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Development and characterization of compatible cellulose blend membranes using cellulose and other natural biopolymers using a novel solvent system. By Eugene F. Douglass, MS, PhD Department of Chemistry Nazarbayev University, Astana, Kazakhstan & Richard Kotek, PhD
Development and characterization of compatible cellulose blend membranes using cellulose and other natural biopolymers using a novel solvent system
Eugene F. Douglass, MS, PhD
Department of Chemistry
Nazarbayev University, Astana, Kazakhstan
Richard Kotek, PhD
TECS, College of Textiles
North Carolina State University, Raleigh, NC USA
June 28, 2010
Reviewing briefly the literature, and previous work with this system. To summarize the recent work developing new fibers and membranes using our novel solvent system.
To show the development of biopolymer blend cellulose membranes, using previous work as a foundation.
To show the characterization of the membranes.
To extend the preliminary goals of the research into a new creative area, developing brand new materials that may have use in the membrane industry, and to characterize these new materials.
Cellulose most abundant naturally occurring polymeric raw material – very cheap raw material
Wood pulp, cotton, other plant fibers, or plant waste
Figure 1- Molecular structure of cellulose.11
Cellulosic fibers and membranes
Natural cellulose fibers: cotton, linen, & flax
Regenerated cellulose: rayon fiber and film, cellophane film
Cellulose dissolved in a solvent: Lyocell fiber and film
Cellulose derivatives: nitrocellulose, celluloid, cellulose acetate fibers and films
Early solution methods – Regenerated cellulose: Cellulose xanthate is made, dissolved, then regenerate the cellulose chemically.
Recent solution methods – Dissolve cellulose in a solvent system
Lyocell process – prime commercial process
Zn+2 > Li+ > Ca+2 > Mg+2 > Ba+2 > Na+ > NH4+ > K+
SCN- > I- > PO4-3 > Br- > Cl- > NO3- > SO4-2 > ClO3-
Order of decreasing swelling of cellulose2
Figure 2 – Swollen cellulose – crystal structure
Ionic interactions assisting dissolution
Figure 3 – Coordination of ED and KSCN in solution9 Frey
Hyun Lee12– developed cellulose fibers from this optimized solvent blend, and did some basic membrane investigation
Possible porous membrane
Severe yellowing upon aging
Figure 4 – Porous cellulose membrane12
Reproducibility is required
Obtained casting table and bars from Byk-Gardner
Obtained casting PET film and drawdown panels for sample membranes
Figure 5 - 7% free flowing ED/KSCN cellulose (DP = 450) solution
Figure 6 – Dissolution apparatus
Table 1 - Different swelling and dissolution mechanisms for cotton and wood fibers in NMMO – water mixtures at various water contents.3
Cellulose and starch are polysaccharides
Bond linkage of glucose units different
Solvent for cellulose works, perhaps would work for starch.
Discussion with Drs. Kotek, Venditti, and Pawlak: Can starch make a membrane with this solvent system? No, could we do a blend??
Attempt blend with starch for membranes; success!
Based on success with starch; chitosan, chitin and soy protein were also tried.
Both porous and nonporous membranes were obtained, this section describes the development of cellulose blended with starch to form a useful membrane.
Figure 7 - Amylose
Figure 8 - Amylopectin
Cross sections of 50/50 cellulose and corn starch blend membranes
Figure 9– 500x cellulose / corn starch blend membrane
Figure 10 – 5000x cellulose / corn starch blend membrane
Cellulose and high amylose starch
Figure 11 – 500x cellulose / high amylose starch blend membrane
Figure 12– 5000x cellulose / high amylose starch blend membrane
Cross-sections of 50/50 cellulose and waxy maize starch blend membranes
1000 nm pore size
Figure 13– 500x cellulose / waxy maize starch blend membrane
Figure 14– 5000x cellulose / waxy maize starch blend membrane
Figure 15- Cellulose membrane: onset 332º C, end 371º C, ash level about 28%
Figure 16: Cellulose / wm starch blend membrane: onset 272º C, end 324º C, ash level about 20%
Cellulose II structure Amorphous structure
Peaks at 16,17 and 23 2θ Broad peak at 20-22 2θ
Cellulose / Waxy Maize Starch membrane
Figure 18– cellulose / waxy maize starch membrane
Figure 17– cellulose membrane
Table 3 - Tensile property comparison of cellulose and cellulose blend membranes
Based on success with Starches, we thought protein might work
First attempt with Brim Soy Protein isolate, received from USDA labs on NCSU campus
ADM soy materials received from NC Soy Council
Sample blend membranes made from each protein, to determine best quality membranes.
Determine ideal mass ratios of Soy protein to cellulose using Profam 974 at 40, 30 and 20% by characterization of each mass percent membrane.
Figure 20 – 50/50 Cellulose/Profam 974
Figure 19– 50/50 Cellulose/brim membrane, 5000x
Figure 21 - Cellulose membrane: Onset 332º C, end 371º C, ash about 28%
Figure 22- Cellulose / brim blend membrane: Onset 241º C, end 342º C, ash about 28%
Figure 23- Cellulose membrane: Onset 332º C, end 371º C, ash level about 28%
Figure 24- Cellulose / Profam 974 blend membrane: Onset 284º C, end 344º C, ash level about 9%
Table 8 - Comparison of TGA results between membranes
Cellulose II Structure Amorphous Structure
Peaks at 16,17 and 23 2θ Broad Peak at 20-22 2θ
Figure 25– Cellulose membrane
Figure 26– Cellulose / Profam 974 membrane
Amorphous Structure Amorphous Structure
Peaks at around 14 and 21 2θ Around 14 and 21 2θ
Figure 27– Cellulose / Brim blend
Figure 28– Cellulose / Profam 974 blend
Table 5 – Comparison of Tensile properties for soy blend membranes
Made blend fibers from cellulose / waxy maize, and cellulose / soy protein blends.
Cross-linked cellulose and cellulose blend membranes to prevent falling apart in long term water contact.
New dissolution process development:
Using a special solvent system of ED/KSCN in a 65/35 mass % ratio, functional porous and non-porous membranes were produced that have comparable physical properties to other methods of making cellulose membranes.
New material development:
Using the same solvent system, starch was blended with cellulose in the solution and cast to make functional porous blend membranes, that are stronger than the cellulose porous membranes developed earlier, and very water absorbent.
Using the same solvent system, soy protein was blended with cellulose to make functional non-porous blend membranes, that are strong and even more water absorbent than the blend membrane with starch.
The casting and drying processes were optimized to deal with issues of shrinkage that causes wrinkling and variable film thicknesses
Other polysaccharides (chitosan and chitin), and protein (keratin from hair) were also used to make functional blend membranes with cellulose, suggesting further applications for this system.
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North Carolina State University, College of Textiles including
Nazarbayev University, Astana, Kazakhstan seed funding to disseminate this work, and develop further work