Picture: Researchers used fish oil to create a material similar to polyurethane. see more
Washington, April 5, 2021—Polyurethane, a plastic, is almost everywhere—in shoes, clothes, refrigerators, and building materials. But these highly versatile materials may have a major disadvantage. Derived from crude oil, synthetically toxic and slow to decompose, traditional polyurethane is not environmentally friendly. Today, researchers are discussing designing what they say should be a safer, biodegradable alternative that comes from fish waste — head, bones, skin, and internal organs — otherwise it might be discarded.
The researchers will present their findings at the American Chemical Society (ACS) spring meeting today. ACS Spring 2021 will be held online from April 5th to 30th. The live conference will be held from April 5th to 16th, and on-demand and online content will continue until April 30th. The conference will deliver nearly 9,000 lectures on a wide range of scientific topics.
The lead researcher of the project, Dr. Francesca Kerton, said that if the development is successful, fish oil-based polyurethane can help meet the huge demand for more sustainable plastics. "It is important that we start designing plastics with end-of-life plans, whether it is chemical degradation to convert materials into carbon dioxide and water, or recycling and reuse."
To make this new material, Kerton's team started with oil extracted from the remains of Atlantic salmon, after the fish was ready to be sold to consumers. "I find it interesting how we can make something useful from the trash that people throw away, and even change the way plastic is made," said Mikhailey Wheeler, a graduate student who demonstrated this work at the conference. Both Kerton and Wheeler are at Memorial University of Newfoundland (Canada).
Conventional methods for producing polyurethane have many environmental and safety issues. It needs non-renewable resource crude oil and colorless and highly toxic gas phosgene. During the synthesis process, isocyanate is produced, which is a powerful respiratory irritant, and the final product is not easily decomposed in the environment. The limited biodegradation that does occur releases carcinogenic compounds. At the same time, the demand for green alternatives is growing. Previously, others have developed new polyurethanes that use vegetable oil instead of petroleum. However, these also have a disadvantage: the oil-producing crops, usually soybeans, require land that could be used to grow food.
The remaining fish has an impact on Kerton as a promising substitute. Salmon farming is the main industry in the coastal area of Newfoundland where her university is located. After the fish is processed, the remaining part is usually discarded, but sometimes the oil is extracted from it. Kerton and her colleagues developed a process to convert this fish oil into a polyurethane polymer. First, they add oxygen to unsaturated oils in a controlled manner to form epoxides, which are similar to those in epoxy resins. After these epoxides react with carbon dioxide, they link the resulting molecules with nitrogen-containing amines to form new materials.
But does plastic smell fishy? “When we started the process with fish oil, there was a faint fish smell, but as we gradually finished it, the smell disappeared,” Kerton said.
Kerton and her team described this approach in a paper in August last year, and Wheeler has been adjusting it ever since. She has recently had some success in replacing amines with amino acids, which simplifies the chemical processes involved. Although the amines they used before must come from cashew nut shells, these amino acids already exist in nature. Wheeler's preliminary results indicate that histidine and asparagine can fill amines by linking together the components of the polymer.
In other experiments, they have begun to study how easy it is for the new material to decompose after the end of its useful life. Wheeler soaked its fragments in water. In order to accelerate the degradation of some fragments, she added lipase, an enzyme that can break down the fat in fish oil. Wheeler said that under the microscope, she later saw microbial growth on all samples, even those in clean water, which is an encouraging sign that the new material may be easily biodegradable.
Kerton and Wheeler plan to continue to test the effects of using amino acids in synthesis and study the material's suitability to the growth of microorganisms that may accelerate its decomposition. They also plan to study its physical properties and see how it might be used in real-world applications, such as packaging or clothing fibers.
A press conference on this topic will be held online at http://www.acs.org/acsspring2021conferences on Thursday, April 8th at 11 am Eastern Time.
The researchers thank the Canadian Natural Sciences and Engineering Research Council and the Memorial University of Newfoundland for their support and funding.
The American Chemical Society (ACS) is a non-profit organization chartered by the US Congress. The mission of ACS is to promote a wider range of chemical companies and their practitioners to benefit the earth and mankind. The society is a global leader in providing chemistry-related information and research through its diverse research solutions, peer-reviewed journals, scientific conferences, e-books, and weekly news journal "Chemical and Engineering News". The ACS journal is one of the most cited, trusted, and read journals in the scientific literature; however, ACS itself does not conduct chemical research. As an expert in scientific information solutions (including SciFinder® and STN®), its CAS department powers global research, discovery and innovation. ACS' main offices are located in Washington, DC and Columbus, Ohio.
To automatically receive press releases from the American Chemical Society, please contact newsroom@acs.org.
Note to reporters: Please report that this research was presented at a meeting of the American Chemical Society.
Waste fish oil used to produce more environmentally friendly polyurethane materials
Polyurethane is an oil-based synthetic polymer that is commonly used to make various materials, such as synthetic fibers or hard plastics. Traditionally, polyurethane is synthesized by the reaction of polyols and isocyanates. The isocyanates are all derived from crude oil and form urethane bonds. In addition to depleting our natural resources, this process may be toxic to humans and the environment. Phosgene is a toxic gas used to make the required isocyanates, which can have a negative impact on health. Isocyanates themselves are also considered toxic, so the production of polyurethane requires a high level of safety measures. Even with a low level of biodegradability, a small amount of polymer degradation can lead to the formation of carcinogenic aromatic amines that are released into the environment. These safety, toxicity, and biodegradability issues have led to the need for safer and more environmentally friendly alternatives to polymer synthesis.
In this presentation, we will discuss more environmentally friendly production methods for polyurethane materials. The previous synthetic route avoided the use of isocyanates by adding vegetable oils in the process. However, the use of these oils for polymer synthesis can compete with food production. Our research combines fish oil derived from aquaculture waste, a biomass-derived material that does not compete for land space. It was found that capelin fish oil or fish oil extracted from salmon offal can be epoxidized and react with carbon dioxide to form carbonated fish oil, which can then be reacted with diamine to form a non-isocyanate polyurethane material (NIPU). The biodegradability of the obtained film was studied under enzymatic conditions to determine the degree of degradation that the polymer will experience. Scanning electron micrographs showed a high degree of degradation. Then by screening the reactivity of biocompatible amino acids in the cross-linking process to try to further improve the synthesis process. Select L-histidine, L-glutamine and L-asparagine, and test the reaction with carbonated fish oil by differential scanning calorimetry. The results showed that an exothermic reaction occurred between carbonated fish oil and L-histidine, showing the potential of cross-linking reaction to form NIPU.
Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of press releases posted to EurekAlert!! Use any information through contributing agencies or through the EurekAlert system.
Katie Cottingham k_cottingham@acs.org Office: 301-775-8455
Copyright © 2021 American Association for the Advancement of Science (AAAS)
Copyright © 2021 American Association for the Advancement of Science (AAAS)