Plasma Surface TreatmentOverview

Feasibility Demonstrated, some engineering remains before scaling.Advantages

Enhanced bonding to existing resins and sizings Higher performing parts with same CF content Lower CF content per part for same mech. performance Bond to new resin systems More environmentally friendly than wet chemical methods. Lower the cost of composites

Compatible with all precursors.

Plasma Surface Treatment – Distinct Advantages

Pre-treatment Oxidation Carbonization Surface treatment Sizing Spooling

Typical PAN-Based Carbon Fiber Conversion

POST-TREATMENT

A Comparison of Surface Treatment MethodsIndustrial Practice

Gaseous Surface Treatment

Key factors Influencing the Fiber/Resin Bond

•Compressive stress at the interface due to the cure volume shrinkage of the matrix: control of the cure of the matrix at the interface and creation of a buffer zone to limit that inherent effect.

Styrene monomer

Vinyl ester monomerCarbon fiber

COOH

OH

Coupling agent

Covalent bonding, functional group reactive with –OH and COOH.

Covalent bonding, functional group reactive with C=C

• Mechanical interlocking: increase of the surface area of the fiber (increase of the roughness of the surface) by thermochemical surface treatment•Presence of defect: removal of the weakly boundary layers located at the surface of the fibers by thermochemical surface treatment•Physical interactions (polar, dispersive): increase of the surface energy of the fiber and its polar component due to the creation of oxycarbonated functionalities (-OH, -COOH mainly) by thermochemical surface treatment, better wetting.•Chemical interactions: creation of covalent bond by the grafting of coupling agents

Gas Phase Surface Treatment – Two Methods

Atmospheric Plasma

Conventio

nal Surfa

ce tr

eatm

ent

Thermo-C

hemica

l Surfa

ce T

ratm

ent (

ORNL)

Atmosp

heric

Plasma (O

RNL)5

11172329

Atom

ic O

xyge

n Co

ncen

trati

on (%

)

PLASMA RESULTS

Triples the oxygen concentration on the carbon fiber surface as compared to Electrochemical industrial practice

Conventional Thermochemical PlasmaSurface Treatment Method

Plasma Surface Treatment – Chemical Flexibility

LAB SCALE DEVICE

CO

OH

OHOH

ONHNH2Amine Imine Carbonyl

Hydroxyl

CO OLactone

3.35Å Carboxyl

3.35Å

Polyurethanes, nylons, polyesters

Nylons

Vinyl EstersS

OOSulfone

Plasma Surface TreatmentScale-Up Conceptual Design (~250 MT-CF/yr.)