New generation plastics allow the recovery of monomers from common additives, even in mixed waste streams, producing only water as a by-product.
#recycling, # biotechnology, #PDK, #plastics
A team of researchers from the Lawrence Berkeley National Laboratory of the US Department of Energy (Berkeley Laboratory) has developed a recyclable plastic that can be decomposed into constituent elements at the molecular level, and then reassembled in different shapes, textures and colors again and again without losing performance or quality. A new material called poly (dicentenoamine) or PDK was published in Nature Chemistry.
All plastics, from water bottles to auto parts, are made of large molecules called polymers, which consist of repetitive bonds of shorter carbon compounds called monomers.
Re-circulated plastics are low-cost products due to residual impurities and degradation of the polymer in each cycle of reuse. Plastics that undergo reversible polymerization can recover valuable monomers and convert them into undamaged materials. However, the recovery of monomers is often expensive, complex and energy consuming. New generation plastics, polymerized using dynamic covalent diketoenamine bonds, allow the recovery of monomers from common additives, even in mixed waste streams, producing only water as a by-product. The extracted monomers can be recovered in the same polymer formulation without loss of productivity, as well as in other polymer formulations with differentiated properties. The ease with which polyethylene (diketenoamine) can be manufactured, used, recycled and reused without loss of value indicates new directions in the development of sustainable polymers with minimal environmental impact.
According to the researchers, the problem with many plastics is that chemicals added to their utility, such as fillers that make plastics rigid, or plasticizers that make plastics flexible, are closely related to monomers and remain in the plastic. Even after being processed in a recycling plant.
During the processing in these plants, the plastics of different chemical compositions (solid plastics, elastic plastics, transparent plastics, colored plastics) are mixed and crushed into pieces. When this mixture of cut plastic melts to create a new material, it is difficult to predict the properties it will inherit from the original plastics.
This heritage of unknown properties and, therefore, unpredictable, has prevented plastics from becoming what many consider the basis of processing: a "round" material whose original monomers can be extracted for reuse for as long as possible or "Recycled" in a new one. A product of the highest quality.
Therefore, when a reusable shopping bag wears out, it can not be recycled to create a new product. According to Helms, once the bag has reached the end of its useful life, it is incinerated to produce heat, electricity or fuel, or it is transported to a sanitary landfill.
A new generation of plastics
Researchers want to remove plastics from landfills and oceans, encouraging their recovery and reuse, which is possible with polymers made from MPCs. "In the case of PDK, the invariable compounds in conventional plastics are replaced by reversible compounds that allow a more efficient processing of plastics," said Helms.
Unlike conventional plastics, PDK plastic monomers can be removed and released from any complex additive simply by immersing the material in a highly acidic solution. The acid helps to break the bonds between the monomers and separates them from the chemical additives that give the plastic an appearance and a sensation.
"We are interested in chemistry that redirects the life cycles of plastics from linear to circular," said Helms. "We see an opportunity to change the situation when there are no recycling options, such as colas, phone cases, watch straps, shoes, computer cables and hot plastic thermoset hard materials.
The researchers discovered the surprising properties of recycling plastics based on MPCs when Christensen applied various acids to the glassware used to make the MPC adhesives, and noticed that the composition of the adhesive had changed. Curious about how the adhesive could be transformed, Christensen analyzed the molecular structure of the sample using an NMR spectroscopy device. "To our surprise, these were original monomers," says Helms.
After testing various foundry molecular compositions, they have shown that they not only divide the polymeric PDK acids into monomers, but also allow the monomers to separate from the blocking additives.
They then demonstrated that the recovered PDK monomers can be converted into polymers and that the recycled polymers can form new plastic materials without inheriting the color or other characteristics of the original material, so that the discarded plastic can find a new use. For example, a computer keyboard, if it is made of plastic PDK, can also be recycled by adding additional functions such as flexibility.
Towards the future of recyclable plastics
Researchers believe that their new recyclable plastic can be a good alternative to the many non-recyclable plastics that are used today.
"We are at a critical point where we need to think about the infrastructure needed to modernize our recycling facilities in the future," said Helms. "If these facilities were designed to recycle the KDP and related plastics, we could make better use of plastics from landfills and oceans - it's an exciting time to think about how to design materials and recycling facilities to allow for the use of recyclable plastics, "said Helms.
The researchers then plan to develop PDK plastics with a wide range of thermal and mechanical properties for various applications, such as textiles, 3D printing and foams. In addition, they seek to expand their formulations to include plant materials and other sustainable sources.
Although these "more environmentally friendly" plastics will help reduce the contamination of plastics in the future, mankind still has to deal with 18 billion pounds of ordinary plastic that reaches our oceans every year, and 6.3 one billion tons. Plastics have been created since 1950. According to a study carried out last year, 79% of the waste is still here, floating in the sea, in landfills or scattered throughout the countryside.
References:
Helms, B. A. & Russell, T. P. Polymer chemistries enabling cradle-to-cradle life cycles for plastics. Chem. 1, 813–819 (2016).
Rahimi, A. R. & García, J. M. Chemical recycling of waste plastics for new materials production. Nat. Rev. Chem. 1, 0046 (2017).
García, J. M. & Robertson, M. L. The future of plastics recycling. Science 358, 870–872 (2017).
Hong, M. & Chen, E. Y.-X. Chemically recyclable polymers: a circular economy approach to sustainability. Green Chem. 19, 3692–3706 (2017).
MacArthur, E. Beyond plastic waste. Science 358, 843 (2017).
Schneiderman, D. K. & Hillmyer, M. A. 50th anniversary perspective: There is a great future in sustainable polymers. Macromolecules 50, 3733–3749 (2017).
Sardon, H. & Dove, A. P. Plastics recycling with a difference. Science 360, 380–381 (2018).
#recycling, # biotechnology, #PDK, #plastics
All plastics, from water bottles to auto parts, are made of large molecules called polymers, which consist of repetitive bonds of shorter carbon compounds called monomers.
Re-circulated plastics are low-cost products due to residual impurities and degradation of the polymer in each cycle of reuse. Plastics that undergo reversible polymerization can recover valuable monomers and convert them into undamaged materials. However, the recovery of monomers is often expensive, complex and energy consuming. New generation plastics, polymerized using dynamic covalent diketoenamine bonds, allow the recovery of monomers from common additives, even in mixed waste streams, producing only water as a by-product. The extracted monomers can be recovered in the same polymer formulation without loss of productivity, as well as in other polymer formulations with differentiated properties. The ease with which polyethylene (diketenoamine) can be manufactured, used, recycled and reused without loss of value indicates new directions in the development of sustainable polymers with minimal environmental impact.
According to the researchers, the problem with many plastics is that chemicals added to their utility, such as fillers that make plastics rigid, or plasticizers that make plastics flexible, are closely related to monomers and remain in the plastic. Even after being processed in a recycling plant.
During the processing in these plants, the plastics of different chemical compositions (solid plastics, elastic plastics, transparent plastics, colored plastics) are mixed and crushed into pieces. When this mixture of cut plastic melts to create a new material, it is difficult to predict the properties it will inherit from the original plastics.
This heritage of unknown properties and, therefore, unpredictable, has prevented plastics from becoming what many consider the basis of processing: a "round" material whose original monomers can be extracted for reuse for as long as possible or "Recycled" in a new one. A product of the highest quality.
Therefore, when a reusable shopping bag wears out, it can not be recycled to create a new product. According to Helms, once the bag has reached the end of its useful life, it is incinerated to produce heat, electricity or fuel, or it is transported to a sanitary landfill.
A new generation of plastics
Researchers want to remove plastics from landfills and oceans, encouraging their recovery and reuse, which is possible with polymers made from MPCs. "In the case of PDK, the invariable compounds in conventional plastics are replaced by reversible compounds that allow a more efficient processing of plastics," said Helms.
Unlike conventional plastics, PDK plastic monomers can be removed and released from any complex additive simply by immersing the material in a highly acidic solution. The acid helps to break the bonds between the monomers and separates them from the chemical additives that give the plastic an appearance and a sensation.
"We are interested in chemistry that redirects the life cycles of plastics from linear to circular," said Helms. "We see an opportunity to change the situation when there are no recycling options, such as colas, phone cases, watch straps, shoes, computer cables and hot plastic thermoset hard materials.
The researchers discovered the surprising properties of recycling plastics based on MPCs when Christensen applied various acids to the glassware used to make the MPC adhesives, and noticed that the composition of the adhesive had changed. Curious about how the adhesive could be transformed, Christensen analyzed the molecular structure of the sample using an NMR spectroscopy device. "To our surprise, these were original monomers," says Helms.
They then demonstrated that the recovered PDK monomers can be converted into polymers and that the recycled polymers can form new plastic materials without inheriting the color or other characteristics of the original material, so that the discarded plastic can find a new use. For example, a computer keyboard, if it is made of plastic PDK, can also be recycled by adding additional functions such as flexibility.
Towards the future of recyclable plastics
Researchers believe that their new recyclable plastic can be a good alternative to the many non-recyclable plastics that are used today.
"We are at a critical point where we need to think about the infrastructure needed to modernize our recycling facilities in the future," said Helms. "If these facilities were designed to recycle the KDP and related plastics, we could make better use of plastics from landfills and oceans - it's an exciting time to think about how to design materials and recycling facilities to allow for the use of recyclable plastics, "said Helms.
The researchers then plan to develop PDK plastics with a wide range of thermal and mechanical properties for various applications, such as textiles, 3D printing and foams. In addition, they seek to expand their formulations to include plant materials and other sustainable sources.
References:
Helms, B. A. & Russell, T. P. Polymer chemistries enabling cradle-to-cradle life cycles for plastics. Chem. 1, 813–819 (2016).
Rahimi, A. R. & García, J. M. Chemical recycling of waste plastics for new materials production. Nat. Rev. Chem. 1, 0046 (2017).
García, J. M. & Robertson, M. L. The future of plastics recycling. Science 358, 870–872 (2017).
Hong, M. & Chen, E. Y.-X. Chemically recyclable polymers: a circular economy approach to sustainability. Green Chem. 19, 3692–3706 (2017).
MacArthur, E. Beyond plastic waste. Science 358, 843 (2017).
Schneiderman, D. K. & Hillmyer, M. A. 50th anniversary perspective: There is a great future in sustainable polymers. Macromolecules 50, 3733–3749 (2017).
Sardon, H. & Dove, A. P. Plastics recycling with a difference. Science 360, 380–381 (2018).
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