Download - Forestry 485
![Page 1: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/1.jpg)
Forestry 485
Lecture 2-3-1: Wood Surface Properties, Part I
![Page 2: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/2.jpg)
Adhesion TheoriesAdhesion Theories
Several mechanisms of adhesion have been proposed, including Mechanical Interlocking, Diffusion Theory, Electronic Theory, Covalent Bonding Theory, and Adsorption Theory (these will be discussed in Lectures 2-4-1 and 2-4-2).
![Page 3: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/3.jpg)
Surface Properties: Wetting
Surface Properties: Wetting
Regardless of adhesion mechanism, optimal adhesion is dependent upon effective contact of adhesive and adherend; contact is dependent upon Surface Wetting phenomenon.
![Page 4: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/4.jpg)
Surface InteractionsSurface Interactions Liquid-vacuum, liquid-gas, liquid-liquid, or liquid-
solid interfaces are the sites of “surface interactions”
Surface interaction parameters:• Surface Energy• Contact Angle• Wetting
![Page 5: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/5.jpg)
All molecules in a material are attracted to each other in order to minimize energy.
Liquid
Solid
Surface Molecule
Bulk Molecule
Surface EnergySurface Energy
![Page 6: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/6.jpg)
Surface Energy Continued
Bulk Molecules experience uniform interactions that minimize energy.
Surface molecules encounter discontinuous interactions. This results in higher “surfaceenergy” also known as surface tension.
![Page 7: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/7.jpg)
From: Fundamentals of Adhesion, ed. Lee, L.H., p.126, Plenum Press, New York, 1991
Surface Energy Measurement
Surface Energy Measurement
Sessile Drop Method
Capillary Rise MethodWilhelmy Plate Method
http://www.ksvinc.com/wilhelmy_plate.htm
![Page 8: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/8.jpg)
Measuring Surface Properties
Measuring Surface Properties
Slide courtesy Dr. Doug Gardner, University of Maine
![Page 9: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/9.jpg)
Sessile Drop Contact Angle Analysis
Sessile Drop Contact Angle Analysis
Slide courtesy Dr. Doug Gardner, University of Maine
![Page 10: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/10.jpg)
Contact angle changes as a function of time…
Contact angle changes as a function of time…
Slide courtesy Dr. Doug Gardner, University of Maine
![Page 11: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/11.jpg)
Dynamic Contact Angle Measurement by the Wilhelmy Plate
Method
Dynamic Contact Angle Measurement by the Wilhelmy Plate
Method
Slide courtesy Dr. Doug Gardner, University of Maine
![Page 12: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/12.jpg)
Surface Energy Measurement of Solids
Zisman Method: Measurement of Critical Surface Energy γC
Zisman Plot
0.5
0.7
0.9
1.1
10 20 30 40 50
Surface Energy (mN/m)
cos
thet
a
γC = 18 mN/m
![Page 13: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/13.jpg)
Interfacial Behavior
Ө
Vapor
Liquid
Solid
γLV
γSVγSL
γSV = γSL + γLVcos Ө
If Ө = 0, Spreading OccursIf Ө < 90o, Wetting is Favorable If Ө > 90o, Wetting is not Favorable
![Page 14: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/14.jpg)
Control of Wetting on Wood Substrates
Two Approaches
Alter Liquid/Resin
Contact Angle will Decrease
as γLV Decreases
Alter Substrate/ Wood Furnish
Contact Angle will Decrease as γSV
is Increased
Dec
reas
ing
γ LV
Incr
easi
ng γ
SV
![Page 15: Forestry 485](https://reader035.vdocument.in/reader035/viewer/2022072014/56812ca5550346895d914c70/html5/thumbnails/15.jpg)
Control of Wetting of Wood Substrates: Means of
Improvement
Control of Wetting of Wood Substrates: Means of
ImprovementMachine Wood Surface
Higher Surface EnergyReduce Roughness
Avoid Deactivating Wood Surface(Minimize time from machining to bonding, minimize
heat treatment, etc.)Add a Surface-Active Agent to the Resin