Characteristics of bioplastics prepared from cassava starch reinforced with banana bunch cellulose at various concentrations

Human activities have led to the pollution of the environment through the accumulation of plastic waste. Since plastics are resistant to decomposition resulting negative impact on the environment, there is a pressing need for the development of bioplastics. Starch is a such of natural material that can be used made of bioplastics. However, bioplastics from starch were needed to improve starch-based bioplastics due to their brittle properties. To address this issue, researchers focused on enhancing starch-based bioplastics by incorporating cellulose, particularly derived from kepok banana bunch fibers and cassava starch variety UJ3. The production process involved adding varying concentrations of 2.5, 5, 7.5, and 10 % (wt) of kepok banana bunch cellulose. The findings indicated that increasing cellulose concentration improved the characteristics of the bioplastic materials significantly. The results showed that the addition of cellulose concentration improved the mechanical properties, water vapor absorption, and biodegradability of bioplastics. With an optimal cellulose concentration level at 7.5%, remarkable enhancements in tensile strength (from 2.92 to 6.72 MPa), reduced elongation percentage (from 20.89 to 4.06%), increased Young’s Modulus values (from 13.98 to 172.52 MPa), decreased water vapor absorption rate (from 15,93 to 11,48%), and enhanced bio-degradability rating (from 29,81 to 50,69%) were observed.


Introduction
The demand for and usage of plastics continues to rise due to their versatility in meeting primary, secondary, and tertiary needs.Plastic bag production is the world's largest production of 60 million tons and the utilization of plastic bags was estimated at a staggering 1 trillion in 2016 [1].Plastic is commonly employed in packaging thanks to its various advantages, including resistance to rust, flexibility, waterproof nature, cost-effectiveness in production, and durability against damage.These merits have led to an increasing need for plastic bags and the consumption of plastics every year [2].However, the widespread use of plastic has also resulted in a substantial environmental issue specifically plastic waste [3].According to research by Sustainable Waste Indonesia (SWI), plastic waste accounts for as much 1309 (2024) 012006 IOP Publishing doi:10.1088/1755-1315/1309/1/012006 2 as 14% of all waste globally, and its proper management remains a significant challenge [4].Mainly, plastic waste can take over a century to decompose fully [5].Therefore, in response to these issues, a shift towards using environmentally friendly alternatives, such as bioplastics is a viable solution.
Bioplastics are a type of environmentally friendly plastic that can naturally decompose.The development interest in bioplastic production is primarily due to its capacity to employ natural raw materials [6].Starch derived from sources such as tubers and cereals, stands out as a key raw material for bioplastic production [7].Starch is a material that has bioplastic production due to its ability to be easily degraded by microorganisms and making it an environmentally friendly choice.Moreover, it is cost-effective, abundant, and a renewable resource [8].Previous research has demonstrated the potential of starch-based bioplastics.Bioplastics made from taro tuber starch exhibited a tensile strength value of 7.595 MPa [9].Bioplastics derived from avocado seeds produce tensile strength values of 6.4 MPa and water absorption ranging from 120.86% to 127.32% at temperatures between 26 to 50 °C [10].Furthermore, bioplastics produced from sweet potato starch demonstrated the ability to degrade in soil within just 8 days [11].Several studies have reported the feasibility of obtaining starch from carbohydrate-rich plant sources such as corn [12], taro [13], and cassava [14].Based on these findings, starch exhibits significant potential as a raw material for the production of bioplastics.
Cassava is one potential source of starch to be developed.According to the Ministry of Agriculture, cassava production in Indonesia in 2019 reached a substantial 21,943,400 tons, with Lampung Province contributing 4,929,044 tons of cassava [15].Cassava can be classified into two types based on the hydrogen cyanide (HCN) content [16].Cassava varieties that contain toxic levels of HCN are unsuitable for consumption but can serve as a valuable source of starch for bioplastic production.One of the toxic cassava is cassava variety UJ3 (Thailand) which has a starch content of 21.37% [17].Previous research produced bioplastics with tensile strength values ranging from 3.3 to 33.76 MPa and capable of degrading in soil over a period of 14 to 15 days [18]- [20].However, starch-based bioplastics exhibit certain disadvantages, including hygroscopicity, low mechanical properties, and high water vapor absorption.To address these limitations, cellulose can be employed as a reinforcing material [21].Consequently, reinforcing materials such as cellulose are the potential for enhancing the characteristics of cassava starch-based bioplastics.
Cellulose can be sourced from plants that are abundantly available in nature.Cellulose offers a range of advantages, including high mechanical properties, low density, environmental friendliness, nontoxicity, and renewability [22].Cellulose is composed of both crystalline and amorphous regions with varying amounts of content based on the source material [23].previous research has reported that the addition of cellulose reinforcement to cassava starch-based bioplastics can significantly enhance their properties.Cassava starch-based bioplastics with the addition of cellulose can increased the tensile strength of bioplastics from 3.3 MPa to 14.3 MPa [20].Additionally, the water vapor absorption properties of these bioplastics can be reduced from 23% to 18%, enhancing their resistance to moisture [24].Moreover, the addition of cellulose can degrade in a more environmentally friendly, with approximately 15 days needed for degradation to reach nearly 95% [25].Cellulose can be sourced from various biomass materials, one of which comes from agricultural waste [26].Cellulose derived from agricultural waste has several advantages, such as low lignin levels, environmentally friendly, and easy renewability [27].Usually agricultural waste is underutilized, typically serving as animal feed without being optimally repurposed.One of the agricultural wastes used is banana bunches, which can be reused as a valuable source of cellulose for various applications, including bioplastics development.
Banana bunches are agricultural waste from banana harvests that have not been utilized properly.Banana bunch waste is often relegated to being animal feed and contributing to environmental pollution if not reused [28].Based on previous research, banana bunches are indicated contain cellulose in the range of 35 to 51.05% [29]- [32].The cellulose content of banana bunches has the potential to serve as a reinforcing material for the enhancement of cassava starch-based bioplastics [33].However, scientific investigations regarding the optimal incorporation of banana bunch cellulose into cassava starch bioplastics have not been previously reported.Therefore, this research aims to determine the optimal banana bunches of cellulose for cassava starch-based bioplastics and analys of the mechanical properties, water vapor absorption, and biodegradability of bioplastic was carried out with the enhancement of cellulose banana bunches.

Methods 2.2.1 Cellulose Extraction of Banana Bunches
The cellulose extraction process refers to research that has been done previously Syafri et al. [34].Banana bunches are selected and peeled to remove the outer skin.This peeling process ensures that only the inner fibers of the banana bunch are used for cellulose extraction.The peeled banana bunch fibers are then mashed to break them down into a fibrous form.The mashed banana bunch fibers are subjected to an alkalization process with a 5% NaOH solution.The alkalization of banana bunch fibers conducted using a hotplate at the temperature of 80 °C and stirred using a magnetic stirrer at a speed of 200 revolutions per minute (rpm) for a duration of approximately 1 hour.After the alkalization process, the fibers are then cleaned using distilled water until the pH of the fibers solution becomes neutral.Once the fibers are properly cleaned, fibers are dried to remove excess moisture.The dried fibers are mashed and filtered to achieve a particle size of 100 mesh.This process essentially isolates cellulose from banana bunches, making it available as a valuable reinforcing material for enhancing cassava starch-based bioplastics.

Cassava Starch Extraction
The extraction process of cassava starch is according to research that has been done previously by Natalia and Muryeti [35].The cassava is cleaned from the cassava roots and removing the outer skin and washed with clear washing water.The cassava is mashed using a blender until it becomes porridge.The cassava slurry is then finely filtered and allowed the starch to settle for a period, typically at room temperature for about 24 hours.After the precipitation period, the resulting cassava precipitate, namely primarily starch is separated from the water.The separated starch is then dried to remove excess moisture.The dried starch precipitate is filtered to achieve a particle size of 100 mesh.

Production of film bioplastics
The film bioplastics produced refers to research that has been done previously Septiosari et al. [36].Cellulose with a variation of 2.5, 5, 7.5, and 10% (wt) is combined with 10 grams of the cassava starch into a beaker containing 200 mL of distilled water.Then, the bioplastic solution is added to 2 mL glycerol and stirred for ± 15 minutes using a hot plate and magnetic stirrer at a speed of 200 rpm at 90 °C.Once the bioplastic solution has been gelatinized, it is left to cool at room temperature for a period of 2-3 hours.This allows any bubbles present in the solution to dissipate, resulting in a smoother and more uniform film bioplastic.The gelatinized bioplastic solution is poured into a petri dish with a diameter 12 cm and the weight is adjusted to 60 grams.The petri dish containing the bioplastic solution is then placed in an oven and dried at a temperature of 50°C for a duration of 20 hours.

Characterization of film bioplastics 2.3.1 Mechanical Properties of Bioplastics
Mechanical properties testing based on American Standard Testing and Materials (ASTM) standard D-882.The test samples have dimensions with a length of 8 cm, a width of 10 cm, and a thickness of < 1 mm.The mechanical properties tests on the bioplastic samples are performed using a Universal Testing Machine (UTM) Zwick Roell type all round 250 kN with a speed of 8 mm.min -1 .The mechanical properties of the bioplastics are analyzed through three parameters which are tensile strength, elongation, and Young's modulus.These properties are calculated using equations following the guidelines specified in the ASTM D5336 standard [23].The resulting tensile strength (Eq.1), elongation (Eq.2), and Young's Modulus (Eq. 3) and can calculate using the following equation: Eq. 1 where σ was tensile strength (MPa), Fmax was maximum load force (N), and A was surface area (mm 2 ) Where ∆l was long grain (mm) and l0 was the initial length (mm).

Water Vapor Absorption
The water vapor absorption of the bioplastic is determined according to research that has been done previously Asyrofi et al. [37].This test helps determine the bioplastic's susceptibility to absorbing moisture from the surrounding environment, which is essential for assessing its performance in various applications, particularly in conditions where humidity levels can impact its properties.The bioplastic samples are cut into small pieces, typically (2 × 2) cm in size.These samples are then dried in an oven at a constant temperature of 50 °C until their weight remains stable and weighed until the weight is constant (W1).The water vapor absorption test is conducted in sealed containers that are filled with saturated salt solutions, maintaining a constant relative humidity of 75 ± 5% at a temperature of 25 °C.The sample is put into a sealed container, ensuring that it is exposed to the controlled humidity conditions.The samples are periodically weighed at specified time intervals, typically at 30 minute.The process continues until the weight reaches a stable final value and a final weight (W2) is obtained.The percentage of water vapor absorption can be calculated using the following equation (Eq.4): Water vapor absorption (%) where W 1 is the initial weight of the dried sample (grams) and W 2 was the final weight of the sample (grams) after exposure in a sealed container filled with salt solutions to controlled humidity conditions.

Biodegradable
The biodegradable of the bioplastic is determined according to research that has been done previously Prachayawarakorn et al. [38].The Experiments were carried out using soil with a clay loam texture.The soil composition used in the biodegradability test had the following characteristics which is a pH of 5.6, nitrogen content of 0.282%, organic organic content of 0.603%, and calium content of 2.17 mg. 100 g - 1 .The test samples were prepared by cutting them into dimensions of (2 × 5) cm in size and dried using an oven at 50 °C until a constant weight was achieved.These dried samples were subsequently placed in the soil for specified durations, including 5, 10, and 15 days.After a specified period, the samples were removed from the soil, and their degraded mass was determined.The extent of degradation was assessed in accordance with the ASTM D5336 standard.The samples were measured the initial and final weights using an analytical balance to determine the percentage of degradation can be calculated using the following equation (Eq.5): where M1 is the initial weight of the sample (grams) and M2 was the final weight of the sample (grams) after degradation.

Data analysis
The experimental design employed in this study followed a simple completely randomized design with a single factor.The treatment given in this study involved introducing various concentrations of cellulose from banana bunches, which is 2.5%, 5%, 7.5%, and 10% (wt), while a control group without cellulose addition was included for comparison.Analysis of experimental data was performed using IBM SPSS Statistics 26.0.The data were subjected to analysis of variance (ANOVA) to assess the impact of cellulose addition on mechanical properties, water vapor absorption, and biodegradability.Subsequently, any difference in the average values of the produced bioplastics were evaluated using Duncan's Multiple Range Test (DMRT).

Mechanical Properties of Bioplastics
The tensile strength results following the addition of cellulose from banana bunches can be seen in figure 1.The addition of cellulose leads to a range of tensile strength values, ranging from 3.36 to 6.71 MPa.Notably, the impact of cellulose addition on the tensile strength of the bioplastics is a markedly different effect.An analysis of variance was performed, with a significance level of α = 0.05, show that the addition of cellulose has a significant effect on the tensile strength value.The tensile strength of bioplastics without the addition of cellulose (0%) displayed a tensile strength of 2.92%.The highest tensile strength value was observed in bioplastics that contained 7.5% banana bunch cellulose, with a value of 6.72 MPa.The results of DMRT showed bioplastics made with the addition of cellulose to a degree of 7.5% are significant different from another cassava starch bioplastics.
The tensile strength values observed in this study do not meet the requirements of ASTM D5336, which mandates tensile strength values falling within the range of 190-2050 MPa.The analysis indicates that the addition of cellulose, particularly at the 7.5% concentration, had a significant impact on enhancing the tensile strength of the bioplastics.However, the tensile strength values obtained in this study are notably lower than the ASTM standards for bioplastics.
The tensile strength values observed in this study exhibited an increase with the addition of cellulose up to 7.5%.This improvement can be attributed to the inherent characteristics of cellulose, which forms long and straight polymer chains, consequently enhancing the tensile strength [39].Additionally, previous research conducted by Maulida et al. [40], indicated the presence of hydrogen bonds formed between cellulose and starch, further contributing to the increase in tensile strength.However, the addition of cellulose at the 10% level resulted in a reduction of tensile strength to 3.33 MPa.The reduction The reduction is primarily attributed to the formation of an inhomogeneous mixture of starch and cellulose, leading to a weakening of the hydrogen bonds formed between the two components [39].Previous studies have also reported that a higher concentration of cellulose can lead to agglomeration within the starch matrix, leading to a diminished bond between starch and cellulose [41].The agglomeration is often a consequence of the uneven distribution of cellulose within the bioplastic matrix, which in turn affects the mechanical properties produced [42].The uneven distribution of cellulose is partly due to its limited solubility, which is can result in an inhomogeneous mixture [43].The elongation resulting from this study are presented in figure 2. The addition of cellulose banana bunches resulted in an elongation value that ranged from 4.06 to 21.24%.The elongation of bioplastics without the addition of cellulose (0%) exhibited an elongation value of 20.90%.The addition of cellulose, specifically at the 2.5% concentration resulted in a decrease in the elongation value to 16.71%.This presented that cellulose addition had a significant influence on elongation values.The analysis of variance (with α = 0.05 significance level) confirmed that the addition of cellulose had a statistically significant effect on the elongation values.The results of DMRT indicated that bioplastics produced with 2.5% cellulose were distinct from the other bioplastics.The elongation values for bioplastics with 2.5% and 10% cellulose align with the ASTM D5336 standard, which mandates elongation values within the range of 9-500%.
The elongation value decreased with the addition of cellulose to a level of 7.5%.This can be attributed to the interaction between starch hydroxyl groups and cellulose carboxyl groups, resulting in the formation of strong bonds that limit the overall strain value [40].The addition of cellulose in the bioplastics imparts rigidity to the tissue structure, leading to an increase in tensile strength and Young's modulus.However, this increased rigidity is accompanied by a decrease in the mobility of the polymer matrix chains, which in turn leads to a continued reduction in elongation.The decrease in the elongation may also be linked to the high flexibility properties of cellulose [18], [44].The elongation value observed in this study present an inverse relationship with tensile strength and Young's modulus, as an increase in these properties corresponds to a decrease in elongation.
The Young's modulus produced in this study are presented in figure 3. Bioplastics without the addition of cellulose (0%) displayed a Young's modulus value of 13.98 MPa.The addition of cellulose results in a Young's modulus value that ranges from 15.73 to 172.52 MPa.The analysis of variance (with α = 0.05 significance level) confirmed that the addition of cellulose had a statistically significant effect on the Young's modulus values.The highest Young's modulus value, reaching 172.52 MPa, was observed when 7.5% cellulose was added.The results of DMRT indicated that bioplastics produced with 7.5% cellulose were distinct from the other bioplastics.The addition of cellulose from banana bunches significantly enhances the stiffness and rigidity of the bioplastics, as indicated by the high Young's modulus value.The Young's modulus values obtained in this study comply with the ASTM D5336 standard, which specifies a range of 2.1-410 MPa for Young's modulus values.The increase in Young's modulus value observed with the addition of cellulose up to 7.5% is consistent with findings from previous research [41], as reported by Yang.The increase in Young's modulus may also can be attributed to the interaction between cellulose and the starch matrix, resulting stronger and more rigid material properties.The increase in Young's modulus is a consequence of the interaction between cellulose and the starch matrix, leading to enhanced strength and rigidity in the material properties [45].Essentially, the addition of cellulose strengthens the bioplastic, making it less prone to deformation under stress.However, the addition of cellulose at the level of 10% decreases the value of Young's modulus.The structural changes that occur in the starch matrix when the cellulose concentration is higher [45].The uneven distribution and agglomeration of cellulose in the matrix leads to a less homogeneous structure.The uniformity of the material is disturbed by the uneven distribution of cellulose, a critical factor in preserving the intended material properties.

Water Vapor Absorption
Water vapor absorption is carried out to determine the ability of bioplastics to absorb water vapor around their environment.The water vapor absorption of bioplastic after addition carried out for 7.5 hours can be seen in figure 4. The resulting water vapor absorption value ranges from 10.14-15.93%.Bioplastics without the addition of cellulose have the highest water vapor absorption value of 15.93%, this phenomenon shows that bioplastics without the addition of cellulose are hydrophilic.The lowest water vapor absorption value at 10% cellulose addition was 10.14%.This indicates that the addition of cellulose can increase the resistance of bioplastics in reducing the rate of water vapor absorption.The results of the analysis of variance (α = 0.05) showed that the addition of cellulose had a significant effect on the value of water vapor absorption.The addition of cellulose has a markedly different effect on the absorption value of water vapor.The results of DMRT showed bioplastics made with the addition of cellulose to a degree of 10% are different from cassava starch bioplastics.
The addition of cellulose to a level of 10% can reduce the absorption value of water vapor from 15.93% to 10.14%.This shows the ability of cellulose from banana bunches to enhance the hydrophilic properties of starch.Similar previous studies that have reported that cellulose can reduce water vapor absorption [24], [46].Cellulose chains are less hygroscopic than starch molecules, so the addition of cellulose has a noticeable effect on the moisture resistance of the bioplastic.Cellulose acts as a barrier, inhibiting the entry of water molecules into the starch matrix [47].The decrease in water vapor absorption has also been reported by Mahardika et al. [48] and is attributed to the strong bond between the filler as cellulose and the matrix, which limits the diffusion of water molecules into the bioplastics.Additionally, the decrease in the rate of water vapor absorption can be attributed to the reduced availability of empty space within starch matrix due to the presence of cellulose.As a result, water molecules find it challenging to diffuse into the bioplastics.Bioplastics with low moisture absorption have the advantage of preserving the quality and condition of the products they package or encapsulate [49].This makes them suitable for applications where moisture control is essential, such as in the food or other items.

Biodegradable
The degradation of the produced bioplastics is illustrated in figure 5.The degradation values for bioplastics subjected to 5 days of degradation ranged from 16.10% to 22.72%, those for 10 days ranged from 22.13% to 28.64%, and for 15 days, the degradation values ranged from 29.81% to 50.6%.The results of the analysis of variance (α = 0.05) confirmed that the addition of cellulose had a significant impact on the degradation values.The addition of cellulose has a markedly different effect on the degradation value of bioplastics.The highest degradation value was observed when 2.5% cellulose was added, reaching 50.6% after 15 days of degradation.In contrast, the lowest degradation value was found in bioplastics without the addition of cellulose, at 29.81% for the same 15-day degradation period.The results of DMRT showed that bioplastics made with the addition of cellulose by 2.5% are different from other bioplastics.The results have demonstrated that the addition of 2.5% cellulose from banana bunches can enhance the degradation of bioplastics.The degradation process of bioplastics is influenced by various factors, including microorganisms, pH, humidity, and environmental conditions, all of which contribute to the rate of degradation [50].The composition of the soil used for biodegradation testing, with a pH of 5.6 and a nitrogen (N) content of 0.282%, suggests that nutrient content can significantly affect the activity of microorganisms in the soil.The presence of nitrogen in the soil is crucial as it influences the production of extracellular enzymes by microorganisms.Higher extracellular enzyme production accelerates the degradation process of bioplastics [51].soil with a pH ranging from 3 to 6 is considered an optimal condition for the growth of soil microorganisms [52].The degradation of bioplastics over the 5, 10, and 15 day periods is depicted in figure 6.
The bioplastics with 2.5% cellulose addition exhibited the highest degradation by day 15.The degraded bioplastic is physically destroyed into small pieces with the addition of 2.5% cellulose.The addition of cellulose to this study can increase the rate of degradation of the bioplastics produced.Previous research also states that the addition of cellulose can accelerate the degradation process of bioplastics because cellulose is a material derived from nature so it is easily decomposed by microorganisms [44], [46], [53].In accordance with the ASTM D5336 standard, which provides guidelines for the length of time required for plastic to completely degrade, bioplastics should fully degrade (100%) within 60 days.The degradation results for bioplastics with 2.5% cellulose addition have met the ASTM D5336 standard, achieving a degradation rate of 50.6% within 15 days.

Conclusion
The addition of cellulose banana bunches up to the level of 7.5% can improve the bioplastic characteristics of cassava starch.The addition of cellulose to starch bioplastics was optimum in addition to 7.5%.The addition of cellulose at the level of 7.5% can increase the tensile strength value from 2.92 MPa to 6.72 MPa, elongation decreased from 20.89% to 4.06%, Young's Modulus increase from 13.98 MPa to 172.52 MPa, decreased water vapor absorption rate from 15,93 to 11,48%, and enhanced biodegradability rating from 29,81 to 50,69%.However, the bioplastics produced from this study have not met ASTM D5336 regarding mechanical properties. 4

Figure 1 .
Figure 1.The value of tensile strength with various variations in cellulose variation.The distinct letters indicate significant difference in each variation in the addition of banana bunch cellulose.

Figure 2 .
Figure 2. The value of elongation with various variations in cellulose variation.The distinct letters indicate significant difference in each variation in the addition of banana bunch cellulose.

Figure 3 .
Figure 3.The value of Young's modulus with various variations in cellulose variation.The distinct letters indicate significant difference in each variation the addition banana bunch cellulose.

Figure 4 .
Figure 4.The value of water vapor absorption with various variations in cellulose variation.The distinct letters indicate significant difference in each variation in the addition of banana bunch cellulose.

Figure 5 .Figure 6 .
Figure 5.The value of biodegradable with various variations in cellulose variation.The distinct letters indicate significant difference in each variation in the addition of banana bunch cellulose.