Tensile strength and elongation at break
A biodegradable composite film must withstand the normal stress encountered during its application and the subsequent shipping and handling of the food to maintain its integrity and barrier properties. Tensile strength is the maximum tensile stress sustained by the sample during the tension test. If maximum tensile stress occurs at either the yield point or the breaking point, it is designated tensile strength at yield or at break, respectively (ASTM, 1991). High tensile strength is generally required, but deformation values must be adjusted according to the intended application of the films. That is, whether it is undeformable material to provide structural integrity or reinforce structure of the food (Gontard et al., 1992). Elongation at break is an indication of films flexibility and stretch ability (extensibility), which is determined at point when the film breaks under tensile testing and is expressed as the percentage of change of the original length of the specimen between the grips of a film to stretch (extend). The tensile strength (TS) and elongation at break (ε) of the rice starch (RS) films reinforced with microcrystalline cellulose from palm pressed fiber (MCPF) or RS/MCPF biocomposite films is depicted in Figure 1. This figure clearly demonstrates the reinforcing effect of MCPF fillers. The TS of the biocomposite films increased from 5.16 MPa to 44.23 MPa when increasing the MCPF fillers content from 0 to 40% (Figure 1A) and this indicated that a high compatibility occurs between starch matrix and MCPF fillers and the performances (e.g., mechanical properties) due to 3D hydrogen bonds network formed between different component (Lu et al., 2005). Regarding the ε, results showed that increases in MCPF fillers from 0 to 15 or 20% provided an increase in ε from 8.5% to 48.32%. However, addition of MCPF fillers higher than 25% resulted in decreased elongation at break (Figure 1B). It is possibly due to the presence of high content of MCPF fillers might contribute to retarding the intermolecular interaction of the starch films. This induces the development of a heterogeneous film structure, featuring discontinuities, resulting in the decrease in ε of the films. In addition, MCPF fillers could not fully homogeneous and form small aggregates when 25-40% of MCPF fillers were filled. The results showed that addition of MCPF fillers provided the better mechanical properties of biocomposite films in this work and they are similar to those of biocomposites of plasticized starch reinforced with cellulose crystallines from cottonseed linter (Lu et al., 2005).
แรงและ elongation ที่แบ่งA biodegradable composite film must withstand the normal stress encountered during its application and the subsequent shipping and handling of the food to maintain its integrity and barrier properties. Tensile strength is the maximum tensile stress sustained by the sample during the tension test. If maximum tensile stress occurs at either the yield point or the breaking point, it is designated tensile strength at yield or at break, respectively (ASTM, 1991). High tensile strength is generally required, but deformation values must be adjusted according to the intended application of the films. That is, whether it is undeformable material to provide structural integrity or reinforce structure of the food (Gontard et al., 1992). Elongation at break is an indication of films flexibility and stretch ability (extensibility), which is determined at point when the film breaks under tensile testing and is expressed as the percentage of change of the original length of the specimen between the grips of a film to stretch (extend). The tensile strength (TS) and elongation at break (ε) of the rice starch (RS) films reinforced with microcrystalline cellulose from palm pressed fiber (MCPF) or RS/MCPF biocomposite films is depicted in Figure 1. This figure clearly demonstrates the reinforcing effect of MCPF fillers. The TS of the biocomposite films increased from 5.16 MPa to 44.23 MPa when increasing the MCPF fillers content from 0 to 40% (Figure 1A) and this indicated that a high compatibility occurs between starch matrix and MCPF fillers and the performances (e.g., mechanical properties) due to 3D hydrogen bonds network formed between different component (Lu et al., 2005). Regarding the ε, results showed that increases in MCPF fillers from 0 to 15 or 20% provided an increase in ε from 8.5% to 48.32%. However, addition of MCPF fillers higher than 25% resulted in decreased elongation at break (Figure 1B). It is possibly due to the presence of high content of MCPF fillers might contribute to retarding the intermolecular interaction of the starch films. This induces the development of a heterogeneous film structure, featuring discontinuities, resulting in the decrease in ε of the films. In addition, MCPF fillers could not fully homogeneous and form small aggregates when 25-40% of MCPF fillers were filled. The results showed that addition of MCPF fillers provided the better mechanical properties of biocomposite films in this work and they are similar to those of biocomposites of plasticized starch reinforced with cellulose crystallines from cottonseed linter (Lu et al., 2005).
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