Most common chemistry experience you see in daily life

                   Biodegradable Polymers:                                                                                                                         

                             Rebirth of Plastic

Introduction

Plastics are being used all over the world. From drinking cups and disposable

silverware to parts for automobiles and motorcycles, plastics are continuing to rise.

Plastics have been an environmental trepidation because of the lack of degradation.

Plastics make up about 20% by volume waste per year. There are over 21,000 plastics

facilities in the US, and the employment rate has increased by an average of three percent

over the past two and a half decades. Plastics are extremely important to the job market

as well as packaging throughout the world. Since plastics are vital to people’s everyday

lives, production of biodegradable plastics to make plastics more compatible with the

environment is necessary.

Biodegradable or compostable?

Compostable plastics are a subgroup of biodegradable plastics and are biologically decomposed under composting conditions and within the relatively short period of a composting cycle.

 Compostable always means biodegradable.

 Biodegradable does not necessarily mean compostable.

The manufacturing of biodegradable polymers can include different procedures without affecting material biodegradability. They can be synthetic (chemical) or bio-technological (effected by microorganisms or enzymes). The most common procedures are:

 Manufacturing plastics from a natural polymer that has been processed mechanically or chemically (e.g. plastics based on destructured starch).

 Chemical synthesis of a polymer from a monomer produced by bio-technological conver-sion of a renewable resource (e.g. use of lactic acid produced from the fermentation of sugars for the production of polyactic acid – PLA). In this case, the polymer is produced chemically based on a renewable resource.

 Production of a polymer by a bio-technological procedure based on a renewable resource (e.g. fermentation of sugars where natural microorganisms synthesize thermoplastic ali-phatic polyesters, such as polyhydroxybutyrate - PHB).

 Chemical synthesis of a polymer based on the components obtained by petro chemical processes from non-renewable resources.

Today, commercial biodegradable plastics are offered on the market by an increasing number of manufacturers. Those most common materials can be classified

Starch-based plastics

 Polylactide-based plastics (PLA)

 Polyhydroxyalkanoate-based plastics (PHB, PHBV, etc.)

 Aliphatic-aromatic-polyester-based plastics

 Cellulose-based plastics (cellophane, etc.)

 Lignin-based plastics

Brief History

Biodegradable plastics began being sparking interest during the oil crisis in the

1970’s. As oil prices increased, so did the planning and creating of biodegradable

materials. The 1980’s brought items such as biodegradable films, sheets, and moldforming

materials. Green materials (or Plant-based) have become increasingly more

popular (Mohanty, 2004). This is due impart to the fact that they are a renewable

resource that is much more economical then they were in the past (Mohanty, 2004).

What they are made of?

Biodegradable plastics can be made from many different sources and materials.

One research group from Cornell is working with “a number of fibers including those

obtained from kenaf stems, pineapple and henequen leaves and banana stems” (Replace

Landfills, 2002). Their team is working with resins made from microorganisms and

commercial resins as well as composites made from soybean protein and plant based

fibers (Replace Landfills, 2002). Australian Researchers are working plastics that are

used from either starches or bacteria (Packaging Greener, 2004). The development of

norder to make a suitable biodegradable material.

Starch Based Plastics

Starch based plastics are mainly harvested from wheat, potatoes, rice, and corn.

Of these four starches, corn is the most commonly used and is the least expensive starch.

Most sales of starch come from the United States, which makes about $1.8 millionew materials is constantly in progress. Researchers must balance many variables .

             Starch when harvested is turned into a white, granular product. According to the

Australian Academy of Science, “starch can be processed directly into a bioplastic, but

because it is soluble in water, articles made from starch will swell and deform when

exposed to moisture, limiting its use”(Packaging Greener, 2004). The starch must be

transformed into an altered polymer iBiodegradable starches can be processed “using conventional plastic technologies such as injection molding, blow molding, film blowing, foaming, thermoforming and extrusion”(Mohanty, 2004). These starch-based plastics resemble many conventional plastics and

are as, “biodegradable as pure cellulose”.

          The process changes the starch from a lactic acid monomer into a polymer chain

called polylacitide (PLA) (Packaging Greener, 2004) or polygloycolic (PGA). Both

PLA and PGA are crystalline polymers, but PLA is more hydrophobic than PGA. PLA’s

are very brittle and stiff and they require plasticizers for most applications. High gloss

and clarity are other features of PLA plastics. PLA is distinctive because it is available in

renewable resources such as the starches (Mohanty, 2004). These renewable resourcesn order to solve the issue of starch deformationare on the leading edge of technology in Germany where they are being used for pharmaceuticals (Mohanty, 2004).

              PLA can also be processed like most thermoplastics into fibers, or it can be thermoformed as well as injection molded. “PLA’s can be used in a wide range of applications such as packaging (wrapping film, film for dry food packaging, board lamination etc.), stationery (pens, cartridges, pencil sharpeners etc.),and personal care items”

                                        

            Australia is using cornstarch as a base in their biodegradable plastic research. The

cornstarch based material has the, “look, feel, and flexibility of conventional plastics and

can be used for a range of items, from cellophane to plant pots and medical devices”

(“Zero Waste”, 2004). When water is added, it completely disappears into the soil over a

period of time. This is excellent for food packaging and farming. This cornstarch blend

of plastic is now cheap enough to compete with conventional plastic. There is a

cornstarch based organic waste bag now on the market. It is called the Biobag (see figure

1.4) and is is made up of cornstarch, biodegradable and compostable polyester and vegetable oil.

After 10-45 days, it is said to be completely biodegraded depending on the certain

conditions and methods. The Biobag is compliant with the FDA and EU requirements

and can be printed using flexo printing. “Another feature of this Biobag is that it

“breathes", and reduces the weight of its contents by up to 25% in five days” (“Bio Bag”,

2004).100% biodegradable and 100% compostable (“Bio Bag”, 2004). 

            A potential re-use feature of the Biobag and other starch-based composites is that

they can be used as feed for farm animals. Some animal feeds are required to contain

some starch along with 13-24% protein (“Green Plastics”, 2004). Starch-protein plastics

were used for food containers from fast food restaurants. They could then be pasteurized

into animal feed, rather than sending the starch-based trash into a landfill, cutting costs in

many areas of society.

The International Food Manufacturer and Packaging Science in Australia have

been on the forefront of developing low cost biodegradable plastics (“Food Industry”,

2002). To reduce costs, case studies are being done that mix lower cost biodegradable

materials with higher cost polymers. In their testing they used, “a low cost starch based

biodegradable polymer blended with higher cost, higher performance polymer” (“Food

Industry”, 2002). This produced a plastic film that when put into the soil fully

diminished after two weeks (“Food Industry”, 2002).

Bacteria Based Plastics

Bacteria are an additional treatment used to create a different type of

biodegradable plastics. Using the polymer chain polyhydroxyalkanoate (PHA). PHA isproduced inside bacteria cells. The bacteria are harvested after they are grown in the

culture, (Packaging Greener, 2004) and then created into biodegradable plastics. The

mechanical properties of their resins can be altered depending on the needs of the

product.

Procter and Gamble has recently begun testing using PHA material, in nonwoven

biodegradable polyesters meant for disposable products. The intent is to use them for

items such as drapes and surgical gowns, which will be thrown away after one use

(“Scheduled”, 2003). The PHA fibers “degrade aerobically and anaerobically, can be

digested under alkaline conditions.” (“Scheduled”, 2003).

Biodegradable Polymers vs. Conventional Polymers

Biodegradable materials are beginning to be accepted in many countries. These

materials are thought to help the environment by reducing waste issues. The two main

reasons for using biodegradable materials, according to Mohanty are, “the growing

problem of waste resulting in the shortage of landfill availability and the need for the

environmentally responsible use of resources”. As the government and many

organizations are working to save the environment, there is a definite advantage to

making biodegradable plastics more of a reality.

Conventional plastics have widespread use in the packaging industry because

biodegradable plastics are cost prohibitive. The key, bringing the costs down, is to have

numerous companies buy a large sum of biodegradable materials. Laws of supply and demand state that increasing demand will drive costs down.

Like conventional plastics, biodegradable plastics must have the same structural

and functional qualities, in addition to reacting the same as conventional plastics when

used by the consumer. The biodegradable plastics also must be inclined to, “microbial

and environmental degradation upon disposal, without any adverse environmental

impact”

           With all of the advantages of biodegradable plastics, there are a number of

disadvantages. Recycling helps the environment and it works well for many plastic

containers such as bottles will in the end there will be waste produced. The cost of recycling plastics, in terms of

energy, can be significantly higher than virgin resin. Toxic gases can be releasing from

burning waste plastics in order to harness the energy for proappear to be biodegradable in reality break down into miniscule bits that can affect both

the soil and animals. Unfortunately, as researchers try to improve the environment with

these new plastics, in essence they may be creating risks, as well.

The Future

The future of biodegradable plastics shows great potential. Many countries

around the world have already begun to integrate these materials into their markets. The

Australian Government has paid $1 million dollars to research and develop starch-based

plastics. Japan has created a biodegradable plastic that is made of vegetable oil and has

the same strength as traditional plastics. The mayor of Lombardy, Italy recently

announced that merchants must make biodegradable bags available to all of theirduction. Many plastics thatcustomers. In America, McDonald’s is now working on making biodegradable

containers to use for their fast food (“Plastics”, 1998). Other companies such as Bayer,

DuPont, and Dow Cargill are also showing interest in biodegradable packaging.

According to Dr. Mohanty, “demands for biodegradables are forecast to grow nearly 16%

per annum.” This increasing interest will allow the technology needed to produce

biodegradable plastics became more affordable and the falling production costs will

eventually lead to an increase in producers (“Plastics”, 1998). America and Japan show

the greatest potentials for the biodegradable markets. The estimated amount of

biodegradable plastics produced per year is about 30,000-40,000 tons over the next five

years

Conclusion

Biodegradable plastics are one of the most innovative materials being developed

in the packaging industry. Comvaluable technology. How widespread biodegradable plastics will be used all depends on

how strongly society embraces and believes in environmental preservation. There

certainly are an abundant amount of materials and resources to create and fund more uses

for biodegradable plastics. The advancement of biodegradable technology has

skyrocketed in recent years and there are growing signs that the public shows a high

amount of curiosity in the product. With the variety of biodegradable plastics available

in the near future, there will be a place for them current Age of Plastics.panies cannot work fast enough to produce this highly