PET Outlook is Sweet

Polyethylene terephthalate – known in the plastics and polymers industry as PET – is a strong, lightweight, transparent plastic. Most PET products are made from terephthalic acid and ethylene glycol which are combined to form a polymer chain. However, according to a recent study conducted by Grand View Research, Inc, and reported in a Plastivision article, the volatile crude oil prices and growing sustainable packaging market have accelerated the demand for bio-based PET products in packaging, automotive and electronic applications.

Although PET doesn’t contain BPA or phthalates, increased greenhouse gas emissions have raised the need for an eco-friendly substitute. Major food and beverage companies have already agreed to work towards developing and using 100% bio-based PET in their product offerings. In fact, a Plant PET Technology Collaborative (PTC) was formed to accomplish this task. The strategic working group has been focused on accelerating the development and use of 100% plant-based PET materials and fiber in their products.

This is not a new concept, though. Almost a decade ago, Scientific American reported on the “new process [that allows] plants to become the root of chemicals, plastics and fuels rather than oil.” By 2010, more than 2.5 billion plastic bottles—partially made from plants—were already in use around the world. And one year ago, it was reported that the world’s first PET bottle made entirely from plants, including sugarcane, was introduced. The beverage company that helped develop the new material estimates that the use of its partially plant-based bottle has already saved the equivalent annual emissions of more than 315,000 metric tons of carbon dioxide, without negative impact on food security. They pride itself on the presumption that the new fully recyclable plastic bottle will have an even lighter footprint on the planet.

Of course before getting to this point, I’m sure there were many trials in the development and processing of the bottle. Different raw materials can behave differently when heated, cooled, or processed. In fact PET is usually created by melt extruding and then stretching the material up to six times the original length to form an endless high-yield point thread. To produce a product of constant quality, the processor needs to know how the flow characteristics of the molten polymer change as a function of the temperature and the shearing rate.

Read Investigation of the Flow Characteristics of PET at Different Temperatures to learn techniques used to investigate these flow characteristics under conditions similar to those encountered during processing.

With a rheometer, the mechanical properties such as the viscosity and the dynamic moduli of polymer solutions, polymer melts as well as semi-solids can be measured as a function of stress, strain, time, frequency, temperature etc., not in only in shear but also in extensional flow. A torque rheometer can provide you with process-relevant material data including: melting behavior, influence of additives, temperature stability, shear stability and melt viscosity.

Once polymer testing is completed in the R&D laboratory, materials with promising properties are manufactured in small scale at a pilot plant. Newly developed polymers must pass the first test: Can the polymer be produced with reproducible quality at moderate cost? What problems can be expected when tons of raw materials are fed into an extruder instead of grams or kilograms? The pilot plant delivers initial quantities of a new polymer to ensure the desired properties in respect to mechanical stability, strength and appearance. Grams or kilograms of a new polymer are essential to conduct standard tests that compare the product with existing materials. Creating product prototypes with the newly developed material further justifies future investments.

You can certainly see how the process can take years to create a fully recyclable plastic bottle made from renewable plant materials. Plant-based materials are new to manufacturing and there needed to be a lot of research and development to ensure that these new materials can function as well, or better than, the old materials. And the research and development will continue as bio-based PET products are introduced into more industries.

The Plastivision article proclaimed that the bio-based PET market is expected to reach 5,800 kilotons by 2020. That’s good news for the plant. Even better news? A more recent headline about PET-based products proclaimed that Japanese Researchers Discovered Bacteria That Eats Plastic Bottles and Bags. Since the new bottles are made of sugarcane, I hope this PET-eating bacteria named ‘Ideonella sakaiensis’ has a sweet tooth.