<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE article  PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "http://dtd.nlm.nih.gov/publishing/3.0/journalpublishing3.dtd"><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" dtd-version="3.0" xml:lang="en" article-type="research article"><front><journal-meta><journal-id journal-id-type="publisher-id">JMMCE</journal-id><journal-title-group><journal-title>Journal of Minerals and Materials Characterization and Engineering</journal-title></journal-title-group><issn pub-type="epub">2327-4077</issn><publisher><publisher-name>Scientific Research Publishing</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.4236/jmmce.2022.105027</article-id><article-id pub-id-type="publisher-id">JMMCE-119506</article-id><article-categories><subj-group subj-group-type="heading"><subject>Articles</subject></subj-group><subj-group subj-group-type="Discipline-v2"><subject>Chemistry&amp;Materials Science</subject><subject> Engineering</subject></subj-group></article-categories><title-group><article-title>
 
 
  Hybrid Composite Based on Natural Rubber Reinforced with Short Fibers of the &lt;i&gt;Triumfetta cordifolia/Saccharum officinarum&lt;/i&gt; L.: Performance Evaluation
 
</article-title></title-group><contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Abel</surname><given-names>Emmanuel Njom</given-names></name><xref ref-type="aff" rid="aff1"><sup>1</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Armel</surname><given-names>Mewoli</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Marie</surname><given-names>Josette Ndengue</given-names></name><xref ref-type="aff" rid="aff3"><sup>3</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Fabien</surname><given-names>Betene Ebanda</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Augustine</surname><given-names>Demze Nitidem</given-names></name><xref ref-type="aff" rid="aff4"><sup>4</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Sandrine</surname><given-names>Biloa Otiti</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Yannick</surname><given-names>Devario Youssi Bang</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Legrand</surname><given-names>Ndoumou Belinga</given-names></name><xref ref-type="aff" rid="aff5"><sup>5</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Pierre</surname><given-names>Marcel Anicet Noah</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Atangana</surname><given-names>Ateba</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib></contrib-group><aff id="aff4"><addr-line>Mechanics and Adapted Materials Laboratory (LAMMA), ENSET, Douala, Cameroon</addr-line></aff><aff id="aff3"><addr-line>Laboratory of Mechanics, University of Douala, Douala, Cameroon</addr-line></aff><aff id="aff5"><addr-line>Laboratory of Engineering Civil and Mechanics, National Advanced School of Engineering, University of Yaoundé 1, Yaoundé, Cameroon</addr-line></aff><aff id="aff2"><addr-line>Department of Mechanical Engineering, ENSET, University of Douala, Douala, Cameroon</addr-line></aff><aff id="aff1"><addr-line>Laboratory of Materials Mechanics, Structures and Integrated Manufacturing, National Advanced School of Engineering, University of Yaoundé 1, Yaoundé, Cameroon</addr-line></aff><pub-date pub-type="epub"><day>30</day><month>08</month><year>2022</year></pub-date><volume>10</volume><issue>05</issue><fpage>385</fpage><lpage>399</lpage><history><date date-type="received"><day>25,</day>	<month>July</month>	<year>2022</year></date><date date-type="rev-recd"><day>27,</day>	<month>August</month>	<year>2022</year>	</date><date date-type="accepted"><day>30,</day>	<month>August</month>	<year>2022</year></date></history><permissions><copyright-statement>&#169; Copyright  2014 by authors and Scientific Research Publishing Inc. </copyright-statement><copyright-year>2014</copyright-year><license><license-p>This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/</license-p></license></permissions><abstract><p>
 
 
  This article contributes to the development of the new class of fully biodegradable “green” composites by combining fibers (natural/bio) with biodegradable resin. The vegetable fibers (
  <em>Triumfetta cordifolia</em> and sugarcane bagasse) treated with NaOH and bleached were incorporated into a natural rubber matrix. The influence of the fiber ratio on the physical properties, tensile strength and surface hardness of the hybrid composites was analyzed. The results show that the addition of fibers in the natural rubber matrix increases the water absorption capacity but gradually reduces it with increasing fiber ratio. The hybrid composites of the NRT50-50B proportions show the best tensile strengths at 20 phr and a shore A hardness of 43.7 at 30 phr. The combination of two fibers has improved the physical and mechanical properties of the hybrid composites which can be used in engineering applications.
 
</p></abstract><kwd-group><kwd>Hybrid Composites</kwd><kwd> &lt;i&gt;Triumfetta cordifolia&lt;/i&gt; Fiber</kwd><kwd> Sugarcane Bagasse Fiber</kwd><kwd> Natural Rubber Shore a Hardness</kwd></kwd-group></article-meta></front><body><sec id="s1"><title>1. Introduction</title><p>Research efforts are currently underway to develop a new class of fully biodegradable “green” composites by combining (natural/bio) fibers with biodegradable resins [<xref ref-type="bibr" rid="scirp.119506-ref1">1</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref2">2</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref3">3</xref>]. The appeal of green composites including natural rubber and natural fibers is that they are environmentally friendly and biodegradable.</p><p>The rubber tree grows in a tropical climate, particularly in Cameroon where many rubber plantations are exploited. This country produced more than 70,000 tons of rubber in 2021, far behind C&#244;te d’Ivoire [<xref ref-type="bibr" rid="scirp.119506-ref4">4</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref5">5</xref>], but the characteristics of this natural rubber (NR) are poorly documented in the literature. NR is one of the main elastomers and is widely used to prepare many rubber compounds [<xref ref-type="bibr" rid="scirp.119506-ref6">6</xref>]. It does not naturally possess the hardness and modulus necessary for commercial acceptability [<xref ref-type="bibr" rid="scirp.119506-ref7">7</xref>].</p><p>Green reinforcements, including vegetable fibers, are an alternative to carbon black [<xref ref-type="bibr" rid="scirp.119506-ref8">8</xref>]. Indeed, vegetable fibers offer a low environmental impact, in addition to being renewable, widely available and healthy; they have relatively high specific mechanical properties combined with a low density [<xref ref-type="bibr" rid="scirp.119506-ref9">9</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref10">10</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref11">11</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref12">12</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref13">13</xref>]; they pose technological problems because they present low compatibility with the rubber matrix and are, an incompatibility related to their hydrophilic character. Indeed, the fibers are coated in surfaces of waxy substances (waxes and pectins) of dusts… which can involve a reduction of the tensile strength [<xref ref-type="bibr" rid="scirp.119506-ref14">14</xref>] without however forgetting the presence of the hydroxyl groups responsible for the hemicelluloses. On this last example, the fiber of Triumfettacordifolia contains a very high rate of hemicellulose (30.8%) [<xref ref-type="bibr" rid="scirp.119506-ref9">9</xref>] which requires treatment before use in such a matrix. These problems are mainly minimized by the use of coupling agents to increase the adhesion between the fiber and the rubber matrix or by the application of chemicals to modify the surfaces of the fillers, thus minimizing water absorption and improving the mechanical properties of the composites [<xref ref-type="bibr" rid="scirp.119506-ref15">15</xref>]. For this purpose, alkaline treatment with sodium hydroxide (NaOH) solution of the fibers improves the adhesion characteristics due to the increase in roughness [<xref ref-type="bibr" rid="scirp.119506-ref16">16</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref17">17</xref>]. In addition, the removal of lignin and other waxy surface substances by alkaline solution increases the interfacial adhesion between natural fibers and polymer matrices [<xref ref-type="bibr" rid="scirp.119506-ref17">17</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref18">18</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref19">19</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref20">20</xref>]. Although very rare in the literature, hydrogen peroxide treatment has also attracted the interest of researchers due to the simplicity of its implementation and the improvements observed on the mechanical properties of the tested materials [<xref ref-type="bibr" rid="scirp.119506-ref21">21</xref>]. The investigations of Ramlee et al. [<xref ref-type="bibr" rid="scirp.119506-ref21">21</xref>] also corroborate this result by SEM on palm nut and sugarcane bagasse fibers; this treatment presented the appearance of pores and fibrils on the fiber surface, which would demonstrate a thermal efficiency. Thus, the effective surface area of the fiber available for binding with the matrix is increased.</p><p>In parallel with the development of green composites, studies indicate that this availability remains low since flax, hemp and coir fibers represent more than 80% of the world’s production of natural fibers excluding cotton [<xref ref-type="bibr" rid="scirp.119506-ref22">22</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref23">23</xref>]. There is a need to diversify the plant resources of reinforcements of rubber composites.</p><p>To this end, the orientation of local biomass is an opportunity for African countries in the equatorial region to develop new fibers such as Cola lepidota (CL) bark [<xref ref-type="bibr" rid="scirp.119506-ref10">10</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref11">11</xref>], fibers from Rhectophyllum camerunense (RC) [<xref ref-type="bibr" rid="scirp.119506-ref24">24</xref>] and Neuropeltis Acuminatas (NA) [<xref ref-type="bibr" rid="scirp.119506-ref25">25</xref>] and Triumfetta cordifolia (TC) bast fiber [<xref ref-type="bibr" rid="scirp.119506-ref3">3</xref>] - [<xref ref-type="bibr" rid="scirp.119506-ref9">9</xref>] Triumfetta cordifolia bast fibers traditionally used to produce ropes are widely available and sugarcane (Saccharum officinarum L.) bagasse fibers mainly used as fuel (in distilleries or sugar mills) [<xref ref-type="bibr" rid="scirp.119506-ref26">26</xref>] are available in Cameroonian biomass and the latter could be very interesting as reinforcement of the natural rubber matrix as they present a potential for many technical applications [<xref ref-type="bibr" rid="scirp.119506-ref3">3</xref>] - [<xref ref-type="bibr" rid="scirp.119506-ref27">27</xref>].</p><p>However, the use of natural rubber (NR) as a green matrix can be considered disadvantageous because the mechanical properties of the final composites at very high strains remain rather poor [<xref ref-type="bibr" rid="scirp.119506-ref28">28</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref29">29</xref>]. This last point can be overcome by using a hybrid reinforcement. With such an appropriate material design, one type of fiber can compensate for aspects of performance that are lacking in the other [<xref ref-type="bibr" rid="scirp.119506-ref18">18</xref>]. Hybridizing these two different fibers (TC, Bagasse) would be a more effective way to improve the mechanical properties of natural fibers [<xref ref-type="bibr" rid="scirp.119506-ref22">22</xref>] - [<xref ref-type="bibr" rid="scirp.119506-ref30">30</xref>]. Therefore, these modern materials require a hybrid combination that cannot be satisfied by monolithic materials, especially for the development of automotive materials (Nair &amp; Joseph, 2014). These materials have many advantages over conventional materials. Most of the hybrid materials consist of lightweight components with significantly better mechanical properties as noted in the literature [<xref ref-type="bibr" rid="scirp.119506-ref18">18</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref28">28</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref29">29</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref30">30</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref31">31</xref>].</p><p>Although many studies have been conducted on fiber-reinforced polymer systems, as mentioned above, the mechanical properties of lignocellulosic fiber-reinforced natural rubber hybrid composites have received little attention.</p><p>The main objective of this work is to investigate the effect of hybridization of plant fibers (Triumfetta cordifolia/Bagasse of sugarcane) on the physical and mechanical properties of the developed natural rubber matrix composites. Thus, the bulk density and water absorption rate were evaluated. Tensile tests were performed according to EN-ISO 37:1998 and finally shore hardness (A) tests were conducted.</p></sec><sec id="s2"><title>2. Materials and Methods</title><sec id="s2_1"><title>2.1. Raw Materials</title><p>Two types of plant fibers are used in this work (<xref ref-type="fig" rid="fig1">Figure 1</xref> and <xref ref-type="table" rid="table1">Table 1</xref>): Triumfetta cordifolia (TC) bast fibers harvested in Mbankomo-Cameroon and extracted by water retting in accordance with the method used in the literature [<xref ref-type="bibr" rid="scirp.119506-ref9">9</xref>] and sugarcane bagasse (BS) fibers harvested in Kyossi-Cameroon. These fibers were reduced to particles and sieved (0.1 to 3 mm). Raw rubber latex was collected from Hevecam rubber plantations in the coastal region of Cameroon. Vulcanizing materials such as zinc oxide, sulfur, stearic acid and acetic acid were supplied by PYCNOLAB (Douala, Cameroon). Sodium hydroxide (NaOH) granules used for alkali treatment were supplied by the same facility.</p><table-wrap id="table1" ><label><xref ref-type="table" rid="table1">Table 1</xref></label><caption><title> Physical and mechanical properties of plant fibers used [<xref ref-type="bibr" rid="scirp.119506-ref3">3</xref>]</title></caption><table><tbody><thead><tr><th align="center" valign="middle"  rowspan="2"  >Fibers</th><th align="center" valign="middle"  colspan="8"  >Characteristics of the vegetable fibers</th></tr></thead><tr><td align="center" valign="middle" >Length (cm)</td><td align="center" valign="middle" >Density (g/cm<sup>3</sup>)</td><td align="center" valign="middle" >Tensile stress (Mpa)</td><td align="center" valign="middle" >Modulus of elasticity (Gpa)</td><td align="center" valign="middle" >A (%)</td><td align="center" valign="middle" >Cellulose (%)</td><td align="center" valign="middle" >Hemicellulose (%)</td><td align="center" valign="middle" >Lignin (%)</td></tr><tr><td align="center" valign="middle" >TC</td><td align="center" valign="middle" >0.1 - 1.3</td><td align="center" valign="middle" >1.47</td><td align="center" valign="middle" >526 &#177; 12</td><td align="center" valign="middle" >12.4 &#177; 6.9</td><td align="center" valign="middle" >2.25</td><td align="center" valign="middle" >44.4</td><td align="center" valign="middle" >30.8</td><td align="center" valign="middle" >18.9</td></tr><tr><td align="center" valign="middle" >BS</td><td align="center" valign="middle" >-</td><td align="center" valign="middle" >1.23</td><td align="center" valign="middle" >220</td><td align="center" valign="middle" >26.8</td><td align="center" valign="middle" >1.0</td><td align="center" valign="middle" >36.9</td><td align="center" valign="middle" >22.67</td><td align="center" valign="middle" >23</td></tr></tbody></table></table-wrap></sec><sec id="s2_2"><title>2.2. Fiber Treatment</title><p>The TC and BS fibers were ground into small sizes and then sieved to have lengths of approximately 0.1 to 3 mm. These fibers were treated to improve their adhesion with the matrix [<xref ref-type="bibr" rid="scirp.119506-ref18">18</xref>]. These plant fibers were soaked for 24 h in the 5% sodium hydroxide (NaOH) solution for alkaline treatment [<xref ref-type="bibr" rid="scirp.119506-ref32">32</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref33">33</xref>]. After that, the treated TC and BS fibers were washed to pH7. Then, the fibers were bleached with peroxide (H<sub>2</sub>O<sub>2</sub>) for 2 hours. Finally, after drying at 70˚C for 24 h, the fibers are ready to be characterized for application in composites.</p></sec><sec id="s2_3"><title>2.3. Characterization of Materials</title><sec id="s2_3_1"><title>2.3.1. FTIR-ATR Spectrometry</title><p>FTIR analysis is performed using a Shimadzu IRAffinity-1 CE instrument equipped with a diamond crystal operating in ATR mode. The ground fiber sample was placed on the crystal and then pressed with a flat-tip piston (150 N). The IR spectra were analyzed in transmission mode and recorded in a wave range of 400 to 4000 cm<sup>−1</sup>, by an accumulation of 24 scans and with a resolution of 4 cm<sup>−1</sup> in a room with a temperature of 23˚C relative humidity 65% RH.</p></sec><sec id="s2_3_2"><title>2.3.2. Determination of the DRC</title><p>The DRC was performed according to the two standards, ISO 124 for total solids content (TMST) and ISO 126 for dry rubber content (DRC) of the latex concentrate respectively. The determination of dry rubber content (DRC) is calculated using Equation (1). A test sample of latex concentrate is diluted to 20% (by mass) of total dry extract and acidified with acetic acid. The coagulated rubber is then formed into a sheet and dried at 70˚C &#177; 5˚C.</p><p>DRC = m 1 m 0 &#215; 100 (1)</p><p>where m 0 = mass in grams of the test sample; m 1 = mass in grams of the dried leaf.</p></sec><sec id="s2_3_3"><title>2.3.3. Examination of the Microstructure by Scanning Electron Microscopy (SEM)</title><p>Scanning electron microscope observations were performed on the longitudinal surfaces of treated and untreated TC and BS fibers. These samples were coated with a thin layer of gold by sputtering with an Edwards metalizer before being analyzed with a HITACHI TM 3000 Scanning Electron Microscope (SEM) with an accelerating voltage of 15 kV.</p></sec></sec><sec id="s2_4"><title>2.4. Manufacturing of Biocomposites</title><p>All materials were weighed and mixed according to the ratios shown in <xref ref-type="table" rid="table2">Table 2</xref>. Mixing of the composite components was performed using a twin-screw mixer rotating in opposite directions. The rotor speed and roll spacing were set at 45 rpm and approximately 3 mm, respectively. The initial mixing temperature was maintained at about 70˚C. The mixed TC/BC/NR plant fiber composites were pressed using a 40-ton hydraulic press with platens heated to 150˚C and shaped into composite sheets (<xref ref-type="fig" rid="fig2">Figure 2</xref>(a)) with dimensions of 150 mm &#215; 200 mm and the thickness of 3 mm was fixed by the use of the metal wedges after dehumidification for 2 hours at 65˚C. Once the sample sheet was ready, it was cut according to the requirements of the test sample (<xref ref-type="fig" rid="fig2">Figure 2</xref>(b) and <xref ref-type="fig" rid="fig2">Figure 2</xref>(c)).</p></sec><sec id="s2_5"><title>2.5. Water Absorption Test</title><p>Ten 20 mm &#215; 20 mm &#215; 3 mm specimens for different composite formulations were prepared according to ASTM D570. The biocomposite specimens were previously dried in an oven at a temperature of 60˚C for 24 h. They were immersed in distilled water for eight days and weighed every 24 h using a balance with an accuracy of 10<sup>−3</sup>. They were immersed in distilled water for eight days and weighed every 24 hours using a balance with a precision of 10<sup>−3</sup>. The water absorption rate was calculated using Equation (2).</p><p>A b s = W ( t ) f − W ( t ) i W ( t ) i &#215; 100 (2)</p><p>where W ( t ) f is the mass of the sample at the time t, W ( t ) i initial mass of a test specimen.</p><table-wrap id="table2" ><label><xref ref-type="table" rid="table2">Table 2</xref></label><caption><title> Composition of Natural rubber mixtures</title></caption><table><tbody><thead><tr><th align="center" valign="middle"  rowspan="2"  >Ingredient</th><th align="center" valign="middle"  colspan="3"  >Composition (phr)</th></tr></thead><tr><td align="center" valign="middle" >NR40T-60B</td><td align="center" valign="middle" >NR50T-50B</td><td align="center" valign="middle" >NR60T-40B</td></tr><tr><td align="center" valign="middle" >NR</td><td align="center" valign="middle" >100</td><td align="center" valign="middle" >100</td><td align="center" valign="middle" >100</td></tr><tr><td align="center" valign="middle" >Stearic acid</td><td align="center" valign="middle" >2</td><td align="center" valign="middle" >2</td><td align="center" valign="middle" >2</td></tr><tr><td align="center" valign="middle" >Zinc oxide</td><td align="center" valign="middle" >2</td><td align="center" valign="middle" >2</td><td align="center" valign="middle" >2</td></tr><tr><td align="center" valign="middle" >Acetic acid</td><td align="center" valign="middle" >5</td><td align="center" valign="middle" >5</td><td align="center" valign="middle" >5</td></tr><tr><td align="center" valign="middle" >Short vegetable fibers (0.1 - 3 mm)</td><td align="center" valign="middle" >0, 10, 20, 30</td><td align="center" valign="middle" >0, 10, 20, 30</td><td align="center" valign="middle" >0, 10, 20, 30</td></tr><tr><td align="center" valign="middle" >Sulfur</td><td align="center" valign="middle" >5</td><td align="center" valign="middle" >5</td><td align="center" valign="middle" >5</td></tr><tr><td align="center" valign="middle" >Soya oil</td><td align="center" valign="middle" >2</td><td align="center" valign="middle" >2</td><td align="center" valign="middle" >2</td></tr></tbody></table></table-wrap></sec><sec id="s2_6"><title>2.6. Determination of Density</title><p>The density of the developed composites was determined in accordance with the NF P 94-054 standard. The composites were cut to dimensions of 30 mm &#215; 30 mm &#215; 3 mm. For this test five samples were prepared. The density was calculated using Equation (3):</p><p>ρ c = m c L &#215; l &#215; e (3)</p><p>where m<sub>c</sub> is the mass of the composite in (kg), L the length in (m), l the width in (m), e the thickness in (m) and ρ c the apparent density in (kg/m<sup>3</sup>).</p></sec><sec id="s2_7"><title>2.7. Mechanical Properties</title><sec id="s2_7_1"><title>2.7.1. Mechanical Properties in Traction</title><p>The tensile elastic properties (tensile strength and elongation at break) of the composite sheets were characterized according to EN-ISO 37:1998 using a universal tensile testing machine (LDW-1, China) in the shape of a dumbbell. The tensile speed was 500 mm/min. Four different dumbbell-shaped specimens (<xref ref-type="fig" rid="fig2">Figure 2</xref>(c)) with an average thickness of 3 mm over the measurement length were tested, and the average value for each formulation was reported.</p></sec><sec id="s2_7_2"><title>2.7.2. Hardness Test</title><p>The hardness of the samples was determined using a Shore A hardness tester with a Leeb hardness tester model TH110g equipment used by Tamwo et al. [<xref ref-type="bibr" rid="scirp.119506-ref34">34</xref>]. Composite samples (50 mm &#215; 50 mm &#215; 3 mm) were used to perform the measurements.</p></sec></sec></sec><sec id="s3"><title>3. Results and Discussion</title><sec id="s3_1"><title>3.1. Examination of the Morphology of Plant Fibers</title><p><xref ref-type="fig" rid="fig3">Figure 3</xref>(a) and <xref ref-type="fig" rid="fig3">Figure 3</xref>(b) show the longitudinal surface of the plant fibers in the study before and after alkaline treatment. It is possible to see in <xref ref-type="fig" rid="fig3">Figure 3</xref>(a) and <xref ref-type="fig" rid="fig3">Figure 3</xref>(b) the presence of impurities and small rough areas on the raw fiber surface of TC and BS. These can lead to a decrease in the tensile strength [<xref ref-type="bibr" rid="scirp.119506-ref14">14</xref>]. With chemical treatment, the surfaces that were covered with impurities become clean. This surface cleaning has also been observed in the literature [<xref ref-type="bibr" rid="scirp.119506-ref17">17</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref18">18</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref19">19</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref20">20</xref>]. However, the treated TC fiber does not show a tilt angle unlike BS fibers which show micro-fibrillar angles. These phenomena observed on the surfaces of treated fibers (<xref ref-type="fig" rid="fig1">Figure 1</xref>(c) and <xref ref-type="fig" rid="fig1">Figure 1</xref>(d)) would contribute to improving the adhesion characteristics due to the increase in roughness which is rather beneficial for adhesion.</p></sec><sec id="s3_2"><title>3.2. Fourier Transform Infrared Spectroscopy (FTIR)</title><p>The FTIR spectra were used to highlight the effect of chemical treatment on TC and BS plant fibers presented in <xref ref-type="fig" rid="fig4">Figure 4</xref>. In this study, an emphasis is placed on the functional groups of lignin, hemicellulose, cellulose which have more influence on the mechanical properties.</p><p>The FTIR spectra are presented in this figure, and show particularly seven characteristic peaks; the first with a length of about 3345.33 cm<sup>−1</sup> represents the hydrogen bonds (O-H) of cellulose and the hydroxyl groups of hemicellulose [<xref ref-type="bibr" rid="scirp.119506-ref10">10</xref>]. An absorption band characteristic of the presence of liquid water is more or less bound to the polymeric network constituting natural fibers. The value 1726.23 cm<sup>−1</sup> represents that characteristic of the bond of the stretching of the carbonyl C=O of the carboxylic acid. It could also possibly be the ester representing the non-cellulosic group internal to pectins, waxes and acetyl groups present in hemicelluloses. The latter is attenuated on the TC fiber by the chemical treatment. Peaks 1604.08 cm<sup>−1</sup> and 1514.10 cm<sup>−1</sup> represent lignin, characteristic of C=C stretches of the aromatic backbone of lignin. The absorption band at 1424.86 cm<sup>−1</sup> is associated with the CH<sub>2</sub> symmetric bending present in cellulose [<xref ref-type="bibr" rid="scirp.119506-ref10">10</xref>] - [<xref ref-type="bibr" rid="scirp.119506-ref24">24</xref>]. The two peaks presented at 1370.80 cm<sup>−1</sup> and 1318 cm<sup>−1</sup> respectively to the bending vibration of (C-H) and (C-O) groups of the aromatic ring in polysaccharides. A reduction of this peak is observed after treatment on the TC fiber. The absorption band 1239 cm<sup>−1</sup> and 1159.68 cm<sup>−1</sup> corresponds to the (-COO) group of the hemicellulose. Finally, the peak at 897.49 cm<sup>−1</sup> can be attributed to the β-1,4 glycosidic bonding of the (C-O) groups of cellulose [<xref ref-type="bibr" rid="scirp.119506-ref10">10</xref>]. This analysis demonstrates not only that sugarcane bagasse and Triumfettacordifolia that the different treatments influence the structure of TC and BCS fibers as observed in the literature [<xref ref-type="bibr" rid="scirp.119506-ref21">21</xref>]. This confirms the increase in the percentage of cellulose in the fibers, especially after hydrogen peroxide bleaching.</p></sec><sec id="s3_3"><title>3.3. DRC Content</title><p>The results of the DRC of the NR are made in duplicate and agree to within 1% (in mass) of the average value according to the standard. The different DRC obtained show the following values 35.981% and 36.923%, with an average value of 36.452% DRC for all experiments.</p></sec><sec id="s3_4"><title>3.4. Characterization of Biocomposites</title><sec id="s3_4_1"><title>3.4.1. Apparent Density</title><p>The bulk density of the composites containing 10, 20, 30 phr of treated TC and BS fibers was analyzed. The TC and BS fibers taken in the mass ratio of 40: 60, 50:50 and 60:40 respectively are presented in <xref ref-type="fig" rid="fig5">Figure 5</xref>. It is observed that the addition of the plant fibers in the virgin NR matrix lightens the composite materials [<xref ref-type="bibr" rid="scirp.119506-ref36">36</xref>]. This could be beneficial for automotive carpets in particular and the lightening of parts used in automotive interiors in general. It is also observed that there is a decrease in density as the volume fraction of fibers increases in the NR matrix. Hybrid composites with an equal fiber ratio (NR50T-B50) offer a good mass gain compared to the others. This can be justified by the density of the TC fiber reinforcement (1.47 g/cm<sup>3</sup>) which is slightly close to that of the BS fibers (1.23 g/cm<sup>3</sup>). At the same time, this increased lightness in the composites is also favored by the chemical treatment performed. Indeed, after such treatment, the decrease in the diameter and weight of the fibers is proven due to the removal of lignin, impurities and non-lignocellulosic compounds that the fibers contain on the surface as indicated in the literature [<xref ref-type="bibr" rid="scirp.119506-ref18">18</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref20">20</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref35">35</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref36">36</xref>].</p></sec><sec id="s3_4_2"><title>3.4.2. Water Absorption</title><p>The trend in the graph (<xref ref-type="fig" rid="fig6">Figure 6</xref>) indicates that as the fiber volume fraction increases, the value of the water absorption coefficient also increases.</p><p>At the same time, the polymer composites with a higher amount of TC fibers (NR60T-40B) showed a lower water absorption value. This suggests that this is the optimal ratio. This, therefore, indicates that the chemical treatment performed on the raw TC fibers decreased the high presence of hydroxyl groups that are responsible for the excessive water absorption and moisture as shown in the FTIR spectra (<xref ref-type="fig" rid="fig4">Figure 4</xref>) and reported in the literature [<xref ref-type="bibr" rid="scirp.119506-ref9">9</xref>], thus enhancing the good adhesion between the fiber and the NR matrix of our composites. Similar work has shown that by treating the fiber, the hydrophilicity was reduced which improves the interfacial bonding between the fiber and the matrix [<xref ref-type="bibr" rid="scirp.119506-ref14">14</xref>] - [<xref ref-type="bibr" rid="scirp.119506-ref36">36</xref>].</p></sec><sec id="s3_4_3"><title>3.4.3. Tensile Behavior</title><p>In the present study, the behavior of composites containing 10, 20, 30 phr of</p><p>treated TC and BS fibers was analyzed. The TC and BS fibers were taken in the ratio of 40:60, 50:50 and 60:40 respectively. It can be seen that the tensile strength of the virgin NR matrix increased with the addition of the plant fibers. This may be an indication of the excellent interactions between the fiber surface and the natural rubber matrix.</p><p>These results corroborate those reported in the literature [<xref ref-type="bibr" rid="scirp.119506-ref37">37</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref38">38</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref41">41</xref>]. From <xref ref-type="fig" rid="fig7">Figure 7</xref>, it is clear that the tensile strength increases up to 20 phr of fibers in natural rubber for composites containing an equal fiber mass ratio (TC/BS) (NR50T-50B20). This family of composites has maximum tensile strength (3.74 MPa) and minimum ductility. This suggests that this is the optimal ratio. However, it is also observed that composites containing a dominant TC fiber mass fraction (NR60T-40B) also offer more interesting mechanical properties in tension than those with more sugarcane bagasse fibers in the constitution (NR40T-60B). Indeed, when the concentration of TC fibers increases, the tensile strength also increases. This suggests that the tensile strength of the composite depends more on the weight of the TC fibers, cellulose (44.4%) rather than that of the sugarcane bagasse fibers (22.7% cellulose), which could be due to the high strength of the TC fiber without forgetting their flexibility and their ability to plug the pores well in the composite. In addition, this improvement in properties also depends on the treatments performed on the fibers. Indeed, it has been reported in the literature [<xref ref-type="bibr" rid="scirp.119506-ref18">18</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref28">28</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref37">37</xref>] [<xref ref-type="bibr" rid="scirp.119506-ref39">39</xref>] that the alkaline treatment increases the roughness of the fiber surface and consequently increases the surface available for contact with the matrix.</p><p>As for the elongation of hybrid composites, it is found that when the volume fraction of the fibers also increases, the elongation at break decreases. This reduction indicates that the ductility decreases when TC and bagasse fibers are added to the natural rubber matrix. Similar observations were observed in the work of Moonart &amp; Utara [<xref ref-type="bibr" rid="scirp.119506-ref39">39</xref>]. The literature Manaila et al. [<xref ref-type="bibr" rid="scirp.119506-ref40">40</xref>] also reports that this behavior is due to the restriction of molecular chain movement by the fiber.</p></sec><sec id="s3_4_4"><title>3.4.4. Hardness</title><p>The hardness of composites containing 10, 20, 30 phr of treated TC and BS fibers was analyzed. The TC and BS fibers were taken in the same proportions as before and are presented in <xref ref-type="fig" rid="fig8">Figure 8</xref>. The maximum hardness is obtained with the addition of the fibers in the NR matrix. This is due to the reduction of elasticity generated by the reinforcement of the molecules [<xref ref-type="bibr" rid="scirp.119506-ref28">28</xref>].</p><p>The results also show that NR40T-60B composites have a low hardness and it remains below 40 whatever the fiber content. On the other hand, the incorporation of soft TC fibers at 50% and 60% mass levels in the hybridization with BS fibers in the NR matrix (NR50T-50B and NR60T-40BS) show a gradual increase in hardness as the fiber content increases. The fiber-rubber interphase is strong and better in the composites as well as the dense arrangement in the composite</p><p>as corroborated by the literature [<xref ref-type="bibr" rid="scirp.119506-ref41">41</xref>]. These composites with strong bonds are harder because they prevent the movement of the matrix in the direction of stress. Thus, the hardness of the developed materials is also improved compared to pure latex.</p></sec></sec></sec><sec id="s4"><title>4. Conclusion</title><p>At the end of this study, hybrid biofibers (Triumfettacordifolia and sugarcane bagasse) were incorporated into a natural rubber matrix. The results obtained during the experimental campaign showed that the chemical treatment carried out improved the quality of the fiber-matrix adhesion. The addition of fibers in the developed hybrid composites increases the water absorption capacity but gradually lightens them with increasing fiber shares. Moreover, in terms of mechanical properties, the addition of plant fibers in the virgin matrix of NR improves the tensile strength and hardness but decreases its ductility. The hybrid composites with equal proportion of plant fibers presented better characteristics with optimal ratio of NRT50-50B. In view of the results obtained, the addition of vegetable fibers in the NR matrix is an alternative to carbon black and these materials can find many technical, industrial and commercial applications such as car mats, shock absorbers for doors in the building industry.</p></sec><sec id="s5"><title>Acknowledgements</title><p>The authors would like to thank the Centre d’Essais Textile Lorrain (CETELOR) in Epinal, (France), the Centre de Caract&#233;risation des Mat&#233;riaux (CeCaM) in Douala (Cameroon) and authors of the references.</p></sec><sec id="s6"><title>Conflicts of Interest</title><p>The authors declare no conflicts of interest regarding the publication of this paper.</p></sec><sec id="s7"><title>Cite this paper</title><p>Njom, A.E., Mewoli, A., Ndengue, M.J., Ebanda, F.B., Nitidem, A.D., Otiti, S.B., Youssi Bang, Y.D., Belinga, L.N., Noah, P.M.A. and Ateba, A. (2022) Hybrid Composite Based on Natural Rubber Reinforced with Short Fibers of the Triumfetta cordifolia/Saccharum officinarum L.: Performance Evaluation. Journal of Minerals and Materials Characterization and Engineering, 10, 385-399. https://doi.org/10.4236/jmmce.2022.105027</p></sec></body><back><ref-list><title>References</title><ref id="scirp.119506-ref1"><label>1</label><mixed-citation publication-type="other" xlink:type="simple">Ndiwe, B., Konai, N., Pizzi, A., Karga, L., Kaoutoing, M.D. and Danwe, R. (2022) Mechanical Performance of a Particleboard Based on Natural Hardener. Wood Material Science &amp; Engineering. https://doi.org/10.1080/17480272.2022.2025899</mixed-citation></ref><ref id="scirp.119506-ref2"><label>2</label><mixed-citation publication-type="other" xlink:type="simple">Ndiwe, B., Tibi, B., Danwe, R., Konai, N., Pizzi, A. and Amirou, S. 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