1 6 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 and biocomposites[17-19]. Henry Ford proposed the idea of using bio-based materials in the early 1930s[17]. These environmentally friendly materials enabled low emissions and lightweight car bodies, which spurred extensive research by Ford Motor Company. On August 13, 1941, at the annual Dearborn Days festival, the first car body made of soybean plastics was unveiled[17]. Soybean, hemp, wheat straw, flax, and ramie were claimed ingredients in the plastic panels, although the exact chemical composition is not available. Nevertheless, it was reported that the car body weight was just two thirds of a standard car of the time. Fig. 3 — Different types of biodegradable plastics[9]. Research into plastic cars was stalled by World War II and war recovery efforts[17]. However, in recent years, Bledzki et al. summarized that natural fibers blended with thermoplastics are well accepted in the automotive industry for use in door liners/panels, parcel shelves, and boot liners[7]. Some examples of fossil fuel-based thermoplastics include polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). Examples of fossil-fuel based thermosets include epoxy, polyester, and vinyl ester. Most of the major car manufacturers including Audi (spare tire lining), BMW (door and head liner panels), Ford (boot liner), Saab (door panels), and Volkswagen (boot lid) have integrated biofibers in their product lists (see Table 6, Ref. 7). By using natural fibers, it is possible to reduce vehicle weight by 34%[8]. As an external application, the 2018 Mercedes-Benz A-Class model uses a natural fiber mat coupled with a thermosetting bonding agent for a sliding sunroof, replacing the traditional sheet steel frame. In 2019, Porsche reported its 718 Cayman GT4 Clubsport as the world’s first car to have exterior parts made of hemp and flax natural fiber-reinforced composites[8]. From these examples, the automotive industry appears to be a pioneer in the design and implementation of sustainable solutions. However, to create a truly sustainable composite system, it is also critical to design a sustainable matrix that can bind the natural fibers. bioplastics[9]. They can be derived by chemical processing, fermentation, and chemical modification of natural products. Polylactic acid (PLA), polyhydroxyalkanoates (PHAs), soy-based resins, and thermoplastic starch are some examples of promising biodegradable bioplastics. PLA is a renewable biopolymer that can be produced from corn and sugarcane[10]. It is one of the most studied sustainable polymers due to its many advantages such as processability, good mechanical properties, biodegradability, and biocompatibility[11]. Brittleness and low toughness are some of its limitations[10]. PHA biopolymers are naturally produced from different microorganisms[12]. Biocompatibility, biodegradability, and a thermoplastic type nature are unique attributes of PHAs[13]. Soybean oil-based triglyceride monomers such as maleinized hydroxylated soybean oil (HSO/M), maleinized soybean oil monoglyceride (SOMG/MA), and acrylated epoxidized soybean oil (AESO) are major components of molding resin and exhibit comparable properties to conventional polymers[14]. Starch is one of the abundant plant-based renewable polysaccharides that is completely biodegradable[15]. For example, thermoplastic starch (TPS) has applications for short life use such as food packaging[16]. AUTOMOTIVE BIOCOMPOSITES: A SHORT HISTORY Figure 4 shows a timeline of automotive applications using bioplastics Porsche’s 2019 718 Cayman GT4 Clubsport is the world’s first car with exterior parts made of hemp and flax natural fiber- reinforced composites. Courtesy of Porsche. GREEN BIOPLASTICS Figure 3 summarizes different types of biodegradable and renewable The “Soybean Car” was unveiled by Henry Ford on August 13, 1941, at Dearborn Days. The steel frame had 14 plastic panels attached to it, made of soybeans, wheat, hemp, flax, ramie, and other ingredients, according to one source. Lowell E. Overly, the car’s chief creator, claims the formula was “…soybean fiber in a phenolic resin with formaldehyde used in the impregnation.” Courtesy of The Henry Ford.
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