Use of glass transition temperature for stabilization of board's cracks of Eucalyptus grandis

• Main Authors: Fred W. Calonego, Elias T.D. Severo, Antonio R. Cunha, Daiane C. Gaia
• Format: Article
• Language: English
• Published: Academia Brasileira de Ciências 2010-09-01
• Series: Anais da Academia Brasileira de Ciências
• Subjects: rachaduras de tábua; Eucalyptus grandis; temperatura de transição vítrea; vaporização de toras; board's cracks; glass transition temperature; logs steaming
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652010000300025

The Eucalyptus grandis logs temperatures were determined and correlated with the board's cracks during steaming. Thermocouples were inserted in the logs center, registering their temperatures during steaming at 90"C. The logs were sawed and the board's cracks measured. It was concluded that: (1) the logistic S-shaped curve explains the logs temperature variation; (2) the logs with diameter of 20 to <25, 25 to <30 and 30 to <35 cm presented, respectively, 84.2"C, 73.1"C and 45.8"C in the steaming; and (3) the cracks lengths significantly decreased in logs that reached the glass transition temperature.<br>As temperaturas em toras de Eucalyptus grandis, durante a vaporização, foram determinadas e correlacionadas com as rachaduras das tábuas. Nos centros das toras foram inseridos termopares e registradas suas temperaturas durante a vaporização à 90"C. As toras foram desdobradas e as rachaduras das tábuas mensuradas. Concluiu-se que: (1) o modelo estatístico sigmoidal logístico explica a variação da temperatura nas toras; (2) as toras com 20 a <25, 25 a <30 e 30 a <35 cm de diâmetro apresentaram, respectivamente, 84,2"C, 73,1"C e 45,8"C ao final da vaporização; e (3) as rachaduras foramsignificativamente menores nas toras que atingiram a temperatura de transição vítrea.