Novel Cellulosic Fibers with Microcellular Porous Structures

1. Novel Cellulosic Fibers with Microcellular Porous Structures By Khaled El-Tahlawy, and Renzo Shamey Textile Engineering, Chemistry and Science College of Textiles, NC State University

2. Outline • Cellulose Chemistry and Background • Introduction about polymer of MCF structure • Future uses of MCF • Previous Experiences on Microcellular Foam • Cellulose Fiber Spinning • Cellulose MCF Using Solvent Exchange Technique • Acetone • Ethanol • Water

3. Cellulose • Structure Composition and Properties • Cellulose is the most abundant biopolymer worldwide . • Cellulose is composed of anhydroglucosidic units connected together through β- 1,4-glucosidic ether bonds. • The number of anhydroglucose units vary from a few hundred units in wood pulp to over 6000 for cotton. • Cellulose is a straight chain polymer: unlike starch. • Cellulose structure is more crystalline than starch • Cellulose has one primary and two secondary OH groups.

4. Cellulose

5. CelluloseSolvents • Dissolution of Cellulose in Organic Solvents: • Ethylene Diamine / Potassium thiocyanate (KSCN). • 4-Methylmorpholine N-Oxide. • Dimethyl sulfoxide / tetrabutylammonium fluoride trihydrate. • Dimethyl imidazolidinone / lithium chloride. • NH3 / NH4SCN solvent system • Dimethylacetamide / Lithium Chloride

6. Polymer MCF • What are PMCFs? • MCF is a polymeric solid matrix that has voids with diameters less than 10 micrometer • Has a high specific surface area • Has an excellent ability to scatter light • Has a high opacity • Has low density

7. Potential Uses of MCFs • As a filler in paper, coatings and paint. • Disposable containers • Encapsulation of volatile compounds • Light weight concrete • Drug delivery • Fiber Technology • Light scattering • Other applications

8. Solvent Exchange Technique • In this technique, solvent of higher surface tension (DMAc/LiCl) is exchanged with another solvent of lower surface tension (ethanol, acetone,…). • The bigger the difference in the surface tension of solvents the better foam structure formation. • The higher molecular weight the better foam structure.

9. Previous Work • Starch microcellular foam was prepared by cross-linking cooked corn starch with glutaraldehyde (15 g/100 g starch) in acidic medium. • Interesting void structures was observed with a range of 1 micron voids when glutaraldehyde is used within the range of 7.5-15 g/100 g starch. • Corn starch of higher M. Wt had a better foam structure than lower M.Wt.

10. Starch Microcellular Foam Khaled El-Tahlawy, Richard A. Venditti, Joel J. Pawlak, Carbohydrate Polymers 67 (2007) 319–331

11. Objectives • To develop a novel cellulosic fiber with a porous surface to increase fiber surface area. • Investigate the effect of different organic solvents on void structure formation. • Understand the effect of CMCF on the optical properties. • Comparing the antimicrobial activity of the new modified cotton fibers with a regular spun fiber.

12. Procedure to Produce Cellulose Foam • Wood Pulp, DP 600, was dissolved in DMAc/LiCl as follows: • Heat/stir the cellulose in DMAc solution at 150°C for 30’. • Cool to 100°C, then add a definite amount of LiCl (10%). • Continue stirring for three hours. • Cool to room temperature, then stir for 24 hours. • Precipitated the cellulose fiber by adding the proper solvent • Change the solvent several times to exchange the DMAc. • The foam was collected on filter paper, then dried. • Major steps and materials used to produce cellulose foam

13. Water Solvent Exchange

14. Acetone Solvent Exchange

15. Ethanol Solvent Exchange

16. Ethanol Solvent

17. Acknowledgments • Thanks are due to …