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1 – 10 of 311Ümran Burcu Alkan, Nilgün Kızılcan and Başak Bengü
The purpose of this study is the development of sustainable and low-formaldehyde emission wood adhesive formulations.
Abstract
Purpose
The purpose of this study is the development of sustainable and low-formaldehyde emission wood adhesive formulations.
Design/methodology/approach
Three-step urea formaldehyde (UF) resin has been in situ modified with calcium lignosulfonate (LS) and/or 1,4 butanediol diglycidyl ether (GE). The structural, chemical, thermal and morphological characterizations were carried out on resin samples. These resins have been applied for particleboard pressing, and UF, UF-LS and UF-GE were evaluated as P2 classes according to EN 312.
Findings
The results show that the improved LS- or diglycidyl ether-modified UF wood adhesives were successful in their adhesive capacity, and the formaldehyde content of the final product was obtained as low as 8 mg/100 g. This paper highlights that the presented adhesive formulations could be a potential eco-friendly and cost-effective alternative to formaldehyde-based wood adhesives for interior particleboard production.
Research limitations/implications
Combination of LS and GE resulted in weaker mechanical properties and fulfilled P1 class particleboards due to temperature and duration conditions. Therefore, in situ usage of LS or GE in UF resins is highly recommended for particleboard pressing. Formaldehyde content of particleboards was determined with the perforator method according to EN 12460-5 and all of the particleboards exhibited E1 class. LS was more efficient in decreasing formaldehyde content than GE.
Practical implications
This study provides the application of particleboards with low formaldehyde emission.
Social implications
The developed LS- and diglycidyl ether-modified UF resins made it possible to obtain boards with significantly low formaldehyde content compared with commercial resins.
Originality/value
The developed formaldehyde-based resin formulation made it possible to produce laboratory-scale board prototypes using LS or GE without sacrificing of press factors and panel quality.
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Bo Wang, Yanhua Zhang, Haiyan Tan and Jiyou Gu
The purpose of the study was to prepare melamine-urea-formaldehyde (MUF) resin that would be resistant to boiling water and high temperature and exhibit low formaldehyde emission.
Abstract
Purpose
The purpose of the study was to prepare melamine-urea-formaldehyde (MUF) resin that would be resistant to boiling water and high temperature and exhibit low formaldehyde emission.
Design/methodology/approach
The authors prepared MUF resin with different F/(M + U) and changed the amount of melamine added, through the analysis of MUF resin properties to get the best reaction parameters, and used different amino acid cure systems including NH4Cl cured the resin.
Findings
Resin’s heat resistance and water resistance are mainly determined by the amount of melamine added, and formaldehyde emission of the plywood can be changed by adjusting F/(M + U). The peak temperature of the curing agent-cured resin increases as compared with the self-curing resin. Stronger the acidity of curing agent, faster the viscosity increased in probation period and lower the bonding strength and heat resistance of the resin.
Research limitations/implications
Melamine improves the heat resistance and water resistance of the resin. When the amount of melamine is more than a certain value, water resistance of the resin decreased.
Practical implications
MUF resin that is resistant to boiling water and exhibits low formaldehyde emission can be used in high temperature, high humidity and strict formaldehyde emission environment and can also be combined with other materials.
Social implications
It was helpful to reduce the effect of formaldehyde emission on people’s health and environmental pollution and is also beneficial for the expansion of the application range of aldehyde resin.
Originality/value
The originality is twofold: the influence of the acid strength of curing agent on the bonding strength of the resin adhesive and the method for preparing high performance MUF resin by following the traditional process.
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Esin Ateş, Nurseli Uyanık and Nilgün Kızılcan
The purpose of the research was as follows. In situ modified urea formaldehyde resins were prepared from clay (montmorillonite) and organoclay in the presence of base catalyst…
Abstract
Purpose
The purpose of the research was as follows. In situ modified urea formaldehyde resins were prepared from clay (montmorillonite) and organoclay in the presence of base catalyst. Different clay contents (1 wt%, 3 wt%, 6 wt%) were used to produce clay modified nanocomposite resins. These nanocomposites were characterized with FT‐IR, XRD as structural analysis and DSC as thermal analysis and their hardness was evaluated as mechanical analysis. The thermal results was compatible with hardness measurements and showed that using clay/organoclay added resin as a surface coating material provides significant improvement.
Design/methodology/approach
During synthesis of the resin, modification was carried out using urea/formaldehyde with molar ratio of 1/1.6, under basic medium with pH=10 and with temperature of 70°C by loading pristine and organomodified layered silicates.
Findings
X‐ray diffraction (XRD) results indicate that the interlayer space of pristine clay was increased significantly by one step, seeing that one step processes are crucial for industrial applications.
Research limitations/implications
The reaction mixture must be stirred continuously. Temperature should be controlled in order to prevent the thermal curing of urea formaldehyde resin.
Practical implications
This study provides technical information for the synthesis of nanocomposite resins. The clay or organoclay modified resins may also promote the adhesive strength of coating and also inhibit corrosion effects to metal surfaces of the coated area.
Social implications
This resin will be used for the coating material.
Originality/value
As Tg‐Tm region of some nanocomposites is enhanced, and by assessing the results of hardness measurements, it is concluded that these samples have further improved mechanical properties as a coating material than urea formaldehyde resin has.
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The paper deals with the mode of film formation from urea–formaldehyde and melamine–formaldehyde resins combined with alkyd resin based on castor oil‐modified alkyd. The…
Abstract
The paper deals with the mode of film formation from urea–formaldehyde and melamine–formaldehyde resins combined with alkyd resin based on castor oil‐modified alkyd. The properties of hardened coatings (such as hardness, chemical stability, and adhesion to substrate) were followed in dependence on the ratios of reaction components. An apparatus was built for measuring the formaldehyde emissions escaping from the solid coating films. The determination was performed by the pararosaniline method. The addition of imidazolidine in a concentration up to 10 per cent can reduce the emissions of formaldehyde escaping from the solid films to a considerable amount.
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Hassan Salah Aly Emira, Yosreya Mostafa Abu‐Ayana and Sanaa Mohammad El‐Sawy
The purpose of this paper is to study the corrosion protective properties of modified urea and/or thiourea formaldehyde resins for steel surface.
Abstract
Purpose
The purpose of this paper is to study the corrosion protective properties of modified urea and/or thiourea formaldehyde resins for steel surface.
Design/methodology/approach
Three butyl alcohol modified amino resins were laboratory prepared. The three modified resins were characterized using thermal gravimetric analysis and infrared; the solid content and refractive index of each were also measured.
Findings
The resins that contain both nitrogen and sulphur have excellent corrosion inhibitive activity compared with that containing nitrogen only.
Research limitations/implications
The modified resins were based on urea formaldehyde resin, mixed urea and thiourea formaldehyde resin and thiourea formaldehyde resin, respectively.
Practical implications
The prepared resins were introduced in different coating formulations based on short‐oil alkyd resin, medium‐oil alkyd resin and plasticized chlorinated rubber. They were then tested and evaluated for corrosion protection of steel surfaces.
Originality/value
All the prepared resins show promising results for corrosion protection of steel surfaces.
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The interaction between formaldehyde and urea or thiourea has been reported by Richard and Gourdenne who used G.P.C. columns packed with reticular polystyrene gel of pore sizes…
Abstract
The interaction between formaldehyde and urea or thiourea has been reported by Richard and Gourdenne who used G.P.C. columns packed with reticular polystyrene gel of pore sizes 3×104, 3×103, 103, 500, 200, 100, 60 and 60 A and which were eluted with N, N‐dimethylformamide at 50°C. These authors prepared precursors such as monomethylolurea and N, N‐dimethylolurea in aqueous base at 4°C which prevented their autocondensation. These materials were positively identified by proton nuclear magnetic resonance spectroscopy, but they were not resolved from one another nor from urea itself on the G.P.C. columns on account of the fact that the strong solvation by the eluent dimethyl‐formamide was not affected by the substitution of one or two methylol groups into the urea molecule. Using an acid solution at room temperature, it was found that the reaction between formaldehyde and urea or disubstituted urea produced substances such as methylene diurea and methylene di (N, N‐dimethylurea) which, respectively, eluted before and after urea itself. When urea or thiourea was reacted with formaldehyde at a molar ratio of 1:1.8 in a 30% aqueous solution of pH 8 at 95°C, it was shown by nuclear magnetic resonance spectroscopy that the individual urea residues were linked by ether bridges only and that methylenic linkages were totally absent. The degree of cross‐linking of the products was expressed in terms of the ratio of the number of protons included in these bridges to the total number of protons in the various methylene groups as determined by nuclear magnetic resonance spectroscopy. Five samples were taken from such a reaction between urea and formaldehyde. Their G.P.C. curves were obtained and they were shown to display a wider molecular size distribution as the calculated degree of cross‐linking increased. The initial sample was found to be comprised of a mixture of mono‐ and dimethylolurea, but the samples taken later on during the reaction were more highly polymerised and could not be assigned individual molecular structures. A similar conclusion was reached using a mixture of thiourea and formaldehyde in the preparation of a resin.
Kaiyan Yang, Xiaowu Gong, Lanli Bai, Yun Zhang and Na Zhou
This study aims to prepare a low-formaldehyde and environmentally friendly glucose-lignin-based phenolic resin.
Abstract
Purpose
This study aims to prepare a low-formaldehyde and environmentally friendly glucose-lignin-based phenolic resin.
Design/methodology/approach
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.
Findings
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%.
Practical implications
The low-formaldehyde and environmentally friendly GLPF has higher bonding strength and lower curing temperature, which is profitable to industrial application.
Social implications
The prepared GLPF has lower free formaldehyde and formaldehyde emission, which is cost-effective and beneficial to human health.
Originality/value
The joint work of lignin and glucose provides the wood adhesive with increased bonding strength, decreased free phenol content and reduced curing temperature.
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F.F. Abd El Mohsen, R.M. Mohsen and Y.M. Abu Ayana
Modern glues are manufactured with high moisture and water resistance; urea‐formaldehyde resins for gluing purposes are based on the fact that excellent control of the…
Abstract
Modern glues are manufactured with high moisture and water resistance; urea‐formaldehyde resins for gluing purposes are based on the fact that excellent control of the condensation reaction is possible by variation of pH, which can be applied easily at the production process. Among conclusions is that the shear stress of these resins is twice that of the unmodified type.
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Formaldehyde and UF foam cavity wall insulation Urea formaldehyde (UF) foam cavity wall insulation was introduced into this country, from Denmark, in 1959. Relatively little was…
Abstract
Formaldehyde and UF foam cavity wall insulation Urea formaldehyde (UF) foam cavity wall insulation was introduced into this country, from Denmark, in 1959. Relatively little was installed until after the oil crisis which followed the Arab‐Israeli War of 1973. In total, some 1.5 million buildings have been insulated with it. UF foam is the cheapest material for retrofit cavity wall insulation. (All well‐installed systems have a comparable heat resistance.)
Gözde Koçak and Seçil Çelik Erbaş
This study aims to produce homogenously prepared polymer composites by adding two different strontium aluminate derivatives (Sr4Al14O25 and SrAl2O4) to urea-formaldehyde (UF) at…
Abstract
Purpose
This study aims to produce homogenously prepared polymer composites by adding two different strontium aluminate derivatives (Sr4Al14O25 and SrAl2O4) to urea-formaldehyde (UF) at different mass concentrations. In the context of this work those strontium-based derivatives were compared in terms of mechanical and luminescent characteristics. Additionally, sodium bicarbonate was integrated with the prepared composites to eliminate/minimize darkening problem, which might arise from the oxidation of Eu +2 to Eu2O3, on the surface of strontium aluminate/urea-formaldehyde composites.
Design/methodology/approach
In this study, strontium aluminate/UF composite materials were produced using a compression molding technique. Their mechanical, thermomechanical and luminescence properties were investigated via various characterization methods. Particle size analysis was used to characterize phosphor derivatives, whereas scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) was conducted for morphological examination.
Findings
The darkening problem was prevented by the introduction of sodium bicarbonate into the composite systems. Based on the characterization and test results, the only addition of strontium aluminate reduced the mechanical properties. However, it was seen that the introduction of sodium bicarbonate into the composites improved those properties positively. The appropriate amounts of strontium aluminate and sodium bicarbonate were determined by conducting an experimental optimization study. The optimum composition of the composite materials was obtained by introducing 2% phosphor and 3% NaHCO3.
Originality/value
The approach used in this study has provided a method to solve the darkening problem, which degrades the aesthetic appearance in industrial production.
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