Synthesis of High-Water-Resistance Lignin-Phenol Resin Adhesive with Furfural as a Crosslinking Agent

In this study, furfural was used as a crosslinking agent to enhance the water resistance of lignin-phenol-formaldehyde (LPF) resin. The effect of the furfural content on the physicochemical properties of the adhesives was explored, and the possible synthesis mechanism of the furfural-modified lignin-phenol-formaldehyde (LPFF) resin adhesives was investigated. Compared with the LPF adhesive, the LPFF adhesive with 15% furfural content and 50% lignin substituent exhibited outstanding properties in all considered aspects; it had a high wet shear strength (1.30 MPa), moderate solid content (54.51%), and low viscosity (128 mPa∙s), which were 38.0% higher, 3.6% higher, and 37.5% lower than those of the LPF adhesive. Analyses via nuclear magnetic resonance and Fourier transform infrared (FTIR) spectroscopy confirmed that the furfural content improved water resistance of the lignin-based adhesive; this improvement was due to the formation of new chemical bonds between furfural and lignin to construct a dense crosslinked network structure. In addition, the decrease in viscosity and the increase in solid content enabled the adhesive to better penetrate into the wood porous structure, showing stronger adhesion. Therefore, the LPFF adhesive has superior water resistance, high strength, and good thermal stability; thus, it has a great potential for industrial applications.

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Preparation of highly water-resistant wood adhesives using ECH as a crosslinking agent

e-Polymers ◽

10.1515/epoly-2022-0010 ◽

2022 ◽

Vol 22 (1) ◽

pp. 99-107

Author(s):

Chen Ding ◽

Ning Li ◽

Zhikang Chen ◽

Yufei Zhang

Keyword(s):

Shear Strength ◽

Water Resistance ◽

Phenol Formaldehyde ◽

Crosslinking Agent ◽

Kraft Lignin ◽

Industrial Applications ◽

National Standards ◽

Type I ◽

Synthesis Mechanism ◽

Wood Adhesives

Abstract In this study, kraft lignin and epichlorohydrin (ECH) were used to prepare no-formaldehyde wood adhesives. The lignin was first treated by ball milling, then reacted with glyoxal to produce glyoxalated lignin under alkaline conditions, and then blended with ECH to prepare lignin-based formaldehyde-free adhesive. The influence of the content of ECH on the physicochemical properties of the adhesives was explored, and the possible synthesis mechanism of the ECH-modified glyoxalated lignin adhesives (glyoxalated kraft lignin-epoxy [GKLE]) was investigated. The results show that ECH was beneficial to improving the plywood shear strength and water resistance; the plywood prepared with GKLE-50 adhesive displays comparable water resistance as phenol–formaldehyde resins and its wet shear strength (type I) was 1.05 MPa, exceeding the Chinese National Standards GB/T 9846-2015. Scanning electron microscopy analysis showed that the increase of ECH content promoted the adhesive to penetrate the wood to form glue nails, improving the wet shear strength of the plywood. Chemical analysis indicated that glyoxalation was used to introduce hydroxyethyl groups into the ortho positions of the aromatic rings of lignin, and then the ring-opening reaction between glyoxalated lignin and ECH occurred forming ether bonds. Overall, lignin has displayed great potential in replacing formaldehyde-based adhesives for industrial applications.

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Enhanced Water Resistance of Recycled Newspaper/High Density Polyethylene Composite Laminates via Hydrophobic Modification of Newspaper Laminas

Polymers ◽

10.3390/polym13030421 ◽

2021 ◽

Vol 13 (3) ◽

pp. 421

Author(s):

Binwei Zheng ◽

Weiwei Zhang ◽

Litao Guan ◽

Jin Gu ◽

Dengyun Tu ◽

...

Keyword(s):

Stearic Acid ◽

Photoelectron Spectroscopy ◽

Composite Laminates ◽

High Density Polyethylene ◽

Water Resistance ◽

Laminated Composite ◽

High Strength ◽

High Water ◽

High Density ◽

X Ray

A high strength recycled newspaper (NP)/high density polyethylene (HDPE) laminated composite was developed using NP laminas as reinforcement and HDPE film as matrix. Herein, NP fiber was modified with stearic acid (SA) to enhance the water resistance of the NP laminas and NP/HDPE composite. The effects of heat treatment and SA concentration on the water resistance and tensile property of NP and composite samples were investigated. The chemical structure of the NP was characterized with X-ray diffractometer, X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectra techniques. The surface and microstructure of the NP sheets were observed by scanning electron microscopy. An expected high-water resistance of NP sheets was achieved due to a chemical bonding that low surface energy SA were grafted onto the modified NP fibers. Results showed that the hydrophobicity of NP increased with increasing the stearic acid concentration. The water resistance of the composite laminates was depended on the hydrophobicity of the NP sheets. The lowest value of 2 h water absorption rate (3.3% ± 0.3%) and thickness swelling rate (2.2% ± 0.4%) of composite were obtained when the SA concentration was 0.15 M. In addition, the introduction of SA can not only enhance the water resistance of the composite laminates, but also reduce the loss of tensile strength in wet conditions, which shows potential in outdoor applications.

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Effect of Technical Aerosil on the Properties of Adhesive Compositions

Lesnoy Zhurnal (Forestry Journal) ◽

10.37482/0536-1036-2021-3-133-144 ◽

2021 ◽

pp. 133-144

Author(s):

Ekaterina G. Sokolova ◽

◽

Dmitry S. Rusakov ◽

Galina S. Varankina ◽

Anatoly N. Chubinsky

Keyword(s):

Water Resistance ◽

Deep Structure ◽

Raw Materials ◽

Phenol Formaldehyde ◽

Physical Adsorption ◽

Urea Formaldehyde ◽

High Water ◽

Complex Compounds ◽

Adhesive Compositions ◽

Wide Range

The main drivers of competition among the products made with the use of adhesive compositions are the toxicity of finished products, the consumption of raw materials and energy resources, the duration of the main technological operations. These drivers can be controlled by using adhesives with different fillings and/or modifications. Adhesives based on phenol-formaldehyde and melamine-urea-formaldehyde resins are used to produce plywood with increased water resistance. Apart from resins, adhesives usually contain hardeners, fillers, and modifiers that affect the properties of the finished product. Technical aerosol is one of the modifiers of synthetic resins with a wide range of action. Aerosil is characterized by three types of interaction: physical adsorption, chemical adsorption (formation of hydrogen bridges by silanol groups), and chemical reactions on the surface layer. The chemical composition of aerosil was analyzed. Technical aluminum fluoride (AlF3) is of particular interest. It can interact with alkali metal fluorides with the formation of complex compounds that improve polymer structuring. The acids that make up aerosil reduce the pH to 2.0–3.5, so they can be catalysts for the curing process of melamine-urea-formaldehyde resins. The effect of technical aerosil on the properties of adhesive systems based on phenol-formaldehyde and melamine-ureaformaldehyde resins has been studied. Viscosity, curing time, and wetting ability of adhesive compositions were determined. The obtained results indicate the possibility of using this modifier in the composition of phenol-formaldehyde and melamine-urea-formaldehyde resins up to 15 pts. wt. The nature of the aerosil action on adhesive compositions was determined using IR spectroscopy. Analysis of the results showed that aerosil promotes deep structure formation of the polymer by increasing the molecular weight of the molecules. These bonds make it possible to form a more structured polymer with bound formaldehyde. Studies of the effect of aerosil on the properties of finished products were carried out. At the same time, an increase in performance indicators was found: the strength of adhesion increases, the toxicity of plywood decreases. The results of experiments on the effect of technical aerosil, taking into account the reduction of bonding time can be applied in the development of technological processes for obtaining plywood of high water resistance. For citation: Sokolova E.G., Rusakov D.S., Varankina G.S., Chubinsky A.N. Effect of Technical Aerosil on the Properties of Adhesive Compositions. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 3, pp. 133–144. DOI: 10.37482/0536-1036-2021-3-133-144

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Properties and Structure of Micro Porous Mullite-Corundum Refractory with High Strength

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.105-106.23 ◽

2010 ◽

Vol 105-106 ◽

pp. 23-26

Author(s):

Juan Wu ◽

Dao Yuan Yang ◽

Kai Zhu ◽

Rui Zhang

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Raw Materials ◽

High Strength ◽

Casting Process ◽

Solid Content ◽

Apparent Porosity ◽

Corundum Refractory ◽

Low Viscosity

Mullite- corundum ceramic was fabricated using bauxite and silica fume as raw materials by gel-casting process. The fluidity of the slurry, as well as strength, apparent porosity, pore size distribution, phase composition and microstructure of sintered specimen were studied. The results showed that: the slurry had low viscosity, good fluidity for casting if pH=9, dispersant 0.33wt% and solid content 60vol%; the strength of material came up to 165MPa even if the apparent porosity was about 30%; the samples were characterized by mullite 70%, corundum 22%, rutile 3%, glass phase only 5%, the size of majority grains was about 2μm, and most crystals with high melting point bonded directly; the average aperture was 264nm, the pore size distribution were divided into 2~30nm, 45~60nm and 1500~4000nm three regions. The distribution probability of nano- aperture was the largest, the volume of micron -aperture was the maximum, but all pores were less than 4μm in diameter, which suggested that the materials had micro porous characteristics. The microcrystalline, crystals combined directly and micro porous structure leaded to high strength of the refractory materials together.

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Fully Renewable Composites Based on Agricultural Waste

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.899.86 ◽

2021 ◽

Vol 899 ◽

pp. 86-91

Author(s):

Victor Klushin ◽

Denis Tokarev ◽

Vera Kashparova ◽

Svetlana Kolesnik ◽

Ivan Brink

Keyword(s):

Mechanical Properties ◽

Composite Materials ◽

Water Sorption ◽

Water Resistance ◽

Resin Composite ◽

Agricultural Waste ◽

Urea Formaldehyde ◽

High Strength ◽

High Water ◽

Strength Properties

In the present work, composite materials with a two wastes - waste goose feather as a filler and resinous waste from HMF production as a binder - have been developed. The mechanical properties and water sorption in dependence with feather/HMF resin composite content were studied. The composites containing 50% of feather have high strength properties up to 46 N/mm2 and low water sorption (lower 1%), which results in high water resistance. Due to these properties, they can become an excellent alternative to urea-formaldehyde resins and plastics based on them.

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HREM interface studies in SiC-whisker-reinforced Al2O3 and Si3N4 ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100105734 ◽

1988 ◽

Vol 46 ◽

pp. 734-735

Author(s):

W. Braue ◽

R.W. Carpenter ◽

D.J. Smith

Keyword(s):

Analytical Data ◽

Base Material ◽

High Strength ◽

Ceramic Composites ◽

Good Thermal Stability ◽

All Ceramic ◽

Sic Whiskers ◽

Base Composite ◽

C 30 ◽

Si3n4 Ceramics

Whisker and fiber reinforcement has been established as an effective toughening concept for monolithic structural ceramics to overcome limited fracture toughness and brittleness. SiC whiskers in particular combine both high strength and elastic moduli with good thermal stability and are compatible with most oxide and nonoxide matrices. As the major toughening mechanisms - crack branching, deflection and bridging - in SiC whiskenreinforced Al2O3 and Si3N41 are critically dependent on interface properties, a detailed TEM investigation was conducted on whisker/matrix interfaces in these all-ceramic- composites.In this study we present HREM images obtained at 400 kV from β-SiC/α-Al2O3 and β-SiC/β-Si3N4 interfaces, as well as preliminary analytical data. The Al2O3- base composite was hotpressed at 1830 °C/60 MPa in vacuum and the Si3N4-base material at 1725 °C/30 MPa in argon atmosphere, respectively, adding a total of 6 vt.% (Y2O3 + Al2O3) to the latter to promote densification.

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Flame Photometry Characterization Procedure for Sodium Content in Brazilian Bentonites for Nanotechnology Applications

Recent Innovations in Chemical Engineering (Formerly Recent Patents on Chemical Engineering) ◽

10.2174/2405520412666190404144547 ◽

2019 ◽

Vol 12 (2) ◽

pp. 122-129

Author(s):

Hellen S. Santos ◽

Karine L. Buarque da Silva ◽

Ariel E. Zanini ◽

Danilo S. Coelho ◽

Marcelo Embiruçu ◽

...

Keyword(s):

Control Process ◽

Sodium Concentration ◽

High Water ◽

Sodium Content ◽

Industrial Applications ◽

Exchange Capacity ◽

Sodium Cation ◽

Flame Photometry ◽

Logarithmic Scale ◽

Average Value

Background: Brazilian bentonites have a low sodium concentration in their interlayer structure. This is a problem with most of the industrial applications that demand the characteristics of sodium bentonites. Objective: As a solution for this limitation, sodium carbonate is added to in natura clays, promoting ion exchange between other interlayer cations with sodium. Methods: A process was used based on the principle of Stokes’ Law (BR Patent 10 2013 016298). For this, we used four glass columns in series, in which a high water flow was considered to obtain purified clays. It was proposed as a simple, fast and economical method for sodium determination that was developed and applied in bentonites by flame photometry. The equipment calibration was performed with a NaCl standard solution in concentrations between 80 and 110 ppm. The bentonites in the suspension were separated by means of centrifugation, being thus analyzed by a flame photometer. Results: The samples were prepared according to the manufacturer’s specifications to contain detectable amounts of sodium by means of flame photometry. A resulting linear relationship between the average value readings versus sodium standard content solution (both in ppm) was obtained by the logarithmic scale, as expected. Conclusion: The procedure allowed to define a method that could be used in the sodification control process, thus making it possible to differentiate the sodium cation content in terms of the value of cation exchange capacity (CEC) from bentonite. X-ray analysis of in natura and the sodified clays showed nanostructural differences related to interlayer distance.

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Weathering Stability and Durability of Birch Plywood Modified with Different Molecular Weight Phenol-Formaldehyde Oligomers

Polymers ◽

10.3390/polym13020175 ◽

2021 ◽

Vol 13 (2) ◽

pp. 175

Author(s):

Juris Grinins ◽

Vladimirs Biziks ◽

Brendan Nicholas Marais ◽

Janis Rizikovs ◽

Holger Militz

Keyword(s):

Uv Light ◽

Phenol Formaldehyde ◽

Wood Decay ◽

Soft Rot ◽

Solid Wood ◽

Solid Content ◽

Molecular Weights ◽

Weathering Processes ◽

Commercial Resin ◽

D 20

This study investigated the effect of phenol-formaldehyde (PF) resin treatment on the weathering stability and biological durability of birch plywood. Silver birch (Betula pendula) veneers were vacuum-pressure impregnated with four different PF resins with average molecular weights (Mw) of 292 (resin A), 528 (resin B), 703 (resin C), and 884 g/mol (resin D). The aging properties of PF resin modified birch plywood were analyzed using artificial weathering with ultraviolet (UV) light, UV and water spray, and weathering under outdoor conditions. The same combinations of PF-treated plywood specimens were then tested in soil-bed tests to determine their resistance against soft-rot wood decay. It was not possible to compare weathering processes under artificial conditions to processes under outdoor conditions. However, the weathering stability of birch plywood treated with PF resins A, B, and C, scored better than plywood treated with commercial resin D (regardless of solid content concentration [%]). Results from unsterile soil bed tests showed improvements in resistance to soft-rot wood decay compared to untreated plywood and solid wood. Mass loss [%] was lowest for birch plywood specimens treated with resin of highest solid content concentration (resin D, 20%). Provisional durability ratings delivered durability class (DC) ratings of 2–3, considerably improved over untreated solid wood and untreated birch plywood (DC 5).

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An Effective Method for Preparation of Liquid Phosphoric Anhydride and Its Application in Flame Retardant Epoxy Resin

Materials ◽

10.3390/ma14092205 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2205

Author(s):

Qian Li ◽

Yujie Li ◽

Yifan Chen ◽

Qiang Wu ◽

Siqun Wang

Keyword(s):

Flame Retardant ◽

Epoxy Resin ◽

Epoxy Resins ◽

Oxygen Index ◽

Decomposition Temperature ◽

Ease Of Use ◽

Limiting Oxygen Index ◽

Good Thermal Stability ◽

Low Viscosity ◽

The Impact

A novel liquid phosphorous-containing flame retardant anhydride (LPFA) with low viscosity was synthesized from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and methyl tetrahydrophthalic anhydride (MeTHPA) and further cured with bisphenol-A epoxy resin E-51 for the preparation of the flame retardant epoxy resins. Both Fourier transform infrared spectroscopy (FT-IR), mass spectrometry (MS) and nuclear magnetic resonance (NMR) measurements revealed the successful incorporation of DOPO on the molecular chains of MeTHPA through chemical reaction. The oxygen index analysis showed that the LPFA-cured epoxy resin exhibited excellent flame retardant performance, and the corresponding limiting oxygen index (LOI) value could reach 31.2%. The UL-94V-0 rating was achieved for the flame retardant epoxy resin with the phosphorus content of 2.7%. With the addition of LPFA, the impact strength of the cured epoxy resins remained almost unchanged, but the flexural strength gradually increased. Meanwhile, all the epoxy resins showed good thermal stability. The glass transition temperature (Tg) and thermal decomposition temperature (Td) of epoxy resin cured by LPFA decreased slightly compared with that of MeTHPA-cured epoxy resin. Based on such excellent flame retardancy, low viscosity at room temperature and ease of use, LPFA showed potential as an appropriate curing agent in the field of electrical insulation materials.

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