Weathering durability of CCB-impregnated wood for clear varnish coatings

Abstract

Outdoor performances of a polyurethane varnish and an alkyd-based synthetic varnish coated over chromium-copper-boron (CCB)-impregnated Scots pine (Pinus sylvestris L.) and chestnut (Castanea sativa Mill.) [10 (R) × 100 (T) × 150 (L) mm] were investigated. These varnishes were also applied to the wood surface as sole coatings or impregnated into wood as water-repellent (WR) solutions. Outdoor exposure was performed in the Black Sea region of northern Turkey (41°N, 39.43°E) where humid weather predominates throughout the year and accelerates decomposition of coated wood surfaces. The wood panels were exposed at 45 ° south on their tangential surfaces. After 9 months of exposure to summer, autumn, and the following winter season, the color and glossiness changes of the exposed surface, adhesion of the coating layer to the wood surface, water absorption through the coating layers, mass loss, and the hardness of the board surface were studied. CCB impregnation greatly stabilized the surface color of varnish-coated panels of both wood species. Gradual decreases of adhesion between varnished layers and preimpregnated surfaces were attributed to probable weakening of interactions at the interface of the treated wood and the film layer. A superficial cleaning process of treated wood is suggested to improve glossiness and adhesion. The coated wood surface became harder with time on outdoor exposure until a maximum hardness occurred followed by softening, whereas the uncoated surface softened steadily. Polyurethane varnish yielded a harder surface than synthetic varnish. Mass losses of wood panels after 9 months of exposure were negligible for all treatments compared with the untreated controls, which were

Surface properties of impregnated and varnished Scots pine wood after accelerated weathering

“…The large molecules created by copolymerisation reactions form the layers of PV (urethane alkyd), and the high molecular cohesion increases the pendulum hardness values [38]. PV-coated wood surfaces were harder than SV-coated wood surfaces in studies by Yalinkilic et al [1], Baysal [23], and Toker et al [34]. Similar findings on some wood species have also been reported by Sonmez et al [38].…”

“…Initial increase in tensile strength after 6 months of ageing was also attributed to the progressive crosslinking of alkyd molecules in a study by Majumdar et al [42]. The hardness of alkyd coatings is a function of their formulations and can be improved by additives [1]. Crosslinking reactions in a solid material are highly dependent on the molecular mobility, which can be increased by raising the temperature or by a humid atmosphere [43].…”

“…As it is commonly accepted that copper-based formulations retard or prevent photodegradation, studying the performance of coatings on wood products treated with copperbased wood preservatives as replacements for CCA and other heavy-metal-containing chemicals is essential [16]. The surface performance of varnishes commonly used in the wood products industry on wood treated with copperbased preservatives is mostly unknown, except for some earlier findings reported by Yalinkilic et al [1,27] and Baysal [23,28]. In the present study, the effect of accelerated weathering on the surface hardness, glossiness, and colour changes of Scots pine wood impregnated with wolmanit-CB, tanalith-E, and adolit-KD5, and then subsequently varnished with an alkyd-based synthetic and polyurethane varnish was investigated.…”

Varnish layer hardness of oriental beech (fagus orientalist L.) wood as affected by impregnation and bleaching

“…16 Conditioned samples were subsequently subjected to the König pendulum hardness test to detect the hardness of the varnish coating according to ASTM D 4366-95. 17,18 Test panels were placed on the panel table and a pendulum was gently placed on the panel surface. The pendulum was then deflected through 6° and released while simultaneously starting the oscillation counter.…”

Effect of artificial aging at QUV on the color of finish treated woods of Pinus sylvestris and Quercus robur

“…Les principaux facteurs de dégradation des composants en bois à l'extérieure sont l'exposition aux rayons ultraviolets et à l'eau [1][2][3][4][5].…”