Delegates from across Europe and further afield travelled to Llandudno, North Wales once again for the International Panel Products Symposium.
The IPPS programme is organised by the BioComposites Centre, a commercial company associated with Bangor University. Delegates came from the Czech Republic, the Netherlands, Germany, Austria, Switzerland, Greece, Norway, Belgium, Ireland, France, Latvia, Poland, Spain, France, Denmark, Slovenia and the UK.
From further afield there were delegates from Canada, Uganda and South Korea. Rob Elias, director of the BioComposites Centre, talked about the challenges facing the industry such as changes in regulations; the issue of volatile organic compound (VOC) release; the skills shortage in the construction sector, particularly in the UK; and the need to include more recycled content in building products.
"My ‘soap box’ message is that we must raise the profile of the industry and of its social, economic and environmental benefits," said Dr Elias.
"We must also develop more networks such as Innovawood to reach out to a far wider audience and there are 10,000 researchers in our sector [to call on]." Dr Elias also talked about the importance of EC-funded COST Actions to the industry, including FP1303, to be covered during the symposium.
REDUCING GLUE LEVELS
Examining the structure of particulate wood composites using x-ray micro-computed technology was a keynote message presented by Philip Evans of the University of British Columbia,
This involves looking at the structure inside particleboard and OSB – for visualising resin distribution in the former and zinc borate distribution (used to deter fungal growth and insect attack) in the latter. The aim of the project was to see if adhesive levels could be reduced whilst maintaining the panels’ properties.
"Improved bonding could lead to wood composites with enhanced properties," said Dr Evans. "Maybe even boats or ships could be made from them."
By rotating the panel samples through 360deg over 14 hours, a series of radiographs were obtained and the data processed on a super-computer.
Dr Evans concluded that x-ray micro-CT examination of composite panels is providing insights as to how current composites could be improved (in some cases without increasing costs) by knowing the precise structure of mats during pressing and that much more is possible, especially in areas of process improvement.
For OSB, he concluded that zinc borate is mainly located in the glue lines and that modi_ cation of the adhesive could possibly be used to change levels of zinc released when OSB becomes wet.
In the area of resins and adhesives, Xiaobin Zhao of Cambond Ltd, showed the potential of "green glue" – basically biomassbased formaldehyde-free bio-resin for the wood panel process.
"UF resins have good costs and properties so how do we maintain low cost, with recyclability and low emissions?" asked the speaker.
"Our solution is our Biomass Crosslinking and Blocking (BCB) technology, which utilises the discovery that algae and Distillers Dry Grain and Solubles (DDGS) in an aqueous medium can be cross-linked by isocyanatecontaining cross-linking agents to form a water-resistant polymeric network."
The conclusion is that the resin works and has no added formaldehyde, while reducing the amount of pMDI used for MDF and particleboard manufacture.
"No major process changes are required to use this resin," concluded Mr Xiaobin, who worked with major Chinese panel maker Dare Global in its development.
Raw material
IPPS’ sessions on "feedstocks, recycling and waste materials" proved to be a lively affair and kicked off with Craig Bartlett of MDF Recovery.
Mr Bartlett said MDF Recovery’s system for recycling MDF back into MDF or insulation bats was patented in 2011 and that a pilotlevel scale-up was now underway.
He said this technology would turn a problematic waste stream into a valuable raw material.
Sergej Medved of the University of Lubljana outlined Partial liquefaction as a method for cleaning waste wood.
His team found that partial liquefaction can be used to remove heavy metals from waste wood and that the material obtained could be used to make particleboard.
Use of coconut husk as a raw material was the focus for Michael Kyriazopoulos of Bern University, Switzerland. The milled husk is used for development of medium and low-density fibreboards bound with formaldehyde-free tannin-based adhesives.
The husk was found to contain high levels of lignin and extractives, with the diffuse presence of silica particles on the fibre surface.
Boards of both 800kg/m3 and 250kg/ m3 were produced, both meeting relevant Japanese JIS standards.
"The impact of blue stain-infected spruce on particleboard properties" was the theme of the talk by Martin Weigl of Wood K Plus, Austria. It was found that blue stain has a significant effect on the mechanical properties of spruce-based particleboard, due to altered resin penetration, hence the degree of blue stain infection needs to be assessed, with electrical conductivity of extracts (EER) being a valuable method for quality control.
Durability and performance
Keynote speaker Callum Hill of the Norwegian Forest and Landscape Institute, covered the environmental impact of wood compared to other building materials – the impact of European Standard EN15804. However, he said that Life Cycle Analysis was very complex to conduct, did not allow valid comparisons between different products and this has led to a tendency to grossly over-simplify the results into a single ‘impact factor’.
He counselled caution when comparing different materials; that the only fair comparison is with a functional unit; and that timber products are always superior when the sequestered carbon is taken into account.
Wenchang He looked at work to reduce the thickness swelling of wood composites by creating a 3-D adhesive network. The hypothesis was that panels have good X and Y (longitudinal and transverse) connections in the adhesive, but poor connections in the ‘Z’ (thickness) direction. This leads to a tendency for thickness swelling.
Veneer samples were used in the experiments, with micro-holes drilled through their thickness to encourage Z cross-linking. The researchers found that good cross-linking in the Z direction did indeed generally reduce thickness swelling, with differences between veneer species. Mr He suggested spiked rollers incorporated into a plywood veneer line could be used to perforate the veneers and he is working on a similar system for OSB strands/flakes.
Staying with plywood, Juris Grinins of the Latvian State Institute of Wood Chemistry, looked at thermo-hydro treated birch plywood with improved surface properties. The team treated birch veneers and then made them into plywood panels and also treated the plywood itself.
In both cases, they found that with increasing treatment temperature and time, the dimensional stability and biological durability of the reference plywood were improved. However, a loss in bending strength and hardness was also observed, due to destruction of hemicellulose.
Various treatment temperatures were tried and it was found that 160degC, for 10 minutes, was almost perfect, according to Mr Grinins.
Bronia Stefanowski of the BioComposites Centre shared research on the absorption of VOCs by modified MDF panels and the effects on mould colonisation and growth.
This research concerns the problems of indoor air quality (IAQ) with increasingly tightly sealed buildings, producing ‘sick building syndrome’. The project used organic scavengers, namely peanut and walnut shells, to actually absorb formaldehyde and VOCs from the surrounding air into panels.
It was found that boards treated with either scavenger did absorb VOCs, but also had increased vulnerability to mould growth, more in the case of walnut shells than peanut shells.
The potential of granulated maize cobs as a substitute for particleboard production was presented by Martin Riegler of Wood K Plus. The corncob granules were mixed with wood particles in the construction of singlelayer particleboards in varying amounts.
It was concluded that the addition of 20% maize cob granules led to slightly decreased mechanical properties. Further research into particle sizes is being carried out.
