## 1 Introduction  
In recent years, increasing research attempts have been directed towards addressing environmental problems and the global warming associated with increased CO\({}_{2}\) emissions [1]. Also, due to the increased use of plastic products, disposal and decomposition of waste plastics, as well as the pollution of soils are becoming serious issues. The use of biopolymers such as polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), and poly (butylene adipate-co-terephthalalate) (PBAT) is an approach towards solving these problems. These biopolymers are intended to substitute non-biodegradable polymers based on petroleum-based synthetic materials, such as polyethylene, polypropylene, and polystyrene, which are commonly used [2].  
Among the bio-based polymers, PLA is a versatile biodegradable polyester that is produced from starch-rich biomaterials, such as corn, beet, and wheat. PLA is an environmentally friendly material in terms of energy consumption when compared with conventional petroleum polymers through life cycle assessment (LCA) methodology [3; 4]. It is renewable, recyclable, and is one of the most abundantly produced biodegradable polymers. This polymer has received much attention as a good substitute for petroleum-based polymers. Though PLA has easy processability and good strength, gloss, transparency, and stiffness, its use is limited due to its high price and brittleness, as well as its low thermal properties. To be applied as end products, the shortcomings of these composites need to be resolved [5; 6; 7].  
Kenaf (_Hibiscus cannabinus_ L.) is an annual warm season fiber crop and a plant in the Malvaceae family. It is also known as Java jute. Kenaf fibers have good thermal properties and low density, and as a perennial plant they are cheap, lightweight, abundant, environmentally friendly, and contribute little to climate change [8]. There are advantages to using natural fibers (which exist in abundance) to enhance the properties of bioplastic materials. For example, the use of such biocomposites reduces carbon dioxide in the atmosphere by increasing the cultivation of fibers and their values. Biocomposites are a generic term for materials that are composed of biodegradable or non-biodegradable polymers filled or/and reinforced with natural fibers. Commonly, natural fibers have lower mechanical properties and elastic moduli compared to glass fibers, but when these properties are normalized with specific gravity, natural fibers are comparable to glass fibers in specific strength and specific moduli. These comparable features imply that biocomposites, with natural fibers incorporated, can compete with conventional glass fiber composites, because of their more favorable price, lightness, and environmental performance [9; 10; 11].  
However, if natural fibers were to be used in combination with plastic polymers, the resulting composites would have low tensile strength values and poor interfacial adhesion because of incompatibility between the kenaf fibers and plastics [12; 13; 14; 15]. In order to compensate for these disadvantages, various chemical treatments have been studied. Among the chemical modifications, acetylation is one of the most commonly used methods, where the -OH groups that are responsible for hydrophilic properties of lignocellulosic are modified by hydrophobic acetyl groups [16]. For example, acetylation can be used to control hygroscopic properties, dimensional stability, durability, and the physical properties of plant-based materials and composites. This chemical modification strategy is regarded as an inexpensive, simple method for lowering the surface energy characteristics of natural fibers to make them more compatible with common polymers [11; 17].  
In this research, biocomposites that are composed of kenaf and PLA were fabricated by first acetylating kenaf. This study will focus on the improvement of mechanical properties, thermal properties, water resistance, and interfacial adhesion of the biocomposites.