Glass-fibre wood: the composite materials used on the reduction of wood in the wood laminated industry

1 ECOWOOD 2008 – 3 rd International Conference on Environmentally-Compatible Forest Products Fernando Pessoa University, Oporto, Portugal, 10-12 September 2008 GLASS-FIBRE WOOD THE COMPOSIT MATERIALS USED ON THE REDUCTION OF WOOD IN THE WOOD LAMINATED INDUSTRY Nuno Calçada Loureiro 1 , José Luís Esteves 2 1 Institute of Mechanical Engineering and Industrial Management - Composite Materials and Structures Research Unit Campus da FEUP Rua Dr. Roberto Frias, 400 4200-465 PORTO - PORTUGAL ([email protected]) 2 University of Porto, Faculty of Engineering - Department of Mechanical Engineering and Industrial Management Rua Dr. Roberto Frias s/n 4200 – 465 PORTO - PORTUGAL ([email protected]) SUMMARY The actual world faces a big environmental problem: the climatical changes, due to the increasing of the greenhouse effect in association with the diminution of the green areas, are changing the entire globe. To reduce the quantity of wood used in a wood laminate, a new technology based in composite materials, has been developed in a partnership between the Department of Mechanical Engineering and Industrial Management of the Engineering Faculty of Oporto University and the Institute of Mechanical Engineering and Industrial Management. This technology creates a new material called GLASS FIBRE WOOD (GFW). The GFW it’s a thermoset matrix laminate without the impregnation in the wood exterior layer, very similar tactile and visually with the usual wood laminates such as MediumDensity Fibreboard (MDF). Meanwhile, the similarities are not much more, because the mechanical behaviour of the GFW is higher, the environmental impact is lower and the wood and energy consumes are also much lower than the MDF. This article presents the GFW and is comparison with one of GFW’s bigger competitor – - the MDF. INTRODUCTION Since the beginning of Time, Man used the natural resources for the production of forms and objects. The use of the stone, first splintery and later polishing, for the production of utensils 2 ECOWOOD 2008 – 3 rd International Conference on Environmentally-Compatible Forest Products Fernando Pessoa University, Oporto, Portugal, 10-12 September 2008 was probably the first indication of this use. In the present, the use of these resources is in such exaggerated way that the Humanity feels the need of rationalize this use and preserving these resources that start to be rare. In these resources we find the wood – used since fuel for heating until structural ends. To minimize the use of natural resources, the wood industry has developed technologies and products that intended the substitution of the wood for other wood base materials such as MDF. However, even so these technologies and products allow the reutilization of wood or of its wastefulnesses, they continue consuming great resources – material and energetic. These raised consumptions of wood lead to a reduction of the green zone, that associates to the biggest fire number, lead to a bigger effect of greenhouse with an increase of the globe temperature and a bigger concentration of carbon dioxide with a lesser global capacity of photosynthesis. The GFW that will be presented in this article is a composite answer for two of the problems of the actuality that have a big impact in the greenhouse effect: The wood waste and the massive consumption of energy to produce wood laminates. ENVIRONMENTAL ASPECTS Polystyrene One of the GFW raw materials is the polystyrene (PS). The PS is a non-biodegradable thermoplastic with an increasing of use due is good properties as we can see in Figure 1. Polystyrene Mundial Demand Evolution 0 2000 4000 6000 8000 10000 12000 14000 16000 1981 1987 1989 1993 1994 1995 1996 2007 year maximal prevision minimal prevision Demand Figure 1: Polystyrene Mundial Demand Evolution. (Source: Brasilian Ministery of Development, Industry and Exterior Trade) 3 ECOWOOD 2008 – 3 rd International Conference on Environmentally-Compatible Forest Products Fernando Pessoa University, Oporto, Portugal, 10-12 September 2008 For applications that not require much mechanical capability, it’s possible to re-use the PS. That’s a mechanical process, indicated in figure 2, composed for five different steps. Figure 2: Mechanical process for re-utilization of the polystyrene After the separation (1) of all parts that are not PS, the PS is washed and miller (2). After that enters in a hot chamber to reduce the water quantity (3) and goes to an agglutination system (4). To finalize de cycle the PS is extruded and cuted in granules (5) that will be the raw material for another PS product. Wood The relation between wood and climatical changes is well known of the entire globe. In Portugal all the possible climatical scenarios say that the country will increase temperature and hot waves intensity. The previsions say that the interior of Portugal will have a temperature increase of 7ºC and the sea-side area an increase of 3ºC. Figure 3: Evolution of the annual medium temperature. (y axis – Medium temperature; x axis – Year) (Source: Portuguese Directorate General of Forestry Resources – 2006) On the other side, the forestry fires decreases the wood available for the industry and increases the soil temperature. All this factors together take us to a climatical state that increases the desert areas and decreases the rain quantity and the quantity of water in the soil, as we can observe in figure 4 which represents the susceptibility to desertification of Portugal. PS Product Waste (1) Separation (2) Milling and Washing (3) drying (4) Agglutination (5) Extrusion Granules 4 ECOWOOD 2008 – 3 rd International Conference on Environmentally-Compatible Forest Products Fernando Pessoa University, Oporto, Portugal, 10-12 September 2008 Figure 4: susceptibility to desertification Map (Source: Portuguese Directorate General of Forestry Resources – 2006) GLASS-FIBRE WOOD – TECHNICAL DETAILS To reduce the quantity of wood used in the wood laminate products, the GFW uses only a wood veneer. This reduction of the quantity of wood used in the production of the wood laminate products will decrease the need of wood and consequentially the diminution of the destruction of the green areas. The Glass-Fibre Wood is a composite material produce by a technological method of composite materials fabrication named Resin Transfer Moulding (RTM). In a RTM system is necessary to have a closed mould. In that mould we put the several layers that will made the final material. After that we close the mould and, under pressure, we inject the resin that will agglutinate all the layers. When the mould is full of resin, and the resin’s cure reaction ends, we open the mould and the material is produce. 5 ECOWOOD 2008 – 3 rd International Conference on Environmentally-Compatible Forest Products Fernando Pessoa University, Oporto, Portugal, 10-12 September 2008 Figure 5: RTM system For the fabrication of GFW we use the next layers: • Pre-composed wenge (Millettia Stuhlmannii) veneer with 0,5mm of thickness • Polystyrene sheet with 0,25mm of thickness • RTM’s Glass-fibre - Rovicore ® 450/B5/450 and we use, also, an epoxy resin SR8100 / SD8824 from SICOMIN EPOXY SYSTEMS Figure 6: GFW’s layers scheme The polystyrene sheet gives isolation between the epoxy resin from the Rovicore core and the wood veneer. For this reason the original mechanical and fisical properties of the wood are preserved. Figure 7: Details of GFW Laminate Pre-composed wenge wood veneer Rovicore ® 450/B5/450 Polystyrene sheet Rovicore ® 450/B5/450 5 mm 6 ECOWOOD 2008 – 3 rd International Conference on Environmentally-Compatible Forest Products Fernando Pessoa University, Oporto, Portugal, 10-12 September 2008 The temperature inside the mould in the RTM process is register by a thermopar and the results are express in the graphic of the figure 7. The reason of the increasing of the temperature is only the heat of the exothermal cure reaction of the epoxy resin. GFW Temperature 0 20 40 60 80 100 120 140 160 180 0 1000 2000 3000 4000 5000 6000 7000 8000 Time (s) Temperature (ºC) Figure 8: Temperature inside the RTM mould With this range of temperature the polystyrene starts to be viscous and “glues” the woodsheet to the fibre-glass core. COMPARATION OF GFW WITH MDF Because MDF veneers have a very similar layer structure to GFW, we have made a comparison between those two products. We studied the mechanical behaviour and the environmental impact of those two products. To study the mechanical behaviour we have made: • Tensile Tests according the ISO 527 standards • Bending Tests according the ISO 178 standards • Determination of density • Microscopic analysis of the joint area To study the environmental impact, we have used the “Design for Environmenttoolkit” (DfE) developed by the Minnesota Office of Environmental Assistance [3]. MECHANICAL TESTS RESULTS The results obtain in the mechanical tests are describe in the next figures and tables. 7 ECOWOOD 2008 – 3 rd International Conference on Environmentally-Compatible Forest Products Fernando Pessoa University, Oporto, Portugal, 10-12 September 2008 Density Material Density Standard Deviation MDF 0,87 1,15 % GFW 1,16 0,50 % Table 1: Experimental density results Tensile Since we already know from other composite materials that the orientation of the exterior fibres could interferer with the mechanical properties, for both materials, we test two different series. The serie “PAR” that have the fibres orientated parallel to the major side of the specimen and the serie “PER” that have the fibres orientated perpendicular to the major side of the specimen. Figure 9: tensile specimen being tested Material Serie Ultimate strength Young’s Modulus (MPa) Standard Deviation (MPa) Standard Deviation MDF PAR 34,92 2,49 % 4817 7,08 % PER 22,77 5,99 % 3622 6,06% GFW PAR 54,87 28,08 % 4796 27,19 % PER 40,29 9,74 % 2714 2,64 % Table 2: Experimental results of the tensile test 8 ECOWOOD 2008 – 3 rd International Conference on Environmentally-Compatible Forest Products Fernando Pessoa University, Oporto, Portugal, 10-12 September 2008 Figure 10: Experimental graphics of the tensile test Bending To maintain a uniform method of comparison, in the bending test we also use the two series alignment that we used in the tensile test. Figure 11: bending specimen being tested Material Serie Ultimate strength Young’s Modulus (MPa) Standard Deviation (MPa) Standard Deviation MDF PAR 68,12 4,28 % 5157 4,05 % PER 41,72 6, 09 % 3024 2,96 % GFW PAR 88,94 4,23 % 3574 12,34 % PER 88,03 3,54 % 2322 5,97 % Table 3: Experimental results of the bending test Tensile Test 0 1 2 3 4 0 0,25 0,5 0,75 1 1,25 1,5 Displacement (mm) Force (kN) MDF/PAR MDF/PER GFW/PAR GFW/PER 9 ECOWOOD 2008 – 3 rd International Conference on Environmentally-Compatible Forest Products Fernando Pessoa University, Oporto, Portugal, 10-12 September 2008 Figure 12: Experimental graphics of the bending test Microscopic analysis We have submitted the two materials to a visualization of its structure into a microscope. As you can see in the next figures the GFW and the MDF have a different process of fix the exterior layer. Figure 13: Microscopic view of the MDF structure. Magnification of 10x (left) and 20x (right) Wood Veneer Core with glue Core