fiber sizing 1-8-08 - Fiber Sizing and Surface Treatments...

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1 Fiber Sizing and Surface Treatments Douglas J. Gardner 1 and Magnus Wålinder 2 1 Professor, 2 Postdoctoral Research Associate Wood-Polymer Hybrid Composites Overview • Surface energetics • Sizing, finish, and coupling agent • Effect of sizing on RTM processing: Wicking and fiber bundles • Local viscosity • The interphase • Sizing solubility
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2 Surface, Interface, and Interphase Condensed phase Surface and interfaces : two dimensional (no thickness) Interphase : three dimensional (has a certain thickness) Matrix Reinforcement Air Surface Interface Matrix Reinforcement Interface Interface Interphase Sizing Surface tension γ Gas Liquid = force/length
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3 Surface Free Energy γ Surface tension Surface free energy Α ic W = 1 2 W c = work of cohesion γ = W/ W = work A = area Interfacial surface free energy (or surface tension) Contact angle θ Liquid Solid Gas Solid-liquid-gas-interline
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4 Young´s equation θ γ LG cos θγ SL SG LG LG SG SL cos = Work of Adhesion W a S L S S L L SL Dupré equation Young-Dupré equation W aL = + (c o s ) 1 SL L S a W + =
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5 The Lewis acid-base concept AB a LW a a W W W + = γγ γ ii LW i AB =+ Pioneered by Fowkes in the 70’s Why Sizing? Sizing (or primer) – Coating (interphase) on fiber or particle surfaces, 0.1 to 10 μ m thick (1 to 2 w%) Functions: • Adhesion promotor (coupling agent) • Protect the surface from damage • Aid in handling • Add strength or stiffness • Reduce absorbency
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6 Sizing Complex mixture of: • Coupling agent (silanes) • Lubricant •B inde r • Antistat •pH con t ro l • Hardening agent • Emulsifying agent Finish Finish or surface modifier – 1 to several monolayer thick film (0.1 w%). The film itself has no contribution to the mechanical properties of the fiber Functions: • Adhesion promotor (coupling agent) • Lubricate • Resin wet-out
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This note was uploaded on 12/21/2010 for the course AEWC 430 taught by Professor Dg during the Fall '08 term at University of Maine Orono .

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fiber sizing 1-8-08 - Fiber Sizing and Surface Treatments...

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