Changes in Surface Properties of Heat-Treated Phyllostachys pubescens Bamboo

Abstract

The wetting phenomena and surface energetic behavior in heat-treated bamboo were studied. The bamboo specimens were heat-treated at temperatures of 100, 140, and 180 °C for 4 h, and an untreated sample served as a control. The sessile drop technique was used to estimate the surface contact angles of the control and heat-treated bamboo samples. The contact angle data were then used to determine the surface free energies using the Lifshitz-van der Waals/acid-based approach. The results revealed that the heat treatment process affects surface wettability. Heat treatment at 100 to 180 °C increased the contact angle of distilled water and formamide, but heat treatment did not cause any increase in the contact angle of diiodomethane. The hydrophobic characteristics of the bamboo surfaces also increased under heat treatment, and the surface free energy and the polarity of the bamboo decreased. Surface analysis by XPS of the samples heat-treated at 180 °C showed a decreased O/C ratio and increased C1 peak, indicating that more lignin and extractives were situated on the bamboo surface. Changes in wettability can greatly impact the use of the material, particularly with respect to the adhesion of paints and coatings.

Effect of Thermal Treatment on the Wettability of Giant Bamboo (Dendrocalamus Asper) and Kawayan Tinik (Bambusa Blumeana) in the Philippines

“…A reduction in the wettability property was observed after heat treatment of spruce, poplar, beech, pine (Petrissans et al 2003) and Pinus pinaster and Eucalyptus globules (Esteves et al 2007). Similar observations were found in Phyllostachys pubescens (Zhang and Yu 2015).…”

“…The observations reported in the present study differed from the other studies. Previous studies by Hou et al 2011, Li et al (2015) and Zhang & Yu (2015) showed a significant increase in the contact angle after the thermal treatment of Phyllostachys pubescens. Similarly, an increase in contact angle was observed in beach wood (Hakkou et al 2005), spruce, poplar, beech and pine (Petrissans et al 2003), Pinus pinaster and Eucalyptus globules (Esteves et al 2007) after heat treatment.…”

Progress of Bamboo Recombination Technology in China

“…In terms of chemical components, the content of alpha cellulose, hemicellulose, starch, and sugar decreased, the content of extraction and lignin increased, the pH value decreased, and the hydroxyl and hydrogen bonds of the cell surface decreased [31]. As for performance, the unit surface free energy and polarity decreased, the density, volume shrinkage, and equilibrium moisture content decreased, the hydrophobicity increased, and the elastic modulus of fibroblast and parenchyma cell wall remained unchanged, and the hardness increased significantly [32][33][34]. In the course of the above changes, the formation of cracks and the increase of grain size are conducive to the subsequent penetration of PF resin into the microstructure of bamboo.…”

Effect of thermal modification on the surface quality of a coating applied to wood via the electrostatic spray deposition technique

“…The utilization of thermally modified wood for indoor or outdoor applications has progressively increased due to its above-mentioned advantages. Previous studies have reported that the surface of the wood after the TM shows some changes when compared to unmodified wood (Hakkou et al 2005;Zhang et al 2015;Miklečić and Jirouš-Rajković 2016;Hill et al 2021). These changes include a decreased wettability and an inactivation of the surface.…”

“…Some chemical reactions occur in the wood during the thermal treatment, e.g., hydrolysis and oxidation, which cause the reduction of free hydroxyl groups and surface inactivation (Hakkou et al 2005;Petric et al 2009;Miklečić and Jirouš-Rajković 2016). Previous studies reported that the surface inactivation caused by the TM influences the wettability, which plays a role in the bonding mechanism between wood and certain coatings (Jarusombuti et al 2010;Hubbe et al 2015;Zhang and Yu 2015). Coating systems need to spread and penetrate the surface of the wood for good bonding to occur.…”