Colorimetric and Chemical Changes in Pre-Hydrolyzed Strand Board Particles of Pine and Eucalyptus

Abstract

Changing wood color with physical treatment is an alternative method to avoid the use of chemicals harmful to the environment. However, despite this advantage, there are few studies on the chemistry and colorimetry of pre-hydrolyzed wood. The objective this research was to evaluate the content of extractives, lignin and holocellulose, lightness (L), red matrix (a*), yellow matrix (b*), saturation (C), and tonality angle (H) on strand board particles of pre-hydrolyzed pine and eucalyptus. Strand board particles measuring 23 x 90 x 0.30 mm in width, length, and thickness, respectively, were pre-hydrolyzed at 130, 150, and 170 °C during 7 or 21 minutes. The temperature had a significant effect on the chemical composition of wood. The pre-hydrolysis temperature of 170 °C resulted in higher chemical modifications. The pre-hydrolysis reduced the equilibrium moisture content of pine and eucalyptus particles, especially at 170 °C. Color modification due to pre-hydrolysis varied according to treatment conditions. Pine particles were more resistant color changing than the eucalyptus particles.

Prediction of the physical, mechanical and colorimetric properties of Eucalyptus grandis heat-treated wood using artificial neural networks

“…At 230°C, the lightness (L*) reduction was less intense, because most of the compounds that darken the wood had been degraded at lower temperatures (BRITO et al, 2008;PEREIRA, 2009). The wood darkening with increasing temperature was also reported for E. grandis , Eucalyptus saligna (CADEMARTORI et al, 2015) and Pinus pinaster heat treated (ESTEVES et al, 2014), besides pre-hydrolysated Eucalyptus grandis and Pinus elliottii (CARVALHO et al, 2014). (PINCELLI et al, 2012), which are degraded by heat.…”

“…Eucalyptus wood has potential to produce solid wood (ANANIAS et al, 2014;SEVERO et al, 2010), but its coloring (CADEMARTORI et al, 2013a;CARVALHO et al, 2014) and high dimensional instability (SRINIVAS;PANDEY, 2012) limits its use for this purpose. Heat treatment can reduce these problems (ESTEVES; PEREIRA, 2009).…”

Wettability and surface free energy on heat-treated Pinus sp. and Erisma sp. woods

“…The process of thermal degradation of wood produces changes in color due to dark-brown quinones formed after oxidation of phenolic compounds (CARVALHO et al, 2014;MOURA;BRITO, 2011). Pinus sp.…”

Equações Para Estimar a Composição Química E O Poder Calorífico De Biomassas Tratadas Termicamente a Partir Da Análise Colorimétrica

“…Esse sistema trabalha com três índices de cor: a claridade (L) que varia de zero (preto) a 100 (branco) e as coordenadas cromáticas do Matiz Vermelho (a*) e do Matiz Amarelo (b*), ambas variando entre -60 e +60 de acordo com suas respectivas purezas (GARCIA et al, 2014;ZANÚNCIO et al, 2014). Os índices foram obtidos com um espectrofotômetro portátil Konica Minolta CM-2500D, efetuando-se as medições por meio do contato direto e perpendicular a superfície das amostras.…”

“…Uma dessas variáveis seria a propriedade de cor do material (BEKHTA & NIEMZ, 2003;ESTEVES & PEREIRA, 2009;GARCIA et al, 2014). Sabe-se que o escurecimento gradual da biomassa provocado pelo tratamento térmico está associado à oxidação e degradação parcial de alguns extrativos e componentes da parede celular (PINCELLI et al, 2012;ZANÚNCIO et al, 2014), que por sua vez tem correlação com a composição química e com o poder calorífico do material resultante.…”