**1. Introduction**

Plastic consumption and its latter disposal have become a problem due to the high volume of waste and the huge environmental impact they have, not only for the human population, but also for ecological systems [1–4]. Plastic is a versatile material with wide applications. However, it is a material that people do not consume correctly as there are no perceived dimensions on the environmental damage that its use entails

[1, 5, 6]. Per capita plastic consumption continues to rise and remains high in highincome countries, despite obvious contributions to the global issue of plastic pollution [1, 7]. In 2015, the World Bank concluded that if waste generation maintains the same dynamic without adequate actions to improve reuse, unsustainable use, and production, it will have become a health emergency issue in most countries. This is in addition to high greenhouse gas emissions by 2030. Our planet is not capable of digesting the plastic waste generated daily, which will continue to happen. In Cameroun precisely in Yaoundé and Douala town, each person consumes an average of 2 kg of plastic per month, 24 kg per year, which means 1250 Mt. per year in those town [8]. The propagation of plastic waste in the environment constitutes a serious threat to public health because it contains in their structures pollutants and heavy metals that have enormous consequences on the health of living beings [9–11]. With the increase in the volume of waste in our cities, it is more than urgent to consider means of reducing these volumes. As a result, while most of the plastic available today is made from non-biodegradable sources, landfilling using plastic would mean burying the harmful material for a period of time until it naturally degrades. However, their degradation rate and bulky nature create enormous environmental risks. In addition, the mass of plastic waste can hinder the movement of groundwater [12], hence the need to give new life to the waste that would constitute a raw material for the construction industry of building materials. Plastic waste can be reused in several sectors of life. Several processes are used. We will cite thermochemical and thermal processes. A very interesting way to dispose of plastic waste is mechanical recycling, which consists of collection, shredding, and granulation followed by its reintroduction into the manufacture of other plastic products [13]. Given the soaring costs of construction materials, the ambient unemployment that many young people suffer, this valuation sector can create jobs and reduce poverty, which results in the valuation of local raw materials as construction materials. The valuation of plastics in construction materials finds many applications in civil engineering. This on the one hand to the economic advantages is provided by this material, which can act as a binder as a substitute for cement. In addition, several waste management processes are used in civil engineering and have shown that the substitution or use of this material could validly replace binders and would constitute an excellent binder but with low compressive strength values. Much work has been done on the recovery and capacity of plastic waste to be used as binders or as a replacement for cement, see the association of plastic cement in concrete. The most commonly used plastics are polyethylene terephthalate (PET) bottles, polyvinyl chloride (PVC) pipes, highdensity polyethylene (HDPE), used plastic waste, expanded polystyrene (EPS) foam, reinforced plastic. Glass (GRP), polycarbonate, recycled thermoplastic polystyrene, polypropylene fiber act as aggregate or mixture in the manufacture of concrete [9].

Reused plastics can be used as reinforcement with natural or synthetic textile fibers in the manufacture of composite materials, the main application of which is the coating of surfaces, walls replacing tiles. Interest in natural fiber-reinforced composites (NFRC) is arising due to their properties of biodegradability, noncarcinogenicity, profitability, and respect for the environment, the absence of health risks, easy collection, and regional availability. They are also used as renewable resource, thus offering a better solution for the sustainability of supply [13]. The different properties of the NFRC show that they would find wide application in the automotive sector, railroad cars, building construction, wall partitions, cabinets, furniture, and packaging manufacturing [6]. NFRCs are viable due to the wide availability of natural fibers and fibers from agricultural residues or mostly lignocellulosic can be used as reinforcements [13, 14]. Several authors have embarked on the search for fibers or natural woody materials having properties similar to synthetic fibers from a physico-mechanical point of view that can be naturally or directly used as reinforcement in composites [13, 15].

*Mechanical Properties and Chemical Stability of Bathroom Wall Composites Manufactured… DOI: http://dx.doi.org/10.5772/intechopen.102457*

Indeed, polymers based on synthetic fibers as reinforcements are expensive and have harmful consequences on the environment. Despite the advantages, natural powder has a high water absorption capacity, hydrophilic in nature, which makes it difficult to manufacture composites. The powder swell is softened when in contact with humidity and consequently absorbs water, which contributes to the reduction of their mechanical properties, while its hydrophilic character affects the dispersion of the fibers within the matrix phase. To improve the interaction between the powder and the polymer matrix, natural fibers must be physically or chemically modified to increase their reactivity and their physico-mechanical properties. Much work has been done on composites reinforced with natural fibers such as kenaf, palm oil, bamboo, jute, sisal, coconut, and pineapple fibers. But there is hardly any work in the literature that uses cocoa shell powder as filler. Cameroon is at the forefront of the production and exportation of certain cash crops, such as cocoa (fifth largest producer in the world), bananas, pineapples. It has embarked on a process of modernizing its agriculture and is currently implementing the so-called second generation agriculture, which aims to boost national agricultural production. This generates a lot of agricultural waste. Thus, in 2013, around 700,368 tonnes of cocoa hulls were produced and around 2,900,000 tonnes will be produced by 2022 [16]. Only a small part has been used as fertilizer and animal feed [17], which poses environmental problems, because these cocoa shells therefore pollute the soil and the rivers. This research aims to use the powder from the cocoa shell to strengthen recycled PET. The tensile strength, bending, water absorption, and resistance to acidic and basic conditions will be evaluated in order to measure the physicochemical and mechanical properties of composites.
