CELLULOSE/POLYSULFONE NANOCOMPOSITES Graduate Student: Sweda Noorani Advisors: Dr John Simonsen Dr Sundar Atre OSU Oregon State University Corvallis,Oregon
INTRODUCTION CONTENTS EXPERIMENTAL METHODS RESULTS CONCLUSIONS ACKNOWLEDGMENTS
INTRODUCTION
MECS Microtechnology for energy and chemical systems
Materials & Process Design for MECS Prof. Sundar V. Atre material polymer metal ceramic composite process injection molding extrusion sintering micromachining application kidney dialysis microreactor thermal management fuel cell
Microchannel Reactors - Steam Reforming Designed for efficient steam reforming Current system: CO and H 2 for 10 kwe fuel cell system
Components - Fractal Desorber Fractal geometry minimizes pressure drop and flux uniformity Applied to heat exchangers, desorbers, mixers and chemical reactors
Microchannel Separations - Portable Kidney Dialysis with HD+ Technology and Treatment Enhancement Through MECS technology and Meso-Scale Manufacturing HD+ will be able to reduce the size of the dialyzer and increase the clearance efficiency over the current fiber based dialyzer modules (MECS @ 90%CE versus FB @ 35%CE). HD+ has signed an exclusive options agreement with OSU for specific MECS technology and manufacturing processes.
Camera Visual Access Blood Adjustable Spacer Quartz Window Membrane Dialysate Prof. Goran Jovanovic, OSU ChE
Prototype Note that impact will be similar in many separation processes
Dialyzers old vs. new MECS dialysis ultrafilter Hollow Fibers Polysulfone High Flux/Good Specificity Mechanically flexible Hollow fiber filter Membrane not optimized for microchannel devices
Microchannel Devices Advantages Smaller size. Lower cost. Dialysis operation can be performed easily. Improved patient treatment. Microchannel membranes should be STIFF and FLAT
Objectives To incorporate cellulose nanocrystals(cnxls) in a polysulfone (PSf) matrix to produce CNXL/PSf nanocomposites. To investigate the properties of these nanocomposites.
EXPERIMENTAL METHODS
Cellulose Nanocrystal Production Native cellulose - Semi crystalline Polymer (~70% crystalline). Crystalline portion Amorphous portion CONTROLLED ACID HYDROLYSIS
TEM image of CNXL L d L/d=Aspect ratio Diameter=5-20nm Length=200-350 nm Aspect ratio=10-70 Agglomeration Single strand
Percolation threshold ~ 1.5% Aspect ratio = 50 Garboczi, et. al. Phys. Rev. Ltrs. E, 1995, 52(1): 819-828
Material Mechanical properties cellulose crystal Aluminum E-glass Steel (high tensile) Graphite Carbon nanotubes** Strength,MPa 7500 620 3400 1860 1700 11000-63000 Stiffness,GPa 145* 73 72 207 250 270-970 Comparison of mechanical properties of various materials (Jones,1975) *Eichhorn, et al. Biomacromol. 2005, 6: 507 **Yu, et al. Science 2000, 287: 637
Polysulfone isopropylidene ether diphenylene sulfone Excellent Thermal Stability Low creep Transparent Rigidity Maintains its electrical and physical properties over a wide range of temperature
Polymer Film Preparation CNXL transferred from water to 1-1 methyl-2-pyrrolidone (NMP) by Solvent Exchange Process. Polysulfone (PSf) dissolved in CNXL dispersed NMP. Films made by phase inversion.
Solvent exchange Mix aqueous dispersion of CNXLs with NMP. Rotovap (remove water). Sonicate to break up any agglomerates. Result = dispersion of CNXLs in NMP. Add PSf powder or pellets, stir to dissolve. Result = CNXL dispersion in PSf/NMP solution.
Phase immersion Conventional process for manufacture of ultrafiltration membranes, including hemodialysis membranes. Polymer solution/dispersion film substrate (glass sheet) Substrate (glass sheet) water bath
Mechanical testing Sintech 1G, Universal testing machine Tensile test mode Data converted to stress-strain strain curves Modulus reported is the initial linear portion of the stress- strain curve Evaluation
Evaluation Thermogravimetric analysis TA Instruments Q500 Temperature range 40-600 o C Heating rate 10 o C/min
Scanning electron microscopy (SEM) Evaluation AMRay 1000A @ 10 kv Coated with Au-Pd film (8-10 nm)
Evaluation Atomic force microscopy (AFM) DI Dimension 3100 (Veeco Instruments) Tapping mode
Water Vapor transmission rate Controlled Environment Chamber Temperature=30 o C Relative humidity = 90% Covered at the ends to prevent loss of water water D
Water vapor transmission rate wt loss (g) 0.6 0.5 0.4 0.3 0.2 0.1 0 0 WVTR 1 2 3 4 5 6 Time (dy) Slope of graph= wt loss/time. Area= area through which WVTR takes place. Flux = slope of graph/area Flux=(g/m^2-dy).
RESULTS
3 Mechanical Properties 2.5 Tensile modulus, GPa 2 1.5 1 0.5 Theoretical percolation threshold agglomeration 0-1 1 3 5 7 9 11 CNXL, wt %
Water vapor transport rate 400 350 Flux (g/m 2 dy) 300 250 200 150 100 50 0-2 0 2 4 6 8 10 12 % Cellulose nanocrystals
Thermogravimetric Analysis dw/dt (%/degc) -2.0-1.5-1.0-0.5 CNXL 0% 2% 11% 0.0 200 300 400 500 600 Temperature ( 0 C)
Morphology
0% CNXL
2% CNXL
11% CNXL
16% CNXL
Conclusions CNXLs can be incorporated into PSf by a novel solvent exchange process. Nanocomposite films can be obtained. Microscopic observations revealed that CNXLs were well dispersed at lower filler loadings. TGA curves revealed interaction between PSf/CNXL at lower filler loadings and poor interaction at higher filler loadings.
Conclusions Modulus and WVTR show a percolation threshold at ~1% filler loading. Modulus and WVTR approximately triple due to presence of CNXLs at low filler loadings (~2 5%). Modulus decreases at filler loadings >7% presumably due to agglomeration. Highly variable results of WVTR at filler loadings >7% maybe due to agglomeration.
ACKNOWLEDGEMENTS This project was supported by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service, grant number 2003-35103 35103-13711. 13711.
Questions