Protection against sun rays
Scientific study activities and laboratory research and development allow updating our formulations continuously.
MATTER AND ELECTROMAGNETIC ENERGY
Visible light and UV rays produced by the sun are radiation of electromagnetic energy, of the same nature as the waves of a radio, a smartphone or a microwave oven: the difference is in the different wavelengths.
The interaction between matter and electromagnetic energy depends on the dimensional compatibility between the molecular structure or the crystal lattice of the materials and the electromagnetic wavelength.
The waves of microwave ovens are calibrated on the size of water molecules. The ceramic saucer, which is devoid of water and is transparent to the waves, remains cold, while the jam contained in the croissant, which is mainly made of water, becomes very hot.
The sunlight is white. A material appears white if it reflects all light. On the contrary, it looks black if it absorbs all the radiations.
If the material absorbs (or modifys) part of the visible radiation, the remaining reflected portion looks colored. Chromophores (or chromogens) are chemical groups that absorb specific wavelengths and are the “generators” of coloring.
The depth of penetration of solar radiation within the wood ranges from 500-2500 μm for visible light to 70-200 μm for UV rays, and in the path, it meets different substances that interact with the radiation, which over time are subjected to degradation.
The first sign is discoloration: substances with chromophoric groups present in lignin macromolecules absorb energy. This phenomenon over time causes the break of weaker and more reactive chemical groups (double bonds). The external wood (sapwood) the young and more colored part of the wood contains a greater quantity of chromophores. The sapwood degrades faster than the heartwood.
The break of the bonds generates the formation of free radicals, highly reactive chemical species which, acting also on carbon-carbon bonds, induce the degradation of lignin (resinous bonding matrix glue in wood) and cellulose (polymeric long fiber structure of wood). Air and water have a synergistic action with UV radiation, and this combination increases the degenerative action.
The first strategy to protect the wood from solar radiation is the creation of a physical barrier by applying surface finishes or in-depth treatments containing shielding additives.
Inorganic pigments (colored, white and black) which by nature do not undergo degradation due to UV rays, absorb specific wavelengths and are able to shield solar radiation.
It is not possible to use colored pigments for the formulation of transparent wood finishes, which needs colorless additives to be used.
UV absorbers of an organic nature are commonly used, although they may impart a slight color and tend to migrate to the surface and suffer the lye of the rain. Alternatively or in combination, inorganic nanostructured additives can be used.
The efforts made in recent years in the research and development of suitable nanomaterials with a low impact on human health and on the environment. The achieved results have enabled the registration and introduction into the market of inorganic nanostructured additives for solar screens.
The first strategy for the protection consists of a preventive physical barrier for reflection, heat dissipation and absorption of solar radiation. A second strategy foresees an intervention on free radicals and on the oxidative agents formed in retrospect by the action of UV rays.
A wide range of stabilizing and highly reactive additives capable of intercepting and blocking the propagation of radicals, neutralizing their wood degradation effect.
Recently a strong barrier effect of hybrid compounds has been discovered.
Organic-inorganic hybrid additives are synthesized by sol-gel technology. They show a synergistic effect and complementary action, that are able to improve the performance of additives with a single organic or inorganic nature.
The commitment of Borma Wachs to improve the performance of exterior finishes is constant. Scientific study activities and laboratory research and development allow updating our formulations continuously.
The improvement of sensorial and aesthetic quality, performance and safety is a mission.