Résumé : |
Documentation of changes in liquid water protection is of outmost importance for the characterization of the durability of an exterior wood coating. The use of the water uptake coefficient, wt, and the dynamics of a liquid water drop contact angle, υ(√t), for the determination of lifetime expectation is described. Both methods are found to give equivalent information regarding changes in water protection of six mainly waterborne unweathered and six-month weathered exterior wood coatings. The advantages of the contact angle method are outlined. Furthermore, a theoretical approach is presented to relate the observed proportionality of the contact angle with square root of time to diffusion controlled processes on the coatings surface. |