Strength Of Plywood Research Articles

Фанера и теплоизоляционные плиты на модифицированном фенолоформальдегидном связующем

The lower curing temperature of phenol formaldehyde binder allows reducing the costs of producing cellulose-containing materials, such as FSF plywood and thermal insulation composites made of plant wastes. However, the low-temperature production mode provides an insufficient degree of the phenol formaldehyde binder curing, leading to a decrease in water resistance of material based on the phenol formaldehyde binder. A modifier should be added to the phenol formaldehyde binder to reduce the amount of free hydroxymethylol groups in the cured binder and to form a stronger cross-linked structure in low-temperature curing conditions. Hydrogen peroxide was used as a phenol formaldehyde binder modifier in this research. The research results confirmed the hypothesis about the effect of hydrogen peroxide on the intensification of the structure formation of cellulose-containing materials based on the phenol formaldehyde binder. In conditions of low-temperature curing (120 °C for FSF plywood and 100 °C for thermal insulation composites made of plant wastes) modification of phenol formaldehyde binder with hydrogen peroxide reduced the binder curing time, the pressing time of FSF plywood, improved the physical and mechanical properties of FSF plywood and thermal insulation composites made of cellulose-containing filler (soft wood waste and irrecoverable flax spinning waste). When 1.0 % of hydrogen peroxide is added to the binder, the binder curing time reduces by 43.6 %. The addition of 1.0 % of hydrogen peroxide increased the shear strength of FSF plywood by 4.4 % and the static bending strength of plywood by 4.8 %. Modification of the binder with hydrogen peroxide increased water resistance of FSF plywood: plywood thickness swelling has been reduced by 2 % over 24 h in water. The strength of thermal insulation composites made of cellulose-containing wastes increased by 5.2 % with the addition of 1.0 % of hydrogen peroxide, thickness swelling decreased by 4.9 % over 24 h. The obtained research results allow recommending a modifying additive of hydrogen peroxide to phenol formaldehyde binder in an amount of 1.0 % of resin mass to increase the strength properties of FSF plywood and thermal insulation composites made of plant wastes. For citation: Vakhnina T.N., Fedotov A.A., Susoeva I.V., Rumyantseva V.E. Plywood and Thermal Insulation Boards Based on the Modified Phenol Formaldehyde Binder. Lesnoy Zhurnal [Russian Forestry Journal], 2022, no. 1, pp. 155–165. DOI: 10.37482/0536-1036-2022-1-155-165

Research of physical and mechanical properties of plywood based on thermally modified veneer

The article presents the results of a study of the physical and mechanical properties of plywood based on thermally modified birch veneer. The implementation of a full-factor experiment in the temperature range from 160 to 200 °C with a duration of 120 to 240 min made it possible to establish the nature of the dependence of the change in strength in static bending and strength in shearing along the adhesive layer on the veneer heat treatment mode. The parameters of veneer heat treatment are determined, which do not lead to a decrease in the strength of plywood, but allow to reduce the indicators of water absorption and swelling by an amount from 20.4 to 33.5%. Plywood based on thermally modified veneer acquires higher strength and water resistance, which significantly expands the scope of application of glued wood based on urea-formaldehyde resins.

Improving the performance characteristics of glued materials based on thermally modified veneer

The performance characteristics of glued materials based on thermo-modified veneer depend on the heat treatment mode. The choice of a mode that does not lead to a decrease in the strength of plywood allows reducing water absorption and swelling by a value from 20,4 to 33,5 %. Plywood based on thermo-modified veneer acquires higher strength and water resistance, which significantly expands the range of application of laminated wood based on urea-formaldehyde resins.

ВЛИЯНИЕ ШЛИФОВАЛЬНОЙ ПЫЛИ, КАК НАПОЛНИТЕЛЯ КАРБАМИДОФОРМАЛЬДЕГИДНЫХ КЛЕЕВ НА ИХ ТЕХНОЛОГИЧЕСКИЕ СВОЙСТВА

One of the main indicators of the quality of plywood is its environmental friendliness, which is characterized by the content of free formaldehyde. To produce plywood with formaldehyde emission class E0, E1, low-toxic urea-formaldehyde resins should be used. These resins have low final viscosity, which can lead to a decrease in the strength properties of plywood due to excessive penetration of glue into the wood. The viscosity of the working solution of the glue can be changed by the use of fillers (wood flour, rye flour, kaolin, etc.). The results of the research have showed that wood flour has high adsorption capacity and 2-5 m. shares of wood flour increase the viscosity of the adhesive from 60 to 180 s by the VZ-4 viscometer. At the same time, a large amount of grinding dust accumulates in the woodworking shops. To assess the possibility of using grinding dust as a filler of urea-formaldehyde resins, a comparative analysis of the properties of grinding dust obtained by grinding various materials and wood flour in accordance with State Standard 16362-86 has been carried out. The results have showed that grinding dust is comparable to wood flour in moisture, bulk density. The fractional composition of the grinding dust is larger, but most of it corresponds to the necessary fractions of 0.25; 0.18; 0.125 after sorting. The article studies the effect of the fraction and the amount of grinding dust on the strength properties of plywood, as well as on the technological properties of the adhesive (dynamic viscosity, pH, gel time). The maximum increase in the strength of plywood has been 63% when using grinding dust of 0.125 fractions in the amount of 1 m.sh. Adding grinding dust to the adhesive solution leads to an increase in its dynamic viscosity and the larger the particle, the more the viscosity changes. Filling of urea-formaldehyde resins with grinding dust shifts the pH of the adhesive solution towards the neutral and slightly acidic medium and reduces the gelatin time to 55-60 sec. The conducted studies show that the use of grinding dust as a filler of urea-formaldehyde adhesives leads to a decrease in internal stresses in the cured adhesive and an increase in the strength of the gluing of plywood

Зменшення вмісту формальдегіду у фанері, склеєній карбамідоформальдегідними клеями з використанням деревинного волокнистого шламу

Щоб зменшити вміст формальдегіду у фанері, карбамідоформальдегідні клеї наповнювали деревинним волокнистим шламом. Під час досліджень використано: сухий подрібнений деревинний волокнистий шлам з розміром частинок менше 0,2 мм і вологістю 10%; карбамідоформальдегідну смолу КФ-МТ; амоній хлорид; березовий лущений шпон товщиною 1,5 мм і вологістю 6%. За допомогою багатофакторного планування експерименту досліджено вплив параметрів режиму склеювання шпону (кількості волокнистого шламу в клеї, витрати клею, тривалості та температури пресування) на вміст формальдегіду у фанері та міцність фанери на зріз. Вміст формальдегіду у фанері визначено методом WKI; міцність фанери на зріз – згідно з ДСТУ EN 314-1:2003 і ДСТУ ЕN 314-2:2006 (клас з’єднання 1). На вміст формальдегіду у фанері найбільше впливають витрата клею, у разі зменшення якої від 130 до 100 г/м2 вміст формальдегіду зменшується на 30-42 %, та температура пресування, в разі підвищення якої від 100 до 150˚С вміст формальдегіду зменшується на 34-41 %. У разі додавання до клею до 4 мас. ч. волокнистого шламу вміст формальдегіду у фанері зменшується на 16-30 %. На міцність фанери на зріз впливають кількість волокнистого шламу, в разі збільшення якого міцність частково знижується на 11-12 %, залишаючись більшою у 2,3-2,5 рази, порівняно з вимогами чинного стандарту, та температура пресування, в разі підвищення якої міцність зростає на 14-17 %. Отримані адекватні та відтворювані регресійні залежності властивостей фанери від досліджуваних факторів дають змогу спрогнозувати вміст формальдегіду у фанері та міцність фанери на зріз від параметрів режиму склеювання шпону.

Thermal Degradation and Combustion Performance Comparison of Plywood Based on Inorganic Adhesive and Phenol-Formaldehyde Resin

The main objective of this work was to study a new inorganic adhesive used for wood-based panel. Inorganic adhesive and its poplar plywood were prepared to investigate their properties. Thermo-gravimetric analysis tests revealed that the total mass loss of inorganic adhesive was 76.24%, which was higher than that of phenol-formaldehyde resin (64.97%). The results showed better thermal stability of inorganic adhesive. For inorganic adhesive plywood, approximately 30% decrease in peak of heat release rate, 62% in total smoke production and 20% in mean CO2 yield, respectively, were seen compared to the control by cone calorimeter analysis. Scanning electron microscopy imaged wider glue line of inorganic adhesives plywood, which was related to the bonding strength of plywood. Thus the inorganic adhesive of fireproofing made in lab could be better used for plywood processing.

Установление регрессионных зависимостей продолжительности склеивания фанеры на ее прочность с использованием смол с различным содержанием формальдегида

The task of the experiment was to clarify the standard modes of bonding plywood using in their produc-tion low toxic urea-formaldehyde resins, and obtain the required bond strength, as well as statistical anal-ysis of the results of research in order to obtain regression equations. The results showed that the bonding strength of plywood on low toxic resins is lower than on resins with high formaldehyde content. To en-sure the preservation of strength is possible only due to increased consumption of adhesive and duration of bonding.

High pressure paper laminates from mimosa tannin resin

Ten-ply high pressure paper laminates were prepared by impregnating filter paper with mimosa tannin solution mixed with furfuryl alcohol and formurea concentrate. Abrasion resistance tests, a cross-cut test, and water vapour resistance measurements were carried out. The effect of 10-ply paper laminates on the shear strength of plywood was also determined. It was demonstrated that 10-ply paper laminates with mimosa tannin resin may increase the dry shear strength of plywood and reduce the absorption of water into the plywood. 10-ply paper laminates pressed at 140°C temperature at 120 kg cm−2 pressure for 600 s gave the best appearance compared to other laminates.

Study on Diallyl Phthalate Modified Phenol-Formaldehyde Resin

This paper aimed to produce the alkaline phenolic resin by the addition of diallyl phthalate into traditional phenolformaldehyde resin. Then the modified resin was characterized using dynamic mechanical analyzer (DMA), differential scanning calorimetry (DSC), fourier transform infrared spectrometer (FTIR) and simultaneous thermal analyzer (STA). The results indicated that: the increase of the diallyl phthalate contributed to the rise of the storage modulus (E) and loss modulus (E), the decrease of the loss factor. Curing temperature also showed a decline trend and was decreased by 5°Cwhen the amount of modifider was 2.5% of the phenol. The improvemnt of Organic ester on curing of alkaline phenolic resin achieved by rapidly promoting resin molecular to generate reactive intermediate quinone methide. The amount of the modifier had little effect on the thermostability of resin, but it reduced the bonding strength of plywood.

Curing kinetics of nano cupric oxide (CuO)-modified PF resin as wood adhesive: effect of surfactant

The effect of nano cupric oxide (CuO) in combination with surfactants on the curing kinetics of phenol-formaldehyde (PF) resin, as well as the bonding strength of plywood prepared using the modified resin was investigated in this study using dynamic and isothermal differential scanning calorimetry. The result showed that the incorporation of nano CuO along with alkane surfactant made in the laboratory clearly reduced the apparent activation energy of the PF resin and improved the addition and condensation reactions of the PF resin. Inclusion of the surfactant had the further effect of compensating the influence of diffusion control caused by nano CuO alone. The shear strength of plywood suggested that the addition of nano CuO (1%) alone or in combination with alkane surfactant (0.55%) or sodium lignosulfonate (0.55%) in the PF resin mixture was sufficient to meet the requirement of wood-based composites manufacturing.

13C CP/MAS NMR studies on the curing characteristics of phenol formaldehyde resin in the presence of nano cupric oxide and surfactants

The effect of nano cupric oxide (CuO) in combination with surfactants on the curing characteristics of phenol formaldehyde (PF) resin analyzed using solid 13C CP/MAS NMR, including the bonding strength of plywood prepared by modified resin, was investigated in this study. The results showed that nano CuO alone improved the cure of PF resin. The intensity of the functional groups of the PF mixture was maintained during the curing process as sodium lignosulfonate was simultaneously introduced. Furthermore, nano CuO and alkane surfactant together modified the PF resin conformation. The shear strength of the plywood showed that the addition of nano CuO (1%) alone or in combination with alkane surfactant (0.55%) or sodium lignosulfonate (0.55%) to the PF resin mixture was effective. And this approach met the important criteria for its application in the manufacture of plywood. POLYM. COMPOS., 35:113–117, 2014. © 2013 Society of Plastics Engineers

Development of a novel polyvinyl acetate type emulsion curing agent for urea formaldehyde resin

High formaldehyde emission and poor water resistance are two main disadvantages of urea formaldehyde (UF) resin. For that reason, a novel polyvinyl acetate (PVAc) type emulsion curing agent was developed in this paper. PVAc type emulsions, including PVAc, the co-polymer of PVAc and N-hydroxymethyl acrylamide (PVAc–NMA), and the ternary co-polymer of PVAc, NMA, and urea (PVAc–NMA–urea), were the main components. Water, aluminum chloride, ammonium dihydrogen phosphate, polypropylene glycol, silicone oil, and urea were the other components. Under heating, aluminum chloride and ammonium dihydrogen phosphate often underwent thermal decomposition and hydrolysis in solution, produce free acid to cure UF resin, so the curing agent could enhance the curing rate, and then shorten the curing time. In this curing agent, ammonium dihydrogen phosphate and urea worked as formaldehyde removers and reacted with free formaldehyde in UF resin, thus the formaldehyde emission exuded from the plywood could be effectively limited and reduced. The bonding strength of plywood was not improved very much, especially the dry bonding strength, but the wet bonding strength was little enhanced for the active hydroxymethyl group contained in PVAc–NMA and PVAc–NMA–urea underwent a self-cross-linking reaction to improve the bonding strength and adhesion force to the bonded substrate. More importantly, the results from the industrial production experiments were shown to be very good.

Study of Amino Polymer Modified Soy Protein Adhesive

For improving the bonding strength and water resistance of plywood bonded with soy protein adhesive (SPA), an amino polymer (AP) was synthesized using polyamines, and the AP was used to modify SPA to prepare a modified soy protein adhesive (MSPA) in this paper. The plywood was prepared using MSPA, and the effects of preparation technology of amino polymer and hot-pressing technology of plywood on the bonding strength of plywood were investigated. The results showed that the optimization preparation technologies of AP were as follow: the molar ratio of polyamine/modifying agents was 0.25/1, the pH value was 5, the reaction temperature was 70 °C, and the reaction time was 1.5 h. The optimization preparation technologies of plywood were that the hot-pressing temperature was 150 °C and the hot-pressing time was 60 s/mm. The bonding strength of plywood made from MSPA on the optimization preparation technology was 1.03 MPa, which meets the requirement of plywood type II (³0.7MPa). The MSPA bonded plywood had a rather low formaldehyde emission, which is close to that of wood itself.

Application of Plywood with Water-Based Phenol-Formaldehyde Resin Impregnated Linerboards as Formwork for Concrete Structure

The front and back layers of plywood formwork consist of veneers made of Oceania timber (Shorea spp.). As the demand for Oceania timber has increased worldwide, it has become difficult to find good front and back layers for plywood. This study, therefore, has investigated plywood made with water-based phenolformaldehyde (PF) resin impregnated linerboards of different basis weights and pulp types. Manufactured plywood with water-based PF resin impregnated linerboards made of Korean recycled linerboard pulp layers, which were pressed at 140° C and 10 kg/cm2 for 3 min, had the highest internal bond strength. Furthermore, the internal bond strength of plywood with K2 linerboard was highest among all those tested. Based on the results of heat and cold cycle tests, alkali tests, abrasion tests, and boiling water tests, three types of linerboards: K2, KAC and KLB were found to be suitable for plywood formwork.

Effect of the addition of Acacia mangium bark on thermosetting of phenol–formaldehyde resin

The effect of addition of Acacia mangium bark powder on the thermosetting processes of two commercial phenol resins, PF-A and PF-B, was examined by bond strength test, torsional braid analysis, and differential scanning calorimetry. When the bark powder was added to PF-A, the bond strength of plywood pressed at 110°C increased and was comparable to that of plywood pressed at 120 and 130°C. However, when the bark powder was added to PF-B, the bond strength of plywood pressed at 110°C was still lower than that of plywood pressed at 120 and 130°C. The relative rigidity and loss tangent of PF-A cured with the bark powder obtained by heating at 100°C were comparable to those at 120 and 140°C, and the reaction enthalpy was increased by bark powder addition. In contrast, chemical reactions for cured PF-B were not enhanced by bark powder addition.

Surface characterization of a series of cured polyurethane adhesives by inverse gas chromatography and adhesion strength testing of plywood

Inverse gas chromatography (IGC) was used to determine the surface properties of a series of polyurethane adhesives, A 1, A 2, A 3 and A 4 cured with water. The weight percentages of isocyanate group (NCO) in polyurethane adhesives were 5.3, 7.0, 13.0 and 19.6%, respectively. Four n-alkanes, C6, C7, C8 and C9 were chosen as non-polar probes to characterize the dispersive component of surface free energy, $$ \gamma_{s}^{d} . $$ Acetone, tetrahydrofuran and ethyl acetate were chosen as polar probes to detect the Lewis acid–base parameters, K a and K b. The trend of $$ \gamma_{s}^{d} $$ and K a and K b of the series of cured adhesives was also shown in this paper. The cured adhesives were all amphoteric, but predominantly Lewis basic. The adhesion strength of the poplar plywood bonded with polyurethane adhesives was tested. The results showed that the adhesion strength of plywood increased with increasing the NCO content of the adhesives and K b/K a of the cured adhesives.

Technologies of liquefaction of bamboo and preparation of adhesive

The technology of liquefying processed-waste bamboo with phenol is investigated by single factor trials and an orthogonal design. We studied the preparation technology and properties of adhesives from this phenol-liquefied bamboo with formaldehyde (BPF). The results show that temperature has a significant effect on liquefaction. The effect of the mass ratio of phenol to bamboo comes second and the catalyst dosage within the range of 2%–4% is the least effective. The optimum conditions of liquefaction are as follows: a mass ratio of phenol to bamboo 3.5, a catalyst dosage of 4%, liquefying temperature 145°C and liquefying time 60 min. The liquefaction rate of bamboo reached 99.1%. For the preparation of the adhesive, a mass ratio of liquefied bamboo products to formaldehyde (37%) is 100 to 164.8–199.5, while the ratio 100 to 108.2 is the best. This adhesive has a lower curing temperature than that of normal PF resin. At a hot-press temperature of 130 or 140°C, this new adhesive provides excellent bonding strength of plywood. The most favorable temperature for hot-pressing is 140°C.

Preparation of liquefied wood-based resins and their application in molding material

To investigate value in use of liquefied wood-based resin applications in molding material, Chinese fir (Cunninghamia lanceolata) and poplar (Populus tomentosa) wood meal were liquefied in phenol. The reactant was co-condensed with formaldehyde to obtain liquefied wood-based resin. For this paper, we investigated the characterization of the resin and its application in molding material. The result shows that the basic properties of liquefied wood-based resin were satisfactory; the bonding strength of plywood prepared with liquefied Chinese fir and liquefied poplar resin can reach 1.54 and 1.00 MPa, respectively. The compression strengths of the molding material prepared with two kinds of liquefied wood resin were 73.01 and 73.58 MPa, almost the same as that of PF resin molding material. The limiting volume swelling of molding material made with liquefied Chinese resin and liquefied poplar resin were 8.5% and 8.3%, thickness swelling rates of water absorption were 3.3% and 4.2%, and the maximum weight ratios of water absorption were 25.9% and 26.2%, respectively. The soil burial test result shows that the weight loss rate of the molding materials made with liquefied Chinese resin and liquefied poplar resin were 8.3% and 9.1% and that of the PF resin molding material was 7.9%. After the soil internment test, the reduction ratio of compression strength of the two kinds of molding material achieved 16.9% and 17.7%, while that of the PF resin molding material was 15.4%. The test results of wood fungi inoculation on the three surfaces of the molding material indicate the breeding rate of molding material prepared with liquefied Chinese resin and liquefied poplar resin were at level 4 and that of PF resin molding material was at level 1 of the ISO standard.

Studies on the relationships between wood properties and the quality of veneer and plywood of plantation poplars

Summary In this study three poplar clones, grown on three different beaches of the Yangtse River, and at three different planting densities (3 m × 4 m, 4m × 5m, 5m × 6m) were used to study relationships between wood properties and the quality of veneer and plywood. The results show: (i) The variance of veneer thickness was highly significantly related to fibre width and the proportion of vessels and fibres; and significantly related to the fibre length, the thickness of the cell wall, the ratio of cell wall to cell cavity, the ratio of cell cavity to cell diameter, the length of vessels and the proportion of rays. (ii) The ratio of lathe check in veneer was highly significantly related to only the diameter of the cell cavity. (iii) The glue-bond strength of plywood was highly significantly related to the fibre length, the fibre width, the diameter of cell cavity, the thickness of cell wall, the ratio of cell wall to cell cavity, the vessel length, the tangential diameter of vessels, the microfibril angle, and the proportion of vessels and rays; and significantly related to the proportion of fibres. (iv) The variance of veneer thickness and the ratio of lathe check in veneer were not related to chemical properties, but the glue-bond strength was significantly related to the pH value of sapwood, and highly significantly related to the pH value of heartwood and the average pH value of sapwood and heartwood. (v) The variance of veneer thickness and the glue-bond strength of plywood were not related to physical-mechanical properties, but the ratio of lathe check in veneer was highly significantly related to the modulus of elasticity, and significantly related to the air-dry wood density.

合板の接着強度に及ぼすカビ類の影響

合板の接着強度に及ぼすカビ類の影響