Commercial Phenol-formaldehyde Resin Research Articles

A Dual Resin Application System for Improved Bamboo-Wood Bonding

In this work, a dual resin application system using commercial phenol formaldehyde (PF) resins with different molecular weight (MW) was investigated to improve bonding performance of bamboo and wood composite laminates. Water droplet contact angle was deemed to be unreliable for assessing resin wettability on bamboo due to its unique tissue structure compared with wood. Microscopic observation of the resin penetration showed high MW PF largely remained in the glueline and only entered the lumens of cut or damaged bamboo cells near the bondline. Low MW PF appeared in cell corners of bamboo parenchyma but not lumens. Applying low MW PF to the bamboo and high MW PF to the wood surface separately significantly improved bond shear strength with reduced difference between dry and wet conditions. The dry and wet bond strengths using the new method were enhanced by 36.5% and 97.4%, respectively, compared to high MW PF alone. The results suggest that low MW PF can permeate bamboo cell walls and fortify them against swelling and stress on the bamboo-resin interface in wet conditions. Further modifications are required to produce a stronger adhesive than the bamboo tissue to improve wet shear fiber failure rates and develop a viable structural bond qualification test for bamboo and bamboo-wood composites.

High-yield carbon derived from commercial phenol–formaldehyde resin for broadband microwave absorption by balancing conductivity and polarization loss

High-yield carbon derived from commercial phenol–formaldehyde resin for broadband microwave absorption by balancing conductivity and polarization loss

Paper-Based Laminates Impregnated with a Hybrid Lignin-Phenol-Formaldehyde Resin

In this study, high-pressure laminates (HPL) impregnated with phenol-formaldehyde (PF) resins enriched with kraft lignin were developed. Pulverised kraft lignin was added to the commercial PF resin in the amounts of 1% and 5% (solid to solid). Laminates were manufactured using pressure impregnation of the resins into the papers and using hot pressing of HPL in a laboratory press. Laminates with a lignin content of 1% (L-LPF-1) showed the highest bending strength (72.42 MPa) and Brinell hardness (9.41); they also exhibited the best moisture uptake (9.61) and thickness swelling after immersion in water (3.32%). Except for impact bending, laminates with a lignin content of 5% (L-LPF-5) had worse properties. However, the differences between the variants are mostly not statistically significant and are comparable with the results of commercial PF resin. Scanning electron microscopy confirmed the homogenous structure of produced laminates and the occurrence of cohesive failures in ruptured L-LPF-1 laminates, whereas in ruptured L-LPF-5 laminates adhesive failures were also observed. Based on the conducted research it can be said that the utilisation of kraft lignin as an additive to PF resin (in the amount of 1%) has a positive effect on the produced HPL.

Preparation and performance of tannin-glyoxal-urea resin-bonded grinding wheel loaded with SiO2 reinforcing particles

In this study, an easily prepared bio-based abrasive grinding wheel based on tannin-glyoxal-urea (TGU)thermosetting matrix is presented.The synthesised resin was prepared via co-polycondensation reaction of glyoxal and ureawith condensed tannin, which is a forest-derived product. Fourier transform infrared spectroscopy and electrospray ionisation mass spectrometry results confirmed that urea and glyoxal react well under acidic conditions and that -(OH)CH-NH-group is primarily involved in TGU cross-linking. Differential scanning calorimetry, thermomechanical analysis and thermogravimetric analysis investigations showed that the preparation of TGU resin is easier compared to commercial phenol-formaldehyde (PF) resin; moreover, TGU resin has a more robust chemical network structure, which contributes efficiently to heat resistance and improved mechanical properties. This observation is supported by Brinell hardness, compression resistance and grinding testing; these showed that the new grinding wheel acquired higher hardness, superior resistance against compression and stronger abrasion resistance compared with a PF-based grinding wheel prepared in the laboratory. Moreover, few holes and no cracks were found in the new grinding wheel.

WASTE MORINGA OLEIFERA GUM AS A MULTIFUNCTIONAL ADDITIVE FOR UNFILLED SBR COMPOUND

ABSTRACT A natural waste (gum) of the drumstick tree, Moringa oleifera, was used for the first time as a sustainable multifunctional additive in an SBR compound. Improved cure rate with lower optimum cure time was obtained by using the gum as an accelerator activator. Tack strength of the M. oleifera gum–SBR compound was superior to both the control and the compound containing commercial phenol–formaldehyde resin at 5 parts per hundred of rubber loading. At different loadings, the gum acted as a plasticizer for the rubber and augmented processing by reducing the viscosity of the compound. The glass transition temperature of the compounds decreased by 2 °C compared with the pristine SBR. Moringa oleifera gum at any loading reduced the die swell of SBR. This study has relevance because the rubber industry is looking for feasible sustainable additives as alternatives to existing petroleum-based compounding ingredients.

Lignin-based resins for kraft paper applications

We investigated miscanthus (MS) and willow (W) lignin-furfural based resins as potential reinforcement agents on softwood and hardwood kraft paper. These resins might be sustainable alternatives to the commercial phenol-formaldehyde (PF) resins. Phenol is a petrochemical product and formaldehyde has been classified as a carcinogen by the U.S. Environmental Protection Agency. The lignin used in this study was derived from hot water extraction (160ºC, 2 h) of MS and W biomass, and may be considered sulfur-free. These biorefinery lignins were characterized for their chemical composition and inherent properties via wet chemistry and instrumental techniques. The resin blends (MS-resin and W-resin) were characterized for their molecular weight, thermal behavior, and mechanical properties. Mechanical properties were measured by the resin’s ability to reinforce softwood and hardwood kraft papers. The effect of adding hexamethylenetetramine (HMTA), a curing agent, to the resin was also examined. Mixtures of PF and lignin-based resins were investigated to further explore ways to reduce use of nonrenewables, phenol, and carcinogenic formaldehyde. The results show that lignin-based resins have the potential to replace PF resins in kraft paper applications. For softwood paper, the highest strength was achieved using W-resin, without HMTA (2.5 times greater than PF with HMTA). For hardwood paper, MS-resin with HMTA gave the highest strength (2.3 times higher than PF with HMTA). The lignin-based resins, without HMTA, also yielded mechanical properties comparable to PF with HMTA.

Water Related Properties of Birch Wood Modified with Phenol-Formaldehyde (PF) Resins

In this study, Silver birch (Betula pendula) wood veneers and solid wood blocks were treated with commercial phenol-formaldehyde (PF) resin water solutions. Birch veneers and solid wood blocks of different size were impregnated with PF resin solutions in water with concentrations of 10, 20 and 30 wt%. The weight percent gain (WPG) and bulking after drying and curing of resin treated wood specimens were determined to evaluate the impact of specimen sizes and density. The leaching procedure according to EN 84 was performed to evaluate the PF resin fixation stability. The anti-swelling efficiency (ASE) of untreated and treated specimens during seven soaking-drying cycles was examined. Higher WPG values were obtained for specimens with lower density, but no correlation was found between the specimen size and WPG. The WPG of veneers and solid wood was 8.7 - 17.7% and 8.5 - 24.4%, respectively. The ASE of wood blocks treated with PF resins after the 1st cycle was in the range of 37 - 51% depending on the resin loading in the wood. However, the ASE values decreased after every next soaking-drying cycle, reaching 33 - 48% after the 7th cycle. After leaching, the WPG of specimens decreased by 2.3 - 3.0%.

A new adhesive from waste wool protein hydrolysate

This study aimed to produce a new non-toxic adhesive system consisting of wool-hydrolysed (WH) and a commercial wet-strength agent for paper (Kymene® 557H) which is an aqueous solution of cationic polyamidoamine-epichlorohydrin (PAE) resins. The WH mixed with Kymene (WH-K) and used as an adhesive for bonding pine veneer. Rheology aspects of the blends measured in different WH-K weight ratios and the effect of reaction time on the lap-shear strengths of wood composites bonded with WH-K adhesives were evaluated. The physicochemical properties of the newly developed wood adhesive system were characterised using FTIR, DSC and TGA. Wood composites bonded with WH-K adhesive had shear strengths comparable to or higher than those bonded with commercial phenol-formaldehyde resins. Wood composites bonded with the new adhesive system demonstrated high water resistance and retained relatively high strength even after treated with boiling water. The new adhesive system is non-toxic, free from formaldehyde and friendly to use for diverse applications. Thus, we anticipate that this new adhesive system will be potential candidate for bio-composites and packaging applications.

Development of hydrolysed protein-based plywood adhesive from slaughterhouse waste: effect of chemical modification of hydrolysed protein on moisture resistance of formulated adhesives.

Specified risk materials (SRM) constitute the proteinaceous waste of slaughterhouses and are currently being disposed off either by incineration or by land filling. Over the last few years, our efforts have focused on developing technology platforms for deployment of this renewable resource for various value-added industrial applications. This report describes a technology for utilization of SRM for the development of an environmentally friendly plywood adhesive with an improved water resistance property. The feedstock (SRM) was first thermally hydrolysed according to a standard protocol, and the hydrolysed protein fragments (peptides) were recovered from the hydrolysate. The recovered peptides were chemically modified through esterification reaction using ethanol, and then chemically crosslinked with polyamideamine-epichlorohydrin (PAE) resin to develop a wood adhesive system. Plywood specimens were then developed using the peptides–PAE resin-based adhesive. The effects of crosslinking time, solid content of the adhesive formulation, ratio of peptides and crosslinking agent in the formulation, and curing conditions of specimen preparation on lap shear strength of resulting plywood specimens were systematically evaluated. Despite the hydrophilic nature of hydrolysed protein fragments, the peptides–PAE resin formulations exhibited remarkable water resistance property after curing. Capping of polar carboxyl groups of peptides by converting them to esters further improved the water resistance property of this adhesive system. Under the optimum conditions of adhesive preparation and curing, the ethyl ester derivative of peptides and PAE resin-based formulations resulted in plywood specimens having comparable dry as well as soaked shear strengths to those of commercial phenol formaldehyde resin.

Modification of beech veneers with lignin phenol formaldehyde resins in the production of laminated veneer lumber (LVL)

Rotary cut beech (Fagus sylvatica L.) veneers were treated with four different lignin phenol formaldehyde (LPF) solutions using dimethyl sulfoxide (DMSO) as a solvent. Four of these veneers were bonded with PF adhesive to produce four-layer laminated veneer lumber (LVL). To synthesize the LPF solutions, a commercial phenol formaldehyde resin (PF resin) was individually mixed with three different technical lignins (Indulin AT, BioChoice lignin, organosolv lignin) and lignin cleavage products (LCP) at a ratio of 3:2 (60%:40%). Differential scanning calorimetry showed an increased curing temperature for the LPF resins in comparison to the PF resin. The mechanical and water-related properties of the LPF-modified LVL were shown to be similar or slightly improved compared to PF-modified LVL. Fungal degradation experiments with white-rot fungus (Trametes versicolor) and brown-rot fungus (Coniophora puteana) exhibited no significant differences in the mass loss of the LPF-modified and PF-modified samples except in one case: LVL made from veneers treated with Indulin AT exposed to the white-rot fungus. The resistance to weathering of LVL samples made from veneers treated with technical lignins was low; however, specimens treated with LCP and the reference PF resin displayed a higher resistance to weathering. It is concluded that technical lignins or LCP can, to a certain extent, be used as a substitute for crude-oil based PF resin.

TECHNOLOGICAL PROPERTIES OF PLYWOOD BONDED WITH PHENOL-FORMALDEHYDE RESOL RESIN SYNTHESIZED WITH BIO-OIL

ABSTRACT In this study, it was aimed to use of bio-oil as an alternative to petroleum-based phenol in the production of phenol-formaldehyde (PF) resin used for making exterior plywood.Bio-oil obtained from pine wood sawdust using a vacuum pyrolysis reactor at 500 °C. The PF resol resins were produced by substituting up to 20 wt% of phenol with bio-oil by modifying the chemical synthesis process. FT-IRanalysis was performed to characterizethe organic functional groups in the bio-oil modified PF resins. In comparison to the commercial and lab-made PF resins, the bio-oil modified PF resins were found to have larger average molecular weights, higher polydispersity indices, and shorter gel times. Six different types of plywood panels were produced from the experimental PF resins which were commercial PF resin, lab-made PF resin, and PF resins modified with bio oil of 5, 10, 15 or 20 wt% contents, respectively. Plywood specimens produced with the PF resin modified with bio-oil up to 20 wt% had better tensile shear strength (wet condition), modulus of rupture, and modulus of elasticity in bending as compared to the commercial and lab-made PF resins.

Preparation and characterization of green adhesives using modified tannin and hyperbranched poly (amine-ester)

Tannin-glyoxalated Kraft lignin (TGKL) resin is a successful substitution for phenol formaldehyde resin in the production of wood adhesives, however it has a poor water resistance. To overcome this obstacle, this research was focused on scalable adhesive through the modified tannin adhesive and oligomeric precursors of a hyperbranched poly (amine-ester) (HBPAE). The prepared glyoxalated Kraft lignin resin (MTGKL), TGKL, HBPAE and commercial phenol formaldehyde (CPF) resin were evaluated by FTIR, 1H and 13C NMR spectroscopy. The tensile strengths and thermal stability were determined. The results indicated that the addition of HBPAE to tannin adhesive could improve the water resistance of MTGKL. This was evident when soaking plywood bonded with TGKL in cool water, where delamination occurred, but it was not evident with MTGKL. The tensile results indicated that the adhesive strengths of MTGKL, 39.72MPa (dry) and 27.62MPa (wet), were higher compared to TGKL and CPF resins.

Enhancing the Adhesive Strength of a Plywood Adhesive Developed from Hydrolyzed Specified Risk Materials.

The current production of wood composites relies mostly on formaldehyde-based adhesives such as urea formaldehyde (UF) and phenol formaldehyde (PF) resins. As these resins are produced from non-renewable resources, and there are some ongoing issues with possible health hazard due to formaldehyde emission from such products, the purpose of this research was to develop a formaldehyde-free plywood adhesive utilizing waste protein as a renewable feedstock. The feedstock for this work was specified risk material (SRM), which is currently being disposed of either by incineration or by landfilling. In this report, we describe a technology for utilization of SRM for the development of an environmentally friendly plywood adhesive. SRM was thermally hydrolyzed using a Canadian government-approved protocol, and the peptides were recovered from the hydrolyzate. The recovered peptides were chemically crosslinked with polyamidoamine-epichlorohydrin (PAE) resin to develop an adhesive system for bonding of plywood specimens. The effects of crosslinking time, peptides/crosslinking agent ratio, and temperature of hot pressing of plywood specimens on the strength of formulated adhesives were investigated. Formulations containing as much as 78% (wt/wt) peptides met the ASTM (American Society for Testing and Materials) specifications of minimum dry and soaked shear strength requirement for UF resin type adhesives. Under the optimum conditions tested, the peptides–PAE resin-based formulations resulted in plywood specimens having comparable dry as well as soaked shear strength to that of commercial PF resin.

Synthesis and Characterization of Bio-Based Phenol-Formaldehyde Resol Resins from Bark Autoclave Extractives

Abstract With the growing concern for fossil fuel depletion and environmental carbon footprint, there is a strong interest in exploring the renewable biomass materials as substitutes for petroleum-based feedstock. In this study, bark autoclave extractives from the mountain pine beetle (Dendroctonus ponderosae Hopkins)–infested lodgepole pine (Pinus contorta Dougl.) were used for partially replacing petroleum-based phenol in the phenol-formaldehyde (PF) resol resin synthesis. The structural characteristics of the bark autoclave extractives were examined using liquid-state 13C nuclear magnetic resonance (NMR). The curing behavior and curing kinetics, bonding strength, and bond development of the resulting bio-based bark extractive–PF resol resins were investigated using differential scanning calorimetry (DSC), lap shear, and dynamic mechanical analysis (DMA) tests, respectively. Results showed that bark autoclave extractives were a complicated mixture containing tannin, degraded hemicellulose, and degraded lignin components. The bark extractive–PF resins exhibited a higher molecular weight, higher viscosity, shorter gel time, and faster curing rate than the laboratory-made PF resin without bark components. The bark extractive–PF resins had comparable bonding strength to a commercial PF resin even when the phenol replacement rate was as high as 50 percent by weight. Bark autoclave extractives obtained from the beetle-infested lodgepole pine are suitable as a partial replacement of petroleum-based phenol in making PF resol adhesives.

Combination of lignin polyol–tannin adhesives and polyethylenimine for the preparation of green water‐resistant adhesives

ABSTRACTIn this study, a green adhesive from renewable lignin and tannin was developed with polyethylenimine (PEI) with a method to improve the water resistance of the lignin/tannin adhesive. Lignin polyols were prepared through the liquefaction of oil‐palm empty fruit bunches. The characteristics of the adhesive samples were compared with those of a commercial phenol–formaldehyde resin. Three plywood specimens bonded with the new adhesive showed a very high tensile strength (63.04 MPa) and were very water resistant. The effect of the solid content of the adhesives on the tensile strength and gel time and various weight ratios of PEI on the tensile strength and water resistance of the plywood specimens were evaluated. Thermal stability tests revealed that the lignin polyol–tannin/PEI adhesives had a high heat resistance (360 °C). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43437.

Preparation of Organic/Inorganic Composite Phenolic Resin and Application in Al2O3‐C Refractories

An organic/inorganic composite phenolic resin (CPR) was synthesized via silicon particles in situ composite with water‐soluble lignin–phenolic resin. It was observed that silicon particles were uniformly dispersed in the organic matrix. The oxidation activation energies of the pyrolytic products from CPR and commercial phenol formaldehyde resin (PF) were calculated as 173.3 kJ/mol and 102.4 kJ/mol, respectively, by nonisothermal kinetics method. Dumbbell‐shaped silicon carbide nanowires were formed on the surface of the pyrolytic carbon from CPR at high temperature. The oxidation resistance and mechanical properties of the Al2O3‐C refractories bonded with CPR were improved.

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

ABSTRACTIn this study, four biorefinery technical lignins were used to synthesize lignin–phenol–formaldehyde (LPF) resin adhesives with a proposed formulation that was designed based on accurate analysis of the active sites in lignin with 31P nuclear magnetic resonance (NMR). The properties of the LPF resin adhesives and the plywoods prepared with them were tested. The structural features and curing behavior of the LPF resin adhesives were thoroughly investigated by solution‐ and solid‐state 13C NMR. Results indicated that the proposed formulation exhibited favorable adaptability for all four of these technical lignins for synthesis of LPF resin adhesives. High‐performance plywood with low emissions of formaldehyde could be successfully prepared with the synthesized LPF resin adhesives. All the LPF resin adhesives exhibited similar structure and curing behavior with the commercial phenol–formaldehyde (CPF) resin adhesive. However, the LPF resin adhesives showed relatively higher curing temperatures as compared with the CPF resin adhesive. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42493.

Rheology Study of Sugar Cane Bagasse Lignin-Added Phenol–Formaldehyde Adhesives

The rheological properties of sugar cane bagasse lignin–phenol formaldehyde (PF) (30% lignin – PF) resins were studied using oscillation tests. The bagasse lignin was introduced in the classic adhesive formulation in order to supply a part of PF. Rheological qualities of optimal lignin–PF (30% lignin – PF) resins and commercial PF resin were assessed by using a rotary rheometer (ARES). Dynamic rheological measurements, performed at low strain in the linear range, are useful to characterize the network properties of resins. The results obtained showed that the time sweep indicates excellent structural stability of optimal lignin–PF (30% lignin–PF) resins and commercial PF resin. The elastic modulus is greater than the viscous one showing a remarkable elastic character of the resins, and the performed frequency sweeps show a typical spectrum of a “weak gels” structure. The time dependence at 125°C shows that the optimum cure time is 7.5 min.

Bark extractives-based phenol–formaldehyde resins from beetle-infested lodgepole pine

In this study, phenol–formaldehyde (PF) resins derived from the bark extractives were synthesized and characterized. Bark of lodgepole pine (Pinus contorta Dougl.) infested by mountain pine beetle (Dendroctonus ponderosae Hopkins) was first extracted with 1% NaOH. The bark extractives with and without acid-neutralization were then dried to the solid state. The neutralized and non-neutralized extractives were used to partially replace petroleum-based phenol for synthesizing the bark extractives-PF resins. In comparison with a commercial PF resin and a laboratory made PF resin (Lab PF), the bark extractive-PF resins were found to have higher molecular weights, higher viscosities, and shorter gel times. Acid neutralization of the bark extractives increased the molecular weight of the extractives and modified the performance and curing behavior of the resulting bark extractive-PF resins. Bark extractive-PF resins (BEPF) showed a similar level of post-cured thermal stability to that of the lab PF at higher temperatures, but they differed significantly from that of the commercial PF resin. The bark extractive-PF resins made from both neutralized and non-neutralized extractives at 30% replacement of phenol (by weight) exhibited similar dry and wet bond strengths to the commercial PF resin. At 50% substitution level, BEPF had dry and wet bond strengths similar to the lab PF resin. Our findings suggest that alkaline extractives from mountain pine beetle-infested lodgepole pine bark are suitable for partially substituting phenol in the synthesis of phenolic resin for use in wood adhesives.

The influence of lathe check depth and orientation on the bond quality of phenol-formaldehyde – bonded birch plywood

Abstract During the rotary peeling of veneer for plywood or the laminated veneer lumber manufacture, checks are formed in the veneer that are as deep as 70–80% of the veneer thickness. The results of this study show that, during adhesive bond testing, deep lathe checks in birch (Betula pendula Roth.) veneer significantly reduce the shear strength and the percent wood failure of phenol-formaldehyde (PF) – bonded plywood. The results also show that specimens tested with the checks pulled open or closed can fail by different mechanisms. Dried rotary peeled birch veneers were sanded to create uniform surfaces with lathe check depths varying from 30% to 90% of veneer thickness. Then, 7-ply plywood was manufactured with a commercial PF resin. After the preparation of the test specimens, the check depth of each specimen was measured microscopically. Subsequently, bond quality was measured according to EN 314. The results show that veneer checking alone can bring EN 314 specimens to the brink of failure even with an excellent adhesive. These findings stress the importance of measuring the depth of lathe checks and considering the orientations of checks during the testing to get a better understanding of bond quality in veneer-based products.