Synthetic materials governed environmental burdens are becoming a crucial concern in this era. Today’s composite age employees’ various synthetic materials to fulfil the performance needs[1]. In our daily life mostly, synthetic fiber reinforced composites goods are experienced having viable mechanical properties in different industrial sectors[1], [2]. Although synthetic fibers reinforced composites are efficient performers, these synthetic composites contribute greatly towards environmental hazards due to their non-biodegradable natures [3]. Moreover, their manufacturing costs are also high compromising their affordability [4]. Ecofriendly natural fibers such as (jute, flax, hemp etc.) are considered promising replacements of harmful synthetic fiber reinforcements (carbon/glass) in fabrication of engineered composites due to low cost, low density, biodegradability and abundancies [5], [6], but they possess some manufacturing and performance drawbacks [7], [8]. Natural fibers are usually hydrophilic in nature, hence offer low compatibility with hydrophobic polymer matrices which in return compromises the mechanical properties of natural fiber reinforced composites [9]–[12]. All these problems put a question mark on the use of natural fibers as a suitable solution of synthetics[8]. The problems can be solved using various surface modification techniques[13].
Surface modifications improve the fiber-matrix interfacial adhesions of natural fibers reinforced composites and contribute towards moisture resistance and mechanical properties enhancement[14]. There are two main techniques (physical and chemical) that are used for natural fiber reinforcement surface modification[13]. Plasma treatment is a mostly employed physical technique for surface modification of various natural fibers[15]. Plasma treatment induces number of functional groups on natural fibers surface that cause better fiber-matrix adhesion via creating strong covalent bonds between fibers and matrix [15], [16]. Chemical surface modification employes alkali, silane, water repellent agents, and peroxide etc. [17]. Alkali treatment enhances the mechanical properties of natural fibers by changing their crystalline structure [18]. Water repellent agents induced hydrophobicity in the natural fibers hence bonding capability is improved [19]. Similarly, silane coupling agents can enhance the fiber-matrix interfacial adhesion making strong chemical bonds[20]. In a nutshell the chemical treatments work more efficiently to overcome the drawbacks of natural fiber reinforced composites [21].
Investigated findings report bamboo fiber reinforced composites mechanical properties enhancement using tannic acid (TA) crosslinked soyabean oils [22]. Zhang et al. investigated antioxidant, anti-bacterial and adsorption of (TA) on silk fiber, the adsorption technique proved to be most suitable for antibacterial and antioxidant properties imparting.
Shibata et al. researched on bio composites fabrication and their properties based on glycerol, tannic acid (TA) and wood floor (WFl) [23].Hasan et al. used different chemicals like tannic acid (TA), chlorine, polystyrene sulphonate and lignin with polyamide resin in a specific range to attain the properties like morphological, chemical, and thermal of carbon fiber by working on pretreated wool fiber [24]. Huang et al. studied the deposition of groups on wood fibers (WF) based gridlocked tannic acid (TA) and situ formation of large molecules of ferrous Fe (II) [25]. Kamaludin et al. worked on the properties improvement of chitosan-filled polylactic acid bio-composites by using tannic acid (TA) treatment [26]. Meng et al. used tannic acid (TA) treated bamboo fibers to monitor the performance of soyabean bio-asphalt/styrene-butadiene-styrene modified asphalt [27]. Yin et al. coated copper ions and tannic acid (TA-Cu) together on the surface of the fabric to impart the UV resistance ability of cotton fabric [28]. Nam et al. worked on the preparation of intumescent fireproof cotton by using tannic acid and sodium hydroxide (TA/NaOH) [29]. Moraczewski et al. investigated on the surface treatment of maize stem by using tannic acid (TA) and polydopamine coatings [30]. Juntarapun et al. worked on the antimicrobial properties of cotton fibers with the help of chitosan and tannic acid (TA) [31]. Gu et al. worked on the formation of waterproof cotton fibers with the help of polyphenol behavior. Mixture of TA and Fe(III) can achieve highly waterproof properties of cotton fabrics, followed the treatment with 1-octadecylamine [32]. Luo et al. fabricated the highly fire resistant, UV resistant and antimicrobial cotton fibers functionalized by using biomass tannic acid (TA) and phytic acid [33]. Pawłowska et al. worked on the treatment of flax fibers through bio-based agent used as reinforcement for the polylactide (PLA) based composites [34]. Zhou et al. analyzed the fabrication of chemically intumescent fireproof cotton fabric having the capabilities of UV retardant and fireproof by using (TA), diethylene triamine and phytic acid (PA) [35]. Many researchers used different treatments like silane, grafting and plasma treatment etc.; however, there is no published literature on tannic acid treatment of jute and flax fiber to enhance the interfacial adhesion of natural fiber-based composites. Hence the study focuses on development of woven jute and flax reinforced composites, and to analyze the influence of different tannic acid concentrations and treatment processing times on mechanical properties of composites.