# Physico-Mechanical Properties of Particleboards Produced from Macadamia Nutshell and Gum Arabic
## 1 Introduction  
Global population growth is increasing the demand for wood for construction and increasing its price. This massive demand has resulted in an increase in deforestation, which is negatively influencing global climate change. Most particleboards produced are made from waste wood and urea-formaldehyde, both of which are in high demand for various applications, including building materials, work surfaces, laboratory whiteboards, and office work surfaces. To manufacture high-quality particleboard, a significant amount of binder is required. Typical particleboards are constructed utilizing wood-based components and synthetic resin adhesives or other manufactured binders. Melamine-urea-formaldehyde (MUF), polycarbonate anhydrides, triglycerides polymeric substance (PTP resin), isocyanides, urea-formaldehyde (UF), and phenol-formaldehyde (PF) are a few examples of such binders [1]. Most particleboard is made with urea-formaldehyde resins; however, the emission of formaldehyde causes negative effects on the human body such as upper respiratory tract infection, eye irritation [2, 3], and even cancer [4, 5, 6]. Researchers produce panels based on natural materials such as chestnut [7] or sugarcane bagasse [8], for example. Affordable housing is one of four main goals in Kenya's strategic plan manifested by the current government. The goals included in the strategy are to create 200,000 housing units and provide affordable quality of living for poorer Kenyans [9]. In addition, theapproach is designed to improve the development of suitable and economical technologies and building materials. The country's population is rising steadily, and substandard housing and underdevelopment, particularly in metropolitan areas, are significantly harming lower-income people. There is government pressure to implement strategies to foster sustainable and environmentally friendly resources, which are used as substitutes for wood [10]. Agricultural waste material and non-wood plant fibers can be utilized in place of wood to produce particleboard. In many parts of the world, agricultural solid waste is discarded or burned, resulting in air pollution, toxic gas, smoke, dust, and residues that may be transferred to water sources, damaging the aquatic ecosystem [11]. Macadamia nutshell farming is a significant source of revenue for cultivators all over the world, particularly shareholder farmers in Kenya. Kenya is the world's third-largest producer of macadamia nuts and thus, there is a large amount of shells in the country [12]. Unfortunately, the enormous quantity of shells is underutilized as a byproduct. The shells are used for many applications--such as cat litter, coffee roasting, filler in the plastics industry, or organic waste for gardening [13]--and they are also used as a source of biomass as a carbon [14]. Macadamia nutshells are composed of isotropic lignocellulosic material and exhibit extraordinary properties comparable to those of wood. They have also been used to manufacture particleboard. They are composed of cellulose (29.5%), hemicellulose (30%), lignin (40%), and ash content (0.31%) [13] and have a modulus of elasticity within the range of 4.2 to 5.2 GPa and tensile strength of 55 MPa [15; 16]. Gum Arabic is derived from the acacia Senegal tree (_Acacia leguminose_), which grows in dry regions ranging from the west coast of Africa to Pakistan and India in Asia. It is one of the oldest and most effective natural gums and possesses unique properties that make it an excellent binder. It is composed of a complex mixture of glycoprotein and polysaccharides characterized by approximately 3% protein and 97% carbohydrates [17]. It has been used in different fields. For instance, it is applied as an emulsifier or thickener in the food industry [18] and has historically been used as a medical treatment for chronic renal (failure) in Sudan [19]. It has been also used as an adhesive to fabricate straw blocks [20] or particleboard made from rice husks [21], for example.