Material relationships at low temperatures were determined for concentrated surfactant solutions using a combination of rheological experiments, cross-polarized microscopy, calorimetry, and small angle X-ray scattering. A lamellar structured 70 wt% solution of sodium laureth sulfate in water was used as a model system. At cold temperatures (5 °C and 10 °C), the formation of surfactant crystals resulted in extremely high viscosity. The bulk flow behavior of multi-lamellar vesicles (20 °C) and focal conic defects (90 °C) in the lamellar phase was similar. Shear-induced crystallization at temperatures higher than the equilibrium crystallization temperature range resulted in an unusual complex viscosity peak. The effects of processing-relevant parameters including temperature, cooling time, and applied shear were investigated. Knowledge of key low-temperature structure-property-processing relationships for concentrated feedstocks is essential for the sustainable design and manufacturing of surfactant-based consumer products for applications such as cold-water laundry.
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http://dx.doi.org/10.1039/d3sm01198d | DOI Listing |
Polymers (Basel)
December 2024
Japan Advanced Institute of Science and Technology, Graduated School of Advanced Science and Technology, Asahidai, Nomi 923-1292, Ishikawa, Japan.
We studied the rheological properties under both shear and elongational flow and crystallization behaviors after shear history for binary blends of poly(lactic acid) (PLA) and ethylene-vinyl acetate copolymer (EVA) with a slightly lower shear viscosity. EVA was immiscible with PLA and dispersed in droplets in the blend. The addition of EVA significantly reduced the shear viscosity, which is attributed to the interfacial slippage between PLA and EVA.
View Article and Find Full Text PDFRep Prog Phys
December 2024
Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong Special Administrative Region of China, People's Republic of China.
ACS Appl Mater Interfaces
December 2024
Zhejiang Provincial Key Laboratory of Fiber Materials and Manufacturing Technology, Zhejiang Sci-Tech University, Hangzhou 310018, People's Republic of China.
Membrane technology is one of the most effective ways to cope with the filtration and separation. However, most polymer membranes are not uniform in pore size and have wide pore size distributions and low porosities, which restrict their application. A high-porosity homogeneous membrane with high filtration accuracy is an effective solution.
View Article and Find Full Text PDFChem Commun (Camb)
November 2024
School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067, India.
The jumping of crystals in the presence of external stimuli such as temperature, light, and mechanical forces is observed due to the release of accumulated strain in the crystal. Thermosalience in molecular crystals is generally induced by anisotropic thermal expansion accompanied by phase transformation. However, a thermosalient effect has not been observed in the same crystal at two different temperature zones caused by two distinct mechanisms.
View Article and Find Full Text PDFSci Rep
November 2024
Department of Plastics Engineering, University of Massachusetts Lowell, 1 University Ave, Lowell, MA, 01854, USA.
In this work, a heat transfer model is developed for thermally-driven material extrusion additive manufacturing of semicrystalline polymers that considers the heat generated during crystallization by coupling crystallization kinetics with heat transfer. The materials used in this work are Technomelt PA 6910, a semicrystalline hot melt adhesive with sub-ambient glass transition temperature (T) and slow crystallization, and PA 6/66, a traditional semicrystalline polyamide with a higher T and fast crystallization. The coupled model shows that the released heat during crystallization depends on material selection, with Technomelt PA 6910 and PA 6/66's temperatures increased by less than 1 °C and up to 6.
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