Paper Number
PO40 

Session
Poster Session

Title
Kinetics of solvation using Time Dissolution Evolution (TiDE) rheometry

Presentation Date and Time
October 13, 2021 (Wednesday) 6:30

Track / Room
Poster Session / Ballroom 1-2-3-4

Authors (Click on name to view author profile)

  1. Owens, Crystal E. (MIT)
  2. Du, Jianyi (Massachusetts Institute of Technology)
  3. Sanchez, Pablo (University of Vigo)
  4. Hart, A. John (MIT, Mechanical Engineering)
  5. McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Crystal E. Owens1, Jianyi Du1, Pablo Sanchez2, A. John Hart1 and Gareth H. McKinley1
1Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA; 2University of Vigo, Vigo, Pontevedra 36310, Spain

Speaker / Presenter 
Owens, Crystal E.

Keywords
experimental methods; applied rheology; non-Newtonian fluids; polymer solutions

Text of Abstract
Textiles have been used by humans for millions of years, and organic fibers still are often preferred over synthetic fibers for their flexibility, strength, durability, and water-repellency. However, the underlying cause of such durability also prevents recyclability: due to strong interchain hydrogen-bonding interactions, the main ingredient of cotton - cellulose - does not dissolve in common solvents, and over 80% of all cotton-based goods end up in landfills. As a possible remedy, ionic liquids progressively solvate cellulose by disrupting hydrogen bonds, which can allow a solvent-based recycling process. But, in order to create an economically viable recycling process, cellulose fibers must not be degraded by the process, and relevant kinetics and solution strength must fall within reasonable processing windows, even for highly concentrated (>5%) solutions. We take advantage of this interesting material to develop a rheometric framework for understanding the kinetics of dissolution of a macromolecule from powder to entangled solution.

We monitor the dissolution of cotton-based textiles in 1-ethyl-3-methyl-imidazolium acetate (EMIMOAc) from chopped fiber to homogeneous dispersion using small amplitude oscillatory shear (SAOS) rheometry. Due to the changing entanglement structure during dissolution, standard time-temperature superposition is inappropriate, and we instead develop a new method of Time Dissolution Evolution (TiDE) to understand and predict this cellulose rheology for a series of cellulose concentrations (0.5-12%) and degrees of polymerization (500-2500). The time-evolving SAOS measurements are described using regression to the Baumgaertel-Schausberger-Winter (BSW) relaxation spectrum model. This results not only in kinetic information but also in observability of the majority of the material relaxation spectrum. The resulting solvent-specific information is useful to guide processing of cellulose into new synthetic fibers, and to inform limits to recycling based on time and viscosity.