium molecular weight phenol formaldehyde (MmwPF) resin. The results showed that MmwPF resin with a solid content of 30% resulted in higher weight percent gain and polymer retention. Veneers treated with 30% MmwPF resin were then pressed for more than 10 min at temperatures above 140 °C. Dimensional stability, shear strength, bending strength, fungal decay resistance, and termite resistance were all tested on the plywood produced. The results of this study revealed that MGE plywood has satisfactory bonding quality and excellent biological durability. Good bending strength was recorded for the MGE plywood with modulus of rupture and modulus of elasticity ranged between 31.03 and 38.85 MPa and 4110 and 5120 MPa, respectively. Rubberwood, as a reference sample in this study, is not durable (Class 5) against white rot fungi and is moderately durable (Class III) against subterranean termite attacks. Interestingly, MGE plywood produced in this study was found very durable (Class 1) against white rot fungi. It is also durable (Class II) and very durable (Class I) against termite attacks, depending on the pressing parameters employed. Based on their outstanding bonding quality, bending strength, and biological durability, the study confirmed the feasibility of OPT plywood for marine applications.

Sorption isotherm and physico-mechanical properties of kedondong (Canarium spp.) wood treated with phenolic resin

Kedondong (Canarium spp.) wood was modified with low molecular weight phenol formaldehyde (LmwPF) resin in order to reduce its hygroscopicity. Kedondong wood were impregnated with LmwPF resin at different concentrations, namely 15, 20 and 30%, followed by curing at high temperature. The physico-mechanical properties, surface wettability, and sorption isotherm of the treated and untreated wood were investigated. Surface wettability of the modified wood reduced as a result of the treatment. Thickness swelling and water absorption of the modified kedondong wood reduced while positive anti-swelling efficiency increased along with increasing resin concentration. However, there was no significant difference observed for mechanical properties between modified and unmodified wood. The equilibrium moisture content (EMC) for unmodified kedondong was higher than impregnated samples. At 95% RH, unmodified kedondong showed an EMC of 19.10% whereas samples treated at 15%, 20% and 30% LmwPF concentration recorded EMC of 18.27%, 18.14% and 17.12%, respectively. Furthermore, the hysteresis loop of untreated sample results was slightly higher than treated sample. The highest hysteresis value was marked at 80% RH with value 3.74% for untreated sample and the value decreased slightly in treated woods. The results indicate that the treatment reduces the hygroscopicity of kedondong wood.

Effects of low and high molecular weight of phenol-formaldehyde (PF) on the properties of strand boards from kiri wood (Paulownia tomentosa)

ABSTRACT Kiri (Paulownia tomentosa) wood is a promising material for lightweight strand boards (SBs); however, kiri SBs have displayed a limited dimensional stability. The aim of this study was to evaluate the possibility of using low molecular weight (LMW) phenol-formaldehyde (PF) resin not only as an adhesive but also as a treatment (impregnating) agent to manufacture SBs. SBs from kiri wood were manufactured with densities of 400 kg m−3 and 500 kg m−3. PF resin with low and high molecular weight as well as its 50-50% mixture was studied at two adhesive formulation contents of 10% and 20% related to the strand mass. At 400 kg m−3 density, internal bond strength (IB), screw withdrawal resistance (SWR) and thickness swelling (TS) of SBs containing LMW PF were significantly higher than those of HMW PF at 10% adhesive content and the differences slightly decreased as the adhesive content increased to 20%. At 500 kg m−3 density, IB, TS and SWR of SBs were considerably enhanced by LMW PF at both adhesive contents. We concluded that using LMW PF may cause higher strength and dimensional stability, at least, when the strand material and the SBs exhibits very low density, which is highly compressed during SBs manufacturing.

Effects of the drying process on the shear strength and morphology of the bonding interface of laminated wood

To investigate the influence of the drying process on the bonding properties of laminated wood, a poplar veneer was impregnated with low molecular-weight phenol formaldehyde (PF) resin and laminated wood was created and studied. The effects of drying temperature, drying time and solid content of the PF resin on the moisture content (MC) of the impregnated veneer after drying and the shear strength of the laminated wood were analyzed with an orthogonal experiment. The microscopic mechanism of the bonding performance of the laminated woods was investigated by fluorescence microscopy. The experimental results showed that the higher the PF resin solid content was, the larger the weight gain percentage of the impregnated veneer was. In addition to drying temperature and drying time, the solid content of PF also had a significant influence on the MC of the impregnated veneer after drying. The shear strength of the laminated wood affected by the drying temperature, solid content of PF and drying time and the drying temperature had a more significant effect than the other two factors. The best drying process was a drying temperature of 50 °C, a drying time of 2 h, and a PF solid content of 30%. The fluorescence analysis showed that the shear strength of the laminated wood was affected by the intensity of the PF resin on the bonding interface, and the average and effective penetration depth of the PF resin in the veneer increased with the increase in the drying temperature.

Fracture Toughness of Medium Molecular Weight Phenol Formaldehyde (MMwPF) Plywood

Currently in Malaysia, most of the plywood industries are using tropical hardwood veneer with combination of rubberwood to form plywood. The used of rubberwood has actively reduced the cost of plywood production but recently the price of rubberwood logs has increased due to the shortage of the supply. Due to the demand from other timber industries such as furniture and medium density board thus, alternative raw material which is not focuses on lignocellulosic material only but also on the residue can be offered. Oil palm stems (Elaeisguineensis Jacq) need to be explored as these stems are abundant after falling from plantations which have not been fully utilized due to their poor properties. The main drawback of oil palm is its low dimensional stability found in the stem parts. Therefore this study investigated the 100% oil palm stem (OPS) plywood denoted as PTA by optimizing the pre drying process of the veneer by using roller pressing machine, steam dryer and platen press machine. After the OPS veneers have been pre-dried, they were treated with Medium Molecular Weight Phenol Formaldehyde (MMwPF) resin before fabrication of OPS plywood. The product could be promoted as concrete foam, light weight partitions, wall panel and floor slabs. The fracture toughness of OPS plywood developed in this study denoted as PTA was investigated. These properties were compared with the properties of another two types of commercial OPS plywood denoted as PTB and PTC which were manufactured using OPS veneer with tropical hardwood veneer for face and back veneer and control plywood denoted as PTD which was manufactured using 100% tropical hardwood veneer. The highest value of plain strain and energy release was showed by PTA compared to commercial plywood. The failure was more prominent in wood which showed by the crack propagated line in the veneer layer.

Fatigue behavior of beech and pine wood modified with low molecular weight phenol-formaldehyde resin

Abstract Modification of wood improves certain properties of natural wood and presents competitive alternatives to synthetic materials that may have larger environmental impacts. One aspect of modified wood that is currently not fully understood is the dynamic performance and how it is affected by the modification process. In this study, low-molecular weight phenol formaldehyde (PF) resin was applied to Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) wood. The effect of this modification was evaluated using a three-point bending test undergoing cyclic loading. Compared to reference samples, modified wood showed higher static performance but revealed a reduction in cyclic fatigue strength (9% for pine and 14% for beech). Cyclic fatigue strength of unmodified wood was found to be 67% of the static modulus of rupture for both species. With PF resin modification, the fatigue strength dropped to 58% for pine and 53% for beech. While fatigue strength decreased, there was no reduction in cyclic modulus or change in the creep rate within the stationary creep phase. It is important to consider the reduction in fatigue strength when using PF modified wood for any construction purposes with expected cyclic loading conditions.

Bolt-Bearing Yield Strength of Three-Layered Cross-Laminated Timber Treated with Phenol Formaldehyde Resin

The effect of impregnation treatment of low molecular weight phenol formaldehyde (MWPF) resin on the bolt-bearing yield strength (BBYS) of a three-layered cross-laminated timber (CLT) composed of two face layers of southern pine (Pinus taeda) and one core layer of sweetgum (Liquidambar styraciflua) was investigated together with two additional factors of material type and loading direction. Experimental results indicated that the amount of low MWPF resins penetrating into sweetgum was more than the ones into southern pine. Sweetgum had more uniform distribution of low MWPF resins penetrating longitudinally than southern pine. Impregnation treatment using a low MWPF resin at a concentration of 20% can enhance the BBYS of three-layered CLTs with a 60% increase. The BBYS of a core layer material in three-layered CLTs can significantly alter the overall BBYS of the three-layered CLTs.

Humidity’s effect on the dynamic-mechanical behavior of phenol-formaldehyde impregnated beech wood veneer

The dynamic-mechanical behavior of phenol-formaldehyde-impregnated beech wood (Fagus sylvatica L.) veneers was evaluated at various relative humidities. The aim was to identify the plasticizing effects of moisture on phenol-formaldehyde-impregnated veneers. Thin beech veneer samples were impregnated with a low and a medium molecular weight phenol-formaldehyde resin. The measurements were performed with a dynamic-mechanical thermal analysis equipped with a humidity generator. The storage modulus and the loss factor of the uncured phenol-formaldehyde-impregnated and the untreated control veneers were determined at a relative humidity of 15%, 60%, and 85% and a constant temperature of 25 °C. The untreated control veneers exhibited the smallest reduction of the normalized storage modulus. In contrast, the phenol-formaldehyde-impregnated samples exhibited a more intense relative reduction of the storage modulus with increasing relative humidity. This effect was more distinct for samples impregnated with low molecular weight phenol-formaldehyde than for those impregnated with medium molecular weight phenol-formaldehyde. In addition, higher solids contents in the resins led to even smaller normalized storage modulus. Consistently, the loss factor indicated a greater softening of the samples with an increasing humidity and higher solids content of the phenol-formaldehyde.

Tensile and Impact Bending Properties of Chemically Modified Scots Pine

This study deals with the influence of chemical modification on elasto-mechanical properties of Scots pine (Pinus sylvestris L.). The elasto-mechanical properties examined were impact bending strength, determined by impact bending test; tensile strength; and work to maximum load in traction, determined by tensile tests. The modification agents used were one melamine-formaldehyde resin (MF), one low molecular weight phenol-formaldehyde resin, one higher molecular weight phenol-formaldehyde resin, and a dimethylol dihydroxyethyleneurea (DMDHEU). Special attention was paid to the influence of the solution concentration (0.5%, 5%, and 20%). With an increase in the concentration of each modification agent, the elasto-mechanical properties decreased as compared to the control specimens. Especially impact bending strength decreased greatly by modifications with the 0.5% solutions of each agent (by 37% to 47%). Modification with DMDHEU resulted in the highest overall reduction of the elasto-mechanical properties examined (up to 81% in work to maximum load in traction at 20% solution concentration). The results indicate that embrittlement is not primarily related to the degree of modification depended on used solution concentration. It is therefore assumed that molecular size and the resulting ability to penetrate into the cell wall could be crucial. The results show that, in the application of chemically modified wood, impact and tensile loads should be avoided even after treatment with low concentrations.

Influence of drying and curing parameters on phenol-formaldehyde impregnated wood veneers

ABSTRACTThe purpose of this experimental research study was to obtain new understanding on adhesion and mechanical characteristics of impregnated spruce veneer samples wherein a low molecular weight phenol formaldehyde (PF) resin simultaneously acts both as impregnant and as adhesive. Impregnated veneer specimens were pre-dried by varying drying temperature and duration in order to obtain samples with different intermediate states of condensation. After bond formation, tensile shear strength and corresponding wood failure amount were determined. In the second part of this study, press parameters (i.e., pressing temperature and pressing time) were varied to obtain knowledge about the curing behaviour of pre-dried PF-impregnated veneer specimens. Tensile shear strength of the adhesive bond, tensile strength, the corresponding modulus of elasticity and hardness of the substrate material were determined in addition.As a result, clear effects of the various investigated parameters could be observed. While drying temperatures mainly affected the tensile shear strength, excessive pressing temperatures and times showed an impact on both, the tensile shear strength and (negatively) on the mechanical properties of the wood substrate.

Resistance improvement of rubberwood treated with zinc oxide nanoparticles and phenolic resin against white-rot fungi, Pycnoporus sanguineus

Phenolic resin or phenol formaldehyde (PF) resin containing different percentage of zinc oxide (ZnO) nanoparticles was prepared and used to treat rubberwood. Three types of treatment solutions were prepared, namely (1) low molecular weight phenol formaldehyde resin (LMwPF), (2) 1.5 wt % nano ZnO dissolved in water (ZnO/H2O), and (3) combination of both LMwPF and 1.5 wt % nano ZnO (LMwPF/ZnO). The rubberwood samples were submerged into the treatment solutions for 60, 90, and 120 min, before vacuum impregnation. The untreated rubberwood samples served as the controlled samples. The thermal stability behaviour and resistance against white-rot fungi (Pycnoporus sanguineus) of the treated rubberwood samples were evaluated. The results reveal that the treated rubberwood had slightly better thermal stability compared to the untreated samples. In terms of decay resistance, the rubberwood treated with LMwPF and LMwPF/ZnO possess very high resistance against white-rot fungi. On the other hand, the rubberwood treated with ZnO/H2O did not attain similar effectiveness as the other two treatments, except for the samples that were submerged in ZnO/H2O for 120 min. The results indicate that 1.5 wt % nano ZnO could be sufficient in imparting superior durability to rubberwood provided that longer submersion time is adopted.

The physical properties of treated oil palm veneer used as face layer for laminated veneer lumber

The depletion of our tropical timber supply has encouraged the Malaysian wood-based industry to seek alternative resources such as fast-growing plantation trees and crops for wood-based products. Oil palm tree (Elaeis guinensis) has been identified as one of the potential alternative raw materials for the production of value-added products such as plywood, laminated veneer lumber (LVL) and even solid oil palm lumber. As we know, the properties of oil palm lumber or veneer is inferior to those of wood. Modification and treatment to the oil palm are needed to enhance the quality and dimensional stability. The main objective of this study is to determine the physical properties of LVLs made from oil palm veneers (OPVs) treated with low molecular weight phenol formaldehyde (LMWPF) resin with different resin solid content and different initial moisture content (MC) of veneer. OPVs were soaked into LMWPF and re-dried to semi gel condition before being hot-pressed. There was no additional resin was added to bond the veneers together into LVL. The physical properties such as density, moisture content, thickness swelling, water absorption and weight percent gain were determined in this study. The results showed that the LVLs made by treated OPVs exhibited better physical properties compared to LVLs made from untreated OPVs but still inferior with rubberwood LVL. It can be concluded that treating OPVs prior to their usage for LVL-making is essential and effective to produce LVLs with convincing physical properties.

Properties of phenol formaldehyde resin modified with silane coupling agent (KH550)

In the present work, the organic silane coupling agent KH550 (γ-aminopropyltriethoxysilane) was added in the preparation of phenol formaldehyde (PF) resin by direct copolymerization. Such an addition modified the thermosetting low molecular weight PF resin, blocking the phenolic hydroxyl and improving its electrical insulation performance in humid environments. The volume resistance and bonding strength of the resins were tested before and after soaking in hot water. The improvement of the properties was studied in terms of resin composition and curing behavior. A common PF resin and a commercial insulation PF resin were used for the comparison. The results showed that KH550 was grafted onto the PF resin, effectively blocking the polar phenolic hydroxyl group, reducing the water absorption and increasing the volume resistance of the cured PF resin. The preparation process was simple and the prepared resin was water-soluble. The low molecular weight PF resin modified with 5% in mass of KH550 (based on the mass of phenol) exhibited better curing properties and superior volume resistance and bonding strength in humid environments.

The Influence of Media Treatments on Color Changes, Dimensional Stability, and Cracking Behavior of Bamboo Scrimber

The purpose of this study is to evaluate the influence of media treatments on color changes, dimensional stability, and cracking behavior of bamboo scrimber, which has many applications in construction. The bamboo scrimber specimens comprised bamboo bundles with a low molecular weight phenol formaldehyde resin which were manufactured via a cold-in and cold-out hot-pressing process. Small clear specimens were sampled and treated under ten different conditions: water immersion at 25°C, 63°C, and 100°C; oil immersion at 100°C and 150°C; air drying at 63°C, 100°C, and 150°C; and infrared drying at 100°C and 150°C. Then, tests were conducted to determine the color changes, dimensional stability, and cracking behavior of the bamboo scrimbers. The results showed that the bamboo scrimber specimens became darker after all treatment conditions, especially the oil treatments and infrared drying. The color of the oil-treated bamboo scrimbers was found to be more homogenous than the others. The dimensional stability of the bamboo scrimbers was more or less influenced by the water treatments, air drying, and infrared drying, and the oil-treated bamboo scrimbers were relatively stable. Moreover, during the 4-hour treatments, cracks were found in the bamboo scrimbers after air drying at 150°C or infrared drying at 100°C or 150°C.

Scrimber board (SB) manufacturing by a new method and characterization of SB’s mechanical properties and dimensional stability

Abstract A novel process has been developed for manufacturing poplar wood scrimber boards (SBs), in the course of which thick veneers are produced first and then the oriented wood fiber mats (OWFMs) are fabricated in a pilot scale fluffing machine. A low molecular weight phenol-formaldehyde (PF) resin is applied for gluing and the cold-prepressing of the mats is followed by hot-curing between 120 and 130°C for 12 h. The mechanical properties and dimensional stability of the SBOWFMs were measured. The new process resulted in significantly better mechanical properties of SBOWFMs compared with those of raw wood and other poplar wood-based composites. All data including the dimensional stability of SBOWFMs increased with increasing density.

Possibility of enhancing the dimensional stability of jelutong (Dyera costulata) wood using glyoxalated alkali lignin-phenolic resin as bulking agent

The utilization of low molecular weight phenol formaldehyde (LmwPF) resin as bulking agent to enhance the dimensional stability of wood brought some disadvantages, such as phenol is derived from non-renewable petrochemicals while formaldehyde is a known carcinogen. Hence, the possibility of using bulking agent made of glyoxalated alkali lignin (GL) incorporated in LmwPF resin to enhance the dimensional stability of wood was investigated. FT-IR spectroscopy showed that polymerization of GL and LmwPF resin was accomplished via the formation of methyl ether (CH2OCH2) bridge. Small amount of crosslinked polymer network was accomplished via the formation of methylene (CH2) bridge. Oven dried jelutong wood was evacuated under vacuum followed by soaking in 15, 20 and 25% concentrations of glyoxalated alkali lignin-low molecular weight phenol formaldehyde (GL-LmwPF) (67% solid of GL: 33% solid of LmwPF based on the total solute content) and LmwPF resins, respectively at ambient temperature for 24 h. The impregnated wood was then cured at 190 °C for 30 min. The weight percent gain (WPG) and dimensional stability in terms of antiswelling efficiency (ASE), moisture excluding efficiency (MEE) and water absorption (WA) as well as leachability of bulking agents were determined and compared with untreated wood and wood treated solely with LmwPF resin. The WPG of GL-LmwPF treated wood was lower than LmwPF treated wood. GL-LmwPF treated wood exhibited positive ASE, but the values were lower compared to LmwPF treated wood. The MEE and WA of GL-LmwPF treated wood were also inferior to LmwPF treated wood and untreated wood. GL-LmwPF resin was leached out from the treated wood whereas no leaching was found for LmwPF treated wood after three leaching cycles in distilled water. The formaldehyde release of GL-LmwPF resin treated wood was 25.76% less than of wood treated with LmwPF resin. Wood treated with 25% GL-LmwPF resin yielded highest ASE value compared to 15 and 20% GL-LmwPF treated wood. Hence, wood treated with 25% GL-LmwPF resin together with external coatings could be used in several end applications such as parquet flooring, paneling and furniture component.

Extrusion of Solid Wood Impregnated with Phenol Formaldehyde (PF) Resin: Effect of Resin Content and Moisture Content on Extrudability and Mechanical Properties of Extrudate

A new deformation technique of wood flow forming is promising for industrial uses of solid wood. Flow deformability, size stability, and good mechanical properties were obtained by using wood impregnated with low molecular weight phenol formaldehyde (PF) resin. In this study, to clarify the effect of the PF resin and moisture contents in wood on the flow deformability (extrudability) and the mechanical properties of the product (extrudate), a lateral extrusion was conducted by using wood impregnated with various contents of PF resin and three levels of moisture content. The results indicated that the extrudability of wood impregnated with PF resin improved with an increase in both PF resin and moisture content. The mechanical properties of the extrudate worsened with increases in the moisture content of the wood impregnated with PF resin. Because most of the water in the wood remained in the mold during the extrusion process, chemical changes of the wood substance and PF resin occurred due to steam forming under the high temperature and pressure of the extrusion. The steam worsened the mechanical properties of the extrudate.

Addition of ammonium hydroxide as formaldehyde scavenger for sesenduk (Endospermum diadenum) wood compregnated using phenolic resins

Compregnated sesenduk (Endospermum diadenum) was produced using low and medium molecular weight phenol formaldehyde resin. 0, 1, 1.5 and 3 % of aqueous ammonium hydroxide (NH3·H2O) were incorporated into the resin to act as formaldehyde scavenger. A maximum of 85.7 % reduction in formaldehyde emission was recorded, but the mechanical and physical properties of the treated sesenduk wood were negatively affected by the ammonium hydroxide addition.