productions is expected to exceed thousands of tons annually in the few coming years [43]. It is believed that during the last three decades, the generation of solid wastes was almost doubled and about one third of these wastes were from packaging materials, especially the food packaging wastes. Hence, using biobased materials just for food packaging can yield a considerable impact on the environment by replacing the nondegradable materials with degradable and composting materials [44–46].
Figure 1.5 Number of publications considering natural fiber composites.
Source: Peças et al. [42]. Licensed under CC BY 4.0.
1.4.1 Green Biomass‐based Composites
An increasing environmental awareness for the people helped in adopting a public trend toward replacing the petro‐based composites with sustainable biobased ones. In general, biobased composites are a combination of fibers and polymer material (matrix), with at least one of them from a natural resource [47–49]. Hence, the combinations of natural fibers and petro‐based polymers, synthetic fibers and biobased polymers, and natural fibers and biobased polymers are all called conventional biocomposites. Here, the first and second combinations are not fully ecofriendly, whereas the third combination, that is the combination of natural fibers and biobased polymers (commonly known as a green biocomposite), is more ecofriendly [6, 50–52]. A biocomposite is called biodegradable when the matrix material is biodegradable. This can be for both biobased and petro‐based composites provided that they are degradable. Biopolymers are different from biodegradable polymers in their raw material. The latter can be formed from either biobased or petroleum‐based composites and can be categorized as green polymeric matrices. When both the fiber and matrix are from renewable resources, they are referred to as biobased composites or biocomposites (fully biodegradable green composite). These biocomposites have less environmental impact.
1.4.2 Selection Considerations
To select the most appropriate alternative materials for various applications, several evaluation criteria have to be considered, most of which may be conflicting. Thus, the selection process and considerations may contain several aspects and may become a sophisticated issue with a manner of multicriteria decision making problem that requires proper decisions to be made via various optimizations as well as other methods like that of analytic hierarchy process, which are utilized in various engineering problems [18, 37, 53–57].
1.4.2.1 Materials Implementation Requirements
Before commercializing a new material for use in industry, it has to undergo a series of sequence steps. First, the new material is introduced. Then a possible application is identified, and the material specifications needed to meet the requirements of this application should be listed. The material specifications are mainly varieties of physical, mechanical, economical, and environmental properties such as density, appearance, strength, cost, availability, reliability, etc. Hence, the new material should meet all the required specifications through a long journey of tests and verifications. In the next step, a prototype is made to check the performance of the proposed material. In the last step, a management plan is established for studying the market needs, supplying raw materials, and ensuring the availability of raw materials in a sustainable manner. The time spent through all these preceding steps is completely unpredictable, adding great stress on the competing manufacturers. After going through all these steps, the new material is now ready for production. However, a manufacturing process must first be established.
1.4.2.2 Material Cost
Cost is very essential in the material selection process for any application, and the target cost is set in the early stages of any application development. A tradeoff between the cost and the performance is sometimes required in the decision‐making stage.
1.5 Biomass Composites Characteristics and Testing
Combining fibers with polymers in biomaterials usually produces composites with totally different characteristics as well as superior desired performance over the utilized constituents. Biobased plastics are dominating the new trends in plastic industry since the petro‐based plastics are nonrenewable (help in depletion of petroleum resources), nondegradable (cause shortage in landfills), and very harmful to the environment. These new trends are focusing more specifically on the renewable plants and on agro waste fiber composites. However, it is not possible to completely replace all the petro‐based productions with biobased ones [25]. In such cases, the concept of combining biomaterials with petro‐based products should be adopted. Natural biocomposites have become well recognized for their low cost and low density. In addition, the ease of shaping and processing due to the low abrasiveness when compared to synthetic fiber‐based composites gives the biobased composites extra advantages. On the other hand, many difficulties arise in using the biobased composites in industry. One of these difficulties is the incompatibility issue between the fiber and the polymer. This is due to both the hydrophilic characteristic of the natural fibers and the hydrophobic characteristic in polymers. Reducing the incompatibility requires physical and chemical treatments for the fibers, as well as using various additives as coupling agents between the fibers and the polymers. Once the composite material is well fabricated, its characteristics are required to be tested and improved. The most critical properties are the mechanical ones, namely the tensile strength, the tensile modulus, the fatigue strength, the creep rate, and the impact strength. Agro waste natural fibers are normally suitable to reinforce polymers due to their relative high mechanical performance and their low densities.
The mechanical properties of the composite materials are the most essential characteristics even if the composites are not used in loaded applications. A certain level of strength is required for the composites to at least maintain their shapes during service. However, for some composites, it is very hard to estimate their mechanical properties as is the case with biocomposites of short natural fibers. This is due to many reasons, such as the fiber dimensions, fiber quality, fiber orientation and distribution, the fiber–matrix interface quality, as well as the matrix characteristics [41, 58]. Table 1.1 demonstrates the mechanical and physical characteristics of some natural fibers.
Improving the composite properties can sometimes be achieved by controlling some key factors, such as the fiber aspect ratio (L/D) and volume fraction of the fibers with respect to the matrix [59]. If the aspect ratio of the fiber is very small, insufficient load will transfer from the matrix to the fiber; in such cases, the fibers will work just as fillers and no considerable improvements will be achieved in the composite's mechanical performance. On the other side, high aspect ratio usually leads to poor fiber dispersion, substantially poor mechanical performance. Regarding the volume fraction, the low percentile causes discontinuities in transferring the load over the fibers; thus, the composite strength will decline. Also, the high percentile can produce the same effect due to fiber clustering.
Table 1.1 Mechanical and physical characteristics of some natural fibers.
Source: AL‐Oqla et al. [16]. © 2015, Elsevier.
| Fiber type | Coir | Date palm | Flax | Hemp | Sisal |
|---|
