## 6 Final remarks and Outlook  
This review summarized the most used methods to extract and to treat banana fibers before their incorporation into the polymeric matrices (thermoplastic polymeric matrices or thermosetting polymeric matrices). Using the different information available, which was sometimes difficult to correlate, an attempt was made to understand the effect of the addition of unmodified or modified banana fibers as a function of the fiber loading, or at fixed fiber loading, into synthetic or biopolymeric matrices, or into plasticized starch matrices. Such an effect can improve the mechanical properties, namely the tensile modulus and strength, flexural modulus and strength, and impact strength of untreated polymeric composites reinforced with untreated banana fibers, untreated polymeric composites reinforced with treated banana fibers, treated polymeric composites reinforced with untreated or treated banana fibers (with maleic anhydride), etc. Various studies were analyzed, and some important conclusions can be drawn. The number of suppliers is still very limited for commercial banana fibers. In fact, the majority of the used banana fibers in the mentioned studies were extracted by local farmers, and after that, they were treated. Banana fibers are most commonly available in tropical regions of developing countries (e.g., Brazil, Colombia, India, Malaysia, and China). This is why they constitute the best buying locations for the acquisition of commercial products made with banana fibers. In Europe, there are fewer material sources, which are mainly located in the Macaronesian region (e.g., Canary Islands and Madeira Island, respectively a Spanish autonomous community and Portuguese autonomous regions) and geographically located near Africa, where there is a need to make all processes (extraction and manufacturing) more efficient and economical when compared to the previously referred regions of the world. The utilization of the banana plants reduces the resulting waste of banana cultivation and allows the extraction of hard banana fibers with five to eight different textures (from coarse to fine and from smooth to rough), which after appropriated treatment can be incorporated into usefully biopolymeric matrices to fabricate green polymeric composites. Similar to natural fibers, banana fibers also are hydrophilic with a moisture absorption tendency, making banana fibers incompatible with the hydrophobic nature of the polymeric composites, causing weak interfacial bonding on the interfacial region (reduction of interactions) and causing failure by intercellular and/or intracellular modes. This is one of the reasons which led, in some cases, to the decrease of the mechanical properties of polymeric composites reinforced with banana fibers, with the addition of banana fibers. To solve this drawback, the research community has developed different surface chemical treatments, which cause morphological changes to the banana fibers and lead to a closer packing of banana fibers. This improves the compatibility between natural fibers (in this case, banana fibers) with the polymeric matrix and induces better mechanical bonding into the interfacial region. Examples of surface chemical treatments are alkalization or mercerization, silanization, acetylation, cyanoethylation, potassium (e.g., permanganate, metabisulfite, hydroxide) treatments, sodium (e.g., lauryl, hypochlorite, chlorite) treatments, acid (e.g., acetic, oxalic) treatments, benzoylation, etc. On the modified banana fibers studied in this review work, the most used surface chemical treatments were alkalization and silanization. An indirect method to treat the natural fibers, namely banana fibers, is by the addition of a compatibilizer into the polymeric matrix. Examples of compatibilizers are graft, block copolymers, or graft copolymers by the modification of polymeric matrices. In general, grafting can be done by monomers (e.g., C18H36O2, C4H6O3, maleic anhydride, and methylacrylate) and acrylic monomers (e.g., 2-EHA), etc.