It is my experience that people often use the term “physical property” when they are actually referring to a mechanical property.
A mechanical property of a material is any of its strength characteristics, such as compression and internal bond strength, or screw withdrawal, or bending stiffness, to name but a few.
In order to measure a mechanical property, one must deform the material – often to destruction – if an ultimate characteristic such as bending strength is required.
Physical properties on the other hand are those such as thermal conductivity, swelling, surface roughness, density and so on. These can be measured without deforming or changing the material.
What about swelling, which changes the dimensions of a product and sometimes irreparably? Well, it is the test that alters the product and not the measurement, which is a measure of thickness, or length, neither of which alter the product.
There is also an overlap with chemistry. For example a panel colour, which is a physical property, may be due to the species of wood used, the colour of which is largely determined by the quantity and type of extractives present, which is a chemical property.
Or the colour may vary from one shift to another because of different temperatures in the dryer or defibrator, among other reasons which may cause chemical changes in the wood.
I mention this topic because COST Action E49, a European network of researchers and professionals with an interest in wood based panels that I have the honour to chair, is organising a one-day conference dedicated to physical properties of panel products. We are expecting presentations on topics like: acoustic performance, dimensional stability, fire resistance, thermal conductivity/insulation, density, machinability, surface roughness, colour assessment, coatability and printability. These properties are vital for certain end-uses of panels, but are often side-lined in conferences.
There is also the possibility for manufacturers and researchers to demonstrate equipment they have developed to measure physical properties. The conference will be held in Istanbul on April 28/29, 2009 so you have plenty of time to submit a presentation or exhibit to the organisers. Information about the conference can be found at www.COSTE49.org.