Page 88 - Handbook of Adhesives and Sealants

56 Chapter Two

TABLE 2.2 Critical Surface Tensions for Common Solids and
Surface Tensions for Common Liquids
Materials Critical surface tension, dyne/cm
Acetal 47
Acrylonitrile-butadiene-styrene 35
Cellulose 45
Epoxy 47
Fluoroethylene propylene 16
Polyamide 46
Polycarbonate 46
Polyethylene 31
Polyethylene terephthalate 43
Polyimide 40
Polymethylmethacrylate 39
Polyphenylene sulfide 38
Polystyrene 33
Polysulfone 41
Polytetrafluoroethylene 18
Polyvinyl chloride 39
Silicone 24
Aluminum 500
Copper 1000
Material Surface tension, dyne/cm
Epoxy resin 47
Fluorinated epoxy resin* 33
Glycerol 63
Petroleum lubricating oil 29
Silicone oils 21
Water 73
*Experimental resin; developed to wet low-energy surfaces. (Note low
surface tension relative to most plastics.)

Much work in adhesion science has centered on the relationship
between W , the calculated work of adhesion, and practical adhesion,
A
7
or the real measured adhesion. Ahagon and Gent indicate that prac-
tical adhesion can be related to the work of adhesion plus a function
describing the energy dissipation mechanisms within an adhesive
bond.

Practical Adhesion W f (W ) .
A A
(zeta) is a factor related to the viscoelastic properties of the adhesive
and, thereby, is related to the mechanical energy absorption charac-
teristics of the joint. This is sometimes related to the amount of energy
absorbed by the deformation of the joint. As shown in Fig. 2.4, the
practical work of adhesion is equal to the theoretical work of adhesion
as determined by interfacial effects and to the mechanical work which
is absorbed within the joint. Thus, with a completely non-deformable