Solvent Systems Screening forSoy Cellulose Fibers

Eugene F. DouglassRichard Kotek

North Carolina State University,College of Textiles

College of Textiles

August 11, 2010

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Objectives -• 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 cellulose / soy protein 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.

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1 - Introduction

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– Layer of material which serves as a selective barrier

– Barrier is between two or more phases– Remains impermeable to specific particles,

molecules or substances– Osmotic forces enable free flow of solvents– Some components are allowed passage into

permeate stream– Others are retained and remain in the

retentate stream

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Membranes – what are they?

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Cellulosic sources• Cellulose most abundant naturally occurring

polymeric raw material – very cheap raw material• Wood pulp, cotton, other plant fibers, or plant waste

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Figure 1- Molecular structure of cellulose.11 5

Examples: 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.

• Viscose process– Rayon – Problems: dangerous solvent, toxicity of waste material

Recent solution methods – Dissolve cellulose in a solvent system• Lyocell process – prime commercial process

– Lyocell – Problems: solvent instability issues, expensive

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Amines and thiocyanate processes Amine and counter ion dissolution

Structure of ramie cellulose I – ethylenediamine complex

A) ac sin γ projection; B) ab projection 2

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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 cellulose 2

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Figure 2 – Swollen cellulose – crystal structure

Ionic interactions assisting dissolution Amine and metal salt association

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+< 20mol%

> 20mol%SCNK

+

NH2CH2CH2NH2

dissociation

association

EDA=

cell-OH

dissolutioncell-OH= cellulose

K+ SCN

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Figure 3 – Coordination of ED and KSCN in solution9 Frey

2 - Development of porous cellulose membranes

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Objective: Dissolution of cellulose (DP 450)

• Simple setup for dissolution, paddle stirrer apparatus

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Figure 4 - 7% free flowing ED/KSCN cellulose (DP = 450) solution

Figure 5 – Dissolution apparatus

3 - Characterization of porous cellulose membranes

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SEM micrographs of cross section of Douglass membrane, 200 nm pore size

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Figure 6 – SEM micrographs of porous cellulose membrane

500 x 5000 x

Cellulose I Structure Cellulose II Structure

Peaks at 16,17 and 23 2θ Peaks at 13, 20-22 2θ

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Figure 7 – Raw wood pulp Figure 8 – Cellulose membrane

WAXS of ED/ KSCN cellulose from wood pulp and membrane

Khare and Douglass Tensile properties compared

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Table 1 – Tensile property comparison of cellulose membranes

Authors Tensile Modulus

(kgf/mm2) Failure Stress

(kgf/mm2) Failure Strain (%)

Khare2 163.1 ± 61 6.62 ± 1.9 6.5 ± 1.5

Douglass

non-porous 166.5 ± 16 5.36 ± 0.7 26.2 ± 10.1

Douglass

porous 33.0 ± 9.3 0.59 ± 0.17 3.9 ± 1.4

Characterization using Water absorbency

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Table 2 – Douglass membranes water absorption after 24 hour immersion in 25o C deionized water, compared to

never dried water swollen membrane (top)

Material Dry mass (g) Wet mass (g) Wet mass increase (%)

Wet cellulose membrane (coagulated

& kept wet ) 0.28 (after) 4.70 (before)

94 decrease, 1580 increase

Cellulose membrane a

0.75 1.34 79

Cellulose membrane b

0.49 1.03 110

Cotton control membrane

0.21 0.42 100

4 - Development and Characterization of cellulose blend

membranes

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Development of cellulose / soy protein 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– Two protein types in the Brim blend– Dissolves well in solvent blend

• ADM soy materials received from NC Soy Council– SAF soy protein– Archon F soy protein concentrate– Profam 974 soy protein isolate (comparable to

Brim)

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5 – Characterization of cellulose / soy protein blend membranes

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SEM cross section micrographs of 50/50 cellulose – soy protein

blends

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Figure 9 – 50/50 Cellulose/brim membrane, 5000x

Figure 10 – 50/50 Cellulose/Profam 974

membrane, 5000x

TGA Analysis - cellulose membrane compared to cellulose/brim soy protein blend

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Figure 11 - Cellulose membrane: Onset 332º C, end

371º C, ash about 28%

Figure 12 - Cellulose / brim blend membrane: Onset 241º C, end

342º C, ash about 28%

20o C 20o C710o C 710o C

100

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Figure 13 - Cellulose membrane: Onset 332º C, end 371º C, ash

level about 28%

Figure 14 - Cellulose / Profam 974 blend membrane: Onset 284º C, end 344º C, ash level

about 9%

TGA Analysis - cellulose membrane compared to cellulose/Profam 974 soy protein blend

20o C 710o C

100

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Summary of TGA results for soy protein / cellulose blend membranes

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Table 3 - Comparison of TGA results between membranes

MaterialsStart temperature

(ºC)Onset temperature(s)

(ºC)Char level @ 710º C

(%)

Cellulose fiber 242 350 11Cellulose

membrane 257 332 28

Profam 974 189 276 27Brim soy protein 193, 285 235, 310 25

Cellulose / Profam 974

mixed185 290, 362 18

Cellulose / Profam 974 membrane

200 283 9

Cellulose / brim mixed 201, 280 234, 355 19

Cellulose / brim

membrane178 241 28

Wide Angle X-ray Scattering of Profam 974 blend membrane

Cellulose II Structure Amorphous Structure Peaks at 16,17 and 23 2θ Broad Peak at 20-22 2θ

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Figure 15 – Cellulose membrane Figure 16 – Cellulose / Profam 974 membrane

Amorphous Structure Amorphous Structure

Peaks at around 14 and 21 2θ Around 14 and 21 2θ

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Wide Angle X-ray Scattering of Stretched Soy Protein blend membranes

Figure 17 – Cellulose / Brim blend

Figure 18 – Cellulose / Profam 974 blend

NoticeNotice

Tensile Properties SummaryCollege of Textiles

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Table 4 – Comparison of Tensile properties for soy blend membranes

Samples Tensile modulus (kgf/mm2)

Failure stress (kgf/mm2)

Failure strain (%)

Thickness (mm)

Cellulose membrane 75 ± 12 2.5 ± 1.2 36 ± 12 0.047 ± 0.015

Cellulose / brim

membrane157 ± 52 3.2 ± 1.6 27 ± 12 0.029 ± 0.003

Cellulose / Profam 974 membrane

200 ± 75 4.7 ± 1.2 16 ± 8.0 0.026 ± 0.001

Cell / PF 40% 220 ± 53 5.0 ± 2.0 29 ± 12 0.026 ± 0.001

Cell / PF 30% 204 ± 74 4.3 ± 2.3 27 ± 12 0.031 ± 0.005

Cell / PF 20% 195 ± 69 2.4 ± 1.8 20 ± 12 0.034 ± 0.003

Water absorbency summary

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Table 5 – Comparison of water absorbency for soy blend membranes

MaterialDry mass

(g)Wet mass

(g)Wet mass increase

(%)

Wet cellulose membrane (coagulated & kept wet ) 0.28 (after) 4.70 (before)

94 decrease to dry,1580 increase

Dried cellulose membrane 0.49 1.03 110

50% Cellulose / 50% brim membrane 0.18 0.81 350

50 % Cellulose / 50% Profam 974 membrane 0.18 0.81 350

Cell / PF 40% 0.07 0.26 370Cell / PF 30% 0.11 0.52 470Cell / PF 20% 0.19 0.60 320

6 – Possible Future work

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Suggested future work

• Attempt to make blend fibers from cellulose / soy protein blends.

• Attempt to crosslink cellulose blend membranes to prevent falling apart in long term water contact.

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7 - Conclusions

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• Using a novel 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

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Conclusions

8 - References

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1. Ott . Cellulose and cellulose derivatives : Molecular characterization and its application. Burlington: Elsevier; 1954.

2. Khare VP, Greenberg AR, Kelley SS, Pilath H, Roh IJ, Tyber J. Synthesis and characterization of dense and porous cellulose films. J Appl Polym Sci 2007;105(3):1228-36.

3. Cuissinat C, Navard P. Swelling and dissolution of cellulose part 1: Free floating cotton and wood fibres in N-methylmorpholine-N-oxide-water mixtures. Macromolecular Symposia 2006;244(1):1.

4. Cuissinat C, Navard P. Swelling and dissolution of cellulose part II: Free floating cotton and wood fibres in NaOH-water-additives systems. Macromolecular Symposia 2006;244(1):19.

5. Fink H, Weigel P, Purz HJ, Ganster J. Structure formation of regenerated cellulose materials from NMMO-solutions. Progress in Polymer Science 2001 11;26(9):1473-524.

6. Swatloski RP, Spear SK, Holbrey JD, Rogers RD. Dissolution of cellulose with ionic liquids. J Am Chem Soc 2002;124(18):4974-5.

7. Zhang . 1-allyl-3-methylimidazolium chloride room temperature ionic liquid: A new and powerful non-derivatizing solvent for cellulose. Macromolecules 2005;38(20):8272.

8. Hafez MM, Pauls HW, inventors. Method for preparing thin regenerated cellulose membranes of high flux and selectivity for organic liquids separations. Exxon Research and Engineering Co., editor. 4496456. 1985 1/29/1985

9. Frey M, Li L, Xiao M, Gould T. Dissolution of cellulose in ethylene diamine/salt solvent systems. Cellulose 2006 04/29;13(2):147-55.

10. Cao Y. Preparation and properties of microporous cellulose membranes from novel cellulose/aqueous sodium hydroxide solutions. Journal of Applied Polymer Science [Internet]. [revised 2006;102(1):920.

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