Chapter 2 Flashcards
what is an adherend?
A material substrate that is bonded to another material by means of an adhesive
what is adhesion?
A molecular or atomic attraction between two contacting surfaces promoted by the inter- facial force of attraction between the molecules or atoms of two different species; adhesion may occur as chemical adhesion, mechanical adhesion (structural interlocking), or a combination of both
what is adhesive?
Substance that promotes adhesion of one substance or material to another.
what is adhesive bonding?
Process of joining two materials by means of an adhesive agent that solidifies.
what is cohesion?
Force of molecular attraction between molecules or atoms of the same species.
what is contact angle
Angle of intersection between a liquid and a surface of a solid that is measured from the solid surface through the liquid to the liquid/vapor tangent line originating at the terminus of the liquid/solid interface; used as a measure of wettability, whereby no wetting occurs at a contact angle of 180° and complete wetting occurs at an angle of 0°.
what is the diffusion coefficient?
Proportionality constant representing the rate at which a substance is trans- ported through a unit area and a unit thickness under the influence of a unit concentration gradient at a given temperature.
what is the glass transition temperature?
(Tg)—Temperature above which a sharp increase in the thermal expansion coefficient occurs, indicating increased molecular mobility
what is heat of vaporization?
Thermal energy required to convert a solid to a vapor.
what is latent heat of fusion?
Thermal energy required to convert a solid to a liquid
what is melting temp/melting point?
Equilibrium temperature at which heating of a pure metal, compound, or eutectic alloy produces a change from a solid to a liquid.
what is a metallic bond?
Primary bond between metal atoms.
what is micromechanical bonding?
Mechanical adhesion associated with bonding of an adhesive to a
roughened adherend surface.
what is self-diffusion?
Thermally driven transfer of an atom to an adjacent lattice site in a crystal composed of the same atomic species.
what is stress concentration?
State of elevated stress in a solid caused by surface or internal defects or by marked changes in contour.
what is a supercooled liquid?
A liquid that has been cooled at a sufficiently rapid rate to a point below the temperature at which an equilibrium phase change can occur.
what is surface energy?
Same as surface tension but expressed in mJ/m2.
what is surface tension?
A measurement of the cohesive energy present at an interface; in the case of a liquid, it is the liquid/air interface. This energy is the result of molecules on the surface of a liquid experiencing an imbalance of attraction between molecules. It has units of mN/m.
what is thermal expansion coefficient?
Relative linear change in length per unit of initial length during heating of a solid per K within a specified temperature range.
what is wetting?
The ability of a liquid to maintain contact with a solid surface; it reflects the intermolecular interactions when the two are brought in intimate contact.
what is a wetting agent?
A surface-active substance that can be applied to a solid substrate to reduce the surface tension of the liquid to be placed on the solid; the purpose is to promote wetting or adhesion.
what is vacancy?
Unoccupied atom lattice site in a crystalline solid.
what are van der Waals forces?
Short-range force of physical attraction that promotes adhesion between molecules of liquids or molecular crystals.
The stiffness or elastic modulus of the material is proportional to the rate of change of the force with a change in displacement that is measured by the slope of the net force curve near equilibrium. A greater slope of the force curve implies a narrower, deeper trough in the energy curve (Figure 2-11, A). Hence, a high melting point is usually accompanied by a greater sti ness.
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In general, the comparatively low surface energies of organic and inorganic liquids permit them to spread freely on solids of high surface energy. is is a prerequisite of good wetting and strong adhesive joints
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