WOOD PLASTIC COMPOSITE MATERIALS MADE FROM RECYCLED WASTE WOOD AND PLASTIC: ASSESSMENT OF FORMALDEHYDE AND VOC EMISSIONS

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1 Topic B6: Prediction and measurement WOOD PLASTIC COMPOSITE MATERIALS MADE FROM RECYCLED WASTE WOOD AND PLASTIC: ASSESSMENT OF FORMALDEHYDE AND VOC EMISSIONS Sabrine TLILI *, Sabine CRUNAIRE, Marie VERRIELE, Nadine LOCOGE and Patrice CODDEVILLE Département Sciences de l Atmosphère et Génie de l Environnement, Ecole des Mines de Douai, Douai, France * Corresponding sabrine.tlili@mines-douai.fr Keywords: Formaldehyde, VOCs, material emissions, waste materials, wood plastic composites. SUMMARY This work investigates the feasibility of indoor use of Wood Plastic Composites (WPCs) manufactured from recycled materials initially intended for landfill. WPCs were manufactured using recycled wood chips and recycled polyethylene (rpe) / recycled polypropylene (rpp). VOCs and formaldehyde emissions from recycled wood chips and plastic polymer were evaluated using a laboratory small chamber method whereas emissions from recycled WPCs were assessed using Field and laboratory emission cell (FLEC). Processing of WPCs leads to a TVOCs reduction of 51% and 40% and a formaldehyde reduction of 94.1% and 92.9% for WPC-A (made with rpp) and WPC-B (made with rpe) respectively. Ketones, aliphatic hydrocarbons, carboxylic acids and aldehydes were the main groups of the emitted compounds from WPCs samples. The toxicological effects of all substances identified were evaluated. An Ri value was calculated for each compound considering a material loading of WPCs that corresponds to an absolute worst case. It has been established that, excepting formaldehyde, none of the emitted compounds would at that scenario induce health effect. INTRODUCTION The growing of environmental concerns, both in terms of limiting the use of finite resources and the need to manage waste disposal has been a driving force for the launch of wood Plastic composites made from plastic and wood wastes. Their indoor applications impose certain chemical requirements and safety certification. However, there is still lack of information on volatile emissions from such material (Felix et al., 2013). This work aims to characterize emissions of volatile organic compounds and formaldehyde from WPCs manufactured using recycled polyethylene (rpe) / recycled polypropylene (rpp) and recycled wood chips (WPC-A and WPC-B respectively). The toxicological effects of the emissions were also evaluated. METHODOLOGIES

2 rpe rwc rpp WPC A WPC B Figure 1. Raw materials (rwc, rpe and rpp) and WPC specimens Figure 2. Experimental system for determining raw materials species and content WPCs were made from landfill-derived wood and plastic materials. Wood particles were screened to obtain particle sizes < 2 mm. The compounding of recycled plastic/wood fibers was carried out at a processing temperature in the range of C. Figure 1 shows examples of the raw materials (rwc, rpe and rpp) and WPCs specimens. VOCs and formaldehyde emissions from recycled wood and plastic polymer chips were evaluated using a laboratory small chamber method (Figure 2) whereas emissions from recycled WPCs were assessed using Field and laboratory emission cell (FLEC) (Figure 3).

3 VOCs are collected using a Tenax tube and then thermally desorbed to a GC-MS/FID system for identification and quantification. Carbonyl compounds are collected onto DNPH (2,4- dinitrophenylhydrazine) cartridges and analyzed by HPLC with UV detection. Figure 3. Experimental system for determining raw materials species and content RESULTS AND DISCUSSION Total Volatile Organic Compounds (TVOCs C6-C16) and formaldehyde emissions from recycled wood chips and plastics (PP and PE) were evaluated (Table 1). Formaldehyde emission factor from wood chips was about 69 and 35 times higher than rpp and rpe respectively. Formaldehyde is contained in wood as a natural material. Besides, it is well known that Urea-formaldehyde (UF) resin and phenol-formaldehyde (PF) resin used in manufacturing wood based products (e.g., plywood, PB, MDF, and oriented and strand board) are a major source of formaldehyde (Kim et al., 2010). Since recycled wood chips were obtained from wide varieties of waste wood panels that may contain high resins residues, formaldehyde emission from recycled wood chips can be attributed to the wood matter itself as well as resins residues. TVOC emissions from both plastic matrixes (rpp and rpe) were found to be about 1.3 times higher than TVOC emissions from recycled wood chips. Thus, one can expect that in WPCs manufactured from recycled wood and plastic PP/PE, wood chips matrix is the major formaldehyde source whereas VOCs emission is a combination of plastic and wood chips emissions. Table 1. TVOCs and formaldehyde emissions from recycled wood chips and plastics Materials TVOCs (µg/kg/h) Formaldehyde (µg/kg/h) rwc rpp rpe

4 Table 2. TVOCs and formaldehyde emissions from WPCs WPCs TVOCs (µg/m²/h) WPC A WPC B Formaldehyde (µg/m²/h) Strict comparison of the emission results from raw materials (Table 1) and manufactured WPCs (Table 2) is difficult since emission is expressed in µg/g/h for wood and plastic chips and µg/ m 2 /h for WPCs. However, when the amount of wood and plastic particles contained in WPC panel of a given density and thickness is known, the emission results can be recalculated to surface of WPC (Figure 4). Figure 4. Calculated and measured TVOC and formaldehyde emissions from WPCs It was found that the calculation overestimate TVOCs and formaldehyde emissions on WPCs surfaces. The manufacturing process of WPCs contributes to the reduction of pollutant emission. The emission reduction could be related to the high temperature levels reached during the process as well as the encapsulating of the pollutants in the manufactured WPCs. In European labeling schemes, the lowest concentration of interest (LCI) is the most widely used concept (Liu et al., 2012). LCI values are considered as quality criteria of the indoor air. In this work, French AFFSET LCI list was used in the toxicological evaluation of emissions from recycled WPC A and B. The toxicological potential of the emitted compounds were evaluated in the most serious case. We supposed that all the room wall surfaces are covered by recycled WPCs which implies a loading factor L=1 m²/m 3. For the evaluation of the toxicological potential of each compound i, the ratio Ri is established as follows: R i = C i /LCI i (1) C i : concentration of chemical compound i (µg/m 3 ).

5 13 compounds were mainly identified (Table 3). Ketones, aliphatic hydrocarbons, carboxylic acids and aldehydes were the main groups of emitted compounds from both WPC A and B. In the worst scenario corresponding to a loading factor = 1, all the identified compounds, excepting formaldehyde, exhibited Ri values <1. Formaldehyde Ri were 1.72 and 1.32 for WPC A and WPC B respectively. Considering French emission labeling, manufactured WPCs meet to the requirements of A labeling classification for loading factor = 1m -1 and A + considering loading factors < 0.6 m -1 for WPC-A and < 0.75 m -1 for WPC-B. Table 3. R-value of recycled WPCs in a standard room at 1m²/m 3 Compound LCI (µg/m 3 ) R i (WPC-A) R i (WPC-B) Acetone Acetic acid Nonanal Decanal Tetradecane Butanol Hexanol,2-ethyl Nonadecane Butanal Heptadecane Formaldehyde Acetaldehyde CONCLUSIONS Small chamber and FLEC methods were applied for the characterization and quantification of formaldehyde and VOCs from recycled plastic/ wood chips and the manufactured WPCs. The emission profile of the final product was different from the raw materials. Processing of WPCs leads to TVOCs and formaldehyde reduction. Emissions from final products could be estimated from those of raw materials. The manufactured WPCs from recycled materials meet to regulations and health safety and could be used for indoor applications at loading factors < 0.6 m -1 for WPC-A and < 0.75 m -1 for WPC-B. ACKNOWLEDGEMENT DENDRITE Project was supported by FUI13 and Regional Council of Nord Pas de Calais. REFERENCES Felix J. S, Domeno C et al (2013) Characterization of wood plastic composites made from landfill-derived plastic and sawdust: Volatile compounds and olfactometric analysis. Waste Management, 33, Kim K.W, Kim S et al (2010) Control of formaldehyde and TVOC emission from woodbased flooring composites at various manufacturing processes by surface finishing. Journal of Hazardous Materials, 176, Liu W, Zhang Y et al (2012) Indoor decorating and refurbishing materials and furniture volatile organic compounds emission labeling systems: A review. Chinese Science Bulletin, 57,