Chapter 2 Flashcards

1
Q

what is an adherend?

A

A material substrate that is bonded to another material by means of an adhesive

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2
Q

what is adhesion?

A

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

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3
Q

what is adhesive?

A

Substance that promotes adhesion of one substance or material to another.

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4
Q

what is adhesive bonding?

A

Process of joining two materials by means of an adhesive agent that solidifies.

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5
Q

what is cohesion?

A

Force of molecular attraction between molecules or atoms of the same species.

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6
Q

what is contact angle

A

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°.

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7
Q

what is the diffusion coefficient?

A

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.

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8
Q

what is the glass transition temperature?

A

(Tg)—Temperature above which a sharp increase in the thermal expansion coefficient occurs, indicating increased molecular mobility

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9
Q

what is heat of vaporization?

A

Thermal energy required to convert a solid to a vapor.

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10
Q

what is latent heat of fusion?

A

Thermal energy required to convert a solid to a liquid

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11
Q

what is melting temp/melting point?

A

Equilibrium temperature at which heating of a pure metal, compound, or eutectic alloy produces a change from a solid to a liquid.

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12
Q

what is a metallic bond?

A

Primary bond between metal atoms.

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13
Q

what is micromechanical bonding?

A

Mechanical adhesion associated with bonding of an adhesive to a
roughened adherend surface.

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14
Q

what is self-diffusion?

A

Thermally driven transfer of an atom to an adjacent lattice site in a crystal composed of the same atomic species.

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15
Q

what is stress concentration?

A

State of elevated stress in a solid caused by surface or internal defects or by marked changes in contour.

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16
Q

what is a supercooled liquid?

A

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.

17
Q

what is surface energy?

A

Same as surface tension but expressed in mJ/m2.

18
Q

what is surface tension?

A

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.

19
Q

what is thermal expansion coefficient?

A

Relative linear change in length per unit of initial length during heating of a solid per K within a specified temperature range.

20
Q

what is wetting?

A

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.

21
Q

what is a wetting agent?

A

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.

22
Q

what is vacancy?

A

Unoccupied atom lattice site in a crystalline solid.

23
Q

what are van der Waals forces?

A

Short-range force of physical attraction that promotes adhesion between molecules of liquids or molecular crystals.

24
Q

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.

A

ye

25
Q

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

A

ye