Formaldehyde Emission Of Plywood Research Articles

Influence of Lignin Content and Pressing Time on Plywood Properties Bonded with Cold-Setting Adhesive Based on Poly (Vinyl Alcohol), Lignin, and Hexamine

The sustainability, performance, and cost of production in the plywood industry depend on wood adhesives and the hot-pressing process. In this study, a cold-setting plywood adhesive was developed based on polyvinyl alcohol (PVOH), high-purity lignin, and hexamine. The influence of lignin content (10%, 15%, and 20%) and cold-pressing time (3, 6, 12, and 24 h) on cohesion, adhesion, and formaldehyde emission of plywood were investigated through physical, chemical, thermal, and mechanical analyses. The increased lignin addition level lowered the solids content, which resulted in reduced average viscosity of the adhesive. As a result, the cohesion strength of the adhesive formulation with 10% lignin addition was greater than those of 15% and 20% lignin content. Markedly, the adhesive formulation containing a 15% lignin addition level exhibited superior thermo-mechanical properties than the blends with 10% and 20% lignin content. This study showed that 10% and 15% lignin content in the adhesive resulted in better cohesion strength than that with 20% lignin content. However, statistical analysis revealed that the addition of 20% lignin in the adhesive and using a cold-pressing time of 24 h could produce plywood that was comparable to the control polyurethane resins, i.e., dry tensile shear strength (TSS) value of 0.95 MPa, modulus of rupture (MOR) ranging from 35.8 MPa, modulus of elasticity (MOE) values varying from 3980 MPa, and close-to-zero formaldehyde emission (FE) of 0.1 mg/L, which meets the strictest emission standards. This study demonstrated the feasibility of fabricating eco-friendly plywood bonded with PVOH–lignin–hexamine-based adhesive using cold pressing as an alternative to conventional plywood.

Research on Flame Retardant Plywood with Different Flame Retardants

The flame retardancy of plywood should be improved as much as possible while minimizing the impact on the bonding strength of plywood. Six commercial flame retardants and three laboratory synthesized phosphorous nitrogen flame retardants were selected. E0, E1 and E2 grade commercial formaldehyde resins (UF) were applied in this study to evaluate the effect of different flame retardants on the curing time of resin, bonding strength, flame retardant performance, and formaldehyde emission of plywood. The results show that the effect of the addition of different flame retardants on the bonding strength of plywood gradually decreased with the increase of the formaldehyde molar ratio of the resin. The effect of flame retardants on the curing time of UF gradually decreased as the mole ratio of formaldehyde increasing, while the amount of formaldehyde emission varied according to the content of formaldehyde in the flame retardant. Compared with plywood without flame retardant, flame retardant of plywood added with phosphorous nitrogen flame retardant was improved.

Improve performance of soy protein adhesives with a low molar ratio melamine-urea-formaldehyde resin

In this study, the low molar ratio melamine-urea-formaldehyde (MUF) resin and sodium hydroxide were used to modify soy protein adhesives, and the addition of MUF was studied as the influencing factor, the properties of soy protein adhesives, formaldehyde emission and bonding strength were studied. The results showed that the solid content and viscosity of the adhesives were suitable for the application of wood adhesives, the formaldehyde emission and wet shear strength of plywood prepared by soybean protein adhesive modified by MUF with 30% addition were 0.38mg/L and 1.25 MPa. Moreover, based on the analysis of the free formaldehyde content of the adhesive and the formaldehyde emission of plywood, it can be inferred that most of the free formaldehyde in the plywood was derived from the unreacted methyl group during the hot pressing process.

The effect of walnut processing by-product filler on properties of plywood

In this study, walnut processing by-product was served as filler to make three-layer plywood, and the physical-mechanical properties were also discussed. The results showed that the formaldehyde emission of plywood corresponding to walnut shell and walnut dregs decreased by 0.0542 mg/L and 0.066 mg/L, respectively. The properties of plywood filled with walnut dregs are better than that of walnut shell filler, and the formaldehyde emission of the corresponding plate is lower. At the same time, compared with flour, the wet bond strength of walnut shell plywood increased by 0.0332 MPa, and that of walnut dregs plywood decreased by 0.123 MPa, but they all met the national standards.

Relationship Between Wood Colour of Seven Tropical Hardwood Species and Formaldehyde Emission of Plywood

There are many factors that affect the formaldehyde emission from plywood such as wood species and moisture content. As for wood species, colour appearance was found to affect significantly the formaldehyde emission. Therefore, the effects of tropical wood species with different colour on the formaldehyde emission of manufactured plywood were studied and determined by the perforator and desiccator method. Veneer of seven wood species, namely Mempisang, Kedondong, Penarahan, Keledang, Rengas, Melembu and Ludai were chosen as samples. 3-ply plywood were manufactured using urea formaldehyde as binders. The formaldehyde emission of the produced plywood was tested using perforator method (EN 120) and desiccator method (MS 1787: Part 15). Colour of the wood veneers were measured using Brightness & Colour Meter through CIE L*a*b* system. Relationship between the wood colour and formaldehyde emission were determined. The results revealed that the formaldehyde emission increased as the lightness (L*) of the wood samples increased. This may be due to higher extractive content in darker coloured wood (low lightness) that acts as formaldehyde scavenger.

Formaldehyde emission behavior of plywood with phenol-formaldehyde resin modified by bio-oil under radiant floor heating condition

Bio-oil was added as a substitute of phenol for phenol-formaldehyde (PF) resin to reduce the cost and formaldehyde emission (FE) in radiant floor heating system. The effects of substitute rate of bio-oil to phenol, temperature and heating time of radiant floor heating system on the FE of plywood with bio-oil phenol-formaldehyde (BPF) resin were examined using desiccator method. The variations on chemical structure of cured BPF resin were analyzed by the Fourier transform infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance (NMR) to understand the FE behavior of plywood. Results showed that the FE of plywood was increased at prolonged heating time and the temperature significantly affected FE of plywood; the initial FE value at 50 °C was 20–30 times as higher as that at 20 °C. Elevated temperature increased the final equilibrium FE value and shortened the time to reach the balance. However, adding bio-oil reduced the initial and final equilibrium FE values, decreasing by 12–49% and 25–51%, respectively. Analytical results revealed that the initial FE was mainly from the residual formaldehyde from the manufacturing of plywood and the subsequent FE released owing to the breakage of C–O–C and CH2 bonds in resin.

Palm kernel meal as a melamine urea formaldehyde adhesive filler for plywood applications

In this work, palm kernel meal (PKM) and palm shell (PS) were studied as a filler for wood adhesive formulations and their efficiency was compared with existing industrial flour (IF). Melamine urea formaldehyde (MUF) was used as resin for formulating the wood adhesives. The effects of the natural fillers (PKM and PS) on shear strength and formaldehyde emission of plywood were analyzed. The optimum hot press temperature and time were found to be 125 °C and 150 s, respectively. Both PKM and IF influenced the shear strength and formaldehyde emission characteristics, with the optimum concentration of filler being within the range of 13% to 18%. The physico-chemical interaction between the wood, resin and filler was investigated using Fourier transform infrared spectroscopy (FTIR) and the interactions among C˭O groups on PKM and N‒H, O‒H groups on wood and MUF were identified. Apart from the bonding strength, the mechanical interlocking between adhesive and wood was found to be very important for adhesive performance which was dependent on the viscosity of the adhesive which in turn was controlled by the filler concentration. The wood –adhesive interface was examined using light microscopy (LM).

Effect of Various Fire Retardant Chemicals in Different Concentrations on Formaldehyde Emission of Plywood

Ozet Calismanin amaci: Emprenyeli levhalar, kontrplak piyasasinda genis bir yer edinmelerine ragmen, bazi ahsap koruyucularla emprenye islemi, yapisma kusurlari, emprenye sonrasi kimyasal atiklarindan dolayi olusan cevre kirliligi gibi bazi problemlere sebep oldugu bilinmektedir. Ahsap esasli levhalardan aciga cikan formaldehit, ic mekanlarin hava kalitesinde etkili olan baska bir problemdir. Bu calismada, yangin geciktirici kimyasallar ile emprenye edilmis kontrplak levhalarinin formaldehit emisyonu miktarlarinin arastirilmasi amaclanmistir. Calisma alani: Bu calisma, Trabzon’daki Karadeniz Teknik Universitesi Orman Endustri Muhendisligi Bolumu Pilot tesisinde yapilmistir. Materyal ve Yontem: Kavak, kizilagac ve saricam ( Pinus sylvestris L.) kaplamalar, kontrplak icin kullanilmistir. Cinko borat, monoamonyum fosfat ve amonyum sulfat, yangin geciktirici olarak kullanilmistir. Kaplama levhalari, %5, 7 ve 10 olmak uzere uc farkli cozelti konsantrasyonu secilmis ve daldirma yontemi kullanilarak emprenye edilmistir. Kontrplak levhalarinin formaldehit emisyonu miktarlari, DIN EN 717-3 standardinda belirlenen sise yontemine gore belirlenmistir. Sonuclar: Cinko borat ile emprenye edilmis kaplamalardan uretilen kontrplak levhalardan aciga cikan formaldehit kontrol gruplarindan daha yuksek bulunmustur ve emisyon degerlerinin, konsantrasyon arttikca arttigi belirlenmistir. En dusuk formaldehit emisyon degerleri, monoamonyum fosfat ve amonyum sulfat ile emprenye edilmis levhalardan elde edilmistir ve emisyon degerlerinin, konsantrasyon arttikca azaldigi belirlenmistir. Arastirma vurgulari: Yuksek direnc ozelliklerinin aranmadigi bazi kullanim yerlerinde, formaldehit emisyonunu azaltmak icin yangin geciktirici kimyasallarla (monoamonyum fosfat ve amonyum sulfat) emprenye edilen kaplamalardan uretilen kontrplak levhalari kullanilabilir.

Effect of waste rubber powder as filler for plywood application

Abstract The study investigated the suitability of waste rubber powder (WRP) use as filler in adhesive formulation for plywood application. Melamine Urea Formaldehyde (MUF) was employed as resin for formulating the wood adhesive. To improve chemical properties and bonding quality of adhesive, WRP was treated by different chemicals like 20% nitric acid, 30% hydrogen peroxide and acetone solution. The treated WRP were analysed by XRD and it showed that inorganic compounds were removed and carbon was remained as major component under the treatment of 20% HNO3. The treatment improved the mechanical properties like shear strength and formaldehyde emission of plywood (high shear strength and low formaldehyde emission). The physico-chemical interaction between the wood, resin and filler was investigated using fourier transform infrared spectroscopic (FTIR) technique and the interactions among N-H of MUF and C=O of wood and WRP were identified. The morphology of wood-adhesive interface was studied by field emission scanning electron microscope (FESEM) and light microscope (LM). It showed that the penetration of adhesives and fillers through the wood pores was responsible for mechanical interlocking. Therefore, chemically treated WRP proved its potential use as filler in MUF based adhesive for making plywood.

Testing parameters affecting gas analysis value of particleboard

The gas analysis method according to EN 717 part 2 is a well-known technique to measure the formaldehyde emission of plywood and coated wood-based materials for quality control purposes. There is an increasing interest to apply this method also for uncoated wood-based panels compared to the perforator method (EN 120: 1992) owing to many reasons. As there is still limited experience in testing particleboard with this method, it is the aim of this study to evaluate the effect of some parameters to ensure correct and precise testing using the gas analysis method. Furthermore, the study aimed to show how the m.c. of panels before testing affects the Gm, and to calculate an m.c. correction factor from these results for particleboard with modern bonding systems at a low emission level. Gas analysis value and m.c. show a very good correlation. Based on this correlation an m.c. correction factor can be determined, which facilitates an m.c. correction of Gm data. This may help to improve the quality of Gm data for quality control and data comparison (i.e. for round robin tests). Combining the sampling for hour 3 and 4 as well as 2, 3 and 4 has no significant effect on the level of formaldehyde emission tested. Also the accuracy of testing was not reduced. Consequently, the change in sampling procedure may lead to a reduction on the required number of water analyses needing to be performed in the laboratory, and therefore to a reduction in consumption of chemical consumables and expenditure of human labour. The reduction of overpressure during gas analysis did not have a major effect on the values as such, but increased the coefficient of variation. Also, an increase in air flowrate did not affect the Gm at lower emission levels.

Effect of Thermal Treatment of Veneer on Formaldehyde Emission of Poplar Plywood.

A large amount of poplar plywood is now being imported into Japan from China, and as a result, formaldehyde emitted from this plywood represents an undesirable chemical that must be controlled using a chemical catching agent. The aim of this study is to find an approach to reduce the formaldehyde emission of poplar plywood using thermal treatment without employing any chemicals. The experimental results obtained show that heating veneer sheets in the temperature range of 150 °C to 170 °C effectively reduced the formaldehyde emission of plywood, without diminishing the mechanical properties of the veneer. By applying Langmuir’s theory and Hailwood-Horrobin theory to the adsorption isotherm obtained in this study, the relationship between the formaldehyde emission of plywood and the adsorption properties of veneer as a material is discussed. When veneer sheets were heated in the temperature range of 150 °C to 170 °C, the amount of hydrated water (monomolecular layer) decreased slightly and that of dissolved water (polymolecular layer) did not change. It is hypothesized that the formaldehyde emission of plywood is related to the condition of the adsorption site of the wood.

Performances of Modified Urea-Formaldehyde Resins for Bonding Plywood

Urea-formaldehyde resin was modified by a modifier with different synthetic processes labelled as UFM1, UFM2, and UFM3 respectively. As a comparison, normal UF resin with a F/U molar ratio of 1.1 labelled as UF0 was synthesized. The thermal behavior of modified urea-formaldehyde resins was studied by TG-DTA techniques, and the properties of plywood bonded with the UFM resins were investigated. The conclusions were as follows: (1) the modifier used in this study could significantly reduce the free formaldehyde content of urea-formaldehyde resin and the formaldehyde emission of plywood; (2) The exothermic peak temperatures of DTA curve were 129.37, 125.05, 120.98, and 116.11 °C for UF0, UFM1, UFM2, and UFM3 respectively. (3) The plywood manufactured with UFM2 and UFM3 resins have high bonding strength (1.28MPa and 1.59MPa) and low formaldehyde emission value (E1 grade).

Study on Curing Behavior of Low Molar Ratio Urea-Formaldehyde Resins with Different Curing Agents

In order to characterize the curing behavior of low molar ratio urea-formaldehyde (UF) resin, the curing time and thermal analysis in curing reaction of the UF resins and the bonding strength and formaldehyde emission of plywood bonded by five kinds of low molar ratio UF resins with six different curing agents were studied. The results indicated that the UF resins with the molar ratio of formaldehyde to urea more than 1.0 could get reasonable curing time. The heat enthalpy of UF resins significantly increased with the enhancing the acidity of curing agent. The plywood manufactured by the UF resins with 1.1 molar ratio showed much higher bonding strength and lower formaldehyde emission.

Preparation and Properties of Low Formaldehyde Emission Plywood with Flame Resistance

In order to improve the flame resistance and reduce the formaldehyde emission of plywood, a multifunctional formaldehyde scavenger with flame resistance (FSFR) was prepared and used to treat plywoods bonded with high molar ratio urea-formaldehyde (UF) resin. The weight percent gain (WPG), formaldehyde emission, oxygen index (OI), and bonding strength of plywoods after FSFR treated were measured to evaluated properties of FSFR. The results showed that the formaldehyde emission of the treated plywood was 0.1-0.32 mg/L, which could meet the E0 grade requirement (<0.5 mg/L ). The flame resistance of treated plywood increased significantly and the bonding strength changed little. The formaldehyde emission decreased 96.8 % and OI increased 47.2 % and the bonding strength kept unchanged when FSFR reached 8.87 % compared with that of untreated plywood.

Empirical correlations between test methods of measuring formaldehyde emission of plywood, particleboard and medium density fiberboard

Since different test methods of measuring the formaldehyde emission (FE) from wood-based composite panels have been used for different countries and regions, this study attempted to establish empirical correlations between three test methods (i.e., 24-hour desiccator, 1 m3 chamber, and perforator) for plywood (PLW), particleboard (PB), and medium density fiberboard (MDF), particularly emphasizing on correlations between the 24-hour desiccator and the 1 m3 chamber method. The desiccator method found statistically high correlations with other two methods, resulting in regression coefficient values ranging from 0.96 to 0.88 for PLW, PB, and MDF samples. In particular, the desiccator method had an empirically high correlation with the 1 m3 chamber method that had been adopted as the reference method of comparing regionally different test methods of measuring the FE of wood-based composite panels by the ISO/TC89.

합판의 포름알데히드방산량 측정방법

합판의 경우에는 제조 시 접착제가 각 단판의 전체 면에 도포되는 것이 아니라 접착 면에만 도포되므로 접착층을 따라서 접착제가 분포하게 된다. 따라서 섬유판이나 파티클보드의 경우와는 달리 전체 표면을 통하여 포름알데히드가 방산되지 않고 접착층을 따라서 방산된다고 판단되어진다. 따라서 기존의 KS M 1998-4 : 2005 방법으로 포름알데히드방산량을 측정하는 방법이 적절하지 않을 수도 있다고 판단되었다. 이에 본 연구에서는 동일한 조건에서 제조한 합판을 4가지 측정 조건에 따라 포름알데히드방산량을 측정하여 이들의 상관관계를 검토하였다. 기존의 전체 표면적을 기준으로 측정하는 방법(KS F 3101-2006)과 일정한 수의 시험편을 이용하는 방법(KS F 3101-1998), 측면 면적만을 이용하는 방법, 그리고 접착층만을 이용하는 방법으로 포름알데히드방산량을 측정하였다. 그 결과 전체 표면적 기준과 시험편의 개수 기준, 측면 면적 기준으로 시험한 방법은 반복실험결과 재현성과 경향성이 없었으나, 접착층만을 고려하여 시험편의 개수를 정하여 측정한 경우에는 재현성과 경향성을 보였다. Unlike other composites boards such as fiberboard and particleboard, plywood is manufactured with sheets of veneers. When the plywood manufactured, the adhesive is spreaded through gluelines on each surface of veneers. For that reason, formaldehyde emission of plywood can be considered as different way. Therefore, this research was conducted to understand the formaldehyde emission pattern of plywood. To measure formaldehyde emission, four different specimen preparing methods were used. The test specimen taken by a total surface area, a given number and a total side area showed inconsistent results. On the other hand, the result of formaldehyde emission showed consistency when considered only the length of adhesive layers.

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The formaldehyde emmision of panel products such as plywood and particleboard bonded with urea formaldehyde (UF) may affect health, especially when they are used in a room with poor ventilation. To reduce formaldehyde emission, the products can be fumigated by a chemical agent. This paper described the effect of fumigation by ammonium hydroxide 25% on formaldehyde emission of UF bonded plywood and particleboard. The effect of fumigation by ammonium hydroxide on formaldehyde emission of plywood and particleboard are higly significant. The longer the fumigation by ammonium hydroxide, the lower the formaldehyde emission of plywod and particleboard. Fumigation by ammonium hydroxide of 1 hour and 1. 5 hours, the formaldehyde emission of plywood and particleboard can meet Japanese Standard on the mean value of 0.632 mg/I and 0.349 mg/I for plywood, and 4.594 mg/l and 2.225 mg/l for particleboard. Meanwhile, fumigation on particleboard of 1. 5 hours and on plywood of all treatment 0.5 to 1.5 hours, the formaldehyde emission can conform with American Standard on the mean value of 0.261 mg/l for particleboard and 0.154 to 0.042 mg/I for plywood. On the basis of formaldehyde emission standards, it is recomended than the fumigation by ammmonium hydroxide 25% may be used in plywood for 70 minutes and on particleboard for 80 minutes.