3.1 Preparation of Taro Starch/PVA Blend Films
The method of [15] was used to make chemically altered taro starch (TS1-3) mix together. Ground taro starch was sieved through a 63µm mesh size. The extrusion process (Ampia made in Italy) was used to create the films. PVA solution was first made by dissolving at 95 0C hot water. A magnetic stirrer (MS-H280-Pro) aid mixer was used to combine taro starch (TS), chemically modified eggshell (ES), and the additives material (GL, BC, and CA) with water for 10 minutes. The mixture was then mixed for 50 minutes at room temperature with a mechanical stirrer (1,200 rpm) to generate a homogeneous gel-like solution. A total of 4 g of taro starch polymer was used. An aspirator was used to eliminate bubbles that formed as a result of the preparation process. In a vented oven for 12 hours and in a cold laboratory chamber at 50 0C for 72 hours, water was evacuated from the samples. Before the examinations, dried films were placed in open polyethylene bags and stored for one week at 25°C and RH of 55%. Table 1 shows the composition of taro starch/PVA/ES/BC added to the additive filler blend films sample.
Table − 1 Composition of Taro starch/PVA/ES/BC plus other additive filler blend films Sample
Samples Name
|
PVA (%)
|
Citric acid (%)
|
Talc powder (%)
|
(TS1-3) (%)
|
GL (%)
|
ES (%)
|
BC (%)
|
BA (%)
|
Drying Temperature (0C)
|
TS1-31
|
4
|
0
|
0
|
4
|
20
|
0
|
0
|
0
|
40
|
TS1-32
|
4
|
1
|
1
|
4
|
20
|
0
|
0
|
0
|
40
|
TS1-3/ ES/ BA(TS1-33)
|
4
|
1
|
1
|
4
|
20
|
1
|
0
|
1
|
40
|
TS1-3/ ES/ BA(TS1-34)
|
4
|
1
|
1
|
4
|
20
|
2
|
0
|
2
|
40
|
TS1-3 /BC/ BA (TS1-35)
|
4
|
1
|
1
|
4
|
20
|
0
|
1
|
1
|
40
|
TS1-3/BC/ BA(TS1-36)
|
4
|
1
|
1
|
4
|
20
|
0
|
2
|
2
|
40
|
3.2 Fourier transforms infrared spectroscopy (FTIR)
The FTIR spectra of the functional groups of polymeric films composed of taro starch/PVA, glycerol, ES, and BC as filler additive materials are shown in Fig. 1, and the absorption peak analysis was presented in Table 2. The FTIR spectra of taro starch and PVA TS1-31 and TS1-32, TS1-33 and TS1-34 and TS1-35 and TS1-36 films with glycerol plasticizer plus additive material revealed typical absorption by functional groups of OH, NH, CH aliphatic, C = O, C-O, C = C, S = O and C-Br in the starch and PVA molecules. The samples TS1-31 and TS1-32 O-H starch, the second TS1-33 and TS1-34, the third one TS1-35 and TS1-36, have a large absorption peak in the area of 3269 cm− 1, 3270 cm− 1, and 3274 cm− 1, respectively. The carboxylic acid was a broad and powerful carboxylic acid. According to the researcher, C-H stretching causes a peak in the 3000–2800 cm− 1 range [19]. Starch and PVA differed from different additives in that they included an amine group that replaced the OH group in amylose and amylopectin in starch. The alkene group vibration is 1642.41 cm− 1 at TS1-31 and TS1-32, 1660 cm− 1 at TS1-33 and TS1-34, and 1650 cm− 1 at TS1-35 and TS1-36. The stretched mono-substituted group C = C had significant symmetry. Furthermore, the FTIR spectra of C-O strong stretching TS1-33 and TS1-34 PVA/taro starch functional group showed that the area of 1280cm− 1 is the only ester novel functional group in the plastic films made with glycerol as a plasticizer. The samples were investigated for the absorption bands associated with amides I and II, which correspond to carbonyl stretching vibration at 1600–1700 cm− 1, NAH bending vibration at 1400–1580 cm− 1, and CAN expanding vibration at 1257 cm− 1, respectively [20],[21]. Furthermore, the result were two further absorptions that distinguished taro starch /PVA and additive material film C-O functional group strong 1035.61 cm− 1stretching primary alcohols TS1-31 and TS1-32 and secondary alcohol 1090, 1080 cm− 1 primary alcohol TS1-33 and TS1-34 1020 cm− 1, TS1-35 and TS1-36 secondary alcohol 1010 cm− 1 primary alcohol 1080 cm− 1 secondary alcohol wave number. In the study where the amount of PVA increased, the vibrations at 1019 cm − 1 gradually moved to a higher wavenumber close to the vibration of PVA plasticizer [22]. The result were S = O functional group strong and stretching at 1335.06, 1160 cm− 1, for TS1-31 and TS1-32 at 1390, 1160 cm− 1 for TS1-33 and TS1-34 then at 1370, 1160 cm− 1 for TS1-35 and TS1-36 sulfonamide. The other change in the intensity and frequency of distinctive absorption bands may have pointed to a novel functional group in the plastic films made with glycerol as a plasticizer. In the previous studied the symmetric and asymmetric S = O stretching vibrations, correspondingly, were responsible for the absorption bands at 1095 cm− 1 and 1033 cm− 1. The samples' high level of cysteine-S-sulfonated residues was revealed by the strong signal at 1034 cm− 1 [20], [21]. The C-O and C-C-C stretching vibrations have precise peaks at 1088 and 1026 cm− 1, respectively [23]. On the other hand, the use of BC and ES as reinforcing fillers in the bioplastic networks C-Br functional group made the functional group strong and stretchable at 579,525,418 cm− 1 TS1-31 and TS1-32 samples; the functional group was 580,538,420 cm− 1 TS1-33 and TS1-34; and finally, 579,534,415 cm− 1 TS1-35 and TS1-36 halo compounds. Some other alterations in the strength and recurrence of recognizable absorption peaks may have indicated the employment of cellulose as a reinforcement material in the biocomposite networks.
Table − 2: Functional group analysis film by FTIR
Bonds
|
Functional properties
|
TS1- 31 and TS1- 32
|
TS1- 33 and TS1- 34
|
TS1- 35 and TS1- 36
|
O-H
|
Strong, stretching and carboxylic acid ,alcohol
|
3270.22
|
3270
|
3274
|
C-H
|
Medium, stretching and alkane
|
2941.64
|
2940
|
2940
|
C = C
|
Strong, stretching, alkene and & mono-substituted
|
1642.41
|
1660
|
1650
|
N-O
|
Strong, stretching
and nitro compound
|
-
|
-
|
1570
|
C-H
|
medium, bending & alkane and methyl group,1,2,3-trisubstituted
|
1446.61,
771,714
|
-
771,712
|
-
771,712
|
C-O
|
Strong, stretching, Strong, stretching primary alcohol and
secondary alcohol
|
-
1035.61
1090,
|
ester 1280
1020,
1080
|
-
1010,
1080
|
S = O
|
Strong, stretching and sulfonamide
|
1335.06, 1160
|
1390, 1160
|
1370, 1160
|
C = C
|
Strong, bending, alkene and disubstituted (trans) ,vinylidene
|
951,
868
|
949,
864
|
938,
864
|
C-Br
|
Strong, stretching and halo compound
|
579,525,418
|
580,538,420
|
579,534,415
|
3.3 Mechanical tensile test strength
The viability of the films in packing applications is significantly influenced by their mechanical strength. When compared to non-biodegradable plastic, biodegradable films often have less mechanical strength [24]. Figure 2 the dog-bone-shaped specimen was used for standard universal testing machine. The chemical composition and the type of film-forming elements are the main determinants of the film mechanical strength. The more hydrogen bonds there were, the more force required to achieve maximum tensile strength [25]. Following an investigation, data for produced film tensile strength and elongation at break were shown in Table 3. The filler development in the biopolymers crystalline structure was one method for improving the mechanical properties of bioplastic film [26]. Figure 3 shows that graphs depicted the tensile strength of the sheets made of pure starch/PVA and fine aggregate additives were used in samples TS1-31, TS1-32, TS1-33, TS1-34, TS1-35, and TS1-36. The results showed that the filler significantly affected the tensile strength and break elongation of the film. The mechanical characteristics of the starch-based film were significantly influenced by the quantity of taro starch plasticizer (PVA and glycerol) and bio filler in the films. Various concentrations of pure taro starch/PVA and glycerol TS1-31 and TS1-32 were used to perform the tensile test on each sheet of film 5.02 MPa and 6.35 MPa respectively. The pure taro starch/PVA TS1-31 sample and TS1-32 sample with talc powder loading film had a break elongation reaching 225.786 and 307.186mm respectively. The low interfacial adhesion between the two phases was the reason. In comparison to pure taro starch/PVA films, the elongation at break dropped dramatically at higher elongation. Incorporating starch into PVA content to increase interfacial adhesion between starch and ES and BC was not practical. The tensile strength of taro starch/PVA with filler ES film was 8.12 and 9.26 MPa, respectively (1 to 2% ES filler added at TS1-33 and TS1-44). Elongation at break was shown in Fig. 3 at 404.711 and 447.832 mm with good results, respectively. Modified filler (ES) was well aggravated for mechanical properties and starched with good performance. The tensile strength was increased when more bio-filler was added to the samples. Furthermore, the results showed that the samples TS1-35 and TS1-36 recorded a lower value of 5.56 and 6.09MPa (1, 2% BC added) respectively. However, plasticizer and bio-filler were used in small amounts. The resulting film split easily and was less elastic. TS1-31 and TS1-35 samples with pure taro starch/PVA and 1% BC added filler into the film, which fractured and was difficult to extrude from the machine, preventing characterization. As the BC filler concentration was raised, the samples TS1-35 and TS1-36 percentage of elongation at breaks (455.256 and 532.408mm for both formulations) increased. As the filler content was raised, the elongation at the break of the taro starch/PVA film increased. The film with a 2% filler BC content resulted in a break elongation. The film with glycerol pure taro starch/PVA has the lowest tensile strength, which was 5.02 MPa. According to research, compared to films made entirely of starch, the percentage of elongation at break is 154.7% for 2-weight percent RB and 155.3% for 4-weight percent RB [27]. Additionally, the tensile strength of the earlier research increased to According to prior research, a bio plastic made from starch cassava was easy and had a high tensile strength 25.31 MPa because of the addition Graphene oxide (GO) fillers [28]. According to the findings, adding nanoclay to bioplastic raises its tensile strength from 5.2 MPa to 6.3 MPa [29]. Based on the nature of the taro starch/PVA/talc powder and the ES and BC as fillers used, it was anticipated the combination of these materials can create bioplastic with much better properties.
Table − 3 Tensile strength force and elongation at break values of developed films.
Films
|
Tensile Strength at break (MPa )
|
Elongation at break(mm)
|
Force at break(N)
|
Modules of elasticity strength(MPa)
|
TS1-31
|
5.02
|
225.786
|
8.66
|
49.82
|
TS1-32
|
6.35
|
307.186
|
4.93
|
31.26
|
TS1-33
|
8.12
|
404.711
|
18.12
|
20.43
|
TS1-34
|
9.26
|
447.832
|
20.65
|
31.30
|
TS1-35
|
5.56
|
455.256
|
13.97
|
10.56
|
TS1-36
|
6.09
|
532.408
|
15.97
|
14.73
|
3.4 Scanning Electron Microscope (SEM) Analysis
JCM-6000Plus INSTRUMENT, TITLE High-vac. SED PC-std. 15 kV x 2000 (44mm) SEM. Figure 4 depicts the morphologies of pure taro starch/PVA with additive material blend films. There were voids in pure taro starch and PVA, indicating that the bubble was trapped in the sample during extrusion. The taro starch phase altered from scattered to amorphous as the taro starch quantity rose, indicating that amorphous taro starch was somewhat miscible with PVA and filler materials. In the PVA matrix, taro starch was finely disseminated. The fractured surface became rougher and more brittle after adding up to 50% additional taro starch. The PVA in the taro starch granules was finely disseminated, yet the starch granules consolidated greatly at the same time. Because starch granules have a substantially higher viscosity than PVA, the mechanical characteristics of the PVA/TS blend deteriorated when the filler additive material concentration was increased from 1–2%. According to the SEM micrograph, the taro starch granules were distributed efficiently in the 50/50 PVA matrix. This dispersion aids in the improvement of the films mechanical properties and was consistent with the tensile property results.
Results for the samples were TS1-31, TS1-32, TS1-33, TS1-34, TS1-35, and TS1-36. The above occurrence can be explained by using a scanning electron microscope (SEM) to examine their morphology, as illustrated in Fig.
4. (a-f). When the granular structure of taro starch was melted by the addition of filler material not melted or dissolved during processing, it was presented as filler or non-reinforcing filler, as seen in Figs. 3c and 3d. At TS1-33 and TS1-34 samples, the dissemination and diffusion of 1, 2 wt % ES additive filler composition in taro starch/PVA matrix appears to be very uniform and homogenous, but at 1, 2 wt % BC filler concentration, agglomeration occurs. The distribution and dispersion of taro starch/PVA in the glycerol matrix are not homogeneous. This was most likely owing to taro starch and PVA hygroscopic nature.
3.5 Moisture-absorption behavior
The films were cut into little square pieces (3 x 3 cm) and weighed after drying at 50°C for 3 days. The MA of the films was determined by blending time after 12 days of storage in desiccator chambers. However, it differs in terms of blending time and water take-up. The MA of TPS native and modified starch/PVA composite films was determined to be as follows:
$$MA=\frac{{W}_{t}-{W}_{0}}{{W}_{0}}$$
Wt is the weight of the sample after time t, and Wo is the weight of the dry sample.
The weights of dried films were determined when the swollen films were entirely dried in an oven at 50 0C and the solubility was determined as the ratio of the weight of the dissolved fraction to the weight of the dried film. Samples (TS1-31 to TS1-36) were made with varying concentrations of taro starch as a co-biopolymer and a reference film without additional reinforcement. Table 5 shows that water take-up was the capacity of bioplastic to assimilate the water sample's moisture content (%). Bioplastic has great water resistance in the event that it has a low rate of water take-up. Figure 5 appears the water take-up of bioplastic synthesized utilizing different ES filler expansion and blending times. It can be seen that the water take-up increments monotonically as the increment of bio filler expansion 35.6% and 27.3% samples TS1-33 and TS1-34 respectively. The previous reported tapioca films had a 50% water uptake value [25]. [30] Expressed that the water resistance properties of a particle depended on the nature of the sample. In this case, the fixings of taro starch/PVA and glycerol utilized are hydrophilic, whereas the BC filler was 34.2% and 22.3 % at samples of TS1-35 and TS1-36 samples. Subsequently, the expansion of BC and ES in bioplastic certainly improves the capacity of bioplastic to retain water due to the nature of hydrophilic filler. It might be credited to the completeness of response between the taro starch/PVA, glycerol, and BC and ES coming about in H2O as illustrated within the past segment. At that point, the longer the blending time, the more total the response and the more water immersed the result. The most elevated water take-up appeared by the test synthesized utilizing the blending time of 12 days, with the rate of ingested water of 38.8% and 17.9% for TS1-31 and TS1-32 samples the highest and lower water absorbed capacity respectively. According to [25] the thermal stability of the films improves as the chitosan fraction rises, as evidenced by a decrease in sample weight loss.
Table 4
Water absorption on taro starch films with sorbitol plasticizer
|
Samples moisture content (%)
|
Time variation (days)
|
TS1-31
|
TS1-32
|
TS1-33
|
TS1-34
|
TS1-35
|
TS1-36
|
3
|
47.8
|
48
|
26.8
|
14.4
|
16.1
|
12.7
|
6
|
57.3
|
22.5
|
29.0
|
32.0
|
30.5
|
26.7
|
9
|
45
|
12.1
|
35.5
|
20.9
|
41.8
|
11.8
|
12
|
38.8
|
17.9
|
35.6
|
27.3
|
34.2
|
22.3
|
3.6 X-ray diffraction (XRD)
The XRD patterns of pure TS1-31 – TS1-36 mass percent taro starch/PVA, and its filler material integrated films are shown in Fig. 6. Pure taro starch /PVA TS1-31 exhibit a typical peak in its diffraction at about 2ፀ= 5.9°, 9.68°, 20.26°, 28.86°, 29.6°, 31.14°, 40.52°, 41.34°, 46.62° showing that it contains both crystalline and amorphous domains in the film matrix. Around 28.86°, 29.6°, 31.14°, 40.52°, 41.34°, 46.62° the maximum result. The strength of the diffraction peak at 2ፀ = 28.86°, 29.68°, 31.2°, 47.7°, 48.82° was found to be increased in film TS1-32 with talc powder at 6°, 11.8°, 19.22°, 28.86°, 29.68°, 31.2°, 47.7°, 48.82°. Around 12.60, 14.60, 18.50, 20.50, 28.35, 29.40, 30.90, 36.8 and 40.2o, carrageenan exhibits a 2 crystalline nature. Additionally, gluco-manner had 3 absorption peaks at 20.90, 28.4, and 40.50 degrees. Chitosan, on the other hand, has a maximum scattering of 2 = 19.70 and 29.40o, which was nearly identical to the highest dispersion of chitosan found by [31], which was 2 lies at = 19.50 and 29.10o. Sample TS1-33 was because the reaction between taro starch/PVA and ES filler causes the film chains to rearrange, enhancing the films crystalline structure at 5.94°, 9.66°, 19.18°, 26.82°, 29.56°, 31.14°, 47.72°, and 48.8° phases. The strength of the peak 2ፀ = 29.02°, 29.92°, 31.36°, 46.82° maximum result. 6.22°, 9.86°, 11.96°, 19.46°, 29.02°, 29.92°, 31.36°, 46.82° was shown to be decreasing from films TS1-34 nevertheless, as GL integration into the taro starch/PVA with BC bio filler matrix increased. According to Crystallization was a critical element that lowered film quality, and high crystallinity may affected the integrity of the seal between films. The microstructure and heat-sealing capabilities of the sealed cassava starch films are affected by the type and quantity of plasticizers used. Additionally, despite the fact that the strength of their seals was discovered, to put it another way, the films did not completely seal[32]. 6.32°, 9.98°, 12.10°, 17.97°, 19.50°, 29.14°, 29.92°, 31.50°,48.02°, 49.06°. Since the TS1-35 acts as a plasticizer and disrupts the taro starch/ PVA with BC filler 29.14°, 29.92°, 31.50°,48.02°, 49.06° was linked to the result. 6.08°, 9.72°, 11.86°, 17.68°, 19.24°, 28.92°, 29.68°, 31.24°, 48.96° the amorphous character predominates in the films TS1-36 this result 28.92°, 29.68°, 31.24°, 48.96° was intended. According to the study, the major peaks for K-60 and KC-60 were 2⋏ = 19°, 23°, and 41° and 2⋏ = 19°, 32°, 41°, 45°, and 66° respectively [33], [34]. The degree of crystallinity or amorphousness increases or decreases with X-ray diffraction angle strength and concentration [35]. The bioplastic composites had diffracted peaks at 13.40, 15.10, 16.70, 17.40, 22.7, and 29.30, with a crystallinity of 20.80% and an amorphous content of 79.20%, respectively. During the production of the composite, the inter and intra-molecular hydrogen bonds in the polymer material are broken, causing damage to the crystalline structure of each polymer [36].
3.7 Differential Scanning Calorimetric (DSC)
The examination of the thermal characteristics of the produced films depends critically on the glass transition temperature (Tg). The produced films underwent DSC examination at temperatures between 45 to 300°C. [32] Low-density polyethylene and high-density polyethylene, which are frequently used packing materials, have melting points of 123.6°C and 131.7°C, respectively. Cassava starch films must therefore be sealed at comparable or lower temperatures. The findings of the film solubility experiments, on the other hand, may be interpreted by the various glass transition temperatures (Fig. 7). The resulting thermo-grams of the PVA-taro starch with additives films that have been cross-linked and had TS1-31 to TS1-36 samples added are displayed in Fig. 6. This demonstrates that BP films melt faster than amylose-only films [37]. The crystallization temperature (Tc) of starch bioplastic was found to be between 205.57 and 271.68°C because it was semi-crystal structured. The second peak point was discovered in the 323.21–365.92°C temperature range, which was the Tm for starch bioplastics [38].
According to [32], plasticizers may alter the thermal characteristics of biodegradable films due to modifications to the physical composition and mobility of the polymer matrix. In this study, the film containing only glycerol had a higher Tm than the film plasticized with sorbitol alone. In addition, there was a slight increase in the Tm of the resulting film with an increasing proportion of glycerol, compared to the film containing only sorbitol[39]. For films, the peaks achieve the maximum Tm temperatures of 267.7°C for sample TS1-33. The Tg of pure taro starch/PVA (TS1-31 and with talc powder sample TS1-32) was 102.4°C and 97.3°C respectively, as can be seen from the Fig. 6 which indicated talc powder reduced the glass temperature of the sample. The primary endothermic peak was observed at an initial temperature range of 80 to 105°C, indicating the melting of amylose-only starch crystallites, according to [37]. The samples TS1-33 and TS1-34 Tg taro starch/PVA-fillers film were dramatically decreased from 238.8°C to 33.4°C when inversely related 1, 2% ES mass percent filler was introduced to the filler matrix. Plasticizers may alter the physical makeup and mobility of the polymer matrix, which could have an influence on the thermal characteristics of biodegradable polymers [40].
Table 5
DSC curves of PVA / taro starch/ gelatin additive materials
Samples
|
Tg(0C)
|
Tc(0C)
|
Tm(0C)
|
TS1-31
|
102.4
|
126.1
|
235.1
|
TS1-32
|
97.3
|
133.5
|
237.2
|
TS1-33
|
238.8
|
261.5
|
267.7
|
TS1-34
|
33.4
|
119.1,69.9
|
155.1,111
|
TS1-35
|
92.7
|
160.5
|
198
|
TS1-36
|
94.8
|
134
|
180.8
|
This is due to the film matrix's ability to be the compact structures that resulted from the less amount of ES fillers reaction between taro starch/PVA with BC and ES. However when 1, 2 mass percent taro starch/ PVA with added BC filler was less hydrogen bonding and giving the films a mostly amorphous appearance film the Tg value marginally raised to 92.7 - 94.8 °C the following TS1-35 and TS1-36 samples result of respectively. Additionally, the melting temperature peaks (T m) for taro starch/PVA film were around 180.8 to 267.7 and 187 °C for the movies TS1-36 to TS1-33 respectively the different values of temperature become bio filler in samples. Nevertheless, it was slightly raised (from 187 to 191 °C) for the movies F-1 to F-5. The PVA-Ge film's breakdown endothermic peak was at 309 °C. The pure gelatin samples DSC curves were identical to those produced by [41] using bovine hide gelatin gels of [42] investigated blends with equal percentages of totally hydrolyzed PVA and found similar DSC curves for pure PVA.