Characteristics and Comparative Study of Sodium Hydroxide Treated Banana Fiber Reinforced Composite Material

Environmental issues have become a worldwide crisis because of the high rate of pollution and changing climate patterns. Due to innovations and discoveries, the need for materials is increasing day by day. Here, composite materials can be substituted for any other mono-clinic materials fulfilling the requirements of those particular materials. However, the maximum composite materials are man-made or artificially fabricated fibers. These are not environmentally friendly and bio-degradable, which creates an environmental hazard. So, scientists are trying to fabricate composite materials from eco-friendly and green resources. The main advantages of natural fibers are their low cost, easy availability, and low density. Besides these acceptable specific properties, ease of separation, increasing energy recovery, carbon-oxide neutrality, and recyclable properties are increasing the popularity of natural fiber. In this study, we have used mainly two types of banana fiber for preparing the composite specimens, especially highlighting the hybrid fiber, which is made by mixing those two types of fiber: “Shobri” and “Champa” banana fibers. These names are renowned locally in Bangladesh. In this study, polyester and MEKP are used as matrix and hardener sequentially. We have accomplished a chemical treatment process. The treating process was accomplished in the alkaline medium with two different molar concentrations of NaOH. These are 1% and 5% solutions of NaOH. After the treatment neutralization process was performed with a 1 gm/L acetic acid solution. In addition, two distinct mechanical tests— the bending and tensile tests—were carried out. The results indicated that the hybrid fiber treated with 1% NaOH had the highest tensile properties; its Young’s modulus was around 625 MPa and its tensile strength was approximately 36.42 MPa. The tensile strength and Young’s modulus of Champa banana fiber treated with 1% and 5% NaOH solutions were the lowest, respectively. Approximate values are 1.82 GPa and 18.3 MPa. The flexural strength of hybrid fiber treated with 1% and 5% NaOH was the highest and lowest in that order. 69.2 MPa and 56.21 MPa, respectively, are their values. Regarding flexural modulus, Champa fiber treated with 5% and 1% NaOH exhibits the highest and lowest values, measuring roughly 4 and 1.82 GPa, respectively.


Introduction and Research Background
An ordinary composite material is a macroscopic system of materials made of two or more components that have been combined and bonded.Typically, reinforcement (fibers, particles, flakes, and fillers) is included in a matrix to create a composite material (polymers, metals, or ceramics).While the reinforcement enhances the matrix's overall mechanical qualities, the matrix holds the reinforcement to create the desired shape.When properly engineered, the new composite material demonstrates more strength than either of the constituent materials alone [1].Composite materials can be made from both natural and artificial resources.Comparatively speaking, dealing with natural fiber-based composites is safer and simpler than with synthetic reinforcements.The most intriguing feature of natural fibers is how beneficial they are to the environment.They are entirely biodegradable and non-abrasive because they are made from a natural resource.After the polymer has degraded, they are simple to remove.Additionally, the cellular structure offers superior insulating qualities [2].Banana fiber is one of the natural fibers that has excellent mechanical properties due to its high abundance and low cost along with more advantages.
A solid bond between the fibers and the polymer matrix is required.Poor interface adhesion prevents a composite from reaching its full potential and makes it vulnerable to environmental attacks, which can weaken it and reduce its useful life.Insufficient adhesion between hydrophobic and hydrophilic polymers and the fibers is the reason for the poor mechanical properties of polymer composites supplemented with natural fiber.Natural fibers play a significant part in the aging of bio-composites in a humid environment or by immersion in water due to their hydrophilic nature [3].Arbelaez used immersion in distilled water at room temperature to study the impact of water absorption on the sorption characteristics of the linen fiber package and polypropylene (PP) compounds.The findings demonstrated that water absorption increased as the content of the fiber bundle rose, which is also evident in the mechanical characteristics [4].To create composite laminates with desired directional qualities, fiber and epoxy are employed as the lamina.Using the rule of mixtures, the mechanical properties of composites are obtained from the characteristics of the fiber and matrix, and the volume percent of the fiber is a key factor in determining the mechanical properties.In this study, the value of the fiber volume percent is calculated by accounting for the components of the fibrous structure, such as random fiber, yarns, or fabric [5].The diameter variability and mechanical characteristics of banana fibers extracted from the stem of the banana plant (Musa sapientum) have been studied, with a focus on fracture morphology.SEM analysis has been used to examine the characteristics of representative stressstrain curves and fractures at various strain rates [6].The excellent physical and mechanical qualities of natural fibers allow for their efficient use in the creation of composite materials for a variety of structural applications.This article provides a general overview of the mechanical characteristics of banana fiber composites.Also covered are the benefits of adopting natural fibers over conventional materials and their potential future expansion.The experimental results showed that composites with 15 weight percent of banana fiber display the optimum mechanical performance [7].In recent years, natural fibers have drawn a great deal of attention and research.They have captured the interest of scientists and researchers due to their exceptional benefits and substantial evidence that materials from natural resources may be obtained and reinforced in environmentally benign ways.Natural fibers are typically categorized by their sources, such as plants, minerals, and animals.In the composites business, plant fibers have recently been employed to reinforce plastics.There are many different plant fibers, including cotton, kapok, flax, hemp, jute, ramie, sisal, and others.A lack of raw resources is a huge challenge for the manufacturing sector.Environmental concerns are another issue.The "greener" trend has sparked interest in this subject among researchers all over the world [8].

Material
Materials that were used for this experiment are 2 types of banana fiber, polyester as the matrix, Methyl Ethyl Ketone Peroxide (MEKP) as a hardener, and two different concentrations of NaOH for treatment purposes.Acetic acid was used to neutralize the effects of NaOH in the fibers.The banana fibers that were used in this experiment were "Champa" and "Hybrid".There was another type of banana fiber called "Shobri" which was used to make "Hybrid fiber" by combining both "Shobri" and "Champa" fibers.

Preparations of composites
At the beginning of this study, banana fiber was collected from the banana trunk, leaves, stems, etc. by combing.The preparation process adopted here is a hand lay-up process followed by applying pressure using compression molding.The fiber mats of uniform thickness were prepared from banana fibers of a particular length.The composite consisted of 3 layers of banana fibers.At first, a polyethylene sheet was put on the glass and a mixer of polyester and MEKP was poured into it.Then the 1st layer of fiber was placed on the mixer.Then again, the mixer was poured and the 2nd layer was placed, and finally, we placed the 3rd layer by a similar process.Lastly, we poured all the mixer on the fiber.This entire process was done manually.Moreover, accurate fiber alignment provided almost zero void in the prepared composite material.As a result, the strength of the banana fiber-reinforced composite increased.After that, the fibers were dried for 24 hours.Then, the fibers were rinsed with distilled water as mineral water could affect the properties.Then they were separated into a batch for treatment with two different concentrations of NaOH solutions.To improve wettability NaOH was used to treat the banana fiber.Some fibers were put into 1% NaOH solution and the rest into 5% NaOH separately for 45 minutes.After that, they were washed with distilled water and kept in the oven for 48 hours at 72°C for drying and then washed again with distilled water before putting them into a 1% acetic acid solution for 45 minutes.For the final step, they were washed and dried again in the oven for 48 hours at 100°C [9].

Tensile Test
The specimens were prepared according to the ASTM D638 standard (T-bone shape) [10].The tensile test was carried out on the Universal Testing Machine (UTM) Make Hounsfield (Model: H10KS, Sl.No. H10KS-0572).In total, 36 Specimens were prepared for the tensile test.However, we used 33 specimens as three of the samples of 1% NaOH+ Champa were damaged during the sample preparation.The process involved placing the test sample in the UTM and applying tension to it until the fracture of the material.As a result of the gauge length increased, the force was then measured and recorded.The gauge section's elongation as a function of the applied force was measured as tension was applied.

T-bone Shape
We calculated the volume fraction of both fiber and matrix from the treated specimens.We tried to keep the fiber percentage near about 15-16%.Details of measurements are presented in Table I.After that, we found the load vs deflection graph, tensile, flexural, Young's modulus, and flexural modulus from those banana specimens.

Load vs Deflection
When the four specimens were compared in Fig. 2, sample 02(i) had the maximum load of nearly 1000N load under the 2mm deflection point.Comparatively speaking to the other two specimens, specimen 01(i) has the second-greatest loading condition.The lowest loading condition on the graph above is for specimen 03(i) and is close to 500N.In Fig. 3 Specimen 07(i) (5% NaOH treated Champa) has the highest level of deflection with a loading range of 400 to 450N.Interestingly, Specimen 06(i) has achieved almost 500N loading conditions with minimum deflection compared to the others.But specimen 06(ii) has achieved the smallest load of 200N with a deflection that is slightly greater than 0.5mm.4 shows that specimens 02(i) and 01(i) have the highest loading condition as well as the greatest deflection when compared to the other two specimens.It is observed that the specimens that are treated with 1% concentrated NaOH have shown stable and higher values than the 5% NaOH-treated specimen.In Fig. 5, specimen 06(i) shows a high loading capacity of about 500 N with minimum deflection.Specimen 06(ii) has given the lowest load among the four specimens.

Stress vs Strain
Fig. 6, shows that specimen 02(i) has the highest stress value with a strain of .07mmapproximately.Moreover, all the specimens show an upward and linear trend.In Fig. 7, it is seen that specimens 06(i) and 10(i) have followed similar patterns in the beginning.But after that, specimen 10(i) shows more strain with stress value than specimen 06(i).Specimen 07(i) has the highest stress along with strain.In Fig. 8, specimen 02(i) has the highest stress value of about 45 MPa and the smallest deflection of.07mm.On the other hand, the 5% NaOH-treated hybrid gives the lowest stress, which is almost 15 MPa.Among the four specimens in Fig. 9, specimen 07(i) can withstand the highest stress with the greatest deflection.Specimen 06(ii) shows the lowest value of stress, which is 10 MPa.

Flexural Test
The flexural specimens were prepared as per the ASTM D790 standards and the test was carried out using the same UTM.The 3-point flexural test is the most common flexural test and was used in this experiment to check the bending strength of the composite materials.The testing process involves placing the test specimen in the UTM and applying force to it until it fractures and breaks.16 specimens were prepared for the flexural test.

Rectangular shape
In Fig. 10, specimens 01(a) and 02(a) have higher flexural load and lower deflection compared to specimens 04(a) and 05(a).It is also seen that the Champa specimens have the lowest load and highest deflection among the four specimens.On the other hand, in Fig. 11, specimen 11(a) has achieved the highest load with linearity along with low deflection.The 5% NaOH treated Champa specimen 06(a) performed almost identically to the hybrid specimen 10(a) until 120N.On the contrary, specimen 07(a) has shown the lowest loading capacity with the greatest deflection.13 shows that specimen 07(a) has the lowest flexural load as well as the greatest deflection.It is also observed that the load was constant, which is 60N, and for this deflection, the range is 6mm to almost 8.5mm.On the other hand, specimen 08(a) followed the linear trend to nearly 4mm of deflection, then the line fell.But still, it has the highest load of all the samples, and the result is slightly greater than 140N.

Tensile Strength Analysis
In Fig. 14, we can see that specimen 2(i) has given the highest tensile strength and specimen 3(i) the lowest, though they are both treated with 1% NaOH, and in Fig. 15, specimen 06(ii), which is a 5% NaOH treated Champa specimen, has the lowest value for tensile strength.Specimen 8(i), which is also Champa fiber treated with the same concentration of NaOH, has the highest value.In Fig. 26, it is noticed that the tensile strength of the 1% NaOH+ Hybrid fiber sample is the highest and the lowest one is 1% NaOH+ Champa Fiber.In Fig. 27, Young's modulus is figured out and it is visible that the highest one is 1% NaOH+ Hybrid fiber and the lowest one is 5% NaOH+ Champa fiber.In Fig. 28, the values of flexural strength are represented.Here, the upscale one is 1% NaOH + hybrid fiber and the downscale one is 5% NaOH+ hybrid fiber.The highest and lowest flexural modulus are of 5% NaOH+Champa fiber and 1% NaOH+Champa fiber.The values are illustrated in Fig. 29.In Fig. 30 it is seen that the tensile strength, Young's modulus, and flexural strength of hybrid fiber treated with 1% NaOH solution are the highest among the four samples.These results indicate that 1% NaOH+Hybrid fiber shows the highest ductility and stiffness.Moreover, it also shows that this specimen needs the highest impact force to bend.Theoretically, it is known that the higher the flexural strength, the higher the flexural modulus.Surprisingly, despite having the highest flexural strength, its flexural modulus is comparatively lower than Champa fiber treated with 5% NaOH solution.Many reasons can be found behind this factor, which can be investigated in the future.Furthermore, Fig. 30 demonstrates that the fibers treated with the least amount of NaOH had superior tensile characteristics compared to the fibers treated with the most NaOH.Similarly, hybrid fiber treated with 1% NaOH has the best value of flexural strength.The hybrid fiber treated with 5% NaOH exhibits the best flexural properties when taken into account overall.But when all mechanical attributes are taken into account, it becomes evident that the treatment with the least amount of NaOH provides the best results.It has also been discovered that the hybrid banana fiber performs better than the Champa fiber in every mechanical property.The hybrid banana fiber's increased qualities are mostly due to the combination of the two distinct forms of banana fiber named "Champa and Shobri".Excessive chemical treatment has denigrated the tensile properties.In terms of flexural strength, 1% NaOH-treated hybrid fiber shows the highest value, which is 69.2 MPa.However the flexural modulus slightly falls in the case of 1% NaOH-treated banana fiber, and the value is 3.14 GPa.The values could be more accurate and precise if we took some extra samples for the mechanical testing.The hybrid banana fiber can be the best choice in this experiment, as the Champa fiber shows poor mechanical properties.In the future, the mechanical properties of banana fiber can be upgraded by blending three or four different types of banana fiber.It is also suggested that excessive chemical treatment should be prohibited as it hampers the overall properties.The presence of any liquid substance could disturb the properties of the tested samples.So, it is suggested that the drying process should be perfect so that no moisture content is present in the fiber.In the future, we can change the fiber alignment and orientation to get better and more desirable mechanical properties.

Table 2 .
Tensile Strength and Young's Modulus

Table 3 .
Specimen Dimensions for Utm with Jaw

Table 4 .
Flexural Strength and Modulus