X-RAY DENSITOMETRY IN THE EVALUATION OF DENSITY IN PARTICLEBOARD PANEL/DENSITOMETRIA DE RAIOS X NA AVALIACAO DA DENSIDADE EM PAINEIS DE PARTICULAS

This study aimed to determine the apparent density, by gravimetric technique and X-ray microdensitometry of particleboard produced with Acacia mangium wood and search existence of correlation between both methods. It was used urea formaldehyde adhesive and commercial tannin Acacia mearnsii applied in powder form directly to the previously glued particles. The panels manufactured using four compression ratios (1.39, 1.55, 1.73, and 2.00) combined four levels of powdered tannin (0, 10, 20 and 30%), making up 16 treatments (4 panels by treatment). The particleboard apparent density parameters (mean, maximum and minimum) and gravimetric density were determined, analyzed and compared. The density profile presented graphically and interpreted by analysis of variance and multiple linear regression. The apparent density, medium, maximum and minimum for particleboard obtained by microdensitometry X- ray ranged 357-697 kg/[m.sup.3], 386-824 kg/[m.sup.3], and 334-634 kg/[m.sup.3], respectively, and gravimetric method 369-742 kg/[m.sup.3]. The technique was effective in determining variations in the density profile in the thickness of the particleboards in all treatments, as well as direct obtain the apparent density. These variations could be reduced if the tannin used was previously hydrated in water. Was found strong correlation ([R.sup.2] = 0.99) between the mean apparent density obtained by X-ray microdensitometer and gravimetric method. Keywords: quality panel; non-destructive analysis; density profile. Objetivou-se neste trabalho determinar o perfil da densidade aparente em painel aglomerado confeccionado com particulas da madeira de Acacia mangium. Utilizou-se a tecnica de microdensitometria de raios X correlacionada com a densidade gravimetrica Foram utilizados os adesivos ureia formaldeido e tanino comercial de Acacia mearnsii aplicado na forma de po diretamente nas particulas previamente encoladas. Os paineis foram fabricados com quatro razoes de compactacao (1,39; 1,55; 1,73; e, 2,00) combinadas a quatro proporcoes de tanino em po (0, 10, 20 e 30%), totalizando 16 tratamentos (4 paineis por tratamento). Foram determinados, analisados e comparados o perfil da densidade aparente (densidade media, densidade maxima e densidade minima) e a densidade gravimetrica dos aglomerados produzidos. O perfil da densidade e apresentado graficamente e interpretado por analise de variancia e regressao linear multipla. Os valores de densidade aparente media, maxima e minima