Effect of ultraviolet radiation on the color of freij\uf3 wood ( Cordia goeldiana Huber) after application of finishing products

A radia\ue7\ue3o ultravioleta \ue9 considerada a mais prejudicial ao uso da madeira afetando suas propriedades, sobretudo a sua cor superficial. A aplica\ue7\ue3o de produtos de acabamentos, como os vernizes, os stains, as tintas, podem minimizar a atua\ue7\ue3o dessa radia\ue7\ue3o. Este trabalho teve como objetivo avaliar o efeito da radia\ue7\ue3o ultravioleta, relativo ao envelhecimento artificial acelerado, na colora\ue7\ue3o da madeira de freij\uf3 ( Cordia goeldiana Huber) tratadas com polisten e seladora (nitrocelulose), com monitoramento por meio de um espectrocolorimetrico. As amostras da madeira foram submetidas a ciclos de radia\ue7\ue3o ultravioleta em um reator fotoqu\uedmico, em tempos de 84 e 168 horas. Os par\ue2metros colorim\ue9tricos (L*, a*, b* C e h*) foram medidos antes a ap\uf3s os tratamentos. O tratamento com polisten foi o que ofereceu maior prote\ue7\ue3o \ue0s radia\ue7\uf5es ultravioletas, dando uma maior estabilidade aos par\ue2metros. O tratamento com seladora foi o que apresentou uma maior altera\ue7\ue3o da cor ap\uf3s a simula\ue7\ue3o de envelhecimento no reator fotoqu\uedmico.Ultraviolet radiation is considered the most damaging radiation to wood, affecting its properties and especially its color. The application of finishing products such as varnishes, stains and inks can minimize the action of this radiation. This study aimed to evaluate the effect of ultraviolet radiation, through artificially accelerated aging, on the color of freij\uf3 wood ( Cordia goeldiana Huber) treated with \u201cpolisten\u201d and sealer (nitrocellulose), by means of spectrocolorimetric tracking. The samples of wood were subjected to cycles of ultraviolet radiation in a photochemical reactor for 84 and 168 hours. The colorimetric parameters (L*, a*, b*, C, h*) were measured before and after the treatments. The treatment with \u201cpolisten\u201d offered greater protection against ultraviolet radiation, yielding greater stability to the parameters. The treatment with sealer led to a greater change in color after the simulation of aging in the photochemical reactor

ENSAIO ACELERADO DE LABORAT 3RIO DE TR\ucaS ESP\uc9CIES DE MADEIRAS DA AMAZ 4NIA CHAMADAS DE TAUARI, EXPOSTAS AOS FUNGOS DE PODRID\uc3O-BRANCA E PARDA E RESPOSTA COLORIM\uc9TRICA DE ACORDO COM O SISTEMA CIE L* A* B*

The purposes of this study were to: evaluate de natural durability of three species of tauari ( Couratari guianensis Aublet, Couratari oblongifolia Ducke & R.Knuth and Couratari stellata A.C.Smith), report the colorimetric parameters according to CIE L*a*b* 1976 system and also show the appearance of control and attacked wood blocks. Two brown-rot [ Gloeophyllum trabeum (Persoon ex Fries) Murril. and Lentinus lepideus Fr.] and two white-rot [ Trametes versicolor (Linnaeus ex Fries) Pilat and Ganoderma applanatum (Pers. ex Wallr.)] fungi were used. Tauari wood was classed as \u201cmoderately resistant\u201d to \u201cresistant\u201d when exposed to Gloeophyllum trabeum, Trametes versicolor and Ganoderma applanatum fungi. All extractives\u2019 contents of attacked samples decreased when compared with the control (sound wood), except Couratari stellata exposed to Ganoderma applanatum. Conversely, all ash contents increased when compared with the control, except Couratari stellata exposed to Gloeophyllum trabeum. All attacked wood blocks and wood meal samples were darker, except wood meal from Couratari stellata exposed to Trametes versicolor, and redder than the control. The \u394E* mean value in attacked wood blocks and wood meal samples attained 29.5 and 14.3, respectively.Os objetivos deste estudo foram: avaliar a durabilidade natural de tr\ueas esp\ue9cies de tauari ( Couratari guianensis Aublet, Couratari oblongifolia Couratari oblongifolia Ducke & Knuth R. e Couratari stellata A.C.Smith), relatar os par\ue2metros colorim\ue9tricos de acordo com o sistema CIE L * a * b * 1976 assim como mostrar a apar\ueancia dos blocos de madeira antes e ap\uf3s o ataque. Dois fungos de podrid\ue3o-parda [ Gloeophyllum trabeum (Persoon ex Fries) Murril. e Lentinus lepideus Fr.] e dois de podrid\ue3o-branca [ Trametes versicolor (Linnaeus ex Fries) Pilat e Ganoderma applanatum (Pers. ex Wallr.)] foram utilizados. A madeira de tauari foi classificada como \u201cmoderadamente resistente\u201d a \u201cresistente\u201d quando exposta aos fungos Gloeophyllum trabeum, Trametes versicolor e Ganoderma applanatum. O conte\ufado de extrativos das amostras atacadas diminuiu quando comparado com o controle, exceto Couratari stellata expostos a Ganoderma applanatum. Por outro lado, os conte\ufados de cinzas aumentaram quando comparados com o controle, exceto para a madeira de Couratari stellata exposto ao Gloeophyllum trabeum. Todos os blocos de madeira atacados e as serragens tornaram-se mais escuras, exceto para a serragem de Couratari stellata exposto ao fungo Trametes versicolor, e mais vermelho do que a amostra sem ataque. O \u394E * m\ue9dio do bloco de madeira e serragem, atacados, atingiram 29,5 e 14,3, respectivamente