Plastics have been around for about 80 years. In that time, they have greatly impacted our lives and provided significant benefits including convenience, health and safety. Weight-saving advantages of plastics over metal have greatly improved fuel efficiency of automobiles, thereby reducing our dependence on foreign oil and reduction of carbon dioxide. Safety helmets and medical devices also rely on plastics.
However, the benefits that plastics bring to our lives are accompanied by concerns about the impact that waste plastics have on the environment.
In particular, single use and disposable plastic items (e.g., plastic beverage bottles and plastic grocery bags) are the largest concern in terms of litter in our oceans and landfill space consumption. In the US, only about 20% of plastic beverage containers are recycled.
Most companies these days are jumping on the “go green” bandwagon and looking for ways to promote their plastic businesses by using certain words and phrases in their corporate mission statements and sales literature. Such terms commonly thrown around include: sustainability, biorenewable feedstocks, environmentally friendly, carbon footprint, and responsible care.
Unfortunately, the fact remains that of the more than 100 billion pounds per year of single use/disposable plastic products manufactured annually around the world, most aren’t recycled and end up as litter or are disposed of in landfills.
Clearly, we must consider better options for reducing the negative impact that the un-recycled plastic containers have on the environment.
One of the technologies that may help reduce the impact of waste is to utilize biodegradable plastics.
What are biodegradable plastics?
Biodegradable plastic decomposes naturally when bacteria in the environment are able to “metabolize” and break down the plastic structure. Biodegradable plastics can either be injection molded (disposable cutlery, medical parts, rigid packaging, etc.) or solid (food containers, leaf collections bags, water bottles, etc.).
Currently, two main forms of biodegradable plastics exist:
- Bio-based plastics – Plastics derived from renewable raw materials (also known as “bioplastics”)
- Fossil fuel based plastics – Plastics composed of traditional petrochemicals, but which are engineered to break down more quickly through the processes of oxidation or hydrolysis.
The problems with biodegradable plastics
Unfortunately, the plastic used to manufacture beverage containers (PET) is not naturally biodegradable, and a naturally biodegradable resin is not currently commercially available that offers the mechanical properties necessary for beverage bottles (e.g., high impact strength, chemical resistance, and gas barrier).
In response, several companies have developed technology that they claim makes PET plastic beverage bottles biodegradable. They claim they have developed additives that, when blended into plastic, will accelerate the environmental degradation. However, experts have yet to see verified data that clearly confirms the efficacy and safety of such products.
Chemicals that are added to PET plastic for use in beverage bottles must pass stringent Food and Drug Administration criteria and be non-toxic to humans and wildlife. Historically, additives are blended into plastics to stabilize products against degradation, which is why blending additives into plastic products to promote their degradation (i.e. prodegradant additives) creates a significant challenge.
For example, how do you control the PET bottle degradation so that it takes place in the environment and not while on the shelf at the retailer or the consumer’s home?
PET stabilizers and prodegradants: a delicate balance
A significant concern with blending chemicals into plastics that promote degradation is the effect the prodegradant containing plastics will have on the usefulness of recycled plastic.
For instance, a major use of recycled plastic is to mold items for use outdoors (e.g., park benches). If the plastic park bench contains plastic containing additives that promote environmental degradation, the park bench will fall apart.
To combat this concern, some companies use mixed additive systems containing both stabilizers and prodegradants wherein the prodegradant can be triggered to overwhelm the stabilizers. There are many variables that control the consumption rate of the stabilizer which keeps the PET from breaking down prematurely — including temperature, humidity and UV exposure.
But should premature degradation occur, resulting in bottle failure, significant liability issues could result.
Making plastic environmentally-friendly
When it comes to plastics and the environment, it seems right now there are more questions than solutions. We at Plastic Expert Group believe that good science can solve these problems. Our plastic scientists are available to advise and assist plastic product manufacturers evaluate the lifecycle of their products and to advise on ways to make products truly more environmentally-friendly.
If your company needs assistance in making products that are more environmentally friendly and/or using plastics that are biobased, we can help. Our plastics scientists and engineers have decades of experience. We specialize in material selection and testing, plastic part design, service life prediction, forensic failure analysis, chemical resistance testing, due diligence studies on new plastic technologies, troubleshooting/problem solving in plastic manufacturing, and consulting on new opportunities and uses for existing products.
Contact us for a free initial consultation to discuss your needs and to learn how we can help.
“We have advised companies that manufacture single-use products on ways to reduce negative environmental impacts and we’ve consulted for companies that manufacture plastic products for long-term use on ways to make their products using bio-based plastics.”Dr. Duane Priddy, Plastic Expert Group, Founder & CEO