Mechanical and Surface Properties of Lignocellulosic Fibres Reinforced Composites

The advantages and disadvantages of natural fibers as hemp, sisal, jute, wood, and flax have been studied in terms of mechanical properties, durability, cohesion between filler and matrix. The development of natural fiber reinforced biodegradable polymer composites promotes the use of environmentally friendly materials [1]. The new materials derived from biodegradable renewable sources are considered as partial solution to environmental pollution caused by the large volume of waste [2]. Even though the fiber determines the mechanical properties like elastic modulus or strength, the matrix provides the physical and chemical durability by protecting the fiber from environmental influences [3]. The use of lignocelluloses composite with polymer matrix in the environment with UV radiation can cause photodegradation which lead to a weakening of the material and micro-cracking of the matrix [4] and [5]. Photodegradation is the main effect of UV environmental radiation on polymeric materials, which is shown by the following phenomena: breaking chemical bonds between the polymer chains, which leads to the formation of free radicals by dissociating C-H bonds from the polymer chains and to the oxidation of its surface because of peroxide radicals [6]. In addition, exposure to UV radiation can make the material more sensitive to the action of other factors (i.e. humidity) [7]. The hydrophilicity is one great drawback when using lignocelluloses fibers as reinforcement in polymer composites. Many approaches studied the tendency of interfacial strength and dimensional stability of bio-composite as results of UV action [8] and [9]. The paper is focused on the photo-degradation mechanism, which influences the surface energy of the lignocelluloses composite. The evaluation of the surface energy of the composite lignocelluloses materials was carried out by the θ contact angle method identifying the hydrophilic/hydrophobic properties of them. Because of the poor interfacial adhesion between fibers and polymers which leads to limitation of natural fibers reinforcement, Azwa et al. [10] studied the improvement of composite behavior due to addition of coupling agent. The effect of the oak particle size on the mechanical and morphological properties has been studied [6]. Mechanical properties of wood plastic composites (WPC), determined by tensile and Mechanical and Surface Properties of Lignocellulosic Fibres Reinforced Composites Stanciu, M.D. – Savin, A. – Nastac, S.M. Mariana Domnica Stanciu1,* – Adriana Savin2 – Silviu Marian Nastac3 1Transilvania University of Brasov, Department of Mechanical Engineering, Romania 2National Institute of Research and Development for Technical Physics, Nondestructive Testing Department, Romania 3‘Dunarea de Jos’ University of Galati, Engineering and Agronomy Faculty, Romania