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

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

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.

Cellulose

Cellulose Solvents  Ethylene Diamine / Potassium thiocyanate (KSCN).  4-Methylmorpholine N-Oxide.  Dimethyl sulfoxide / tetrabutylammonium fluoride trihydrate.  Dimethyl imidazolidinone / lithium chloride.  NH 3 / NH 4 SCN solvent system  Dimethylacetamide / Lithium Chloride  Dissolution of Cellulose in Organic Solvents:

 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 Polymer MCF

 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 Potential Uses of MCFs

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.

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 g/100 g starch.  Corn starch of higher M. Wt had a better foam structure than lower M.Wt.

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

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.

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  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 Major steps and materials used to produce cellulose foam

Water Solvent Exchange

Acetone Solvent Exchange

Ethanol Solvent Exchange

Ethanol Solvent

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