Formaldehyde emission materials

MUF resin is widely used as an adhesive in wood industries, coating technology, paper industries and a main material in kitchenware production. In various applications, different resin properties are needed to suit its application. Important resin properties are for example higher resin solubility, low curing period with lower temperature and catalyst amount, good stability for longer shelf life, and lower free formaldehyde emission, as formaldehyde is very toxic, and can cause cancer [1]. One of the factors that affecting the MUF resin properties is the mole composition. The mole composition is a ratio of formaldehyde to amino compoimd... 

The results of the study show that temperature has significant effect on both the partition coefficient and the diffusion coefficient of formaldehyde emissions from the four materials tested. For all four materials, the partition coefficient decreases while the diffusion coefficient increases with increasing temperature. 

Zhang, Y., Luo, X., Wang, X., Qian, K. and Zhao, R. (2007) Influence of temperature on formaldehyde emission parameters of dry building materials. Atmospheric Environment, 41 (15), 3203-16. 

Another strong factor is age. Inasmuch as formaldehyde emission is due to the diffusion of residual material from the center core, the emission is proportional to the concentration, and decreases as the concentration decreases. If all formaldehyde were present as formaldehyde gas, or methyIenegIycoI, the emission process should be strictly exponential. It has indeed been proposed that one can model emission according to ... 

Formaldehyde as a pollutant in the indoor air is usually connected with the use of formaldehyde based resins in e.g. building materials and in furniture. This article presents measurements of the formaldehyde emission from various products containing urea-formaldehyde (UF) or phenol-formaldehyde (PF) resins. The emission from all test objects have been measured in a ventilated test chamber at the standardized testing atmosphere 23 C, 50 % RH according to the International Organization for Standardization (ISO). The emission from woodbased panels and other materials have been measured at a loading factor of 1.0 m /m and at an air change rate of 1.0 h . ... 

It should be emphasized that the values presented apply to the particular materials that we studied, and that the absolute values cannot be considered as generally valid. We believe, however, that they can serve to illustrate the relative reductions in formaldehyde emission that can be achieved. 

Air chamber test, material standards for formaldehyde emission, 224... 

EC-European Commission (1989) Formaldehyde Emission from Wood Based Materials Guideline for the Determination of Steady State Concentrations in Test Chambers. Indoor Air Quality and its Impact on Man. Report No. 2, Luxembourg. 

The reactivity of a resin at a certain molar ratio F/U or F/(NH2)2 is determined mainly by its preparation procedure and the quality of the raw materials used. Figure 1 shows the comparison of two straight low formaldehyde emission (El) UF resins with the same molar ratio, but prepared according to different manufacturing procedures. The differences between the two resins are clearly evident by their different rates of strength increase obtained in the so-called ABES (Automatic Bonding Evaluation System) test [96]. Resin A shows a distinctly quicker increase in bond strength than resin B, a fact which also has been verified in the industrial scale production of boards. 

In our research we used AESO resin for producing wheat straw particleboards. Since both raw materials are derived from nature, this kind of particleboard is totally a bio-based product, without any use of forestry resources (wood particles) or any formaldehyde emissions (because AESO does not contain any formaldehyde). We made the boards, evaluated their physical and mechanical properties and eventually compared the results to wood particleboard EN-standards. 

As wood adhesives, isocyanates have found applications as binders for composition board (100). The advantages of isocyanates are many high adhesive and cohesive strengths, flexibility in formulation, versatility of various cure temperatures and curing rates, excellent structural properties, ability to bond with material having moisture content, and lack of formaldehyde emission. The most important advantage is their ability to form waterborne adhesives. 

For the laminator there are increasing concerns about free formaldehyde emissions along with other resin derived chemicals, and all producers have programmes to reduce or eliminate such emissions. The question of disposal of the laminate at the end of its life cycle receives much attention. They are not biodegradable incineration raises objections. Much work is being done to find other useful materials that might be made from reconstituted laminate. Some producers have processes which allow a proportion of waste laminate to be re-cycled in new production, as part of the core-material. 

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