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Effect of Nanoclay on Physical, Mechanical, and Microbial Degradation of Jute-Reinforced, Soy Milk-Based Nano-Biocomposites.

INTRODUCTION

Global warming, deforestation, and day-to-day increment in use of synthetic plastic products not only creates environmental pollution but also alters green world to slump world due to plastic decomposition all over the place. In order to reduce the use of these eco-hazardous plastic and plastic-reinforced composites, natural fiber-reinforced biodegradable composites are possibly the best alternative solution. Research on natural fiber-based composites brings a mile stone on the arena of composite science and technology as these composites are ecologically sound and less hazardous. Plant-based fibers such as jute, hemp, flax, coir, sisal, banana, and ramie have been already reported as good reinforcing material for both thermoset and thermoplastic matrices (1-3) to produce natural fiber-reinforced composites. But complete biodegradation of these composites is a great challenge due to slow rate of degradation of above matrices (4-6). Although bio-resin can reduce environment pollution as it is completely degradable in nature, but poor mechanical properties, poor processability, and high hydrophilicity limit their application in fabrication of natural fiber-reinforced composite (6-8).

The properties of bioresin and their composites can be enhanced by modifying the resin with the use of additives or fillers (9-10) Nanofillers are considered as high potential filler materials for bioresin to improve physical and mechanical properties of biocomposites by making synergic bonding with matrix (9-11) These nano biocomposites are a new class of highly desired engineering materials having improved features like thermal and mechanical properties, flame retardancy, and heat distortion temperature than the conventional polymer composites (9-11). Nanoclay either intercalates or exfoliates in bioresin to improve the physical and mechanical properties of bioresin. In case of intercalation, silicate layers of nanoclay allow the resin for penetration between different layers by increasing the d-spacing (clay platelet interlayer spacing) among them, while in exfoliation, silicate layers completely separate from each other by the action of resin (12) Numerous investigations on nanoclay-modified bioresin have reported that the exfoliation structure of nanoclay facilitate for better enhancement in physical and mechanical properties of nano-biocomposites than the intercalation (9-13). Nanoclay-modified bioresins are of different kinds. Among them some bioresins are naturally occurring, for example, chitosan, lignin, starch, protein as soy protein concentrate, and soy protein isolate (9), (13-16). Some are synthetically produced, for example, poly(lactic acid) (PLA), poly(urethane) (PU) (17), (18), and others are manufactured from petrochemicals, for example, poly ([epsilon]-caprolactone) (PCL), and poly(butylene succinate) (PBS) (19), (20). But high processing cost and abundance of above bioresins are the prime factors to develop low cost nano-biocomposites.

In order to avoid above issues and produce an economical natural fiber-reinforced composite which can fulfill the demand of consumer market, a new agro-based locally available, low cost bioresin, that is, soy resin was chosen as matrix with jute as reinforcing material for composite fabrication. In this research work, montmorillonite (MMT) and Cloisite 20A, which are natural and organically modified nanoclay respectively, were used for modification of soy resin. These modified soy resins were utilized as matrix along with jute as reinforcement, glyoxal as crosslinking agent and glycerol as plasticizer for the fabrication of jute-reinforced nano-biocomposites. Developed nano-biocomposites were characterized mechanically and found physically strong with sound impact properties. In order to check the biodegradability, composites were kept in microbial culture and found to be biodegradable in nature unlike thermoplastic based jute composite. The objective of this study is to promote utilization of agro-based products (both jute and soy) and develop mechanically stronger composites [jute-soy (JS)] without use of any hazardous chemical solvent (either for surface treatment of jute or for modification of soy resin) followed by simple industrial process (i.e., compression molding) such that these composites can be utilized in different sectors like automobile, packaging, furniture, and so on, to reduce amount of eco-hazardous plastic.

EXPERIMENTAL

Materials

Jute felt was obtained from Gloster Jute Mills Limited, Bauria, West Bengal, India. MMT and Cloisite 20A were obtained from Southern Clay Products (Gonzales, TX, USA). Glyoxal (Merck, India), Glycerol (Merck, India), ammonium hydroxide ([NH.sub.4]OH) (Merck, India), acetone (Merck, India), and soy bean were procured from the market.

Preparation of Soy Milk, Nanoclay-Modified Soy Resin, and Their Resin Film

Extraction of Soy Milk. Soy milk was extracted from water-soaked (4 h) soy seeds (1:4 w/v of soy seed to water) by grinding and filtering through nylon cloth. It was made alkaline by using ammonium hydroxide (5 m1/100 ml soy milk, pH 9) for better shelf stability. About 10 ml of soy milk was taken in a 10 cm diameter petridish and weighed ([W.sub.1]), then kept in a thermal chamber at 70[degrees]C for 12 h before taking final weight ([W.sub.2]) of dry soy milk. Solid content of soy milk was calculated by using the Eq. I:

Solid content (%) = [([W.sub.2] - [W.sub.1])/[W.sub.1]] x 100 (1)

Preparation of Soy Resin Film (SRF). Different weight percentages of glyoxal (1, 5, 10, 15, and 20) (with respect to solid content of soy milk) along with 10 wt% of glycerol (with respect to solid content of soy milk) were added to required amount of soy milk and then stirred for 30 min to prepare soy resin. About 100 ml of soy resin was poured on a flat glass petridish of diameter 15 cm and was kept in a thermal chamber at 130[degrees]C for 20 min. Then dark brown SRF was formed and were coded as SRF1, SRF5, SRF10, SRF15, and SRF20 with respect to wt% of glyoxal. The resin film was kept in open air for 30 min to absorb some moisture, which helps for easy peeling. Tensile specimens were prepared from different sets of SRF and mechanically tested. Optimum amount of glyoxal was utilized for preparing nanoclay-modified soy resin.

Preparation of Nanoclay-Modified SRF (MSRF). Different weight percentages of MMT (1, 3, 5, 7, and 10 wt%, w/w of solid resin wt) were dispersed in acetone (25 ml) by stirring for 30 min in separate batches. Then each batch of dispersed nanoclay was added to soy resin (optimized) with continuous stirring for another 30 min to prepare MMT modified soy resins. Similarly different weight percentages of Cloisite 20A (1, 3, 5, 7, and 10 wt%, w/w of solid resin wt) were utilized by following above process to prepare cloisite modified soy resins. Following above resin film making process, MMT-modified SRFs and cloisite-modified SRFs were prepared from their corresponding soy resins.

Fabrication of Jute-Reinforced Nano-Biocomposites

Fabrication of JS Composite. Jute felts (20 cm X 20 cm in size) (60 wt%) were soaked in optimized soy resin (soaking time 10 min) and partially dried in an oven at 70[degrees]C for 2 h. Partially dried soy resin impregnated jute felts were compressed in a hydraulic press at 135[degrees]C under 10 ton pressures for 15 min to obtain JS composite. Prepared composites were post cured at 100[degrees]C for 1 h to remove trapped moisture.

Fabrications of Jute-MMT Modified Soy and Jute-Cloisite Modified Soy Composites. Jute felts (20 cm X 20 cm) (60 wt%) were soaked in different percentages of MMT-modified soy resin and compressed by the following procedure to prepare jute-MMT modified soy (JMS) composites. Similarly jute- cloisite modified soy composites (JCS) were developed by using cloisite modified soy resin and jute by following above experimental condition. All JMS and JCS composite formulations are reported in Table 1.

TABLE 1. Composite formulation for JS, JMS, and JCS.

                   Joy
                 resin
                   (40
                 wt %)

           Jute    Soy  Glyoxal  Glycerol  Nanoclay  Type of
            (wt   milk   (wt %)    (wt %)    (wt %)  nanoclay
Composite    %)    (wt
                    %)

J.S          60     80       10        10         0  MMT

JMS1                79                            1

JMS3                77                            3

JMS5                75                            5

JMS7                73                            7

JMS10               70                           10

JCS1         60     79       10        10         1  Cloisite
                                                     20A

JCS3                77                            3

JCS5                75                            5

JCS7                73                            7

JCS10               70                           10


CHARACTERIZATIONS

Mechanical Properties Analysis

Tensile moduli of jute fiber, SRFs, and nanoclay-modifled SRFs were measured as per ASTM D 3822-01 and D638-03, respectively, at a crosshead speed of 2 mm/min. Tensile and flexural properties of IS, JMS, and JCS composites were measured at room temperature (35 [+ or -] 2[degrees]C) as per ASTM D638-03 with specific gauge length of 50 mm, at a crosshead speed of 5 mm/min and ASTM D790-05, at a crosshead speed of 2 mm/min, respectively, using universal testing machine (HOUNSFIELD H1OKS UTM instrument). From each of the sample, eight specimens were tested and average of tensile and flexural value was reported.

Series, parallel, and Guth models are the simple methods for predicting the tensile modulus (E) of polymer composites (21-23). Theoretical tensile moduli of composites were determined by using rule of mixture (parallel), inverse rule (series) of mixture, and Guth model as per Eqs. 2, 3, and 4, respectively:

E = [E.sub.m] [[phi].sub.m] + [E.sub.f] [[phi].sub.f] (2)

1/E = [[phi].sub.m]/[E.sub.m] + [[phi].sub.f]/[E.sub.f] (3)

E = [E.sub.m][1 + 2.5[[phi].sub.f] + 14.1[[phi].sub.f.sup.2]], (4)

where [E.sub.m] and [E.sub.r] are the Young's modulus of soy matrix and jute and [[PHI].sub.m] and [[PHI].sub.f] are the volume fraction of soy matrix and jute, respectively.

X-ray Diffraction Analysis

Mechanically optimized composites (JMS5 and JCS5) along with nanoclays were analyzed by X-ray diffractom-eter (WAXD, ULTIMA-III, Rigaku, Japan), using nickel-filtered Cu[K.sub.[alpha]], radiation with a wavelength of 0.154 nm generated at 40 kV and 100 mA. The range of diffraction angle ([theta]) was 1[degrees] to 30[degrees] with a scanning rate of 1[degrees]/min. The intensity was plotted against [theta] values. From the position of the peak, the corresponding d-spacing was calculated by using Bragg's equation:

n[lambda] = 2d sin [theta], (5)

where n is the order of reflection, [lambda] is the wavelength of radiation, 0 is the angle of diffraction, and d is the interlamellar spacing.

Transmission Electron Microscopic Analysis

Transmission electron microscopic (TEM) analysis was used to provide a visual confirmation of the intercalated or exfoliated nature of nanoclay in nano-biocomposites. JMS5 and JCS5 composite powders were dispersed in acetone and a drop of this dispersion was taken on a carbon-coated copper grid for visual analysis using a TEM (JEM-1230, JEOL, Japan) instrument with an acceleration voltage of 100 kV in high vacuum.

Impact Testing

The impact resistance of notched JCS and JMS composites was tested according to ASTM D256-97 using Izod impact instrument (S. C. Dey & Co., India) at room temperature (35 [+ or -] 2[degrees]C). From each of the composites, eight specimens were tested and average value of impact was reported.

Microhardness Measurement

Microhardness of JCS and JMS composites was measured to determine the hardness of nano-biocomposite samples using Vicker's hardness (UHL VMHT, Germany) instrument. The loading force and dwelling time were set as 100 g force and 12 s, respectively. Five points on each sample were dwelled for averaging the result to maintain accuracy.

Dynamic Mechanical Analysis (DMA)

The dynamic mechanical behavior of the JS, JCS5, and JMS5 composites were studied using dynamic mechanical analyzer (NETZSCH DMA 242). The experiments were carried out at fixed frequency of 1 Hz and at a heating rate of 10[degrees]C/min in a single cantilever mode. The tests were conducted at a temperature range of 40-225[degrees]C using specimen of dimensions 40 mm X 10 mm x 3 mm.

Biodegradation Analysis

Curvularia lunata, a cellulase producing fungus, was used for degradation study of composites. The fungal stock cultures were maintained in Czapek Dox Broth containing mineral salt solution of [NH.sub.4][NO.sub.3] (0.3%), [K.sub.2]HP[O.sub.4] (0.22%), K[H.sub.2]P[O.sub.4] (0.014%), NaC1 (0.001%), MgS[O.sub.4](0.06%), Ca[Cl.sub.2] (0.004%), FeS[O.sub.4] (0.002%), and glucose (0.5%). Preweighed composite samples of JS, JMS, and JCS (90 mm X 15 mm) ([W.sub.0]) were mixed with spore suspension of Curvularia lunata (1:10 w/v) and incubated for 60 days at 28[degrees]C in an incubator-cum-humidity chamber maintaining 80% humidity. The spore suspension was prepared by mixing the fungal spore with the sterilized Czapek dox broth. The Czapek dox medium contains lower amount of glucose for initial growth of the fungus. A glucose-free Czapek dox broth (10 ml) was added every 7 days for proper growth of the fungus. After different time interval (7, 15, 30, 45, and 60 days, respectively), composite samples were taken out and washed in 70% ethanol to remove cell mass from the residual sample and dried in oven at 45[degrees]C for 24 h [24]. Then final weight ([W.sub.1]) of the composite was taken to estimate weight loss percentage of composite by using Eq. 6.

Weight loss (%) = 100 x [[W.sub.0] - [W.sub.1]]/[W.sub.0] (6)

Tensile analysis and field emission scanning electron microscopy (FE-SEM) photographs of composites before and after degradation were compared to evaluate the extent of degradation. FE-SEM of specimens was analyzed by using FE-SEM (SUPRA-40, Germany) instrument at an accelerating voltage of 5 kV to study the morphology. Specimens of the composites were mounted on aluminum stubs and gold coated to avoid electrical charging during examination.

RESULTS AND DISCUSSIONS

Mechanical Properties Analysis of SRF, JMS, and JCS Composites

Tensile Analysis of SRF. The results of the tensile properties of different percentage of glyoxal crosslinked SRFs are shown in Fig. I. SRF (SRF10) prepared with 10 wt% glyoxal (w/w, solid soy wt) and 10 wt% (w/w, solid soy wt) of glycerol showed the highest tensile strength of 0.97 MPa, which may be due to better crosslinking between soy protein and glyoxal. The probable crosslinking between different amino acids of soy protein and glyoxal is obtained due to presence of more than one N[H.sub.2] group in soy protein. These N[H.sub.2] groups react with glyoxal and produce strong primary electrovalent bonds to improve mechanical strength of the crosslinked resin (25-27). Addition of excess of glyoxal does not increase tensile strength as there is less number of available sites in protein of soy milk for bonding. Hence, 10 wt% of glyoxal was considered optimum as crosslinking agent.

Mechanical Properties Analysis of SRF, JMS, and JCS Composites

Mechanical properties of JMS and JCS composites are shown in Figs. 2 and 3, respectively. The JS composite without nanoclay has tensile strength of 32.8 MPa and tensile modulus of 980 MPa. Possible synergic bonding between soy matrix and jute fiber might have helped to achieve such strength and modulus of JS composite (28). The tensile and flexural strength with modulus of JS composite increased suddenly with 0 to 5 wt% loading of MMT. JMS5 composite have tensile and flexural strength of 44.8 and 47.2 MPa, respectively. This might be due to better synergic bonding between the cellulose of jute, silicate layers of nanoclay, and glyoxal crosslinked soy protein. A schematic illustration showing possible chemical interaction between functional groups of jute, soy protein and nanoclay is shown in Fig. 4. Further increase in clay loading (more than 5 wt%) decreased the mechanical strength of JMS7 and JMS10. That may be due to possible agglomeration of nanoclay in soy resin as higher percentage of clay loading reduces compatibility between jute and nanoclay-modified soy resin (29). Similar trends were also obtained for mechanical properties of JCS composites as shown in Fig. 3. Tensile, flexural strength and tensile, flexural modulus were found to be enhanced with increment of Cloisite 20A loading upto 5 wt%. JCS5 composite showed tensile strength of 53.4 MPa and flexural strength of 52.8 MPa. The improvement in mechanical strength of JCS5 may be due to good dispersion of nanoclay that improved wettability and compatibility at fiber-matrix interface. Also intercalation/exfoliation of nanoclay at the interphase might be another cause for such improvement in mechanical properties as reported earlier (4), (10). Elongation at break values of JMS and JCS composites gradually decreased as the clay loading increased from 0 to 10 wt%. The decrease in such value is due to increase in brittleness property of soy matrix (30), (31).

Tensile modulus of JS. JMS, and JCS composites is predicted using rule of mixture, inverse rule, and Guth models (Table 2). The tensile modulus of jute fiber is determined to be 20 GPa. Volume fraction of jute fiber (60 wt%) and matrix (40 wt%) is constant for calculating tensile moduli of composite used for various models. The predicted tensile moduli of JCS and JMS composites by Guth's model are found nearly equal to that of the experimental result. A relation between theoretical tensile modulus value (rule of mixture) and experimental value is shown in Fig. 5. Theoretical predictions of composite tensile modulus was evaluated to be around 12000 MPa, however, experimental value was found to be 1000 MPa (Fig. 5). The vast differences between both the values are obtained due to the use of nonwoven jute fabrics (in which fibers are in random orientation) and might be due to the presence of voids in composite. Inverse model shows lower tensile modulus values, while rule of mixture model predicts higher values than that of the experimental results. The tensile moduli of JCS and JMS composites remarkably improved by incorporation of inorganic particles in soy matrix, due to its nano size and extent of dispersion in soy matrix. The presence of silicate layers provides a large surface area which may restrict the mobility of the matrix leading to improvement in stiffness and modulus of the nano-biocomposites (32), (33).

TABLE 2. Experimental and theoretical calculation of tensile
modulus for JS, JMS and JCS composites.

                           Theoretical
                          calcula tion
                            of tersile
                               nodulus
                 Tensile         (MPa)
                 modulus
                   (MPa)

        Teibile
        modulus   Experi       Rule of  Inverse    Guth
Compo  of resin   mental       mixture    model   model
sites     (MPa)                  model

JS         82.1    980.2         12032    203.9     622

JMS1      125.6   1082.6         12050    311.1   951.5

JMS3      147.4   1178.3         12059    364.4  1116.7

JMS5        178   1362.7         12071    439.1  1348.5

JMS7      142.2   1181.2         12056    351.7  1077.3

JMS10      93.2    871.8         12042    261.9   800.1

JCS1     1.32.2   1103.1         12052    327.3  1001.5

JCS3        165   1281.8         12066    407.4  1250.1

JCS5      192.8   1497.7         12077    475.1  1460.6

JCS7      159.6   1204.6         12063    394.3  1209.1

JCS10     102.2    875.4         12040    253.5   774.3


XRD Analysis of Optimized JMS and JCS Composites

In order to check intercalation and exfoliation between clay and resin XRD analysis of MMT, Cloisite 20A, JMS5, and JCS5 was carried out and their diffractograms are shown in Fig. 6. For Cloisite 20A, a characteristic peak was obtained at around 3.74[degrees] with 2.4 nm basal spacing numerically equal to that of the reported value (29). In case of JCS5, the diffraction peak is absent indicating the formation of exfoliated morphology inside nano-biocomposites. The absence of peak indicates that nanoclay platelets were separated during composite fabrication. Similarly, MMT shows its characteristic XRD peak at around 7.1[degrees] with basal spacing of 1.25 nm (8). For JMS5, the corresponding peak shifted towards lower angle at about 6.31[degrees] with basal spacing of 1.4 nm. The increase in basal spacing (d spacing) may be due to the fact that soy matrix has entered the silicate layers and forced them to remain away from each other. That forms intercalation morphology at the fiber matrix interphase in the composite. Due to this exfoliation and intercalation nature of nanoclay, mechanical strength of JCS and JMS composites was found more than that of JS composite. This exfoliation/intercalation nature of nanoclay has been verified through TEM analysis.

TEM Analysis of Optimized JMS and JCS Composites

For visual confirmation, TEM analysis of optimized composites was carried out and micrographs of JMS5 and JCS5 are given in Fig. 7. JMS5 composite shows intercalation of nanoclay inside the soy matrix (Fig. 7a). In Fig. 7b, different clay platelets are distributed in soy resin and nanoclay layers are arranged parallel to each other due to intercalation. Individual silicate layers of MMT in JMS5 are found straight and parallel to each other in Fig. 7c. TEM photograph of JCS5 (Fig. 7d) demonstrated the exfoliation nature of silicate layers of clays, which are well separated and dispersed randomly in the soy matrix (Fig. 70. That leads to formation of an exfoliated nanocomposite structure. Both the intercalated and exfoliated structures of nanoclay facilitate to improve the physical and mechanical properties of JMS5 and JCS5 composites, respectively (8). The TEM pictures support the XRD result for the formation of nano-biocomposites.

Impact Testing of JMS and JCS Composites

The impact energy observed by the nano-biocomposites is shown in Fig. 8. One of the factors for increasing impact strength is the amount of fibers present in composite as reported by Rehman et al. (34). Higher amount of fiber loading requires higher force to break the composite. Jute--reinforced, soy-based composite (JS) had shown impact strength of 13.3 kJ/[m.sup.2] due to the presence of high amount of jute (60 wt%). Both JCS and JMS composites exhibit impact strength around 14-16 kJ/[m.sup.2]. The impact values of JMS5 and JCS5 were found to be 15.4 and 16.2 kJ/[m.sup.2], respectively, having 60 wt% of jute loading. Considerable improvement in impact strength of nano-biocomposites (JMS5 and JCS5) obtained due to the incorporation of nanoclay, which assists to increase the area for energy absorption of composites (31). It may be due to better compactness of jute and nanoclay-modified soy resin. The impact strength of the JCS5 composite was found about 16% higher than that of the JS composite due to better fiber--matrix-nanoclay interaction (Fig. 4) and better load absorption by the composite.

Microhardness of JMS and JCS Composites

The variation of composite hardness with the weight fraction of nanoclay is shown in Fig. 9. For JS (0 wt% clay loaded) composite, the micro-hardness number is recorded as 11.4. With increase in nanoclay loading from 0 to 5 wt%, Vicker's hardness number for corresponding composites enhanced. JCS5 shows highest hardness number of 15.2, while for same amount of MMT loaded composite (JMS5) it is 15. Strong interfacial bonding between jute fiber and nanoclay modified soy matrix may be responsible for improvement in hardness number of nano-biocomposites. There may be a possibility that nanoclay produces hard surface on JS composite by increasing stiffness of composite.

DM Analysis of Optimized JMS and JCS Composites

Dynamic mechanical analyzer (DMA) was used to measure the strength of nanoclay reinforced jute composites as a function of temperature under dynamic condition. Results indicate that addition of nanoclay has increased storage modulus of composites (Fig. 10). Nanoclay based mechanically optimized composite JCS5 and JMS5 show storage modulus of 3.2 and 2.9 GPa, respectively, as compared to 0.98 GPa of JS at room temperature. It indicates that JCS5 composite has highest storage modulus and load bearing capacity as compared to other composites. The tan [delta] value of composites describes the damping characteristics of the composite. The higher the damping at the interface, the poorer is the interaction between fiber and matrix. Low tan [delta] value of JCS5 composite describes better interfacial bonding between the modified soy resin and jute surface as compared to other two. From Fig. 10, it is found the tan [delta] peak for the nano-biocomposites (both JMS5 and JCS5) is shifted towards lower temperatures than their corresponding clay free composite (JS). This may be due to introduction of nanoclay which reduces the magnitude of tan [delta] peak by shifting the [T.sub.g] towards lower temperature, indicating that it has been able to affect the segmental motion of the soy resin (35), (36).

Microbial Degradation Analysis of Composites

The weight loss and tensile loss percentage of JS (control), JMS, and JCS composites after different biodegradation periods are shown in Table 3. It has been found that after 7 days of degradation JS, JMS5 and JCS5 showed weight loss of 9.2, 4.8, and 3.7% respectively. Initially, the weight loss is possibly due to degradation of polysaccharides and protein chains present in resin matrix. Rapid degradation of soy matrix from the fiber surface of composites results in decrement of mechanical properties. Reduction in tensile and flexural strengths for JS, JMS5, and JCS5 were found to be 95.6%, 93.7, 93.8, 97.8, 97.6, and 97.7%, respectively, after 15 days of biodegradation. The loss in mechanical properties of JS is more than that of JCS5, after 7 and 15 days of biodegradation, that might be due to breaking of inter-hydrogen bonding between fiber and matrix.

TABLE 3. Weight loss and tensile loss of composites after microbial
degradation.

Composite                     7                 15           30     45
                           days               days         days   days

Loss in properties  W (%)    TS    FS  W (%)    TS    FS  W (%)  W (%)
                            (%)   (%)          (%)   (%)

JS                    9.2  84.6  90.8   16.5  95.6  97.8   25.7   30.8

JMS1                  5.1  83.7  90.4   14.2  94.1  97.8   19.3   26.5

JMS3                  4.9  83.7  90.3   14.2  93.8  97.2   19.3   26.4

JMS5                  4.8  83.7  90.3   14.1  93.7  97.6   19.2   26.5

IMS7                  4.6  84.4  90.4   14.0  94.5  98.4   19.0   26.2

JMS10                 4.5  84.6  90.5   14.0  94.9  98.3   18.8   26.1

JCS1                  3.8  81.8  88.5   12.9  94.6  98.0   19.2   25.1

JCS3                  3.7  81.7  88.2   12.8  94.2  97.5   19.1   24.8

JCS5                  3.7  81.5  88.2   12.5  93.8  97.7   18.9   24.7

JCS7                  3.3  81.7  87.5   12.4  44.2  98.2   18.9   24.3

JCS10                 3.2  81.9  88.7   12.2  94.7  98.0   18.6   24.2

Composite              60
                     days

Loss in properties  W (%)

JS                   33.2

JMS1                 28.7

JMS3                 28,6

JMS5                 28.6

IMS7                 28.5

JMS10                28.1

JCS1                 28.5

JCS3                 28.2

JCS5                 27.8

JCS7                 27.6

JCS10                27.4

W. weight; TS, tensile strength; FS, flexural strength.


Degraded composite after 30 days were found to be fragile and hence tensile and flexural testing could not be carried out further. After 60 days, JS, JMS5, and JCS5 composites were found to be highly fragile and porous with weight reduction of 33.2, 28.6, and 27.8%, respectively. After different biodegradation periods it was found that nanoclay reinforced composites (JMS and JCS) lost less weight as compared to JS composite indicating better stability and durability. The less degradation might be due to the presence of silicate layers (nanoclay), which hinders the microorganisms attack to break internal bonding as reported (37).

Both digital and SEM photographs of composites are shown in Fig. 11. The digital photograph (Fig. 1la and b) shows composite specimen in cultured medium after 60 days of biodegradation. In Fig. 1la fungal growth is more (JS) as compared to that of Fig. I lb, which might be due to presence of nanoclay (37). Figures 11c, d, and e show the composite surface of JS, JMS5, and JCS5 before microbial degradation, while Figs. 11f, g, and h show after 60 days of microbial degradation. After 60 days of microbial degradation all composite surfaces were found pale, having pits and grooves. In Fig. 11(f), the composite (JS) surface is completely covered by fungus as compared to that of JMS5 and JCS5. Smooth surface of composites before degradation has been changed to rough, and full of grooves confirming the bio-degradation of composites after 60 days under microbial condition (38).

CONCLUSIONS

The biodegradable nature of both jute and soy is the prime factor to choose jute and soy resin as reinforcing fiber and matrix respectively to develop completely biodegradable JS composites. Nonwoven, jute-reinforced, nanoclay-modified soy composites were prepared by existing compression molding process without any chemical treatment on jute surface and use of any hazardous chemical solvent. Composite fabricated with 5 wt% of Cloisite 20A (JCS5) showed maximum tensile strength of 53.4 MPa and flexural strength of 52.8 MPa, respectively. XRD and TEM analyses of JMS5 and JCS5 confirmed about the formation of nano-biocomposites. Due to intercalation and exfoliation of nanoclay in soy resin, impact strength and hardness of nanoclay reinforced composite improved as compared to that of nanoclay-free JS composite. Storage modulus of JCS5 was found 226% higher than that of the nanoclay-free jute soy composite due to formation of nano-biocomposites. Microbial degradation study of composites revealed all composites are biodegradable in nature. Developed composite was found mechanically strong and environmentally safe products thus can be utilized in automobile sector, packaging, railway wagon interior, computer cabinets, and furniture in place of nondegradable plastic and plastic-based composites.

Correspondence to: Basudam Adhikari; e-mail: ba@matsc.iitkgp.emet.in

Contract grant sponsor: National Jute Board (formerly JMDC), Kolkata, Govt. of India.

DOI I0.1002/pen.23556

Published online in Wiley Online Library (wileyonlinelibrary.com).

[c] 2013 Society of Plastics Engineers

REFERENCES

(1.) C. Merlini, V. Soldi, and G. Barra, Po/ym. Testing, 30, 833 (2011).

(2.) Z. Ruixiang, P. Torley, and P.J. Halley, J. Mat. Sci., 43, 3058 (2008).

(3.) M. Hach R. Burgueno, A. Mohanty, and M. Misra, Campos. Sci. Technol., 68, 3344 (2008).

(4.) X. Huang and A. Netravali, Compos. Sci. Technol., 67, 2005 (2007).

(5.) K. Dean, L. Yu, and D. Wu, Compos. Sci. Technol., 67, 413 (2007).

(6.) W. Tan, Y. Zhang, Y. Szeto, and L. Liao, Compos. Sci. Technol., 68, 2917 (2008).

(7.) S. Sahoo, M. Misra, and A. Mohanty, Campos. Part A, 42, 1710 (2011).

(8.) Q. Zhou and M. Xanthos, Polym. Degrad. Stab., 93, 1450 (2008).

(9.) L. Song, Y. Hu, Y. Tang, R. Zhang, Z. Chen, and W. Fan, Polym. Degrad. Stab., 87, 111 (2005).

(10.) S.S. Ray, J. Bandyopadhyay, and M. Bousmina, Polym. Degrad. Stab., 92, 802 (2007).

(11.) S.S. Ray and M. Okamoto, Macromol. Mater. Eng., 288, 936 (2003).

(12.) F.A. Aouada, L.C. Mattoso, and E. Longo, hid. Crops Prod., 34, 1502 (2011).

(13.) A.B. Morgan, J.W. Gilman, and C.L. Jackson, Macromol., 34, 2735 (2001).

(14.) S.F. Wang, L. Shen, Y.J. Tong, L. Chen, I.Y. Phang, P.Q. Lim, and T.X. Liu, Polym. Degrad. Stab., 90, 123 (2005).

(15.) P. Chen and L.N. Zhang, Biomacromolecules, 7, 1700 (2006).

(16.) A. Sasmal, D. Sahoo, R. Nanda, P. Nayak, P.L. Nayak, J.K. Mishra, Y.W. Chang, and J.Y. Yoon, Polym. Compos., 30, 708 (2009).

(17.) S.S. Ray and M. Bousmina, Prog. Mater. Sci., 50, 962 (2005).

(18.) A. Sorrentino, G. Gorrasi, and V. Vittoria, Tr. Food Sci. Technol., 18, 84 (2007).

(19.) L. Liao, C. Zhang, and S. Gong, Macromol. Rapid Comm., 28, 1148 (2007).

(20.) L. Zhao, Y. Li, and H. Shimizu, J. Nanosci. Nanotechnol., 9, 2772 (2009).

(21.) C. Chan, Z. Wu, J. Li, and Y. Cheung, Polymer, 43, 2981 (2002).

(22.) M. Haghighat, A. Zadhoush, and S. Khorasani, J. Appl. Polym. Sci., 96, 2203 (2005).

(23.) E. Guth, J. Appl. Phys., 16, 20 (1945).

(24.) L. Byungtae, L.P. Anthony, F. Alfred, and B.B. Theodore, Appl. Environ. Microb., 57, 678 (1991).

(25.) S. Chabba and A.N. Netravali, J. Mat. Sci., 40, 6263 (2005).

(26.) A.K. Behera, S. Avancha, R. Sen, and B. Adhikari, J. Appl. Polym. Sci., 127, 4681 (2013).

(27.) R. Kumar, V. Choudhary, S. Mishra, and 1.K. Varma, Front. Chem. China, 3, 243 (2008).

(28.) A.K. Behera, S. Avancha, R.K. Basak, R. Sen, and B. Adhikari, Carbohydr. Polym., 88, 329 (2012).

(29.) L.B. Paiva, A.R. Morales, and T.R. Guimaraes, Mat. Sci. Eng., 447, 261 (2007).

(30.) T.B. Tolle and D.P. Anderson, J. Appl. Polym. Sci., 91, 89 (2004).

(31.) A.S. Zerda and A.J. Lesser, J. Polym. Sci. Polym. Phys.. 39, 1137 (2001).

(32.) X. Huang and A.N. Netravali, Biomacromolecules, 7, 2783 (2006).

(33.) R. Sothornvit, J.W. Rhim, and S. Hong, J. Food Eng., 91, 468 (2009).

(34.) R. Rahman, M. Hasan, M. Huque, and N. Islam, J. Rein] Plast. Compos., 29, 445 (2010).

(35.) J.E. Lee and K.M. Kim, J. Appl. Polym. Sci., 118, 2257 (2010).

(36.) G. Ji and G. Li, Mat. Sci. Eng. Part A, 498, 327 (2008).

(37.) P.K. Sahoo, G.C. Sahu, P.K. Rana, and A.K. Das, Adv. Polym. Technol., 24, 208 (2005).

(38.) S. Ochi, Materials, 4, 457 (2011).

Ajaya Kumar Behera, (1) Sridevi Avancha, (1) Suvendu Manna, (1) Ramkrishna Sen, (2) Basudam Adhikari (1)

(1) Materials Science Centre, Indian Institute of Technology Kharagpur, West Bengal 721302, India

(2) Department of Biotechnology, Indian Institute of Technology Kharagpur, West Bengal 721302, India
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Author:Behera, Ajaya Kumar; Avancha, Sridevi; Manna, Suvendu; Sen, Ramkrishna; Adhikari, Basudam
Publication:Polymer Engineering and Science
Geographic Code:9INDI
Date:Feb 1, 2014
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