Bio-derived plastics

A bio-derived plastic on the other hand is biopolymer that is chemically modified to improve its properties. Cellulose from plants can be acetylated to yield cellulose acetate, the bio-derived plastic used in cigarette filters. It can also be xanthated and extruded into cellophane (or Rayon), a bio-derived plastic. Chitin, a biopolymer from crab shells, can be processed (by converting the amide functionalities into amine functionalities) into its amine analog to obtain a bio-derived plastic, chitosan. 

Using renewable feedstock to make plastics is a key dictum in environmental sustainability. An abundance of biomass that can be used as raw material is available. Of the 170 billion tons of biomass produced annually by nature, less than 4% is used by humans (mostly for food and wood-based industries (Thoen and Busch, 2006)). The first bio-derived plastic, celluloid, was invented back in 1860 followed by a few others in the 1940s. But with the discovery of oil, these inventions were never developed into commercial scale. With future shortage of fossil fuels, the time is ripe to exploit bio-based and bio-derived technologies (Momani, 2009). 

PLA The popular bio-derived plastic PEA is made from lactic acid obtained by fermenting starch into glucose and then into lactic acid (Bordes et al., 2009 Jem et al., 2010 Okada, 2002) (see Fig. 4.14). The lactic acid as with most bioproducts is in the l form and can be condensed into a L-lactic acid polymer. Elowever, if a mix of d- and L-form monomers are used, the properties of the plastic depend strongly on the ratio of the stereoisomers (or d l) in the... 

The terms biodegradable plastics and bio-based or bio-derived plastics were already defined in Chapter 4. Plastics can be classified in terms of the source of raw materials into four classes plastics based on fossil-fuel feed stocks, biopolymers made by living organisms, modified biopolymers, and bio-based plastics derived from renewable biomass feedstock. Members of each of these classes can be either inherently biodegradable or recalcitrant when placed in an appropriate biotic environment. BiodegradabiUty is a property or characteristic of plastics and is independent of the feedstock it is based on. This distinction was discussed in detail in Chapter 4 and is further illustrated in Figure 6.11. 

Currently, materials derived directly from starch by physical processing or by continuous chemical modification, as in reactive extrusion, are considered the most promising options for bio-based plastic production, particularly on economic grounds. A brief historical view of such starch-based materials is offered in the next section. 

The term bioplastics covers two different concepts that we tend to confuse. The first categorizes the so-called bio-sourced plastics from agricultural resoinces, a priori renewable, they are not necessarily degradable. The second includes biodegradable plastics they are not necessarily bio-soinced they are also polymers derived from fossil resources and chemistry. 

Bio-based plasticizer is environmentally friendly and derived from renewable resources (see US Patent US20100010127 to find details about this plasticizer). The PVC dry blend compositions prepared according to the process of the invention provide improved output feed rates as compared to the output feed rates of a PVC dry blend prepared from conventional phthalate. PVC and stabilizer are first mixed together and heated to stock temperature. Plasticizer preheated to 60°C is pumped into PVC stock mixture, then filler is added and mixture compounded until discharge temperature is reached. 

Figure 1.1 gives an overview of bio-based plastics. The distinction between materials based on natural polymers and those polymerized from bio-derived monomers can be seen from this. 

The book addresses the most important biopolymer classes like polysaccharides, lignin, proteins and polyhydroxyalkanoates as raw materials for bio-based plastics, as well as materials derived from bio-based monomers like lipids, poly(lactic acid), polyesters, polyamides and polyolefines. Additional chapters on general topics - the market and availability of renewable raw materials, the importance of bio-based content and the issue of biodegradability - will provide important information related to all bio-based polymer classes. 

Despite the fact that they are chemically identical, it is possible to analytically identify bio-based plastics apart from identical fossil fuel-based plastics. Carbon dioxide in air has two isotopic forms of carbon, CO and CO, in equilibrium with each other, and plastics derived from plant sources will therefore have both these isotopes. Any isotopic carbon in fossil fuel deposits, however, had long decayed over the millions of years since their formation (half-life of C is 5730 years) into C and fossil fuels, and plastics made from them do not have significant levels of Burning a sample of plastic and measuring the ratio in the CO using liquid scintillation counting or isotope-ratio mass spectrometry therefore provide a test as to the origin of the plastic (ASTM D 6866). 

Responsible use of non-renewable resources is one of the three emphasis areas in the sustainable growth (Chapter 2). Any technologies that help conserve fossil fuel reserves help achieve that goal. Using renewable bioresources to make plastics, especially types of plastics used in high volume, is therefore a sustainable move by the industry (Philp et al., 2013 Reddy et al., 2013). Biomass raw materials can yield the same basic chemical intermediates that are derived from fossil fuel raw materials, making bio-based synthesis of conventional and novel plastics a possibility. The option is particularly attractive where the embodied energy as well as the carbon emissions associated with manufacture of the bio-derived variety is at or below that of conventional plastic material. 

A continuous increase in oil prices and environmental concerns about the use of common petroleum-based plastics have recently led to a growing interest in bio-based plastics. Poly(lactic acid) (PLA), a plastic derived from fermented plant starch, is fast becoming one of the popular alternatives to traditional petroleum-based plastics. Even though PLA has been known for more than a century, it has only been used commercially in recent years in a number of biocompatible/ bioabsorbable biomedical device market, packaging applications, and so on. A number of factors contribute to the success of PLA in these applications, including its physical properties as well as favorable compostable and degradation characteristics [1]. 

Regioselective hydroformylation of hexene produces 1-heptanal, which can be converted into the short-chain fatty acid heptanoic acid by oxidation. The latter is used to manufacture polyol esters and plasticizer alcohols. When hydroformylation of hexene is followed by a reaction with bio-derived glycerol in the presence of /)-toluenesulfonic acid (PTSA), corresponding five-membered and six-membered cyclic acetals are formed, which are green fuel additives, partly generated from renewable resources (Scheme 4.8) [45]. 

The second stage of transformation will likely result in synthesis of new bio-based plastics such as polyhydroxy alkanoates and polylactic acid. Such plastics are chemically and structurally different from conventional plastics, but will be similar to the latter in terms of their properties, making them potential alternatives to both petroleum and bio-derived conventional plastics. Both the first- and second-generation transformations are, however, likely to generate concerns about the use of food-based precursors for synthesizing plastics, given that they will divert crucial food resources meant for human and animal consumption. 

Bio-based plastics "Plastics in which 100% of the carbon is derived from renewable agricultural and forestry resources such as com starch, soybean protein and cellulose" as defined by Materials (2007). 

Bio-based plastics "An organic material in which carbon is derived from a renewable resource via biological processes" as defined by ASTM (Institute, 2006). 

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