Effectiveness of Two Different Hydrophobic Topcoats for Increasing of Durability of Exterior Coating Systems on Oak Wood

Miloš Pánek,Ondřej Dvořák,Kristýna Šimůnková,Aleš Zeidler,Eliška Oberhofnerová

doi:10.3390/coatings9050280

Abstract

A top hydrophobic layer can increase the durability of exterior coatings applied on wood. Two hydrophobic topcoats - synthetics and waterborne acrylate resin with wax additives, were tested as top layers on twenty-four different coating systems applied on oak wood in this experiment. Artificial accelerated weathering lasted for six weeks. Changes of color, gloss, surface wetting were evaluated, and microscopic analyses of coated surfaces were done during weathering. The results have shown that a top hydrophobic layer increases the durability of tested coating systems in most cases. However, the effectiveness of the two tested hydrophobic topcoats turned out to be different depending on the specific coating systems used.

Highlights

Wood in outdoor applications is subjected to degradation caused by abiotic and biotic factors [1].Even without ground contact, the rapid degradation of surface layers caused by the interaction of water and solar radiation takes place [3]
The objective of this study is to evaluate the efficiency of transparent and semi-transparent coating systems applied on oak wood and possible enhancement of their durability by application of top hydrophobic layers
The changes of surface properties of tested coating systems during Artificial Weathering (AW) exposure were evaluated with respect to the type of polymer base and hydrophobic topcoat—see Figure 1

Summary

Introduction

Wood in outdoor applications is subjected to degradation caused by abiotic and biotic factors [1].Even without ground contact (class 3 by EN 350 [2]), the rapid degradation of surface layers caused by the interaction of water and solar radiation takes place [3]. The hydrophobic compounds generally decrease the amount of absorbed water, which leads to reduction of wood swelling and shrinkage [6,9] This limitation of dimensional changes leads to a slower degradation process outdoors [10]. Nanoparticles based on titanium dioxide [21], silica nanoparticles [22] or zinc oxide were applied as hydrophobic treatments to wood. Many of these approaches have a negative environmental impact and cause damage to the ecosystem because of the possibility for hazardous chemicals to leak from the surface [6]

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