|
|
|
WOOD COATINGS Coatings on wood fulfill variety of function, ranging from purely aesthetic to protection from the element in exterior exposures. Another important role of coatings is in maintaining dimensional stability of wooden objects. Dimensional stability is greatly effected, because of variations in relative humidity and temperature and sometimes because of severe changes in climatic conditions, when the surface temperature may go as high as 50 Degree C. Coatings have to perform to their best in exterior conditions than the interior conditions, which normally protects from an occasional, accidental wetting. In a nutshell, we may say that, coating act as stabilizing agent. The basic purpose of coating should be to reduce moisture content gradients, there by reducing any warping tendency of wood and also to protect the wood from various types of vapours and gases other than moisture. Any coating effectiveness will depend on its specific permeability and the film thickness. That is the reason that, PU coatings are more effective than normal coatings, because of higher thickness built up as compared to air-drying solvent base systems. You can calculate effectiveness of the coating if you can know the MEE (Moisture Excluding Effectiveness) equation. The formula is given as under:
MEE = N* - N**
(100) N* is the weight gain of a coated sample which has been exposed under 97% RH condition at 25 Degree C. for 7 days. N** is the weight gain of an uncoated control sample of the MEE values may vary from 0% to 100%. SOME USEFUL INFORMATION'S
|
Contact Us | Disclamair 02
Sreechem Resins Limited
|