The demand for polymer composites reinforced or filled with natural fibers and powders for various industrial applications (construction, automobiles, furniture, and sporting goods) is growing because they retain good environmental performance, low cost, and easy of production compared to traditional materials [1–3]. Low price, low weight and minimized impact on environmental pollution are the key reasons for the rapid development of polymer composite materials. Recent research efforts are aimed at finding alternative fillers to replace inorganic fillers . In addition to inorganic fillers, the use of natural fibers (organic fillers) also has the following advantages: low-cost, low density, non-abrasive, biodegradable, availability from natural resources, they are recyclable, and they are renewable natural resources [5–6]. Natural fiber reinforced FRP can solve efficiency and environmental issues.
Luffa cylindrica is a naturally occurring cucumber vine in many countries. Luffa 's young cylindrical fruits are edible and contain a number of compounds, including ribosome-inactivating flavonoids, phenols, triterpenes, and proteins. For medicinal purposes, such as immunostimulants and anti-inflammatory agents, the Luffa fruit has been used effectively . Luffa sponge has been successfully used in the biosorption process of heavy metals in waste water and is an essential natural fiber. This emerging cash crop has the full potential to improve the economies of developing nations [7–10]. There is 84% holocellulose, 66% cellulose, 17% hemi-cellulose, 15% legnine, 3.2% extractives, and 0.4% ashes in Luffa fiber physical properties. The physical properties of Luffa fiber are 820 kg / m3 mass, 25–60 µm diameter and 59.1 crystallinity index [11–13]. Oboh et al. Have given functions and applications of Luffa fiber in agriculture, medicine and science and technology. Msahli et al. Studies have shown that the bending strength and adhesion between Luffa fibers and the polyester matrix can be strengthened by acetylation and cyanoethylation of Luffa fibers.
In order to improve performance and reduce costs, fillers are used with different commodities and engineering polymers. The use of inorganic mineral fillers in plastic resins will increase the different physical properties of the material, such as mechanical strength and modulus. Generally, the mechanical properties of particle-filled polymer composites largely depend on the size, shape, distribution of filler particles in the polymer matrix, and degree of interfacial adhesion between filler and matrix [14–17]. Calcium carbonate, kaolin, mica and talc are most commonly used as fillers to minimize production costs and enhance thermoplastic properties such as crystallinity, stiffness, stiffness, flexural modulus, resilience, dimensional stability, electrical conductivity and thermal conductivity. In order to prepare particle composites, Al-Asade and Al-Murshdy studied the addition of kaolin into an unsaturated polyester matrix. The addition of 3–9% of kaolin to the unsaturated polyester resin indicates that the kaolin acts as a binder, and the resulting composite material acts as a particle strengthening agent, resulting in the improvement of the mechanical properties of the unsaturated polyester . Ahmed et al. studied another study of kaolin composite polyester. In this study, a polymer composite made of diethylene glycol and untreated kaolin (based on PET waste derived from unsaturated polyester) was tested. Thermal and chemical methods have been carried out to process kaolin. These treatments affect the mechanical and electrical properties of kaolin filled polymer composites . These reports motivated us to consider the inspiring possibility of incorporating the fine micron-sized kaolin particles in a composite comprising of luffa reinforced polyester to study their effects on the mechanical properties of the composites.
The hybridization of fibers with fillers has been utilized to enhance the properties of composites. A wise choice of matrix and reinforcing phase contribute to a composite with a combination of strength and modulus comparable to or even better than those of conventional metallic materials. Improving the properties of polymers and their composites by adding particulate filler materials in industrial and structural applications has shown great promise, and has recently attracted great attention. Sakthivel M et al., reseached on the feasibility of using luffa fibers/coir as reinforcement for a polymer such as polypropylene in particulate form. They found that the addition of both reinforcement materials based on lignocellulose, resulted in improved mechanical properties, and there was continuous proof of consistency between the two materials . Srinivasan C. studied the effect of fiber treatment and addition of SiO2 nanoparticles on the properties of composite materials. Fiber treatment has been proven to improve the efficiency of the fiber/matrix interface, and the mechanical properties can be improved by adding SiO 2 nanoparticles . Panneerdhass R. et al., used luffa fiber and peanut shell particles to reinforce epoxy resin. It was found that the tensile, compressive, flexural, and impact strength were observed at the reinforcement volume fraction . Fayomi O. et al., the effect of fiber and particles of luffa cylindrica on the mechanical properties of epoxy resin was studied. The samples were machined for mechanical and microstructure analysis. The result is that the mechanical and morphological properties of epoxy resin are modified by the addition of luffa fiber and particulate matter. The composite material surface suggests that a higher weight can cause a brittle fracture .
Based on the literature reviews the use of kaolin and luffa cylindrica together so far has not been examined as reinforcing filler in the production of composite. The present work aims to investigate the effect of kaolin as filler in luffa fiber reinforced polyester hybrid composites. Tensile strength, flexural strength, impact strength, and hardness values were measured for both unfilled and kaolin filled luffa/polyester composites. The results of the mechanical properties are presented and discussed.