Speaker: Associate Professor Karin Odelius
Title: What about chemical recycling?
Abstract: Chemical recycling of plastics is at times considered a farfetched solution, yet for a selection of plastics it is likely the best course of action. The aliphatic polyesters and polycarbonates fall into this category, as they are synthesized via equilibrium reactions that can be pushed to form polymer or conversely monomer. Still, even though chemical recycling through ringclosing depolymerization sounds simple enough, challenges are plentiful when energy efficient routes leading to high purity and yield product is pursued. In this presentation, some of our suggested solutions to achieve just that will be discussed.
Materials with Cyclic Silicones
Nikoline Frederiksen [1]
Anne L. Skov[1]
[1]Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical
University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
Cyclic polymers, also called ring polymers, are polymers without chain-ends. This endless structure means that cyclic polymers have different physical properties compared to their linear analogues such as higher thermal stability, lower melt viscosities, and lower hydrodynamic volume. 1 The most prominent limitation in the research on cyclic polymers has been the limited quantity of cyclic polymer that could be prepared. Improvements in synthetic procedures in the recent years have opened for the possibility of incorporating cyclic polymers into topological materials.2,3
In this project we are developing strategies to prepare silicone networks containing cyclic polymers. Hereafter the properties of the networks containing cyclic polymers are analysed and compared to those of classical silicone networks.
References
[1] H. R. Kricheldorf, Journal of Polymer Science, Part A: Polymer Chemistry 2010, 48, 241–284.
[2] F. M. Haque, S. M. Grayson, Nature Chemistry 2020, 12, 433–444.
[3] J. Tran, J. Madsen, A. L. Skov, ACS Omega 2022, 7, 46884-46890.
Synthesis and applications of bio-based poly(hydroxyphenylacetate)
Matina Terzi [1]
Jeppe Madsen[1], Anders Egede Daugaard [1]
[1]Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical
University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
The implementation of bio-based polymers into the plastic industry has gained significant attention in recent years. Consequently, there is a particular focus on testing and assessing novel bio-based monomers, generated through biological processes for their conversion into polymers. Among the monomers synthesized within the UPLIFT project, 4-hydroxyphenylacetic acid (HPA) is of particular interest.
Being a hydroxy-acid, HPA is eligible of condensating into a polymer of promising thermal and mechanical properties. Through copolymerization, these bio-based polymers can play a role in improving the characteristics and performance of widely used bio-based polymers, such as PLA, and find numerous applications in the food and drink packaging industry. Here, the synthesis of poly (4-hydroxyphenylacetic acid) is optimized and its potential as additive for the synthesis of degradable blends is being investigated.
Hydrogen bond-rich, self-healable poly(dimethyl siloxane) networks
Pavle Ramah[1]
Anne Ladegaard Skov[1], Anders Egede Daugaard[1]
[1]Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical
University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
Thiol-maleimide conjugation is a well-established coupling method in biochemistry but with little reported use within silicone materials. A facile synthetic route of functionalised poly(dimethyl siloxane) (PDMS) to a prepolymer species capable of non-metal-catalysed cross-linking via Thiol-Michael addition is presented. Two systems are compared: Maleimide (MI) terminated PDMS and its precursor, maleamic acid amide (MA) terminated PDMS. Despite the traditional view of maleamic acid amide functionalities as of inferior value to their maleimide counterparts, we argue for their potential. The increased relative concentration of polar groups in a robust MA network matrix can be exploited for better electrical properties for self-healable dielectric elastomer actuators, as demonstrated by the MA networks with their quadruple hydrogen bonding centres, self-healing capabilities, increased polarity, good electrical breakdown strength, and increased dielectric permittivity over both commercial and MI PDMS networks.
Influence of Processing Conditions on the Incorporation of Gelatin Bio-filler in Silicone Elastomers
Florina-Elena Comanici[1]
Frederikke Bahrt Madsen [1), Anne Ladegaard Skov [1]
[1]Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical
University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
Silicone elastomers are a class of materials known for their unique properties such as temperature resistance, flexibility, and chemical inertness, making them ideal for applications in the automotive, healthcare, and electronics industries. The elastomers usually contain polydimethylsiloxane crosslinked polymers and fillers. Commonly used fillers include silica, carbon nanotubes, and silver particles. Recent advancements focus on integrating bioderived polymers from renewable resources, such as carbohydrates and proteins, to develop green additives and bio-fillers, which offer enhanced biodegradability and mechanical properties.
This work focuses on the incorporation of gelatin, a protein fragment, as a bio-filler in silicone elastomers. Furthermore, the impact of the processing conditions on the structure and physical properties of the elastomer is being investigated.
Silicone elastomers with concatenated rings network: synthesis and functionalization
Cristina Nedelcu[1]
Anne L. Skov[1], Frederikke B. Madsen[1]
[1]Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical
University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
Polydimethylsiloxane is a material that is widely used in the field of soft robotics due to its unique properties, including softness, flexibility, mechanical stability, and biocompatibility. These characteristics enable the creation of a range of innovative components, including soft actuators, sensors, and other adaptive elements that are capable of mimicking human muscles. The hydrosilylation reaction represents a highly efficient method for the synthesis of organosilicon compounds and is regarded as one of the most significant reactions in the fields of organic and silicon chemistry.
In this project, a telechelic hydride-terminated polydimethylsiloxane was functionalized with 1,5,9-decatriene to prepare an organosilicon copolymer with carbon-carbon double bonds of different reactivity within the polymer backbone. The resulting polymers were utilized to design an elastomer network constituted of concatenated cyclic polymers, with preserved carbon-carbon double bonds within the backbone. The presence of carbon-carbon double bonds within the ring network enables post-curing functionalisation.
Recyclable silicone elastomer achieved by a simple method
Sofia Lindström [1],[2]
Panch Svensson [1], Pierre Berglund [1], Anders E. Daugaard [2], Anne L. Skov [2]
[1] Roxtec International AB, Rombvägen 2, 371 65 Lyckeby, Sweden
[2] Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
Crosslinked elastomers, or rubbers, have a network structure formed by chemical and/or physical crosslinks between the polymer chains. Recycling rubber materials is very challenging, mainly due to the crosslinks being irreversible chemical bonds, which will prevent reprocessing methods that traditionally are being used for thermoplastic materials.1
A novel silicone elastomer is in this work proven to be recyclable by a simple method. The elastomer is made by crosslinking a hydroxyalkyl modified polydimethylsiloxane (PDMS) with a polysilazane (PSz), which leads to chemical crosslinks in the form of hydrolysis sensitive silyl ethers.2,3 It is found that swelling the crosslinked network allows for example an acid to access and hydrolyse the silyl ethers, re-forming the hydroxyl groups, ultimately leading back to polymers very similar to the ones before crosslinking. The polymers can then be crosslinked again using new PSz to form new elastomers.
References
- Marks, J.E. Applied Plastics Engineering Handbook 2017, 2nd Edition, 109-125, doi.org/10.1016/B978-0-323-39040-8.00006-7
- Sønderbæk-Jørgensen, R.; Meier, S.; et al. Macromolecular Materials and Engineering 2022, 307, 2200157, doi.org/10.1002/mame.202200157
- Nelson, T.; Crouch, D. Synthesis 1996, 1996, 1031-1069, doi.org/10.1055/s-1996-4350
Modifying electrical properties of PDMS membranes for electrostatic actuators.
Christopher D. Woolridge [1]
Anne L. Skov [1]
[1]Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical
University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
Dielectric elastomer actuators (DEAs) typically consist of two compliant electrodes separated by a dielectric elastomer (DE) material. DEAs’ flexible and lightweight nature makes them attractive for usage in wearable robotics. Polydimethylsiloxane (PDMS) elastomers are good candidates for DEs as they show acceptable dielectric permittivity, low Young’s modulus and high breakdown strength.
This project attempts to introduce charge separation within the DE itself to influence the electrical properties, initially focusing on improving the dielectric permittivity. This is achieved via inclusion of ionic liquids and also electret type materials that capable of storing charge via a phase change occurring in an applied electric field.
Adaptable foam for treatment of chronic wounds
Sofie Helvig Eriksen [1]
Nikolett Kis [1], Anne L. Skov [1]
[1] Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical
University of Denmark, Søltofts Plads, Building 227, 2800 Kgs. Lyngby, Denmark
Globally, close to 50 million people are suffering from chronic wounds. Current wound dressings struggle to create a perfect fit to the wound bed, absorb sufficient exudate, and retain wound exudate during compression.
This work introduces a novel approach to chronic wound treatment: A silicone-glycerol foam. The formulation is applied directly into a cavity, whereafter it foams and cures. The in-situ foaming technique ensures a perfect fit to the wound bed. In a simulated wound bed, the silicone-glycerol foam demonstrated exceptional liquid absorption of up to 0.99 g/cm2/24h, placing it in the category of highly absorbing dressings. Even after a 25% compression, the foams retained over 97% of the absorbed fluid, confirming excellent fluid retention.