Bioplastics

=Introduction = toc Bioplastics are defined as plastics either partly or wholly made up of [|polymers]that are derived from biological sources. Examples of biological sources are plant starches and/or cellulose. Bioplastics are categorized as either bio-based, [|biodegradable], or both. As such, the term bioplastic does not indicate a single entity but describes a spectrum of materials that fit the above description. With their promise of [|biodegradation]and/or production from renewable resources, bioplastics bring promise of sustainability to an ever-expanding industry ([|plastics]) that relies on an ever-dwindling resource ([|petroleum]).

=History = The use of biologically-derived resins can be traced back to ancient times. In Roman times and throughout the Middle Ages materials like [|amber], [|shellac], and [|gutta-percha] have been documented being used for various utilitarian purposes. In the 1869 the first documented commercialization of bioplastics appeared with John Wesley Hyatt, Jr.’s patent on a cellulose derivative for coating billiard balls, instead of the typical ivory (Green). Around 1890 PLA was discovered. However, this discovery was displaced by the discoveries made with petroleum-based plastics (Green). In the 1920's, Henry Ford began experimenting with plastic car parts made from soybeans. However, the technology never took off (Green). In the 1960's [|cellophane], a material produce from cellulose, was created. It has lived through the heavy growth of the synthetic plastics industry and is still used today in the packaging of candies, cigarettes, and other various products (Green). The demand for bioplastics has steadily grown throughout the early 2000's and is projected to grow pretty steadily (see Market below) With various countries, cities, and municipalities putting bioplastic requirements in place, the growth in bioplastics looks to be on the upside (Green).

=Applications = In general, bioplastics can be engineered to be a direct substitute for its petroleum-based equivalent (Mines). They can be used to for applications such as, soda bottles, plastic utensils, biomedical applications, such as sutures, pharmacological applications, such as pill coatings, automobile interiors, and so on.

Specific Implementation
Coca-Cola, Nestle, Dell, among many other companies have made plans and/or are already implementing bioplastics in the manufacturing of their products. On May 20, 2014, the DELL computer company announced it would be using a bioplastic compound will be used in the production of one of their lines of laptops, the Latitude (DELL). The bioplastic used will be a [|polyhydroxy alkanoate] that is derived from chemical reactions with methane and Carbon Dioxide.

The Nestlé corporation has joined with the World Wildlife Fund and seven other companies (The Coca-Cola Company, Danone, Ford, H.J. Heinz Company, Nike, P&G, and Unilever) to seek sustainable alternatives to petroleum-based products, specifically the use of bioplastics (Nestlé). The name of this alliance: the Bioplastic Feedstock Alliance. Nestlé has already been implementing bioplastics in their product lines. in fact. Since 2012, their VITTEL bottled water line has been using [|PET] bottles made from 30 per cent plant-based materials (Nestlé).

Drawbacks and Challenges
A problem with both plastics and bioplastics is that only about 30 per cent of PET bottles are collected for recycling in the U.S. each year. Some cite this as a drawback to putting effort into implementing bioplastics at all. However, others see this as one of the main arguments for bioplastics; since, no matter the end fate, a bioplastic material theoretically will biodegrade.

Another key drawback to bioplastics is the problem of correctly sorting them when they arriving at the sort facility during recycling. Inter mixing of various plastics (bio-based or petroleum-based alike) can contaminate the desired plastic the plant is aiming to recover. Therefore, lowering its resell value and quality. Additionally, a plastic that is a blend, (part bioplastic-part oil-based), may be biodegradable but not compostable. The problem of mistaking this plastic for compostable and being thrown into the municipal compost is very possible.

A serious problem faced by bioplastics comprised of composites of certain plant fibers is the strong polar character of many plant fiber, leading to a material that is more hydrophilic than hydrophobic (Terzopoulou, 77). This can cause serious problems in certain applications in which the material’s goal is to hold in water or other liquid, possibly volatile, solutions.

Another challenge facing the development of bioplastics is with many explicitly plant-fiber based composites, thermal-resistance becomes a major issue (Terzopoulou, 74). Therefore, the right mixture of composites are needed to keep the material from being extremely flammable while at the same time maintaining its mechanical strength goals.

=Types = <span style="font-family: Arial,Helvetica,sans-serif;">As mentioned, the term bioplastics does not denote a single entity but is an over-arching term for a wide range of materials made up of polymers that are derived from biological means. These include aliphatic polyesters, polyhydroxyalkanoates, cellulose- and starch-based materials, bio-derived polyethylene, and genetically modified bioplastics. Each material has its own specific application, including being the sole material of a product to being one of the constituent polymers of a material. Likewise, each material, or conglomerate of materials, has its own degrade time and conditions needed for biodegrading to occur. And similarly, each material has particular recycling classifications. Thus, extreme care is needed when either choosing the application or when separating for recycling. This reason, among others, are the areas in which the drawbacks of bioplastics are often cited. The most popular forms of bioplastics are listed below.

<span style="font-family: Arial,Helvetica,sans-serif;">Aliphatic Polyesters
<span style="font-family: Arial,Helvetica,sans-serif;">The majority of aliphatic polyester-based polymers are responsive to [|hydrolytic][|degradation], while some are [|enzymatically][|degradable]. Further, a smaller number are biodegradable or biorecyclable. Some classes of aliphatic polyester structures can generate metabolites upon degradation or biodegradation, such as poly alpha- and beta-hydroxy alkanoates. Thus, many of these types of materials are used in medical processes, such as surgery or pharmacology.

<span style="font-family: Arial,Helvetica,sans-serif;">PLA
<span style="font-family: Arial,Helvetica,sans-serif;">PLA (poly-lactic acid matrix), a compostable and fully biodegradable polymer, is derived from monomers such as [|L-lactic acid] or ring-open [|polymerization]. Mostly derived from starches, such as corn, PLA is mostly a clear plastic that rivals many petroleum-based plastics ([|PET], PS, or PE) used in ordinary plastic soda bottles and the like Through a stereo-controlled polymerization process using optically active L-lactic acid as monomer, a semicrystalline polymer is obtained with a melting point around 165–175◦C (Terzopoulou, 64).

<span style="font-family: Arial,Helvetica,sans-serif;">Poly(hydroxy alkanoates) (PHA)
<span style="font-family: Arial,Helvetica,sans-serif;">Polyhdroxy alkanoates (PHAs) are naturally occurring polyesters produced by bacteria. Some derivitives of PHA include poly(hydroxy butyrate) (PHB) and poly(hydroxy valerate) (PHV) (Terzopoulou, 75). PHAs have low mechanical properties and thermal stability, however. Other fibers can be added to improve mechanical performance (Terzopoulou, 75). In terms of its ability to biodegrade, PHA resins biodegrade rapidly in soil, sludge, and seawater (Rotkowski, 9822).

<span style="font-family: Arial,Helvetica,sans-serif;">Poly(hydroxy butyrate) (PHB)
<span style="font-family: Arial,Helvetica,sans-serif;">Poly 3-hydroxybutarate is a member of the polyhydroxyalkanoate group of polymers is produce by various bacteria when grown in nutrient-deficient cultures. However, carbon is made abundant in the culture and, thus, the carbon the bacteria produces is held as PHB in intracellular reserves (Shivakumar, 225). The PHB is extracted by various means (some on-going research in this area) and is a prime candidate for alternatives to non-biodegradable [|thermoplastics].

<span style="font-family: Arial,Helvetica,sans-serif;">Cellulose-base and other bioplastics derived directly from plants


<span style="font-family: Arial,Helvetica,sans-serif;">[|Cellulose] can be found in most fibers from the outer layers of the stems of various plants, called bast fibers. These fibers can easily be extracted from plants, are low weight, and can be added to various polymers to add reinforcement. Some of their drawbacks lie in their low impact strength, fluctuations in quality, lower durability, flammability, moisture absorption, fluctuating price and irregular fiber lengths (Terzopoulou, 62). <span style="font-family: Arial,Helvetica,sans-serif;">Among the other directly plant-derived materials are hemicellulose, lignin, and pectin.



<span style="font-family: Arial,Helvetica,sans-serif;">[|Hemicellulose] are usually copolymers based on glucose or xylose (Terzopoulou, 61). They can be degraded by both chemical and enzymatic hydrolysis.

<span style="font-family: Arial,Helvetica,sans-serif;">[|Lignin] is a glue-like material that holds cellulosic fiber together. It is produced from removing water from sugars during plant growth. What is left behind is very mechanically sound material, which is also impervious to microorganisms. However, the exact structure of lignin remains unknown.

<span style="font-family: Arial,Helvetica,sans-serif;">[|Pectin], also found in plant fibers in small amounts, is the main component of the [|middle lamella]. Pectin is a group of [|polysaccharides] rich in [|galacturonic] acid (Terzopoulou, 61). Its exact structure is not known, but its believed constituents parts (homogalacturan and ramnogalacturan I & II) are covalently bonded on the [|primary cell wall] and on the [|middle lamella], forming a complicated pectin network (Terzopoulou, 61).

<span style="font-family: Arial,Helvetica,sans-serif;">Starch-based
<span style="font-family: Arial,Helvetica,sans-serif;">Thermoplastic starch-based (TPS) bioplastics make up for the majority of plastic used. Currently contributing to two-thirds of worldwide bioplastic use (Singh). The main example and also the most widely used is Poly-lactic Acid (PLA).

=<span style="font-family: Arial,Helvetica,sans-serif;">Conclusion = <span style="font-family: Arial,Helvetica,sans-serif;">In summary, bioplastics bring promise to the challenges posed by nearly innumerable amounts of petroleum-based non-biodegradable materials (plastics) being produced each year. More specifically, they bring promise to the environmental problems posed by the large percentage of plastics that are not recycled—discarded into landfills or discarded as litter into the environment. On the basis that a bioplastic can potentially be fully biodegradable, the end-of-life fate of a given bioplastic is less concerning for the environment than that of petroleum-based. This is not to say that these new plastics should be discarded into the environment without care. This is also not to say that bioplastics are without their problems. Problems of cost, supply and demand, sorting in recycling, and mechanical and thermal properties still pervade. However, as demand increases the future of bioplastics looks promising, and with increased demand, a solutions to these problems will most likely inevitably be found.

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