Discipline: Chemistry and Chemical Sciences
Subcategory: Chemical/Bimolecular/Process Engineering
Room: Exhibit Hall
Jenna E. Peitsch - Shelton State Community College
Co-Author(s): Joseph T. Danner, The University of Alabama, Tuscaloosa, AL;Steven T. Weinman, The University of Alabama, Tuscaloosa, AL
Polyvinylidene Fluoride (PVDF) is used with and in many things, particularly as water treatment membranes; however, the solvents used to process PVDF are very toxic. Additionally, PVDF is one of the most challenging polymers to use for several reasons. First, it has high surface tension properties, making it difficult to mix with certain solvents. Second, its heat deflection temperature is one of the highest among fluoropolymers, and its melting point is the lowest. Lastly, it also has an outstanding resistance to acids, hydrocarbons, and solvents, making it difficult to alter; although, strong bases and ketones can break it down.My hypothesis is that if we alter PVDF membranes by changing the solvent and the amount of polymer, then we will make membranes as good or better than commercial membranes while being environmentally friendly. To test my hypothesis, I investigated and experimented with different solvents, such as N,N-Dimethylacetamide (DMAC) and N-methylpyrrolidone (NMP), to prepare PVDF dope solutions. I did cloud point measurements to investigate the thermodynamics of each polymer-solvent system. I hand-casted PVDF membranes using the non-solvent induced phase separation or NIPS method using a doctor’s blade to control casting height on either glass or a non-woven fabric and a water non-solvent bath. Then, I tested the membranes for their pure water permeance using a pressurized dead-end or direct-flow filtration cell. Additionally, some membranes were characterized using scanning electron microscopy (SEM). I compared my results to that of a commercial PVDF membrane I was trying to mimic.The cloud point tests showed that the DMAC-PVDF solutions were slightly more stable than the NMP-PVDF solutions. The SEM results showed that the membranes had a mixture of spongy cross-sections and macro-void, finger-like cross-sections, similar to the commercial membrane control. The water permeance results showed that casting thickness played a critical role in the membrane permeance properties, with a 70-micrometer thick membrane cast on a non-woven fabric performed similar to the commercial control membrane. Interestingly, similar thickness membranes, with one casted on a non-woven fabric and one casted on glass, yield extremely different permeance results, with the glass-casted membrane having ~1 order of magnitude less permeance.I investigated numerous properties related to PVDF membrane casting over the 6-week UPWARDD program. Future work will involve investigating greener solvents, such as cyclopentanone, which is synthesized from cellulose-derived polymers, 2-methylpyrazine, which is present in sesame seeds, and glycerol-derived solvents, with glycerol being a waste product in bio-diesel production. When this research becomes successful, we can modify PVDF in ways that will help reduce its negative impact on the environment.
Funder Acknowledgement(s): NSF REM Supplement as part of NSF EFRI grant EFMA-2029387
Faculty Advisor: Dr. Steven T. Weinman, firstname.lastname@example.org
Role: All of it.