1 5 A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A Y / J U N E 2 0 2 2 Fig. 1 — Different types of (a) bioplastics[2] and (b) fibers[5]. Fig. 2 — Plot of (a) density and (b) tensile strength of natural fibers. Lower limit is plotted from the reference. Data from Table 4, Ref. 6. (b) (a) (b) (a) Substituting biomass for fossil fuel-based precursors in plastics manufacturing holds promise for achieving certain sustainability goals[1]. It is estimated that manufacturing plastics from biogenic resources could reduce greenhouse gas emissions by up to 225%[2]. Further, plastics that feature end-of-life biodegradability have potential to alleviate some of the environmental issues stemming from plastics use[2]. More specifically, bioplastics have emerged as a promising solution. They can be classified into three main categories: (a) bio-based and nonbiodegradable, (b) bio-based and bio- degradable, and (c) petroleum-based and biodegradable (Fig. 1). Currently, global use of bioplastics is <1% of the annual plastics production of roughly 367 million tons. However, it is predicted that bioplastics production will increase from around 2.41 million tons in 2021 to approximately 7.59 million tons in 2026 (>2% of global plastics production)[3]. This article focuses on the potential of biomass and bioplastics in the automotive industry. NATURAL FIBERS Natural fibers such as bamboo, sisal, cotton, jute, kenaf, coir, industrial hemp, and banana have emerged as practical options for natural reinforcements in polymers[4]. Faruk et al. classify fibers according to the schematics in Fig. 1b[5]. Figure 2 shows density and tensile strength for several natural fibers[6]. The combination of low cost, high specific strength, low density, renewability, biodegradability, and good thermal properties make these fibers suitable for a variety of applications[7]. Regarding density, both flax and hemp are 40% lighter weight than glass fibers. Some disadvantages of natural fibers involve quality issues that are further compounded by weather, the hydrophilic nature of the fibers resulting in poor moisture resistance, low fire resistance, limitations on processing temperatures, residual smell, and price fluctuations due to harvesting variations[6,7]. Thus, manufacturers and end users must balance the advantages and disadvantages for large-scale use of these fibers. For example, high quality jute fibers are standardized as Tossa Grade D[7].
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