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Lignin precipitated from different black liquors wasted from the cooking of rice straw, bagasse and cotton stalks, to produce pulp and paper, can replace phenol by up to 40 per cent in phenol formaldehyde resin. The properties of the resin produced from bagasse lignin formaldehyde are nearly the same as when the resin IS produced from phenol formaldehyde. Replacement of phenol by lignin in phenol formaldehyde resin has an economical effect and reduces the pollution caused by draining black liquor into rivers and streams. The properties of the resin produced from rice straw lignin are lower than resin from bagasse and cotton stalk lignin. The effect of increasing the content of lignin in the resin on the resin properties was studied. The effect of polymerization time and temperature on the resin properties is also clarified. The molecular structure of the lignins used plays an important role on the properties of the phenol lignin formaldehyde produced.

This study aims to prepare a low-formaldehyde and environmentally friendly glucose-lignin-based phenolic resin.

The authors directly used lignin to substitute formaldehyde to prepare lignin-based phenolic resin (LPF) with urea as formaldehyde absorbent. To improve the performance of the adhesive, the biobased glucose was introduced and the modified glucose-LPF (GLPF) was obtained.

The results showed that when the replacing amount of lignin to formaldehyde reached 15 Wt.%, the physical properties of the prepared LPF met the Chinese national standard, and the bonding strength increased by 21.9%, from 0.75 to 0.96 MPa, compared with PF. The addition of glucose boost the performance of wood adhesive, for example, the free phenol content of the obtained GLPF was significantly reduced by 79.11%, from 5.60% to 1.17%, the bonding strength (1.19 MPa) of GLPF increased by 19.3% in comparison to LPF and the curing temperature of GLPF decreased by 13.08%.

The low-formaldehyde and environmentally friendly GLPF has higher bonding strength and lower curing temperature, which is profitable to industrial application.

The prepared GLPF has lower free formaldehyde and formaldehyde emission, which is cost-effective and beneficial to human health.

The joint work of lignin and glucose provides the wood adhesive with increased bonding strength, decreased free phenol content and reduced curing temperature.

Bagasse and rice straw lignins undergo different treatments, e.g. acid hydrolysis, oxidation with hydrogen peroxide and thermal treatment, before being used as a partial replacement for phenol in phenol formaldehyde resin. These treatments improved the resin formation properties of the lignin. The effect of these treatments on the improvement of the properties of the resin produced has the following sequence: lignin treated with HCl (1‐3N) > lignin treated with H₂O₂ (1‐3 per cent) > thermally treated lignin (120‐140°C). The improvement of the properties of the resin produced from bagasse lignin is greater than that produced from rice straw lignin. The treatment of rice straw lignin with acid increases its ability to form a resin. Treatment of rice straw lignin with acid leads to its increased concentration in the phenol lignin formaldehyde resin with good properties. In general, the resin produced from treated lignin has better properties than resin produced from untreated lignin.

The purpose of this paper is to examine the preparation of adhesive by incorporation of kraft lignin as an agricultural waste into phenol formaldehyde (PF) resin structure and to evaluate the mechanical properties of lignin phenol formaldehyde (LPF) as wood adhesive.

PF resin (resole) was prepared using sodium hydroxide as a catalyst. Different concentrations of lignin were incorporated into PF resin structure. The effect of lignin concentration, formaldehyde to phenol molar ratio, catalyst concentration, temperature and time upon solid content, adhesive strength and gel time was studied. The kraft lignin, PF and LPF resins were characterised using FT‐IR and thermal analysis.

The incorporation of lignin into PF resin (resole) increases adhesive strength and decreases gel time. The highest adhesive strength and the lowest gel time were achieved at 90 per cent of kraft lignin, formaldehyde to phenol molar ratio, 7.2 and 10 per cent of catalyst, after 4 h and at 80°C.

The effect of different concentrations of kraft lignin, formaldehyde/phenol molar ratio, catalyst concentration, temperatures and time upon solid content, gel time and adhesive strength was studied.

Incorporation of kraft lignin into resole leads to adhesive with improved mechanical properties.

It was found that LPF resin is better than PF resin from the economical point of view and has the better mechanical properties.

The purpose of this paper is to describe the development of an eco‐friendly tannin‐phenol formaldehyde resin (PFT) applicable in the wood composite industry.

The bark of oak (Quercus castaneifolia) contains a large amount of condensed tannin. Condensed tannin, with a large amount of Catechol groups was considered for reducing the formaldehyde emission level on the adhesive system. Physical characteristics of synthesized PFT resin were evaluated.

For optimal extraction, three solvents were used in the extraction process. The results showed that a mixture of water‐methanol (1:1 v/v) as extracting solvent is the best solvent and yields about 14 per cent tannin based on dry weight of bark. For producing tannin phenol formaldehyde adhesive, 10 per cent, 20 per cent and 30 per cent (based on PF dry weight) of PF, substituted with natural extracted tannin. For evaluating PFT performance effects of percentage amount of substitution tannin content on the gel time, viscosity, pH, and density of adhesives were evaluated. Based on emission test (JIS A 1460‐2001) formaldehyde emission of PFT 10 per cent, 20 per cent and 30 per cent were 1.13, 1.12 and 0.4 mg/100 g, which is very low compared with tannin‐free PF.

Tannin‐PF adhesive compared to PF adhesive had lower PH, higher viscosity and shorter gel time.

The method developed provides a simple and excellent renewable resource “tannin” which can be used or partially substituted in phenol formaldehyde adhesive.

Results showed that replacing PF for tannin reduces modulus of rupture (MOR) and modulus of elasticity (MOE) slightly but has significant effects on IB, water absorption and thickness swelling.

This paper aims to evaluate the effect of multiple additions of sodium hydroxide (NaOH) on the properties of bark‐phenol‐formaldehyde (BPF) adhesives, and to lay the foundations for further studies on bark utilisation.

Synthetic technologies that used multiple additions of NaOH were developed for the production of BPF adhesives. Differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and plywood bond were used to evaluate properties of the PF and BPF adhesives.

The number of NaOH additions had an important effect on many BPF adhesive properties, such as gel time, free formaldehyde content in adhesive, thermosetting peak temperature, molecular weight distribution, as well as the wet shear strength and free formaldehyde release of the bonded plywood panels. The study determined that a two‐step process for adding NaOH offers a prospective synthetic technology for BPF adhesive production. This technology made it possible to use 28.6 per cent bark by weight and resulted in plywood with properties comparable with those of plywood bonded with a commercial PF adhesive. However, BPF adhesives prepared with more than two NaOH additions were fast‐curing.

BPF adhesives are very complex systems with many unknown variables, such as the chemical structures of bark derivatives from phenolation and adhesive synthesis. To further improve the curing rate and adhesion of BPF, future investigations should be based on a two‐addition process or attempt to increase the amount of NaOH in the second addition.

The BPF adhesive prepared with two NaOH additions and 28.6 per cent bark was comparable with a commercial PF adhesive in terms of adhesive properties and plywood bond quality. These results indicate that this technology shows potential for commercial applications.

Synthetic technologies using multiple additions of NaOH were developed to produce BPF adhesives. The BPF with two additions of NaOH seemed to be comparable with a commercial PF adhesive.

The purpose of this paper is to evaluate the effect of different amounts of sodium hydroxide (NaOH) introduced during the resin synthesis on the properties of bark‐phenol‐formaldehyde (BPF) adhesives aims at achieving a balance between storage life and other properties of BPF adhesives.

Based on the best synthetic technologies for the production of BPF adhesives obtained in a previous study, a new synthetic technology is developed for the production of BPF adhesives that involve a three‐step addition of NaOH using different amounts of NaOH in the third charge. Gel permeation chromatography is used to evaluate properties of the phenol‐formaldehyde (PF) and BPF adhesives.

The amount of NaOH in the third charge has an important influence on many BPF adhesive properties. The paper determines that the synthetic technology involving three‐step NaOH additions with only water introduced in the third charge of NaOH produces a BPF adhesive with the longest storage life and best bonding strength.

BPF adhesives are very complex systems with many unknown variables.

The improved storage life of the BPF adhesive prepared with the new synthetic technology is comparable to that of a commercial PF adhesive, which indicates that this new technology shows greater potential for commercial applications.

A new synthetic technology is developed to produce a BPF adhesive that is more comparable to commercial PF adhesives than other BPF adhesives in terms of storage life and other resin properties.

In this study, organo clay modified alkyd resins were synthesised and these modified alkyd resins were cured with different ratios of phenol formaldehyde resin. The purpose of this paper is to investigate the physical and chemical properties of the films and thermal behaviours of the resins.

Alkyds formulated to have an oil content of 40 percent were prepared with phthalic anhydride (PA), glycerine (G), coconut oil fatty acid (COFA), dipropylene glycol (DPG) and organo clay. “K alkyd constant system” was used for the formulation calculations of the alkyd resins. Alkyd resins were blended with 30 percent of a phenol–formaldehyde. The films of the alkyd–phenol formaldehyde (A‐PF) resins were prepared from 60 percent solid content xylene solutions by using 50 μm applicators. After the films were cured at 150°C for 2 h in an oven, properties of the films were determined.

The effect of organo clay addition on the film properties such as drying degree, hardness, adhesion strength, impact resistance, water, acid, alkaline, solvent resistance and thermal behaviours of the resins were investigated. The addition of organo clay has a positive effect on the physical and chemical film properties for phenol formaldehyde resin.

The paper reports on a study in which organo clay modified A‐PF resins for manufacturing of industrial baking enamels were synthesised for the first time.

The purpose of this paper is to study the effect of various stoichiometric ratios for synthesised epoxy phenolic novolac (EPN) resins on their physicochemical, thermomechanical and morphological properties.

In the present study, EPN (EPN-1, EPN-2, EPN-3, EPN-4 and EPN-5) resins were synthesised by varying five types of different stoichiometric ratios for phenol/formaldehyde along with the corresponding molar ratios for novolac/epichlorohydrin. Their different physicochemical properties of interest, thermomechanical properties as well as morphological properties were studied by means of cured samples with the variation of its stoichiometric ratios.

The average functionality and reactivity of EPN resin can be controlled by controlling epoxy equivalence as well as cross-linking density upon its curing as all of these factors are internally correlated with each other.

Epoxy resins are characterised by a three-membered ring known as the epoxy or oxirane group. The capability of the epoxy ring to react with a variety of substrates imparts versatility to the resin. However, these resins have a major drawback of low toughness, and they are also very brittle, which limits their application in products that require high impact and fracture strength.

Epoxy resins have been widely used as high-performance adhesives and matrix resins for composites because of their outstanding mechanical and thermal properties. Because of their highly cross-linked structure, the epoxy resin disables segmental movement, making them hard, and it is also notch sensitive, having very low fracture energy.

Epoxy resin is widely used in industry as protective coatings and for structural applications, such as laminates and composites, tooling, moulding, casting, bonding and adhesives.

Systematic study has been done for the first time, as no exact quantitative stoichiometric data for the synthesis of EPN resin were available on the changes of its different properties. Thus, an optimised stoichiometric composition for the synthesis of the EPN resin was found.

The purpose of this paper is to investigate the effects of multi-hydroxymethylated phenol (MHMP) on the properties of moisture-curing polyurethane (PU) resin, especially on the heat resistance.

The MHMPs with various active sites from 2.52 to 3.91 were synthesised and used as a modifier. The bond test (according to the JIS K6806-2003 standard) and thermogravimetric analysis (TGA) were used, respectively, to characterise the bond durability and heat resistance of MHMP-modified PU resin.

The MHMP with various F/P mole ratios had great effects on the properties of resultant PU resins. The increase of active sites of MHMP can improve the water resistance of resin due to the more cross-linking densities, while the decrease of active sites of MHMP can improve heat resistance of resin because more stable benzene ring introduced into the PU backbone.

In cases where heat resistance of the PU resin is of primary concern, the use of MHMP with fewer active sites or a lower F/P ratio is recommended. In other cases where bond durability is focussed, the modifier MHMP shall be synthesised with higher F/P ratio.

MHMP as a modifier can be used to improve the heat resistance of PU resin.

The MHMPs with various hydroxymethyl groups were synthesised and used as modifier of moisture-curing PU resins to improve their heat resistance.