1 / 20

Enhancing Mechanical Recycling with Compatibilizers

Enhancing Mechanical Recycling with Compatibilizers. Megan L. Robertson University of Houston Closing the Loop on the Plastics Dilemma Chemical Sciences Roundtable, National Academies Washington, D.C. May 9, 2019. Disparate Plastics Cannot Be Easily Mixed!. Homogeneous.

tconstance
Télécharger la présentation

Enhancing Mechanical Recycling with Compatibilizers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Enhancing Mechanical Recyclingwith Compatibilizers Megan L. Robertson University of Houston Closing the Loop on the Plastics Dilemma Chemical Sciences Roundtable, National Academies Washington, D.C. May 9, 2019

  2. Disparate Plastics Cannot Be Easily Mixed! Homogeneous Flory-Huggins theory: T Phase separated Entropy change of mixing Enthalpy change of mixing Li and Shimizu, Macromol. Biosci. 2007, 7, 921. 1 Adapted from: Wang and Robertson,ACS Appl. Mater. Int. 2015, 7, 12109-12118. • Phase behavior governed by: • Flory Huggins interaction parameter () • Degree of polymerization (N) • Component volume fractions (i) Most polymers are immiscible due to large size of molecules. Flory, P. J. J. Chem. Phys. 1942, 10, 51-61. Huggins, M. L. J. Chem. Phys. 1942, 46, 151-158.

  3. Poor Physical Properties Without Control of Structure • Immiscible polymers form phase-separated blends • Processing methods can impart some degree of control over structure • Inferior properties are typically observed due to: • Large domain sizes • Poor interfacial adhesion • Lack of entanglements at interface (due to large ) HDPE / iPP70/30 Xu, Eagan, LaPointe, Coates, Bates, et al., Macromolecules 2018, 51, 8585-8596.

  4. Inspiration: Surfactants for Immiscible Small Molecule Mixtures alkane (A) water (B) alkyl polyethylene glycol ether(A-C) A T repulsion repulsion B C attraction 7 vol. % C part of the surfactant exhibits attractive interactions with water and repulsive interactions with oil (oil:water = 50:50) Can we similarly control the structure of polymer mixtures by designing a surfactant? Adapted from:Strey, R. Colloid Polym. Sci.1994,272, 1005-1019.

  5. How Can We Design Polymeric Surfactants? A A B B Immiscible A C D C Favorable interactions with polymer A Favorable interactions with polymer B • Increasing number of distinct components enhances system tunability, albeit also increases complexity of surfactant design • Blend phase behavior governed by all binary interactions present (AB, AC, AD, etc.)

  6. The Gold Standard: A-B Diblock Copolymers A Phase B Phase AB A-B diblock copolymer diblock Adapted from: TL Morkved, Bates, Lodge, et. al. J. Chem. Phys.2001, 114, 7247. • A-B diblockcopolymers stabilize interface between immiscible A and B polymers • Domain coalescence is inhibited; interfacial strength is enhanced • Numerous parameters impact compatibilizer effectiveness: molecular weight of components, composition • Some compatibilizer is lost to micelles

  7. Compatibilizer Design through Tailored Thermodynamic Interactions Modifying diblock copolymer design significantly changes blend phase behavior. A-C Diblock Copolymer AB AC BC Bicontinuous microemulsion 1% A-C • A-C compatibilizer design mimics oil/water/non-ionic surfactant systems • Bicontinuousmicroemulsion observed with addition of only 1% A-C diblock copolymer Ruegg and Balsara, et al. Macromolecules 2007, 40, 1207. Ruegg and Balsara, et al. Macromolecules 2006, 39, 1125.

  8. Control Over Architecture: Beyond Linear Diblock Copolymers • Compatibilizers come in many forms: copolymers of various architectures, nanoparticles, ionomers, etc. • Diverse types of interactions can be leveraged: van der waals, dipole interactions, hydrogen bonding, etc. • Compatibilizers can be preformed: synthesized and then added during blending, or formed through reactiveor in situprocesses Maris, Fontaine, Montembault, et al. Polym. Degrad. Stab. 2018, 147, 245-266. Walther, Matussek, Müller. ACS Nano 2008, 2, 1167-1178.

  9. From Compatibilizer Science to Recycling Applications? • A diverse body of research has identified numerous strategies for polymer blend compatibilization • Signficant efforts in industry have led to commercial development of blend compatibilizers How do we bridge the gap between existing compatibilizer science and technology and the recycling industry? What challenges must be addressed?

  10. Architecture Design to Improve Compatibilizer Efficiency • Challenge: Compatibilizers are costly • Key idea: Improving compatibilizer efficiency can reduce required concentration • One approach: architecture and molecular weight control • Multiblock architecture improves blend interfacial adhesion and toughness Polyethylene (PE) / isotactic polypropylene (iPP) blends Eagan, LaPoint, Bates, Coates, et al., Science 2017, 355, 814-816.

  11. Architecture Design to Improve Compatibilizer Efficiency • Challenge: Compatibilizers are costly • Key idea: Improving compatibilizer efficiency can reduce required concentration • One approach: architecture and molecular weight control • Significant improvement even at 0.5-1% block copolymer content! Polyethylene (PE) / isotactic polypropylene (iPP) blends Xu, Eagan, LaPointe, Coates, Bates, et al., Macromolecules 2018, 51, 8585-8596.

  12. Architecture Design to Improve Compatibilizer Efficiency • Challenge: Compatibilizers are costly • Key idea: Improving compatibilizer efficiency can reduce required concentration • One approach: architecture and molecular weight control • Significant improvement even at 0.5-1% block copolymer content! Polyethylene (PE) / isotactic polypropylene (iPP) blends Xu, Eagan, LaPointe, Coates, Bates, et al., Macromolecules 2018, 51, 8585-8596.

  13. Complicated Interactions in Multi (>2) Component Blends Challenge: Increasing the number of blend components increases the number of binary interactions governing the mixture phase behavior Key idea: Compatibilizer must be designed to work for all blend components One approach: Employ diverse mechanisms for each blend component, as needed Polypropylene Compatibilizer: Poly(propylene-g-(maleic anhydride-co-styrene)) PP PP/PA PP/PS PP Polyamide Polystyrene PA St PA/PS Wang, Xie, et al. Polymer 2011, 52, 191-200.

  14. Significance of Thermal Degradation in Compatibilizer Design Challenge: Thermal degradation changes polymer molecular weight distribution, and thus compatibilizer requirements Key idea: Presence of compatibilizer can arrest thermal degradation Polypropylene Qian, et al. Polym. Bull. 2011, 67, 1661-1670. Waldman, et al. Polímeros2013, 23, 7-12. • Significant changes observed in polymer molecular weight distribution during processing • Properties degrade under multiple recycling cycles • Compatibilizer addition can slow rate of property decline • Degraded polymer mixtures may require different compatibilizers

  15. Overcoming Composition Variations with Advanced Characterization and Sorting Challenge: Recycled plastic feedstocks contain many impurities (other polymers, low molecular weight compounds, etc), and their presence will impact blend properties and compatibilizer efficiency Key idea: Developing better sorting techniques and more accurate analytical methods will aid compatibilizer design Laser induced break down spectroscopy X-ray fluorescence • Spectroscopy • Fluorescence • Calorimetry • Electrical conductivity • Gravity/density • Imaging • Etc. Singh, et al. Comp. B: Eng. 2017, 115, 409-422. Unnikrishnan, Santhosh, et al. RSC Adv.2013, 3, 25872-25880.

  16. Towards a Universal Compatibilizer? • Challenges: • Compatibilizers must be tailored to a targeted blend composition • Recycled plastic waste streams vary in composition and even types of materials present (i.e. plasticizers, flame retardants, etc.) • One approach: Use nanoparticles as compatibilizers HDPE / PET / Organoclay Poly(vinylidene fluoride) / Polylactide / Reactive Si02 Styrofoam / Plexiglas / Clay Si, Rafailovich, et al. Macromolecules 2006, 39, 4793-4801. Wang, Li, et al. ACS Appl. Mater. Int. 2017, 9, 14358-14370. Chen, et al. J. Appl. Polym. Sci. 2015, 132, 42287.

  17. Towards a Universal Compatibilizer? • Challenges: • Compatibilizers must be tailored to a targeted blend composition • Recycled plastic waste streams vary in composition and even types of materials present (i.e. plasticizers, flame retardants, etc.) • One approach: Use nanoparticles as compatibilizers Efficacy parameter R: % reduction in droplet size normalized by nanoparticle content • Mechanisms still under discussion: • Nanoparticles in bulk phases: suppress droplet coalescence • Rheological effects: changes in viscosity ratio • Shielding of coalescing droplets in matrix • Nanoparticles at interface • Act as compatibilizers: decrease interfacial tension, improve interfacial adhesion, suppress coalescence • Modify interfacial rheology: reduced mobility at interface slows coalescence Salzanode Luna and Filippone, Euro. Polym. J. 2016, 79, 198-218.

  18. Towards a Universal Compatibilizer? • Challenges: • Compatibilizers must be tailored to a targeted blend composition • Recycled plastic waste streams vary in composition and even types of materials present (i.e. plasticizers, flame retardants, etc.) • One approach: Form in situ compatibilizers through reactive compatibilization LLDPE / PET Maleic anhydride-based compatibilizer • Diverse chemistries for reactive or in situ compatibilization • Maleic anhydride-based compatibilizers • Radical processes • Irradiation • Mechanochemistry • Etc. In situ / reactive compatibilization vs. preformed compatibilizers: simplicity vs. specificity Zhang, Wu, et al. Polym. Degrad. Stab. 2009, 94, 1135-1141.

  19. Towards a Universal Compatibilizer? • Challenges: • Compatibilizers must be tailored to a targeted blend composition • Recycled plastic waste streams vary in composition and even types of materials present (i.e. plasticizers, flame retardants, etc.) • One approach: Employ more than one type of compatibilizer simultaneously PA6/PS/PP/SEBS (70/10/10/10) Addition of SEBS-g-(MAH-co-St) SEBS: poly(styrene-b-(ethylene-co-butylene)-b-styrene] Li, Xie, et al. Polymer 2017, 123 (Supplement C), 240-246.

  20. Challenges, or Opportunities for Compatibilizer Design? • Scientific and technology advancements can help overcome current limitations of the application of compatibilizers to recycling processes • Open challenges remain: • Developing “universal” compatibilizers for diverse, ill-defined, or varying waste streams • Reducing compatibilizer content and associated costs • Maintaining compatibilizer efficiency and blend properties over multiple recycling (i.e. high temperature processing) cycles Maris, Fontaine, Montembault, et al. Polym. Degrad. Stab. 2018, 147, 245-266. Funding acknowledgement: National Science Foundation

More Related