#polyesters

Catalytic process can transform natural polymer into customizable biodegradable plastics

A new study led by Colorado State University Distinguished Professor Eugene Chen outlines a path to creating advanced, recyclable plastics. Published in Nature, the study describes a breakthrough method for upconverting a natural polymer that is usually made by microorganisms into a wide range of new and more sustainable high-performance materials as well as valuable chiral small molecules for organic and polymer synthesis. The method is an important step toward a circular materials economy in which products are designed to be bio-based, reused, repurposed or recycled rather than ending up in landfills—greatly reducing the burden of chemicals and plastics on the environment. The study centers on the innovative utilization of poly(3-hydroxybutyrate) or P3HB—a biodegradable polyester produced by microbes. P3HB belongs to a family of materials called polyhydroxyalkanoates (PHAs), which can be redesigned to perform similarly to petroleum-based plastics but with one key advantage: they can break down naturally in soil and oceans.

Enhancing the sustainability of plastics using sulfur waste

Researchers at the University of Bayreuth have found a way to make plastics more sustainable by utilizing sulfur waste from the petroleum refining process. They have developed a method that allows so-called dynamic sulfur bonds to be easily integrated into polyesters. Their findings have been published in the journal Angewandte Chemie International Edition. Polyesters are versatile plastics found in many everyday items such as PET bottles, packaging, rucksacks, and clothing. They are popular due to their potentially easier degradability, making them more sustainable than other types of plastic. However, even polyesters have room for improvement when it comes to recyclability: during thermal and mechanical recycling processes, quality can deteriorate, meaning that recycled polyester often has inferior properties compared to virgin material. As a result, polyesters cannot be recycled indefinitely.

Researchers use architected auxetics to achieve 300 times more flexibility in new 3D printing design

There are young children celebrating the holidays this year with their families, thanks to the 3D-printed medical devices created in the lab of Georgia Tech researcher Scott Hollister. For more than 10 years, Hollister and his collaborators have developed lifesaving, patient-specific airway splints for babies with rare birth defects. These personalized Airway Support Devices are made of a biocompatible polyester called polycaprolactone (PCL), which has the advantage of being approved by the Food and Drug Administration. Researchers use selective laser sintering to heat the powdered polyester, which binds together as a solid structure. Devices made of PCL have a great safety record when implanted into patients. Unfortunately, PCL has the disadvantage of having relatively stiff and linear mechanical properties, which means this promising biomaterial has yet to be applied functionally to some other critical biomedical needs, such as soft tissue engineering. How do you make a firm thermoplastic into something flexible, and possibly capable of growing with the patient? Hollister's lab has figured out how.

New biobased recyclable polyesters exhibit excellent tensile properties beyond polyethylene and polypropylene

The research group of Professor Kotohiro Nomura, Tokyo Metropolitan University, in cooperation with the research group of Director Hiroshi Hirano, Osaka Research Institute of Industrial Science and Technology, has developed biobased polyesters from inedible plant resources, which can be easily chemical recyclable and exhibit promising mechanical properties in films than commodity plastics. The work has been published in ACS Macro Letters. The development of high-performance, sustainable, recyclable plastics is important for the creation of a circular economy. Biobased polyesters made from plant resources are expected to become a promising alternative to commodity polymers such as polyethylene and polypropylene produced from petroleum. However, there have been few examples of the development of high-performance materials that exceed required mechanical properties such as tensile strength and elongation at break.

Your old plastic bottle … reborn as a towel, bag or swimsuit

As technology finds innovative ways to recycle, waste products are being used in an unlikely range of goods in high street stores.

First it was “bags for life”, chunky doormats and, more recently, clothing such as fleeces, swimwear and pack-away macs. Now towels made from recycled plastic bottles are to go on sale in the UK for the first time in August – the latest initiative in the war against single-use plastics and the result of a technological breakthrough that has produced a fabric deemed soft and fluffy enough to use on human skin.

The new range of eco-friendly bath towels will go on sale online and at 18 branches of John Lewis in the last week of August, after nearly two years of extensive testing and work with suppliers. The polyester from the recycled plastic bottles accounts for 35% of their content, while the rest is regenerated cotton.

Polymer researchers discover path to sustainable and biodegradable polyesters

There's a good chance you've touched something made out of the polyolefin polymer today. It's often used in polyethylene products like plastic bags or polypropylene products like diapers.

As useful as polyolefins are in society, they continue to multiply as trash in the environment. Scientists estimate plastic bags, for example, will take centuries to degrade.

But now, researchers at Virginia Tech have synthesized a biodegradable alternative to polyolefins using a new catalyst and the polyester polymer, and this breakthrough could eventually have a profound impact on sustainability efforts.

Rong Tong, assistant professor in the Department of Chemical Engineering and affiliated faculty member of Macromolecules Innovation Institute (MII), led the team of researchers, whose findings were recently published in the journal Nature Communications.

One of the largest challenges in polymer chemistry is controlling the tacticity or the stereochemistry of the polymer. When multiplying monomer subunits into the macromolecular chain, it's difficult for scientists to replicate a consistent arrangement of side-chain functional groups stemming off the main polymer chain. These side-chain functional groups greatly affect a polymer's physical and chemical properties, such as melting temperature or glass-transition temperature, and regular stereochemistry leads to better properties.

One-step production of aromatic polyesters by E. coli strains

KAIST systems metabolic engineers defined a novel strategy for microbial aromatic polyesters production fused with synthetic biology from renewable biomass. The team of Distinguished Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering produced aromatic polyesters from Escherichia coli (E. coli) strains by applying microbial fermentation, employing direct microbial fermentation from renewable feedstock carbohydrates.

This is the first report to determine a platform strain of engineered E. coli capable of producing environmentally friendly aromatic polyesters. This engineered E. coli strain, if desired, has the potential to be used as a platform strain capable of producing various high-valued aromatic polyesters from renewable biomass. This research was published in Nature Communications on January 8.

Conventionally, aromatic polyesters boast solid strength and heat stability so that there has been a great deal of interest in fermentative production of aromatic polyesters from renewable non-food biomass, but without success.

However, aromatic polyesters are only made by feeding the cells with corresponding aromatic monomers as substrates, and have not been produced by direct fermentation from renewable feedstock carbohydrates such as glucose.

Polymers: Polyethylene terephthalate

As the most common thermoplastic polymer resin of the polyester family (polymers with an ester functional group in the main chain), polyethylene terephthalate (PET) is often simply referred to as polyester, as well as the brand names Dacron, Terylene, and Lavsan, among others (Mylar is PET with a specific structure). 

The benzene ring in this polymer’s structure (shown above) gives PET a rigid structure, leading to stronger polymers with higher melting points. The polymer is also nonreactive and shatterproof, and can be easily extruded or molded into almost any shape at economical costs. PET can exist as either an amorphous or semi-crystalline polymer, depending on the processing, and can be transparent, opaque, or white as well.

PETs ability to not degrade when in contact with a variety of materials (such as foods and beverages) makes it a highly preferred and safe material as a container, but also leads to waste that will remain for many years. Luckily, PET can be recycled many times over.

Most of the PET produced is used to make fibers, with a large amount also used for packaging (such as bottles). The fibers themselves are commonly used in clothing, sometimes alone and sometimes blended with natural fibers such as cotton. Bottles made from PET can be distinguished by the number 1 surrounded by triangular arrows - a symbol reserved only for PET. Because of its higher strength, PET is also used in applications such as conveyor belts and hoses, or the suits and parachutes used by skydivers. As one of the most produced polymers in the world, PETs applications are endless.