Colloids and Surfaces A: Physicochem. Eng. Aspects 380 (2011) 89–99 Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects journal homepage: www.elsevier.com/locate/colsurfa Wetting behaviour and surface properties of technical bamboo fibres C.A. Fuentes a,∗ , L.Q.N. Tran a , C. Dupont-Gillain b , W. Vanderlinden c , S. De Feyter c , A.W. Van Vuure a , I. Verpoest a a Department of Metallurgy and Materials Engineering (MTM), Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001, Leuven, Belgium b Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Louvain-la-Neuve, Belgium c Division of Molecular and Nanomaterials, Katholieke Universiteit Leuven, Leuven, Belgium article info Article history: Received 29 December 2010 Received in revised form 15 February 2011 Accepted 18 February 2011 Available online 2 March 2011 Keywords: Natural fibre Bamboo Wilhelmy Wetting Contact line Molecular kinetic theory abstract Bamboo fibres recently attracted interest as a sustainable reinforcement fibre in (polymer) compos- ite materials, due to specific mechanical properties which are comparable to glass fibres. To achieve good wetting and adhesion of the bamboo fibre with different polymers, the fibre surface needs to be characterized. The wetting behaviour of technical bamboo fibres is studied experimentally by using the Wilhelmy technique, and the results are modelled using the molecular-kinetic theory. A novel proce- dure, based on an autoclave treatment, allows stable and reproducible advancing contact angles to be measured. In this way, meaningful information on interfacial interactions can be obtained, allowing improvement of the bamboo-polymer interface. Additionally, for comparison, the wetting behaviour of synthetic poly(ethylene terephthalate) (PET) fibre is studied. This article aims at contributing to a better understanding of the complex phenomena occurring during wetting of natural fibres. The results indi- cate that the high concentration of lignin on the surface of bamboo fibres is responsible for their wetting properties, whereas typical phenomena affecting wetting experiments on plant fibres can be minimized. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Among the many different kinds of natural fibres used in com- posite materials, bamboo is deemed to have one of the most favourable combinations of low density and good mechanical prop- erties: the specific strength and stiffness of bamboo fibres are comparable to those of glass fibres [1]. However, many natu- ral fibres have several disadvantages such as poor wettability, incompatibility with some polymeric matrices and high moisture absorption by the fibres [2]. A major difficulty is related to the fibre–matrix adhesion. Bond- ing between the reinforcing fibre and the matrix has a significant effect on the properties of the composite since stress transfer and load distribution efficiency at the interface is determined by the degree of adhesion between the components. Using the experimen- tal data obtained from wetting measurements, fibres and matrices can be examined and matched in terms of their surface components in order to improve the interfacial properties; predicting and ver- ifying their compatibility allows more suitable combinations and therefore better composites to be made. ∗ Corresponding author. E-mail address: Carlos.Fuentes@mtm.kuleuven.be (C.A. Fuentes). There are a variety of techniques for measuring wetting of sin- gle fibres. The most common methods include both the Wilhelmy technique and fluid geometry analysis. The former consists in a measurement of the liquid weight lifted in the meniscus by the spreading of the liquid upwards on a fibre, while the latter is con- cerned with the profile determination of a barrel-shaped volume where the fibre is wetted by a finite volume of liquid (a droplet) [3–5] or of a meniscus in the case of fibre wetting by an infi- nite reservoir [6,7]. In the case of natural fibres, both methods are hardly applicable due to surface irregularities and perimeter variation. To avoid these complications, the characterization of the wetting behaviour of natural fibres has been reported through the use of the modified Washburn or capillary-rise method [8]. However, this method does not allow the influence of wetting velocity on the determined contact angle to be studied. If surface irregularities are minimized, the Wilhelmy technique represents a good option to study the wetting of solids at different immersion velocities. The interpretation of experimental wetting data depends on wetting theories. These have been derived to describe wetting on an ideal surface wherein complexities in relation to their wetting behaviour such as the viscoelastic response of a polymer surface to a wetting liquid [9], contact angle hysteresis due to surface irregu- larities or chemical heterogeneity [10,11] are assumed to be absent. Therefore, wetting phenomena can be modelled with some success 0927-7757/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2011.02.032