Novel Cellulosic Fibers with Microcellular Porous

Structures By

Khaled El-Tahlawy, and Renzo Shamey

Textile Engineering, Chemistry and ScienceCollege of Textiles, NC State University

OutlineOutline 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 AcetoneAcetone EthanolEthanol

WaterWater

CelluloseCellulose 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.

CelluloseCellulose

CelluloseCellulose SolventsSolvents

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

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 MCFPolymer 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 MCFsPotential Uses of MCFs

Solvent Exchange TechniqueSolvent 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 WorkPrevious Work Starch microcellular foam was prepared by cross-Starch microcellular foam was prepared by cross-

linking cooked corn starch with glutaraldehyde (15 linking cooked corn starch with glutaraldehyde (15

g/100 g starch) in acidic medium.g/100 g starch) in acidic medium.

Interesting void structures was observed with a range Interesting void structures was observed with a range

of 1 micron voids when glutaraldehyde is used within of 1 micron voids when glutaraldehyde is used within

the range of 7.5-15 g/100 g starch.the range of 7.5-15 g/100 g starch.

Corn starch of higher M. Wt had a better foam structure Corn starch of higher M. Wt had a better foam structure

than lower M.Wt.than lower M.Wt.

Starch Microcellular FoamStarch Microcellular Foam

Khaled El-Tahlawy, Richard A. Venditti, Joel J. Pawlak, Khaled El-Tahlawy, Richard A. Venditti, Joel J. Pawlak, Carbohydrate Polymers Carbohydrate Polymers

67 (2007) 319–33167 (2007) 319–331

ObjectivesObjectives 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 Procedure to Produce Cellulose FoamFoam

Wood Pulp, DP 600, was dissolved in DMAc/LiCl as follows:Wood Pulp, DP 600, was dissolved in DMAc/LiCl as follows:

Heat/stir the cellulose in DMAc solution at 150°C for 30’. Heat/stir the cellulose in DMAc solution at 150°C for 30’.

Cool to 100°C, then add a definite amount of LiCl (10%).Cool to 100°C, then add a definite amount of LiCl (10%).

Continue stirring for three hours.Continue stirring for three hours.

Cool to room temperature, then stir for 24 hours.Cool to room temperature, then stir for 24 hours.

Precipitated the cellulose fiber by adding the proper solvent Precipitated the cellulose fiber by adding the proper solvent

Change the solvent several times to exchange the DMAcChange the solvent several times to exchange the DMAc.

The foam was collected on filter paper, then dried.The foam was collected on filter paper, then dried.

Major steps and materials used to produce cellulose foamMajor steps and materials used to produce cellulose foam

Water Solvent ExchangeWater Solvent Exchange

Acetone Solvent ExchangeAcetone Solvent Exchange

Ethanol Solvent ExchangeEthanol Solvent Exchange

Ethanol Solvent Ethanol Solvent

AcknowledgmentsAcknowledgments

Thanks are due to …Thanks are due to …

Fiber and Polymer Science Program