Low Formaldehyde Emission Research Articles

Tannin Resorcinol Formaldehyde as Potential Glue for the Manufacture of Plybamboo

1 2 3 The tannin extracted from mangium ( Wild) tree bark exhibits strong affinity toward formaldehyde when both being reacted forming the tannin formaldehyde polymer which further could serve as resin adhesive. To improve the bonding strength and enhance the curing process, the tannin and formaldehyde is co-polymerized with resorcinol to form tannin resorcinol formaldehyde (TRF) resin. This resin is expectedly useful in the gluing work for the manufacture of reconstituted wood or other ligno-cellulosic products such as plywood, glue laminated timber, and laminated veneer lumber. In relevant, the tannin extract (T) was prepared from mangium bark, then allowed to copolymerize through the reaction with resorcinol (R) and formaldehyde (F) to produce the TRF resin. In such copolymerization, the mole ratios of T : R : F was such that the mole portion of R varied at consecutively: 0.2, 0.5, 0.7, 0.9 and 1.1, while the mole portion of T and F was constant at the ratio of 1 : 1. The course and phenomena that might occur during the TRF polymerization was scrutinized using XRay diffraction (XRD) and Differential Thermal Analysis (DTA) to determine the optimum ratio of T : R : F in formulating the TRF adhesive. The resulting formulated TRF was later to be used in the gluing of ply-bamboo assembly consisting of 7 plies, which were virtually the veneers prepared from tali bamboo ( ) species. The already shaped seven-ply-bamboo further sustained the hotpressing at 20 kg/cm employing 130 C for 20 minutes. Afterwards, the resulting 7-ply-bamboo panel was examined of its physical and mechanical (strength) properties, glue-bond quality and formaldehyde emission. Result revealed that the TRF resin with mole ratio of T : R : F at 1 : 0.5 : 1 exhibited the highest crystallinity (51.33 %) and melting glass transition at 277.14 C. In addition, the TRF adhesive at such mole ratio exhibited the thermogram and diffractogram characterization which were similar to those of the conventional PRF (phenol-resorcinol-formaldehyde) adhesive. Consequently, the TRF with such ratio was judged as the optimum formulation to be used as adhesive for the gluing of ply-bamboo assembly. The resulting ply-bamboo exhibited particular characteristics, i.e density 0.904 g/cm MOR 1,214.62 kg/cm , MOE 19,493 kg/cm , bonding strength 38,40 kg/cm and zero percent (0%) delamination, and formaldehyde emission 0.043 mg/L. The properties of ply bamboo could mostly satisfy, except the MOE, the criteria of Indonesian and Japanese standard for structural that used the conventional non-renewable adhesive (PF and UF). As a result, the TRF adhesive as derived from the renewable stuff (tannin from mangium bark), with remarkably low formaldehyde emission seems more consecutively prospective environmentally friendly, significantly potential to replace sooner or later the non-renewable and less environmentally friendly conventional adhesive (UF and PF), thereby indicatively taking part in greening the environment and mitigating the global warming.

Preparation and Formaldehyde Emission and Bonding Performance of Novel Modified Urea-Formaldehyde Resin Adhesive

Low formaldehyde emission and high bonding strength were two basic criterions of a good urea-formaldehyde resin adhesive (UFRA). In our study, melamine modified methylolurea solution (MUS), was synthesized and used as modifier for UFRA. The bonding strength and formaldehyde emission of urea-formaldehyde resin adhesives(UFRA) were influenced by some factors such as F/U molar ratio of the main resin, F/U molar ratio of modifier, melamine content, mixing ratio of main resin with modifier, which were investigated by a series of single-factor experiments. The results showed that the best adhesive bonding strength of UFRA was 0.93MPa and the lowest formaldehyde emission was 0.43mg / L, when F/U molar ratio of the main resin was 1.5, F/U molar ratio of the MUS was 0.5, the mass fraction of melamine addition level was 5wt.% of MUS, and the mixing mass ratio of methylolurea solution (MUS) to the main UF resin was 20:80.

Alternative to latent catalysts for curing UF resins used in the production of low formaldehyde emission wood-based panels

This paper studies alternative catalysts to ammonium sulfate for curing urea-formaldehyde (UF) resins. When using a latent catalyst like ammonium sulfate, hexamine is formed as by-product of curing reaction. It is believed that hexamine hydrolysis may contribute to formaldehyde release during the life-time of wood-based panels produced with UF resins. Orthophosphoric acid, on the other hand, catalyzes resin cure without by-product formation and was compared to ammonium sulfate. The pot-life of adhesives with both catalysts was evaluated at 40 °C with a Brookfield rheometer. Mechanical resistance tests performed with ABES (Automated Bonding Evaluation System) showed that orthophosphoric acid effectively catalyzes UF resin cure. Particleboards were produced using both catalysts and the most important properties evaluated, according to European Standards: formaldehyde content, internal bond, moisture content, thickness swelling and density. Particleboards cured with orthophosphoric acid and stored under forceful conditions of humidity and temperature presented similar internal bond and lower formaldehyde content than those produced with ammonium sulfate.

Production of melamine fortified urea‐formaldehyde resins with low formaldehyde emission

AbstractMelamine can be incorporated in the synthesis of urea‐formaldehyde (UF) resins to improve performance in particleboards (PB), mostly in terms of hydrolysis resistance and formaldehyde emission. In this work, melamine‐fortified UF resins were synthesized using a strong acid process. The best step for melamine addition and the effect of the reaction pH on the resin characteristics and performance were evaluated. Results showed that melamine incorporation is more effective when added on the initial acidic stage. The condensation reaction pH has a significant effect on the synthesis process. A pH below 3.0 results on a very fast reaction that is difficult to control. On the other hand, with pH values above 5.0, the condensation reaction becomes excessively slow. PBs panels produced with resins synthesized with a condensation pH between 4.5 and 4.7 showed good overall performance, both in terms of internal bond strength and formaldehyde emissions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Real-time Monitoring of Formaldehyde Concentrations in the Built Environment

Background and Aims: Volatile organic compounds (VOCs) are a major concern in indoor air quality investigations and formaldehyde, in particular, is the subject of considerable environmental health and monitoring research[1,2, 3]. New regulatory standards are focused on reducing formaldehyde levels in both residential settings and building materials manufacturing. In order to develop new tools to meet lower national thresholds [4], there is need for research on the design, implementation and testing of a wireless formaldehyde monitoring systems. The objectives of this research are to 1) compare the performance of commercially available sensors within the network architecture, 2) identify fine scale spatio-temporal patterns in formaldehyde emissions, and 3) provide improved information integration models for the assessment of environmental and personal exposure events. Methods: (Arial, 8pt, bold) The formaldehyde monitoring system consists of wireless sensor nodes, a base station, a Sensor Observation Service (SOS), a database system, and a web-based user interface. Sensor nodes collect data and then pass it to the Sensor Observation Service (SOS) that provides a web-based user interface to enable users to view the latest sensor readings and historical analysis results. Results: (Arial, 8pt, bold) Although the full results of this prototype system will not be available until current testing is completed this spring, anticipated issues this research will be able to address include: efficient and effective wireless communication configurations, comparison of data storage and processing methods, representation of conceptual model that can adequately capture both personal exposure and general area exposures, and ensuring effective user interface design. Conclusions: (Arial, 8pt, bold) Applications of this research will benefit manufacturing industry and wood composite researchers as they move towards producing materials with lower formaldehyde emissions as well as the environmental epidemiology community looking for new tools and methods for collecting and analyzing the longitudinal impact of formaldehyde exposure at lower levels.

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.

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).

Low formaldehyde emission particleboard panels realized through a new acrylic binder

AbstractThe effectiveness of acrylic resins as low formaldehyde emission binders for particleboard production was explored. In particular, a multifunctional methacrylic monomer, ethoxylated bisphenol A dimethacrylate, classified as nonskin and eyes irritant, was selected and tested. In comparison panels realized with classic urea‐formaldehyde (UF) binder were also prepared. No significant differences were found through the morpholocigal analysis of samples prepared with the two different binders. Moreover, particleboard panels realized with the acrylic binder showed better mechanical properties and lower water absorption and thickness swelling in comparison with corresponding panels realized with the UF binders. Furthermore, the replacement of the UF with the acrylic binder did not affect thermal insulation properties of the panels. Formaldehyde release tests revealed that particleboard panels obtained by applying the acrylic binder can be classified as E1 following the European classification and even F**** following the stricter Japanese classification. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Production of Low Formaldehyde Emission Particleboard by Using New Formulated Formaldehyde Based Resin

In order to preserve the global market competitiveness, the particleboard industry was affronted with challenges to reduce formaldehyde emission while maintaining the quality strength properties of particleboard. To counter the issue, particleboards with five different surface-to-core ratio were fabricated by applying newly formulated UF and MUF resins which were 30% surface: 70% core (3:7); 40% surface: 60% core (4:6); 50% surface: 50% core (5:5); 60% surface: 40% core (6:4) and 70% surface: 30% core (7:3) based on dry particle weight respectively. Formaldehyde emission and strength properties of the fabricated particleboard were investigated based on Japanese Industrial Standard, which are JIS A 1460 and JIS A 5908, respectively. All the MUF-bonded particleboard complied with the type 18 standard, whereas all the UF-bonded particleboard produced complied with type 13 except thickness swelling of the UF-bonded particleboard. The surface-to-core ratio applied in three layered particleboard for both resins exerted considerable influence on the strength properties and formaldehyde emission of particleboards produced from both resins. MUF-bonded particleboard with 40% surface and 60% core recorded the lowest formaldehyde emission (0.09 mg L-1) and highest strength properties. For UF-bonded particleboard, the ratio of 60% surface and 40% core showed the lowest formaldehyde emission (0.28 mg L-1) with better strength properties. This study highlighted the potential of MUF resin to replace UF resin due to its ability to produce F**** particleboard with better strength properties and lower formaldehyde emission according to JIS A 5908.

Preparation and Characteristic of Urea Formaldehyde Modified with Hexamethoxymethyl Melamine

Hexamethoxymethyl melamine (HMMM) was used to modify UF resins to obtain good performance with low formaldehyde emission. The effect of urea to formaldehyde ratio, HMMM content on the properties of UF resin was studied in detail. The results suggested that urea to formaldehyde ratio to be 1:0.9 and 20% HMMM content is the optimum formulation to afford desired UF resin. The viscosity, solidification time, bond strength and formaldehyde emission of the modified UF resins were also studied. The results revealed that the performance of the modified UF achieved the chinese standard.

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.

Synthesis and Application of a Modifier with Low Formaldehyde Emission to Enhance General Wood Properties

A preparation method of Urea-formaldehyde performed polymer(UFP) with low molecular weight and high reactivity is presented. The UFP can impregnate into wood along trachea from the ends with pressurized impregnation method. In the following heating and pressing processes of the wood, the UFP polymerizes, and it enhances stability and strength of the wood. The impregnating-pressing-drying method avoiding the disadvantage of dealing with the large specimens using vaccum-pressing method is suitable for industrial production. Results from test showed the degree of crystallinity tested by XRD were 30%, 32% in different dosage of the modifier. Utilizing a combination of low molecular weight resin impregnation and pressing resulted in a density increase of UFP treated wood from 0.214 to 0.268g/cm3. At the same time, the Young’s modulus and bending strength increased from 1.407GPa to 1.759GPa and 64MPa to 74.5MPa, respectively. But the formaldehyde emission is great reduced from 0.5% to 0.008%. It can be concluded that the effective utilization of UFP impregnated in wood is a promising technique for the production of high-strength in the drying and pressing processing.

Preparation of Water-Resistance Plywood with UF Resin Modified by Emulsifiable Polyisocyanate

The purpose of the study was to manufacture water-resistance plywood with using UF resin modified by emulsifiable polyisocyanate. The emulsifiable polyisocyanate which contains plenty of hydrophilic segments and teminal isocyanate groups were synthesized by reaction between various kinds of polyether polyols and polymeric methane dipthenyl diisocyanate (pMDI). A type of composite adhesive was obtained from the mixture of emulsifiable polyisocyanate and urea formaldehyde resin. The process parameters, such as the molar ratio of –NCO and –OH, mass fraction of emulsifiable polyisocyanate in UF resin and accessory ingredient have a great influence on the composite adhesive. X-ray photoelectron spectroscopy (XPS) had been used to analyze the chemical structure of bonding interface. The results showed that the composite adhesive consisting of UF resin and emulsifiable polyisocyanate content of 7.5% and kaolin content of 1.5% was used in plywood with high physical and mechanical properties, water resistance and low formaldehyde emission.

Fast Curing Phenol-Formaldehyde Resin Catalyzed by a Complex Catalyst

For increasing the curing rate and decreasing the curing temperature, modified phenol-formaldehyde (PF) resins were synthesized under a complex catalyst. The bonding strength and formaldehyde emission of the plywood bonded by them were measured according to Chinese National Standards methods. The curing behavior was conducted by differential scanning calorimetry (DSC) measurement. The results indicate that PF resins catalyzed by the complex catalyst show more moderate pH values, lower curing temperature and shorter gel time comparing with control ones. Plywood bonded with modified PF resins shows good bonding strength and low formaldehyde emission even at low hot press temperature (110 °C), which is closed to the plywood bonded with normal control PF resin at high hot press temperature (130 °C).

Resin Suppliers' Perspectives on the “Greening” of the North American Interior Wood Composite Panel Market

Eight North American resin suppliers, representing 100 percent of the polymeric diphenylmethane diisocyanate (pMDI) market and >95 percent of the urea-formaldehyde (UF) market for interior wood composite panels (IWCPs), participated in an exploratory phone survey conducted in July and August 2008 that was designed to better understand their product positioning and “green” resin strategies. These eight firms were identified as the largest suppliers to the IWCP industry, which includes particleboard, medium density fiberboard, hardwood plywood, and hardboard. In 2007, the IWCP resin industry was highly concentrated and dominated by UF resins. Resin suppliers rated research and development work and technical support as the most important competitive advantage factors they used. Moreover, resin suppliers perceived the following product and service attributes to have the greatest importance to their IWCP customers: low formaldehyde emissions from finished panels (4.8 of 5), fast resolution of customer complaints (4.5), reduced volatile organic carbon emissions during panel pressing (4.3), support during resin trials (4.3), and on-time delivery (4.2). The regulatory environment (i.e., California Air Resources Board [CARB]) was the most important driver of IWCP resin manufacturers' green resin programs. Results showed a trend of increasing importance for green IWCP resin market development for the time periods defined as today, next 2 years, next 5 years, and next 10 years for pMDI suppliers, whereas UF suppliers rated green IWCP resin market development highly important over all four time periods.

Optimization of the Synthesis of Urea-Formaldehyde Resins using Response Surface Methodology

In the near future, companies will face the need to produce low formaldehyde emission resins, i.e., not above the emission level of natural wood. However, for producing this new generation of urea-formaldehyde resins (UF), it is necessary to optimize the synthesis process. This work describes an optimization procedure for UF resin synthesis, following an alkaline–acid process, focusing on the conditions of the condensation step. A design of experiments methodology was employed to optimize the 3 selected factors (number of urea additions, time span between urea additions, and condensation pH), in order to produce particleboards with maximum internal bond strength and minimum formaldehyde release. The condensation pH played a significant role in increasing the Internal Bond (IB) strength and reducing the Formaldehyde Emission (FE). The sequential addition of urea also has a noticeable influence on resin performance. Optimum conditions for production of UF resins have been proposed and tested by the response surface methodology using the desirability function.

Phenol–formaldehyde‐type resins made from phenol‐liquefied wood for the bonding of particleboard

AbstractLiquefaction of southern pine wood in phenol in 30–40 : 70–60 weight ratios resulted in homogeneous liquefied materials, which were directly used to synthesize phenol–formaldehyde (PF)‐type resins. The synthesized resins showed good physical and handling properties: low viscosity, stability for storage and transportation, and resin applicable by a common sprayer. Particleboard panels bonded with the synthesized resins showed promising physical properties and significantly lower formaldehyde emission values than those bonded with the urea–formaldehyde resin control. One deficiency observed for the synthesized resins was lower internal bond values, which might be overcome the use of a hot‐stacking procedure. Overall, the process of wood liquefaction with limited amounts of phenol as a solvent was shown to have the potential of providing practical, low‐cost PF‐type resins with very low formaldehyde emission potentials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Production of innovative hemp based three-layered particleboards with reduced raw densities and low formaldehyde emissions

The possibility to substitute wood by hemp for the production of wood based panels and the possibility to produce lightweight panels by using hemp are the main research focuses of this project. The regular density of three-layered particleboards (650 kg/m³) shall be decreased to less than 400 kg/m³ by the utilisation of hemp. Another quite interesting aspect that we want to analyse in line with this project is to reduce the formaldehyde emissions of urea-formaldehyde-, melamine formaldehyde- orphenol-formaldehyde-resin bonded wood based panels by using natural binder systems such as proteins and starches.

Secondary VOC emissions from flooring material surfaces exposed to ozone or UV irradiation

Chemical reactions on the surface of building materials can lead to secondary emissions from these materials that influence indoor air quality. Many studies have been made on the physical processes that influence material emissions. However, there are only a few studies on secondary emissions resulting from exposure of building material surfaces to ozone or ultraviolet (UV) irradiation. Therefore, this study was aimed at elaborating on the emission of chemicals resulting from chemical reactions initiated by the exposure of the surface of flooring materials to ozone or UV irradiation. The laboratory tests were conducted to estimate gas-phase emissions from the flooring materials when they were exposed to ozone or various kinds of light irradiation (infrared, sunlight, UV-A and UV-B lamps). The infrared and sunlight lamps significantly increased the temperature of the test specimens and, in turn, increased the emission rate for various organic compounds. The flooring materials used in this study had been treated with UV-cured surface coatings during their manufacturing. As a result, when exposed to UV irradiation, chemical transformations occurred resulting in the emission of a number of secondary products, including formaldehyde, acetaldehyde, cyclohexanone and benzaldehyde. Ozone reacted with chemicals present in the flooring materials to increase the emission rates of formaldehyde and acetaldehyde. Hence, the exposure of ozone and UV irradiation increased the secondary emissions of formaldehyde, even though the low formaldehyde emission type of flooring material was employed.