It is dynamic in that visitors to the site can vote for the research topics proposed; the number of votes received can change the list order. In addition, votes cast some time ago have a lower weighting than those cast recently. Consequently, the list order changes regularly.
The top three research topics at the time of writing are: understanding formaldehyde emission from panels; ecological glues for panel manufacture; lightweight panels.
I have covered formaldehyde emission in previous columns and the second topic is also linked to the first, so I will address the third topic in this issue. Lightweight panel is the term usually used to describe a product that has relatively thin panels for faces, which are joined together by a low density core. The core material is most commonly a paper-based honeycomb, but can equally be made from aluminium honeycomb, low density wood such as balsa or cork, and rigid plastic or metal foams. These products are used extensively in the making of furniture – especially for boat, camper van and caravan building, where weight is of considerable importance.
These lightweight panels are macro-composites in that they are made by combining several different materials. The utopia sought after by panel manufactures is to make truly low-weight products in one step.
The lowest density MDF I have seen on sale is around 500kg/m3 – I would be happy to hear from anyone who makes something lighter! However, this is still rather heavy compared to most of the macro-composites described above.
Throughout the panel manufacturing sector there has been a tendency to reduce panel weight in order to reduce manufacturing costs and to address the market desire for panels that are easier to handle, cut and shape.
MDF, OSB and particleboards are pressed to high densities in order that the small droplets of glue applied to the wood elements have a chance of sticking two or more elements together. If they were not pressed together then too many of the droplets would harden without forming a bridge between particles and the product would be weak. Consequently, when weight is reduced we normally reduce the board’s mechanical properties too.
In theory, if we could perfectly align the particles in a mattress, like a jigsaw, then we could make strong panels that have the same density as the original raw material and with very little adhesive. Although this is not possible (yet!), careful attention to particle size distribution in the furnish, together with excellent resin distribution, has enabled some manufacturers to lower their product density without detriment to mechanical properties.
The reductions in density may be only 10- 15kg/m3 but this adds up to a lot of material saved over the course of a year – for example around 6,000 tons for a modern, high-capacity production line of 400,000m3/year.
Clearly the light-weight panel is the way to go.