primol m

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Preliminaries

Nowadays more than ever wood counts among the materials used for manifold purposes. It is highly estimated because of its many positive characteristics, such as
a whole variety of treatment, its ratio of strength to weight, good thermal insulation and acoustic qualities and finally its beauty – wood has become an absolutely essential material. Apart from these and other positive features wood has, compared with other materials, one disadvantage. Because of its high hygroscopicity it is due to processes of shrinking and swelling which consequently lead to interstices.
Therefore optimizing the stability of dimensions of wood by various physical and chemical methods is one of the priorities of international wood research. So far more than 25 methods of improving the stability of dimensions of wood have been known.
Only few of them are applied in production, though.

Structure of the tests

The goal of a research project – Prime Wood GmbH Swiss - was the improvement of the stability of dimensions of a beech floor by using various resins which we were offered by partners in industry. For impregnation we chose impregnation by vacuum in various cycles optimized in several pre-tests. The hardening of the resin was achieved by heat. In order to carry out realistic research impregnated lamellas were glued to a floor topping with glue for parquet floors. One floor was – apart from the refinement – additionally sealed with a water-based system. These test floors were exposed to various climates, winter and summer conditions symbolically simulated. While being put to strain, the floors were regularly measured and the changes of the interstices taken down in lists. Furthermore, surface standards, such as resistance to scratching and abrasion were tested.

Screen from a probe			Blue beech

Results

The results reveal a stability of the dimensions of up to 80 % depending on the treatability process and PRIMOL MA and PRIMOL H used.
With reference to the density of the beech wood an increase in weight of up to 56% was achieved. The microscopic tests prove a significant absorption of the resin into the cell wall. The resin in the lumen which basically hardly adds to improvement, was partly removed in a final vacuum state at the end of the impregnation. The idea is to reduce the water content and possibly the size of the molecules. The results have also proved significantly better standards of scratching and abrasion. Tests will be carried out to obtain results for exposure to various weather conditions, as well as mycological tests in our own laboratory.
The equipment for the impregnation consists of a vacuum pressure tube having a vacuum range between -0.8 up to 6 bar. It´s more or less the same the wood preservation industry has been using for a long time.