Formaldehyde emission development

Formaldehyde emission regulations, 15 776 Formaldehyde gas, 12 110 Formaldehyde-hydroquinone developers, 19 210... 

Horrocks, A.R. and Roberts, D. 1998. Minimization of formaldehyde emission. In Proc. Conf. Ecotextile 98 Sustainable Develop., Bolton, U.K., Woodhead Publishing Ltd., Cambridge, U.K., 1999. 

Over the last 20 years, environmental concerns have become an important consideration in adhesive formulation and use. Firstly, in the plant the adhesive may require particular handling or the use of protective equipment. Secondly, volatile emissions arising from adhesive reactions both in the hot press and subsequently when the panels are in service are subject to tight regulatory control. In particular the reduction formaldehyde emissions from wood-based panels has been a major objective in adhesive development over the last few years, both because formaldehyde-based adhesives are the major type used and because these have been implicated in environmental and health concerns. 

This has been made possible by the development of suitable adhesive systems that are able to bond the partieles together. The synthetie adhesives offer a consistency of performance that is diffieult to aehieve with natural produets sueh as tannins, and at a cost that has enabled rapid growth to be aehieved. At the same time the adhesive systems have shown a toleranee to a range of wood properties that has enabled most wood residues sources to be used. The environmental effects of formaldehyde emissions from panels made using UF adhesives have been successfully addressed. Initially these required higher resin addition rates to offset a loss in physieal property levels, but further development has reclaimed much of this additional cost. 

Product tests. Clearly, the best product test is full-scale testing of finished panels under actual use conditions. This has been done (27,38) but is expensive, because several full-sized panels of each product must be pre-conditioned at constant temperature and humidity for at least a week. The next best approach is to test product samples in air chambers under standardized conditions. A summary of such methods is contained in Table I. A very large effort has been made over the last three decades world-wide to develop quick, reliable and meaningful product tests. Wittmann (16), Zartl (20), Plath (17), Verbestel (1, Neusser (21,22), Roffael (25), HUD, the U.S. Forest Products Industry (39,40), many standaraization organizations (41-43) and others have published many viable methods, but the testing involves a combination of complex factors and there is simply no single test that fulfills everybody s specific needs. Table I list some of the currently accepted test methods for formaldehyde emission from particleboard, plywood and medium density fiberboard. 

Manufactured Home Construction and Safety Standard, Air Chamber Test Method for Certification and Qualification of Formaldehyde Emission Levels," U.S. Code of Federal Regulations, Vol. 24, Part 3280.406, (U.S. Department of Housing and Urban Development), and F eral Register, Vol. 48, pg 37136-37195, 1983. 

Large Scale Test Method for Determining Formaldehyde Emission from Wood Products Air Chamber Method, FTM-2" National Particleboard Assocaiton, Hardwood Plywood Association, U.S. Department of Housing and Urban Development, Federal Register, 1982, 48, 37169. 

G. Gramp, W. Groah. "Evaluation of the relationship between formaldehyde emission from particleboard mobile home decking and hardwood plywood wall paneling as determined by product test methods and formaldehyde levels in experimental mobile homes." U.S. Dept. of Housing and Urban Development, 1982. 

Because phenolic panels have not presented formaldehyde-related problems in the marketplace, there has not been much need to develop information on formaldehyde emissions from these products. 

An automated and microprocessor-controlled flow injection analysis system was developed for formaldehyde emission measurements. This system was based on the modified pararosaniline method and a sampling rate of about 40 samples/hour was obtained. 

Furnishing. The formaldehyde level in a room at actual conditions depends on several factors, and is not an arithmetical sum of various sources (10), (11). In order to estimate the contribution of formaldehyde emission from single pieces of furniture the test objects have been exposed in area to air volume proportions to which they can be found in a small room or a kitchen. The assumption that the formaldehyde level in the chamber and in the actual room is the same, is based on a theoretical model originally developed for particle boards (4). At constant climate the emission from a test object is determined of the relation between the loading factor and the air change rate. 

The U.S.Department for Housing and Urban Development s rule 3280.308 established formaldehyde emission standards for particleboard and hardwood plywood paneling used in mobile homes. These standards took effect February 11, 1985. The certification program under this rule requires each manufacturer to develop a quality control in-plant testing program that relates to tests conducted in a large scale environmental chamber. 

One month after pressing, the boards were cut and triplicate samples for each duplicate board tested according to the dessicator method, using Purpald solution and a colorimeter, for formaldehyde emission over a period of 24 hours and 30 minutes Purpald development. After this initial assessment the samples were placed in a laboratory fan-exhaust oven at a temperature of 50 C to accelerate the test for a period of two months. The samples were tested at regular intervals of three weeks over the two months period. The formaldehyde emission results obtained are shown in Table I. 

A. Berge et al. (3) and J.J. Hoetjer ( 4) have developed models for the formaldehyde emission from particleboard which can be presented as follows ... 

Dyno has contributed to the development of a method, named the Bell method, for the quantitative determination of the formaldehyde emission from a panel surface ( 5). A glass flask or bell having a plane flange is placed on the surface to be measured. A tight sealing between the flange of the bell and the panel surface is very important. The air can be kept in circulation by means of a membrane pump, pumping about 2 liters per minute in a closed loop, which also contains a gas burette. After a predetermined time the formaldehyde concentration of the air in the gas burette is determined by a sensitive analytical method. 

This area is still in flux. One major problem is that one needs to develop better measurement methods for formaldehyde at low levels, and one needs to have a better field measuring protocol for measuring meaningful formaldehyde levels that are dependent on age of the product, temperature, humidity, and ventilation rate as well as the activities of occupants. All these problems could be reduced, if formaldehyde emission would be effectively controlled at the source. 

Development and Validation of a Test Method for Formaldehyde Emissions... 

Within the frame of a project focused on the reduction of formaldehyde emissions from wood-based panels a number of M-DME and U-DME derived resins have been tested [5, 12]. The aim of the project was the development of... 

Within the scope of the project several new adhesive formulations were developed and tested. The formulations were based on DME (dimethoxyethanal) resin and the products derived from it to produce formaldehyde-free wood adhesives. The investigated adhesives were evaluated on laboratory scale in order to study their technical performances, their gluing parameters, their reactivity as well as their formaldehyde emissions. It was found that all formulations met the requirements of current standards EN 319 1993-08 and that for class P2 particleboards for general uses. From the technical point of view, major advantages of the tested systems were found to be colourless, low toxicity, easy handling, and high stability at room temperature (long shelf-life, pot-life and open-time). The formaldehyde emissions of the boards produced were found to be comparable with those of solid untreated wood (F JIS A 1460 2001 standard). 

Last, but not least, a serious interest is to reduce formaldehyde emissions coming from all types of glued products. This is the reason for development of new formaldehyde-free products such as polyurethane adhesives and emulsion polymer isocyanate (EPI) adhesives for load bearing structures. 

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