Как выбрать гостиницу для кошек
14 декабря, 2021
Сегодня каждый, кто собирается в отпуск и не знает, с кем оставить своего котика или кошку, может во[...]
Biocomposites Using Lignocellulosic Agricultural Residues as Reinforcement
Biocomposites from Renewable Resources
Agricultural residue • Lignocellulose • Synthetic polymer matrix • Compatibilizer • Palm • Banana • Sugarcane bagasse • Curaua fiber • Reinforcement
A simple method of developing biocomposites is to use agricultural residues in their native form as reinforcement. In one such attempt, agricultural residues such as sunflower stalks, cornstalks, and sugarcane bagasse have been used as reinforcement for polypropylene composites. Fibers were obtained from the agricultural residues by mechanical pulping by steaming for 15 min at 175 °C under 7 MPa pressure. Some of the properties of the residues and fibers obtained from the residues are listed in Table 68.1. In addition to neat polypropylene (PP), two different types of maleic acid-grafted PP were also studied as matrices. The fibers and matrices were melt compounded in a twin screw extruder with various levels of compatibilizers. Extrudates obtained were compression molded into composites at 170 °C and 3 MPa of pressure. Tensile, flexural, and impact resistance properties of the composites are compared in Table 68.2. The inclusion of the reinforcements improved the properties of the composites, and the addition of compatibilizer further increased the tensile, flexural, and impact resistance properties due to better binding between the reinforcement and matrix [10Ash]. In a similar approach, cornhusks were mechanically split into various lengths and used to reinforce lightweight polypropylene (PP) composites [09Hud1]. As seen in Table 68.3, the cornhusk-reinforced PP composites had similar or better properties than the jute fiber-reinforced composites. The cornhusk-reinforced composites also had better sound absorption than the jute fiber-reinforced composites as seen in Fig. 68.1. A digital image of the split husk-polypropylene composite is shown in Fig. 68.2. In addition to using the cornhusks in their native form, fibers extracted from cornhusks using alkali and enzymes were also used to reinforce PP composites [08Hud1]. The cornhusk fiber-reinforced composites developed had properties similar to that of
© Springer-Verlag Berlin Heidelberg 2015 391
N. Reddy, Y. Yang, Innovative Biofibers from Renewable Resources,
DOI 10.1007/978-3-662-45136-6_68
|
Table 68.1 Comparison of the properties of the sunflower, cornstalks, and bagasse and fibers obtained these residues [10Ash]
|
jute fiber-reinforced composites under their respective optimized conditions as seen in Table 68.4 [08Hud1].
Agricultural residues such as rice husks, bagasse, and fish waste were mixed with pure and maleated PP in various ratios and injection molded. Later, the injection molded samples in the form of strands were later reinjection molded into composites [14Nou]. Properties of the rice husk and bagasse fibers used as reinforcement are given in Table 68.5. Considerable variations are observed in the properties of the rice husk and bagasse fibers as seen in the table. Rice husk fibers have higher aspect ratio and therefore can be expected to provide better composite properties [14Nou]. In general, addition of fish waste was found to decrease the mechanical properties. Degradation (weight loss) based on soil burial tests showed that the addition of the reinforcement, especially fish waste, promoted the degradation of the composites. As seen in Fig. 68.3, about 8 % degradation for bagasse and 10 % degradation for rice husk fibers were seen in the composites [14Nou].
In another study, bagasse was separated into outer and inner parts manually and separately used as reinforcement with 0, 5, 10, and 15 % by weight of reinforcement in the composites [08Lee]. The addition of 10 % fibers provided the highest flexural strength for both the pith and rind fibers. Tensile stress increased with the addition of the fibers up to about 15 %, and rind fibers provided better strength than the pith fibers. The presence of the fibers in the composites increased the moisture sorption from 0 to 8 % [08Lee]. Bagasse fibers pretreated with 10 % sulfuric acid were also used to reinforce polypropylene in 5, 10, and 20 % by weight [11Cer]. Adding the bagasse fibers resulted in an increase in tensile properties as seen in Table 68.6. About 15 % increase in tensile strength and 50 % increase in modulus were obtained when 20 % bagasse was used in the matrix. Similarly, 35 % increase in flexural strength and 32 % increase in flexural modulus were observed.
Bagasse fibers with average lengths of 9.1 mm were treated with various concentrations of alkali and used to reinforce biodegradable aliphatic polyester (Randy CP-300) up to 65 % by weight [06Cao]. Fibers treated with 1 % alkali provided better properties to the composites than fibers treated with 3 % alkali. Tensile strength was found to decrease with increasing fiber diameter. Tensile, flexural, and impact resistance properties of the bagasse reinforced biocomposites are shown in Table 68.7.
 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Table 68.3 Comparison of mechanical properties of mechanically split husk (MSH)-PP and jute — PP composites [09Hud1]
|
|
Fig. 68.1 Comparison of the sound absorption coefficients of the split cornhusk-reinforced composites compared to jute fiber-reinforced composites [09Hud1]. Reproduced with permission from John Wiley and Sons |
Instead of using the traditional matrix polymers, lignocellulosic agricultural residues such as cornstalk, soy stalk, and wheat stalk and the renewable ligno — cellulosic perennial switchgrass were studied as potential reinforcement for the biodegradable polymers PHBV/PBAT [13Nag1, 13Nag2]. The agricultural residues were chopped to short lengths and used as reinforcement. Based on microscopical analysis of fibers obtained after dissolving the matrix, the average length of the fibers was found to be between 2.9 and 7.7 mm for the different
![Подпись: Fig. 68.3 Biodegradation of the polypropylene composites reinforced with three different levels (5, 10, and 15 %) of bagasse fibers (left) and rice husk fibers (right) [11Cer]. Reproduced with permission from John Wiley and Sons](/img/1179/image332.png "image332") |
|
Table 68.4 Comparison of flexural properties and noise reduction coefficient (NRC) of cornhusk fiber-polypropylene and jute-polypropylene composites in their respective optimized conditions [08Hud1]
|
|
Properties |
Rice husk fiber |
Bagasse fiber |
|
Cellulose (%) |
48.9 |
95.3 |
|
Lignin (%) |
19.1 |
21.0 |
|
Extractive (%) |
2.5 |
2.9 |
|
Ash (%) |
12.3 |
1.9 |
|
Fiber length (mm) |
0.80 |
0.96 |
|
Aspect ratio |
89 |
42 |
|
Table 68.5 Selected properties of the rice husk and bagasse fibers used as reinforcement in polypropylene composites [08Lee] |
|
Table 68.6 Properties of polypropylene composites reinforced with 5-20 % of bagasse fibers [11Cer]
|
|
Table 68.7 Tensile and flexural properties of biocomposites reinforced with various levels of untreated and alkali-treated bagasse fibers [06Cao]
|
reinforcing materials used. Table 68.8 provides a comparison of the properties of the reinforcing materials used, and Table 68.9 provides a comparison of the properties of the composites obtained using the different lignocellulosic materials. Fiber lengths and widths for the different materials were similar, but the tensile and flexural properties obtained with these reinforcing materials were considerably different as seen in Table 68.7. Reinforcing the matrix with the fibers resulted in marginal increase in strength, but the modulus increases considerably, and elongation nearly decreases by a factor of 9-10. Flexural strength and modulus also showed improvements with the addition of the fibers. However, no major differences in properties were observed between the various reinforcing materials used. Soy stalk fibers had better thermal stability, and the soy stalk-reinforced composites showed the highest thermal resistance. Although composites were developed using various agricultural residues, no pretreatment or fiber extraction was done. It can be expected that the properties of the composites can be improved
|
Agricultural residue |
Fiber length (mm) |
Fiber width (mm) |
Cellulose (%) |
Hemicellulose (%) |
Lignin (%) |
|
Switchgrass |
1.6 ± 0.4 |
0.46 ± 0.26 |
36.1 |
28.2 |
10.2 |
|
Miscanthus |
1.5 ± 0.5 |
0.45 ± 0.17 |
50.2 |
20.5 |
15.1 |
|
Soy stalk |
1.5 ± 0.5 |
0.46 ± 0.27 |
45.0 |
11.4 |
13.9 |
|
Corn stover |
1.5 ± 0.5 |
0.43 ± 0.19 |
44.8 |
22.7 |
10.6 |
|
Wheat straw |
1.1 ± 0.2 |
0.47 ± 0.17 |
47.9 |
24.0 |
11.0 |
|
Table 68.8 Comparison of the properties of the different lignocellulosic raw materials considered as reinforcement for PHBV/PBAT [13Nag1] |
by chemical modification of the raw materials, using extracted fibers with high cellulose content or by the addition of compatibilizing agents. However, the presence of lignin, hemicelluloses, and other impurities in the reinforcing materials may affect the properties and/or performance and the utility of the composites. For instance, under simulated biodegradation conditions, soy and wheat straw added into PLA had higher than 70 % degradation within 45 days of aerobic degradation. As seen from Fig. 68.4, the degradation of the composites was higher than that of neat PLA demonstrating that addition of the lignocellulosic components could increase the degradability of the matrix [10Pra].
![Подпись: Fig. 68.4 Comparison of the degradation (%) of PLA composites reinforced with soy and wheat straw with neat PLA [10Pra]. Reproduced with permission from Elsevier](/img/1179/image333.png "image333") |
 |
PHBV was reinforced with corn straw (CS), wheat straw (WS), and soy stalk (SS) cut into 0.25 mm length individually or in a combination, and the influence of the reinforcements on the mechanical, thermal, and dynamic mechanical properties was investigated [11Aha]. Table 68.10 lists the tensile properties of the composites obtained using various ratios of the different reinforcing agricultural residues. Adding the residues had varying effects depending on the type of reinforcement and the treatment done and the ratio in the PHBV matrix. Overall, alkali-treated biomass provided higher increase in flexural strength and modulus due to the
 |
||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||
 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
removal of noncellulosic substances and increase in surface roughness that promotes better adhesion [11Aha]. In addition to the tensile and flexural properties, the heat deflection temperature (HDT) also increases from 108 up to 133 °C as seen from the table. Increase in HDT suggests compatibility between the reinforcement and the matrix. Although composites with good mechanical properties have been obtained from PHBV and the agricultural residues, the performance of the composites in high humidities or in water was not investigated.
Similar to using agricultural residues obtained after harvesting cereal grains, the residues or by-products obtained after processing oil crops have also been used for composite applications. For example, fibers obtained from date palms have been used as reinforcements for biocomposites, and the influence of various fiber properties and composite formation conditions on properties of the composites was compared and critiqued [14AlO]. It was reported that date palm fibers have similar aspect ratio compared to coir and hemp, higher elongation than hemp and sisal, and available at a cost $0.02 per kg, 15 times cheaper than coir and 60 times cheaper than hemp. Therefore, attempts have been made to utilize palm fibers as reinforcements for biocomposites [14AlO]. Starch-based composites were developed by reinforcing with date palm and/or flax fibers. Fruit-bearing branches of date palms were retted in water and later treated with NaOH at 90 °C for 3 h between 80 and 90 °C. After several such treatments and neutralization, the fibers obtained were manually cut into lengths of 15-30 mm [14Ibr]. Starch was treated with glycerin (30 %) and water (20 %) and processed between 60 and 80 °C to obtain thermoplastic starch. Various ratios of the fibers were mixed with the thermoplastic starch and compression molded at 160 ± 3 °C for 30 min at 5 MPa pressure. Morphological analysis showed that the fibers and matrix had good adhesion, but the presence of voids was observed when the ratio of fibers in the matrix was high due to the lack to sufficient matrices seen in Fig. 68.5 [14Ibr]. The strength of the composites increased from 5 to 30 MPa when the concentration of the fibers was increased from 0 to 50 %, and a similar increasing trend (5-17 MPa) was observed for the modulus. However, both the strength and modulus decreased when the fiber content was above 50 % [14Ibr].
Similar to date palms, oil palms have also been extensively studied as potential reinforcements for composites with various matrices [11Shi]. Oil palm fibers have been combined with polyester, polyurethane, natural rubber, phenol formaldehyde, and others. Composites with properties suitable for various applications have been obtained, and several different pretreatments and addition of plasticizers and compatibilizers have been done to improve the properties of the composites [11Shi]. However, limited attempts have been made to develop completely biodegradable composites using oil palm fiber and to understand the biodegradability of the composites developed [11Shi].
In addition to date and oil palms, fibers from another variety of palm, sugar palms (Arenga pinnata), have also been used as reinforcement for composites. Several reports are available on developing polyester composites reinforced with sugar palm fibers. In fact, sugar palm fibers have been used with glass fibers to reinforce unsaturated polyester and made into boat shown in Fig. 68.6 [13Ish]. Some
|
Fig. 68.5 (a) SEM images of date palm fiber-reinforced starch-based composites reveal areas with voids and (b) places with good adhesion [14Ibr]. Reproduced with permission from Elsevier |
|
Fig. 68.6 A boat developed using sugar palm fibers and glass fibers as reinforcement [13Ish]. Reproduced with permission from Elsevier |
|
Table 68.11 Mechanical and physical properties of sugar palm fiber-reinforced unsaturated polyester composites [13Ish]
Ijuk refers to a natural fabric-like structure found wrapped onto the palm trunk |
of the properties of sugar palm fiber-reinforced unsaturated polyester composites are given in Table 68.11, and properties of alkali-treated sugar palm fibers used as reinforcement for epoxy composites are shown in Table 68.12.
Agave fibers were manually extracted by retting and processed to obtain fibers with a diameter of about 0.3 mm and length of 12 cm and used as reinforcement for epoxy. Further, the fibers were also treated with 5 % alkali for 30 min to remove extractables and increase the surface roughness and promote adhesion to the matrix [11Myl]. Stress-strain curves did not show a major difference in properties between
|
Table 68.12 Comparison of the properties of alkali-treated sugar palm fiber-reinforced epoxy composites after treating with two different concentrations of alkali at various treatment times [13Ish]
|
|
A — PHBV/PBAT; B — PHBV/PBAT + 20% SG; C — PHBV/PBAT + 25% SG; B — PHBV/PBAT+ 30% SG; E — PHBV/PBAT+ 40 % SG Fig. 68.7 Tensile properties of PHBV/PBAT composites reinforced with various amounts of switchgrass [13Nag2]. Reproduced with permission from the American Chemical Society |
the untreated and treated composites, but considerable differences were observed in flexural and impact resistance. The alkali-treated agave fibers provided better flexural properties and thermal resistance than the untreated fibers [11Myl]. Similar to agave, sisal fibers have also been extensively studied as possible reinforcement for various types of matrices [00Li]. However, sisal is an exclusive fiber crop, and therefore sisal-based composites have not been reviewed here.
Switchgrass, a renewable biomass crop considered as a potential feedstock for cellulosic ethanol production, has been studied as possible reinforcement for PHBV-based biocomposites [13Nag2]. Switchgrass fibers (average length of 4— 8 mm) were mixed with a commercially available (ECOFLEX) 45 % PHBV and 55 % PBAT matrix in various ratios and processed through a twin screw compounder to obtain the composites. A compatibilizer pMDI was included to improve the compatibility between the fibers and the matrix. The amount of switchgrass used in the composites was 25, 30, or 40 %. Figure 68.7 shows the tensile and
|
Fig. 68.8 SEM images showing the improved adhesion between the switchgrass fibers and matrix before (a) and after (b) addition of the compatibilizer [13Nag2]. Reproduced with permission from the American Chemical Society |
flexural properties of the composites developed. As seen from the figure, the properties of the composites decreased when the amount of fibers increased above 30 %. The addition of the compatibilizer increased the tensile and impact resistance properties due to improved adhesion between the fibers and matrix as seen in Fig. 68.8.
Pineapple leaves were processed to obtain whole ground pineapple leaves (WGL), pineapple leaf fibers (PALF), and non-fibrous material (NFM), and these components were used as filler or reinforcement for polypropylene composites [14Ken]. The composition of the three components obtained from the pineapple leaves is shown in Table 68.13. The components extracted from the pineapple leaves were added at various extents into polypropylene and compression molded into composites. Figure 68.9 shows the flexural and tensile properties of the composites developed. As seen from the figure, the addition of the PALF composites substantially improved the flexural and tensile properties except for the decrease in tensile strength observed at high ratios of NFM. Among the three pineapple leaf components studied, PALF provided substantially higher improvement in properties because of the higher aspect ratio and also probably due to the higher cellulose and lower content of impurities [14Ken]. It was suggested that the properties of the composites could be controlled by varying the type and amount of reinforcement.
Pineapple leaf fibers were made into nanofibers through steam explosion and used to develop bionanocomposites for medical and other applications
|
Table 68.13 Composition of the three types of materials extracted from pineapple leaves [14Ken]
|
|
Fig. 68.9 Flexural modulus (a), flexural strength (b) and tensile strength (c) of PP composites reinforced with various amounts of components extracted from pineapple leaves [14Ken]. Reproduced with permission from Elsevier |
[11Che]. PALF fibers were steam exploded in an autoclave at 138 kPa pressure in the presence of 2 % NaOH. Steam-exploded fibers were further bleached and steam exploded eight times to obtain nanofibrils (69 % yield). Fibers (5-15 nm diameter) were made into films and nonwoven mats for potential use as reinforcement for composites. Biodegradable polyurethane was developed and used as the matrix. Composites were developed by placing layers of the nonwoven mats between polyurethane films and compression molding between 150 and 200 °C. The composites were molded into heart valves and implants shown in Fig. 68.10. Tensile properties of the pure polyurethane and cellulose reinforced composites are shown in Table 68.14. As seen from the table, the addition of the nanocellulose leads to more than threefold increase in strength and tenfold increase in modulus. The composites developed were considered to be suitable to manufacture wound dressing, glove, surgical drapes, and medical disposables [11Che].
PALF fibers of two lengths, long fibers >300 mm, and having a unidirectional arrangement and short fibers of 40 mm that had a random arrangement were used as reinforcement for low-density polyethylene and polypropylene composites [ 11Cho]. Incorporating the fibers in the matrix leads to considerable decrease in crystallinity and heat of fusion. Tensile properties of the composites are shown in Table 68.15.
|
Table 68.14 Mechanical properties of composites made from pure polyurethane embedded with cellulose [11Che]
|
 |
![Подпись: Fig. 68.10 Digital image of a heart valve developed from PALF nanofiber-reinforced polyurethane [11Che]. Reproduced with permission from Elsevier](/img/1179/image343.png "image343") |
As seen from the table, increasing the amount of fibers in the matrix increased the strength continually for both the LDPE and PP matrix. At similar levels of reinforcement, the long fibers provided better strength than the short fibers. However, the type of matrix did not make a significant difference in terms of strength of the composites. A study was conducted to understand the influence of fiber content on the thermal and water resistance of polyester composites reinforced with pineapple leaf fibers [04Uma]. The resistance of the composites to water was measured by immersing the samples in room temperature water for several weeks and also by boiling in water for 7 h at atmospheric pressure. Thermal resistance studies were conducted by heating the samples at 100 °C for 48 h [04Uma]. Changes in the properties of the composites before and after aging are reported in Table 68.16. As seen from the table, boiling in water resulted in about 35 % decrease in strength and 18 % decrease in modulus. Heating causes considerably lower decrease in strength of about 6 %, but the modulus decreased by as high as 52 %. Higher loss of modulus after aging was suggested to be due to the degradation of the fiber [04Uma].
Banana fibers were modified using various chemical treatments and added into PLA to improve the properties of the composites [13Jan]. Fiber bundles were cut into lengths of 13-15 cm and washed with detergent to remove impurities. Later, the fibers were mercerized using NaOH and also silane treated using [3-amino propyltriethoxysilane (APS) or bis-(3-triethoxysilylpropyl)tetrasulfane (Si69)].
|
Table 68.15 Properties of LDPE and PP composites reinforced with long and short fibers [11Cho]
|
|
Table 68.16 Properties of polyester composites reinforced with 30 % PALF fibers before and after water and thermal aging [04Uma]
|
These chemically modified fibers were cut into lengths of 2-3 mm before using as reinforcement. Properties of composites reinforced with the various banana fibers are shown in Table 68.17. The addition of the banana fibers progressively increased the tensile strength and modulus but decreased the elongation and impact strength as observed for other composites. Fibers treated with the silane coupling agents, especially with bis-(3-triethoxysilylpropyl)tetrasulfane (Si69), showed substantial increase (more than doubled) in tensile strength and modulus, and an increase in elongation was also observed [13Jan]. In addition, organically modified nanoclay cloisite 30B was included to improve the processability and properties of the composites which were made into plastic cutlery shown in Fig. 68.11.
In an effort to develop completely biodegradable composites, curaua fibers milled to 10-30 mm in length were mixed with cellulose acetate as the matrix and injection molded into tensile bars using dioctyl phthalate (DOP), triethyl citrate (TEC), or glycerol triacetate (GTA) as the plasticizing agent [12Gut]. In addition, fibers were also treated with acetone or mercerized to improve adhesion and compatibility with the matrix. Properties of the composites obtained are displayed in Table 68.18. As seen from the table, the addition of the plasticizer increased the tensile properties of the fibers, and the inclusion of the fibers decreased the thermal coefficient [12Gut]. Chemical treatments caused fibrillation and improved the bonding between the fibers and the matrix leading to better properties. In further continuation of their work, the effect of plasticizer and fiber content on the
|
Material |
Tensile strength (MPa) |
Tensile modulus (MPa) |
Elongation at break (%) |
Impact strength (J/m) |
|
PLA |
38 ± 3.3 |
3,546 ± 37 |
2.9 ± 1.1 |
24.7 ± 2.5 |
|
PLA/BF (90/10) |
10.6 ± 1.2 |
3,963 ± 45 |
1.5 ± 0.2 |
14.7 ± 1.7 |
|
PLA/BF (80/20) |
13 ± 1.6 |
4,210 ± 56 |
1.1 ± 0.6 |
15.2 ± 1.5 |
|
PLA/BF (70/30) |
14.6 ± 1.4 |
4,631 ± 38 |
1.1 ± 0.3 |
19.1 ± 1.4 |
|
PLA/BF (60/40) |
7.8 ± 1.8 |
4,705 ± 34 |
0.9 ± 0.5 |
13.5 ± 2.4 |
|
PLA/NaBF (70/30) |
16.0 ± 1.5 |
4,636 ± 56 |
0.7 ± 0.1 |
19.7 ± 2.4 |
|
PLA/APS-BF (70/30) |
17.5 ± 2.4 |
4,703 ± 23 |
0.9 ± 0.2 |
25.0 ± 2.4 |
|
PLA/Si69BF (70/30) |
34.4 ± 2.6 |
4,815 ± 29 |
2.3 ± 0.5 |
30.0 ± 2.2 |
|
Table 68.17 Tensile properties and impact strength of PLA composites reinforced with various ratios of banana fibers with and without chemical treatments [13Jan] |
|
Fig. 68.11 Plastic cutlery manufactured from banana fiber-reinforced PLA and nanoclay [13Jan]. Reproduced with permission from Elsevier |
 |
mechanical, morphological, and thermal performance of curaua fiber-reinforced composites was studied [14Gut]. Influence of plasticizer content and type of fiber on the tensile properties is shown in Table 68.17. When the concentration of the plasticizer is increased from 20 to 30 %, the non-reinforced fibers show a 100 % decrease in modulus and 120 % increase in elongation as seen in Table 68.19. Chemical treatment was found to increase modulus but decrease impact strength. However, the type of treatment (acetone/NaOH) did not make a significant difference in tensile properties [14Gut].
Curaua fibers were also used as reinforcement for PHBV composites in ratios up to 30 %. The blend was first processed in a single screw extruder between 150 and 160 °C and later in a twin screw extruder at 170 °C [13Ros]. FTIR spectra of the neat PHBV and fiber-reinforced composites did not show any major difference suggesting that the fabrication process did not alter the chemical structure of PHBV. Figure 68.12 shows that the addition of the fibers increased the tensile
|
Table 68.18 Influence of the type of plasticizer and chemical modification of curaua fibers on the modulus, impact strength, and thermal properties of cellulose acetate-based composites [14Gut]
|
and flexural strength and modulus up to a reinforcing fiber content up to 30 %. Tensile modulus increased from 3 to 5 MPa at a fiber content of 30 %. Contrarily, the addition of the fibers decreased the impact strength due to the reduction of the mobility of the polymer chains.
Lignocellulose fibers obtained from the borassus fruits (borassus fruit fibers) (BFF) were used as reinforcement for PP composites. BFF fibers were used as reinforcement without any treatment and also after treating with sodium hydroxide. To improve the compatibility between the matrix and reinforcing fibers, PP was also maleated [13Sud]. The mixture of PP and the fibers was pelletized and later injection molded into specimens for tensile testing. FTIR spectra suggested strong interaction between the matrix and the borassus fruit fiber. However, fiber agglomeration and pullouts were seen under scanning electron microscope at higher levels of fiber loading. Some of the properties of the composites developed are given in Table 68.20. Figure 68.13 provides a comparison of the properties of the PP-BFF composites with coir, jute, and sisal fibers. Increasing the amount of BFF in the composites up to 15 % continually increased the tensile and flexural strength, but the strength slightly decreased at 20 % BFF. However, tensile and flexural modulus was found to increase even at 20 % BFF.
Jatropha, a plant that is widely promoted as a promising biodiesel crop, produces considerable amounts of by-products that have been used for biocomposite applications [13Abd]. The oil cake obtained after processing the jatropha seed for oil has been used to develop composites. However, so far, the jatropha oil cake has been used as reinforcement with styrene butadiene and glass-epoxy as matrix/ reinforcement. In addition to the oil cakes, other parts of the jatropha plant such
 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
0 10 20 30 0 10 20 30 Fiber cement (%) Fiber content (%) Fig. 68.12 Influence of fiber content on the tensile and flexural strength (a) and tensile and flexural modulus (b) properties of curaua fiber-reinforced PHBV composites [13Ros]. Reproduced with permission from John Wiley and sons |
|
Table 68.20 Tensile, flexural, and impact resistance properties of borassus fruit fiber (BFF)- reinforced PP composites at various levels of fiber content [13Sud]
|
as protein isolate, stem of the plant, and shell of the jatropha oil seed, can also been used for reinforcement [13Abd].
Bamboo has been one of the most preferred and widely used biomass to develop biocomposites. Various approaches have been used to process bamboo and make it suitable for use as reinforcement with several different kinds of polymers as matrix [12Kha]. Bamboo-based composite materials have been used to develop several products, and many such products are commercially available. Figure 68.14 shows some of the products developed using bamboo composites. Properties of some of the bamboo-based composites are listed in Table 68.21. A wide variation in properties is observed across the table due to the differences in the amount of reinforcement used, the type and amount of matrix, and the products developed and testing conditions employed. Several researchers have also suggested that bamboo can replace up to 25 % of glass fibers without any decrease in composite properties.
Micro — and nanofibrils obtained from bamboo were combined with modified soy protein concentrate to develop completely biodegradable composites. A dispersion of the bamboo fibrils (10-40 %) was added into a dispersion of soy protein
ВйШІ Flexural Strength
50 20 10
PP 5BFF 10BFF 15BFF 20BFF Coir Jute Sisal
Tensile Modulus
ШоЗ Flexural Modulus
PP 5BFF 10BFF 15BFF 20BFF Co r Jute S sa
Fig. 68.13 Influence of percentage of borassus fruit fibers on the tensile and flexural strength (a) and tensile and flexural modulus (b) of PP composites [13Sud]. Reproduced with permission from Elsevier concentrate containing glycerol, and the mixture was made into sheets. The sheets obtained were then compression molded at 120 °C for 25 min under a pressure of 8 MPa [09Hua]. To further improve the properties of the composites, the soy
|
Fig. 68.14 Examples of products that have been developed using bamboo composites [12Kha]. Reproduced with permission from Elsevier |
protein concentrate was chemically modified using (3-isocyanatopropyl) triethoxysilane (ITES) as the cross-linking agent. Properties of the composites developed using various ratios of the bamboo microfibrils and glycerol are shown in Table 68.22. The influence of chemical modification of soy protein concentrate on the mechanical properties is also provided. As seen in Table 68.23, increasing the ratio of glycerol decreased the stress and modulus but increased the strain and moisture content. Cross-linking the soy protein results in a marginal increase (6 %) in the tensile strength and a 7 % increase in modulus. However, the toughness of the composites was increased to 4.6 MPa compared to 2.1 MPa without using the crosslinking agent [09Hua].
Bamboo fibers were used to reinforce poly(butylene succinate) (PBS) before and after grafting poly(ethylene glycol) methyl ether methacrylate [11Bao]. Bamboo
|
Table 68.21 Comparison of the properties of composites developed using bamboo as reinforcement [12Kha]
|
|
Table 68.22 Comparison of the properties of the bamboo fibril-reinforced soy protein-based composites at various ratios of glycerol [09Hua]
|
fibers were cut into length of 3-5 mm, extruded with PBS in a twin screw extruder, and later compression molded into composites. SEM images of the fracture surface showed that composites containing unmodified bamboo fibers had smooth surfaces and long length fiber pullouts indicating poor compatibility. On the contrary, the grafted bamboo fibers showed rough fracture surfaces and holes due to fiber pullouts indicating good compatibility. Table 68.24 shows the properties of the PBS composites reinforced with various levels of unmodified and modified bamboo fibers. As seen from the table, the addition of the grafted bamboo fibers increased
|
Table 68.23 Comparison of the properties of the bamboo fibril-reinforced soy protein-based composites after cross-linking with various levels of the cross-linking agent [09Hua]
|
The composition of the composites was 100 % soy protein concentrate, 30 % bamboo fiber, and 2 % glycerol
|
Table 68.24 Properties of composites reinforced with unmodified and grafted bamboo fibers [11Bao]
|
the tensile strength, elongation, and modulus due to the improved interfacial adhesion [11Bao].
Coir fibers were treated with basic chromium sulfate and sodium bicarbonate salt in acidic media to improve biocompatibility, and various levels (10, 15, and 20 %) of the modified fibers were used to reinforce polypropylene composites [13Mir]. Tensile strength of the composites containing raw coir fibers was lower than that of the chemically modified fibers. Increasing the content of the raw or the chemically treated fibers decreased the tensile strength as seen in Fig. 68.15. However, flexural strength and impact resistance were found to increase with increasing fiber content. Lower moisture absorption and better mechanical properties were obtained for the CrSO4-treated samples followed by the NaHCO3-treated fibers. A coir fiber content of 20 % was found to provide the most optimum properties for the polypropylene composites [13Mir].
|
Fig. 68.15 Changes in the tensile and flexural strength and flexural modulus with increasing content of coir fibers [13Mir]. Reproduced with permission from Elsevier |
Apart from the lignocellulosic fibers or agricultural residues that have been used as reinforcement for composites, poultry feathers that are available in large quantities at almost no cost have also been extensively studied for composite applications. In addition to their low cost and large availability, feathers have unique hierarchical structure and low density that make them ideal for developing lightweight composites for automotive and other applications. Composites have been developed using whole feather, feather fiber, and powdered quill as reinforcement for composites. Table 68.25 presents the properties of the feather-reinforced composites in comparison to jute-reinforced composites. As seen from the table, feather-reinforced composites provide similar tensile and flexural properties to the composites compared to the synthetic polymer-based composites. In addition, the noise reduction coefficient of the feather-reinforced composites is considerably higher than that of the traditional fiber-reinforced composites.
 |
|||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||
[00Li] Li, Y., Mai, Y. W., Ye, L.: Compos. Sci. Technol. 60, 2037 (2000)
[04Uma] Uma Devi, L., Joseph, K., Nair, K. C.M., Thomas, S.: J. Appl. Polym. Sci. 94,
503 (2004)
[06Cao] Cao, Y., Shibata, S., Fukumoto, I.: Compos. Part A 37, 423 (2006)
[08Hud1] Huda, S., Yang, Y.: Macromol. Mater. Eng. 293, 235 (2008)
[08Hud2] Huda, S., Yang, Y.: Compos. Sci. Technol. 68(3-4), 790 (2008)
[08Lee] Lee, S. C., Mariatti, M.: Mater. Lett. 62, 2253 (2008)
[09Hua] Huang, X., Netravali, A.: Compos. Sci. Technol. 69, 1009 (2009)
[09Hud1] Huda, S., Yang, Y.: Ind. Crops Prod. 30, 17 (2009)
[09Hud2] Huda, S., Yang, Y.: J. Polym. Environ. 17, 131 (2009)
[10Ash] Ashori, A., Nourbakhsh, A.: Waste Manag. 30, 680 (2010)
[10Pra] Pradhan, R., Misra, M., Erickson, L., Mohanty, A.: Bioresour. Technol. 101, 8489 (2010)
[11Aha] Ahankari, S. S., Mohanty, A. K., Misra, M.: Compos. Sci. Technol. 71, 653-657 (2011)
[11Bao] Bao, L., Chen, Y., Zhou, W., Wu, Y., Huang, Y.: J. Appl. Polym. Sci. 122, 2456 (2011)
[11Cer] Cerqueira, E. F., Baptista, C. A.R. P., Mulinari, D. R.: Procedia Eng. 10, 2046 (2011)
[11Che] Cherian, B. M., Leao, A. L., de Souza, S. F., Costa, L. M.M., de Olyveira, G. M.,
Kottaisamy, M., Nagarajan, E. R., Thomas, S.: Carbohydr. Polym. 86, 1790 (2011) [11Cho] Chollakup, R., Tantatherdtam, R., Ujjin, S., Sriroth, K.: J. Appl. Polym. Sci. 119, 1952 (2011)
[11Myl] Mylsamy, K., Rajendran, I.: Mater. Des. 32, 3076 (2011)
[11Shi] Shinoj, S., Visvanathan, R., Panigrahi, S., Kochubabu, M.: Ind. Crops Prod. 33,
7 (2011)
[12Gut] Gutierrez, M. C., Paoli, M. D., Felisberti, M. I.: Compos. Part A 43, 1338 (2012)
[12Kha] Khalil, H. P.S. A., Bhat, I. U.H., Jawaid, M., Zaidon, A., Hermawan, D., Hadi, Y. S.:
Mater. Des. 42, 353 (2012)
[13Abd] Abdul Khalil, H. P.S., Sri Aprilia, N. A., Bhat, A. H., Jawaid, M., Paridah, M. T., Rudi, D. A.: Renew. Sustain. Energy Rev. 22, 667 (2013)
[13Ish] Ishak, M. R., Sapuan, S. M., Leman, Z., Rahman, M. Z.A., Anwar, U. M.K., Siregar, J. P.: Carbohydr. Polym. 91, 699 (2013)
[13Jan] Jandas, P. J., Mohanty, S., Nayak, S. K.: J. Clean. Prod. 52, 392 (2013)
[13Mir] Mir, S. S., Nafsin, N., Hasan, M., Hasan, N., Hassan, A.: Mater. Des. 52, 251 (2013) [13Nag1] Nagarajan, V., Misra, M., Mohanty, A. K.: Ind. Crops Prod. 42, 461 (2013)
[13Nag2] Nagarajan, V., Mohanty, A. K., Misra, M.: ACS Sustain. Chem. Eng. 1, 325 (2013)
[13Ros] Rossa, L. V., Scienza, L. C., Zattera, A. J.: Polym. Compos. 34, 450 (2013)
[13Sud] Sudhakara, P., Jagadeesh, D., Wang, Y., Prasad, C. V., Devi, A. P., Balakrishnan, G.,
Kim, B. S., Song, J. I.: Carbohydr. Polym. 98, 1002 (2013)
[14AlO] Al-Oqla, F. M., Sapuan, S. M.: J. Clean. Prod. 66, 347 (2014)
[14Gut] Gutierrez, M. C., Paoli, M. D., Felisberti, M. I.: Ind. Crops Prod. 52, 363 (2014) [14Ibr] Ibrahim, H., Farag, M., Megahed, H., Mehanny, S.: Carbohydr. Polym. 101, 11 (2014)
[14Ken] Kengkhetkit, N., Amornsakchai, T.: Mater. Des. 55, 292 (2014)
[14Nou] Nourbakhsh, A., Ashori, A., Tabrizi, A. K.: Compos. Part B 56, 279 (2014)