Paper Number
RS25                         My Program 

Session
Real-World Rheology & Sustainability

Title
Effects of additives on the flow behavior of lamellar structured concentrated surfactant solutions

Presentation Date and Time
October 15, 2024 (Tuesday) 1:50

Track / Room
Track 7 / Room 502

Authors (Click on name to view author profile)

  1. Kelkar, Parth U. (Purdue University, School of Materials Engineering)
  2. Kaboolian, Matthew (Purdue University, School of Materials Engineering)
  3. Williams, Evan (Purdue University, School of Materials Engineering)
  4. Lindberg, Seth (Procter & Gamble Co.)
  5. Erk, Kendra A. (Purdue University, School of Materials Engineering)

Author and Affiliation Lines (in printed abstract book)
Parth U. Kelkar1, Matthew Kaboolian1, Evan Williams1, Seth Lindberg2 and Kendra A. Erk1
1School of Materials Engineering, Purdue University, West Lafayette, IN 47906; 2Procter & Gamble Co., West Chester, OH 45069

Speaker / Presenter 
Kelkar, Parth U.

Keywords
flow-induced instabilities; real-world rheology; surfactants; sustainability

Text of Abstract
Cleaning products like shampoos and detergents often contain a large amount of water, a critical component that is typically required at all stages of the product's lifecycle. The water we use in the shower is sufficient to dilute personal care products and use them effectively. Changing their consistency from a slow-flowing liquid to a thick paste would have significant economic and environmental benefits. Making concentrated formulations, however, is more complicated than simply removing as much water as desired. Conventional production methods cannot process concentrated surfactant-based materials without altering their microstructure and potentially compromising material performance. Unless multiscale material relationships are developed, industry will continue to waste resources on unsustainable manufacturing processes. Here, material relationships at low temperatures were determined for concentrated surfactant solutions using a combination of rheology, cross-polarized microscopy, calorimetry, and small angle x-ray scattering (Kelkar et al., Soft Matter, 2024). A lamellar structured, aqueous 70 wt.% solution of sodium laureth sulfate was used as a model system. At cold temperatures, the formation of surfactant crystals resulted in high viscosity. Shear-induced crystallization at temperatures (10–12.5 °C) higher than the equilibrium crystallization temperature range (5–9 °C) resulted in an unusual viscosity peak. The effects of processing-relevant parameters - temperature, cooling time, and applied shear were investigated. Industrially relevant additives – sodium chloride, propylene glycol and cetostearyl alcohol – were separately added (0.25-20 wt.%) and material relationships were experimentally established. Sodium chloride and propylene glycol behaved as desiccants and plasticizers, respectively, while fatty alcohols increased surfactant bilayer thickness. Outcomes from this study answer unexplained processing behavior for concentrated feedstocks and will improve the sustainability of consumer products.