Cold Plasma Treatment on Ceiba Pentandra Fiber to Enhance Mechanical Properties of Their Reinforced Polymer Composites

Abstract

Plant fiber and its reinforced composite products have gained enough attention from researchers and industries due to the growing environmental awareness and environmental protection regulations [1]. Kapok fiber (Ceiba Pentandra Fiber) is a natural seed fiber decorated with wax and fatty acids on its surface. Wax and fatty acids on the surface of the fiber make it incompatible at the interface of the fiber and matrix of the composites [2]. So, the structure of the fiber is modified, and the surface of the fiber is activated by the cold plasma surface modification technique. The plasma treatment provides surface corrosion and improves the adhesion properties of the fibre with the hydrophobic polymers [3]. Highly energetic radicals and ions activate the surface without heating the specimen. The micro-nano binary surface structure of the fiber is conformed from contact angle measurement and is verified by SEM. Modification of the structure of the fibre is investigated using X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Field emission scanning electron microscope (FESEM) techniques. Small-angle X-ray scattering (SAXS) technique is used to investigate the structural modification of the fibre by cold plasma treatment in the macromolecular range. Different coupled parameters, such as the volume fraction of the matter phase, the volume fraction of the void phase, the width of transition layers, the transversal length in the matter region, the transversal length in the void region, etc., are calculated using a Fortran code developed by our research group [4]. The mechanical properties of the untreated and plasma-treated kapok fiber-reinforced polymer composites are characterised using flexural, tensile and impact tests. Ultimately, the cold plasma surface modification technique of the fibre may improve the interfacial adhesion between fibre and matrix and significantly enhance the mechanical properties of their reinforced polymer composites. The enhanced mechanical properties of the composite are correlated with the structural modification of the fiber.