Adhesive Flashcards
1
Q
Five (5) widely known theories of adhesion
A
Mechanical Theory
- Electrostatic (Electronic) Theory
- Diffusion Theory
- Wetting Theory
- Chemical Bonding
2
Q
the action or process of adhering to a surface or
object.
A
ADHESION
3
Q
penetration of adhesives into pores, cavities, and other surface irregularities on the surface of the substrate.
A
Mechanical Theory
4
Q
adhesive + substrate
A
mechanical interlacking
5
Q
- Caused by the displacement of air at interface by adhesives
A
Mechanical Theory
6
Q
Mechanical theory
Enhanced adhesion by
A
- (1) mechanical interlocking,
- (2) formation of a clean surface,
- (3) formation of a highly reactive surface, and
- (4) an increase in contact surface area.
7
Q
- Caused by surface irregularities
- Better adhesion** at rough interface** sites
- Applying force along the junction of smooth surface site
causes zipper-like effect
A
Mechanical interlocking
8
Q
adhesion takes place due to electrostatic effects between
the adhesive and the adherend.
A
Electrostatic (Electronic) Theory
9
Q
- Caused by the difference in electronic band structures
- Primary explanation for the polymer-metal adhesion
A
Electrostatic (Electronic) Theory
10
Q
adhesion is developed through
the interdiffusion of molecules in between the adhesive and
the adherend.
A
Diffusion Theory
11
Q
Diffusion Theory applicable when both the adhesive and the
adherend are polymers with relatively _______
capable of movement
A
long-chain molecules
12
Q
applicable when both the adhesive and the
adherend are polymers with relatively long-chain molecules
capable of movement
A
Diffusion Theory
13
Q
process of establishing continuous contact
between the adhesive and the adherend
A
Wetting Theory
14
Q
adhesion results from molecular
contact between two materials and the surface forces that
develop
A
Wetting Theory
15
Q
In wetting theory, for an adhesive to wet a solid surface, the
adhesive requires a ___________
than the critical surface tension of the solid
A
lower surface tension
16
Q
This mechanism attributes the formation of an adhesion
bond to surface chemical forces
A
Chemical Bonding
17
Q
Chemical Bonding
(highest E to lowest)
A
Ion-ion 450
Covalent 350
Ion-dipole 33
Hydrogen bonding 24
Dipole-dipole and London Dispersion 2
18
Q
made from naturally occurring raw materials which
includes any animal or agricultural by-products such as
organic materials.
A
NATURAL ADHESIVES
19
Q
manufactured from man-made materials such as
polymers.
A
SYNTHETIC ADHESIVES
20
Q
produced from materials possessing high strength and
durability
A
Structural Adhesives
21
Q
o hold structures together and to
resist high loads without any significant deformation
A
Structural Adhesives
22
Q
possess shear strengths that exceeds a 1000 psi and
are resistant to common operating environments
A
Structural Adhesives
23
Q
epoxies, phenolics,
polyurethanes, acrylics, cyanoacrylates, ureaformaldehydes, and bismaleimides.
A
Structural Adhesives
24
Q
Not required to hold substantial amount of loads.
A
Nonstructural Adhesives
25
creep under conditions of moderate load and can
degrade after long term exposure to the environment.
Nonstructural Adhesives
26
pressure-sensitive adhesives, hot melt, and
water emulsion adhesives
Nonstructural Adhesives
27
Often used together with mechanical fasteners
Nonstructural Adhesives
28
Also known as “holding adhesives”
Nonstructural Adhesives
29
Cannot be heated and softened during repeated
cycles after initial curing.
Thermosetting Adhesives
30
Thermosetting Adhesives
After curing and crosslinking, the adhesive bond _____________ through the application of heat
can
be softened
31
can generally degrade and weaken
over time due to **oxidation or molecule chain session**.
Thermosetting Adhesives
32
Thermosetting Adhesives
Cure themselves through an **irreversible chemical
reaction** known as
crosslinking
33
solvent medium for brushing and
spray applications
Thermosetting Adhesives
34
During curing of Thermosetting Adhesives, the crosslinking reaction occurs
between the linking of ____________ which then
forms a crosslinked structure.
two linear polymers
35
reactions may require heat for initiation and
completion while it can also be completed at room
temperature.
Crosslinking of Thermosetting Adhesives
36
they generally
do not cure when subjected to heat.
Thermoplastic Adhesives
37
initially in solid form that merely soften or melt when
heated.
Thermoplastic Adhesives
38
can either be linear or branched.
Thermoplastic Adhesives
39
Upon the application of the adhesive to the substrate,
the parts are joined together, and the adhesive
hardens by
cooling
40
ex of Thermoplastic Adhesives
hot-melt adhesives
41
Have unique rheological properties
Elastomeric Adhesives
42
Based on synthetic or naturally that possess high toughness and
elongation.
Elastomeric Adhesives
43
Made from polymeric resins that are capable of high
degrees of extension and compression.
44
Has a great ability to absorb energy and they offer
high strength in joint designs having nonuniform load
Elastomeric Adhesives
45
Sold as solvent solutions, water dispersions,
pressure-sensitive types, and single or multiple part
solventless liquids or pastes
Elastomeric Adhesives
46
Highly viscoelastic materials
elastomers
47
high degree of elongation, low
modulus, and high toughness
Elastomeric Adhesives
48
used as sealants, vibration dampers, and sound enclosures
elastomers
49
Produce by combining thermosetting, thermoplastic,
and elastomeric adhesives
Hybrid (Alloy) Adhesives
50
high temperature, rigid resins are
**combined with flexible, tough elastomers** or
*thermoplastics* to provide improved **peel strength and
energy absorption**
Hybrid (Alloy) Adhesives
51
Earliest approaches combat brittle failure which
included the development of adhesive formulations
by blending a flexibilizing resin into the body of
another resin (resin + resin)
Hybrid (Alloy) Adhesives
52
Nitrile-phenolic, epoxy-polysulfide, and other resin
blends provided resilience and toughness due to the
elastomeric ingredients in the formulation
Hybrid (Alloy) Adhesives
53
Due to the elastomeric component, the glass
transition temperature (Tg) is ____________ and the
resistance to elevated temperatures and chemicals is
also weakened
lowered
54
could
significantly limit the characteristics of
the adhesive in the particular
application
method of curing
55
A type of reaction wherein a side product is also produced, which is
commonly water
Condensation reaction
56
considered the oldest of the
synthetic adhesives in Condensation reaction
phenolic and amino resins
57
Usually necessary to also apply pressure to overcome the **deleterious effects
of the volatile by-products**
phenolic and amino resins
58
No formation of by-products.
Addition reaction
59
Includes polyesters, epoxies, urethanes, cyanoacrylates, anaerobics, and
radiation curable polymers.
(majority of elastomers and acrylics)
Addition reaction
60
Only contact pressure is necessary for these adhesives, and so they are well
suited for bonding large articles.
Addition reaction
61
epoxy, polyurethane, modified
acrylic, cyanoacrylate, and anaerobic systems
cure by chemical reaction
62
cure by chemical reaction
1. Single component systems
2. Multiple component systems
63
Composed of two or more components
that **must be kept separate** until just before
the bonding process
Multiple part adhesive systems
64
Epoxies, polyurethanes, acrylics, phenolics,
and silicones
multiple systems
65
Multiple part adhesive systems
1. ratio
2. mix
3. dispersed
66
Typically consist of two or more premixed
components
Single component systems that cure via catalyst or hardener
67
In Single component systems that cure via catalyst or hardener, curing agent or hardener is
incorporated with the
resin base and all the
other fillers and additives.
68
Requires refrigerated conditions and have
limited shelf life
Single component systems that cure via catalyst or hardener
69
epoxy, epoxy hybrids, polyurethane,
polyimide, polybenzimidazole, phenolic, and
phenolic hybrids
Single component systems that cure via catalyst or hardener
70
Use the humidity in the ambient air to react
with the base resin in the adhesive
formulation
. Moisture curing adhesives
71
Generally can cure completely at room
temperature
Moisture curing adhesives
72
common
single component adhesives that cure by
reacting with environmental moisture
Polyurethanes and silicones
73
Can cure by exposure to radiation
UV/light curing adhesives
74
employed to many assembly
operations where high throughput or
delicate components are prevalent
UV/light curing adhesives
75
Require the presence of the correct
wavelengths of light at sufficient intensity to
produce strong structural bonds
UV/light curing adhesives
76
UV/light curing adhesives use _____________ to activate the free
radical curing mechanism
photoinitiators
77
Single component adhesives that can cure
via a chemical reaction mechanism that
uses the **active or live metal ions on the
substrate** as a catalyst.
Adhesives catalyzed by the substrate
78
Also called anaerobic adhesives because
they cure only in the absence of oxygen.
Adhesives catalyzed by the substrate
79
Adhesives catalyzed by the substrate First developed during the 1950s and 1960s
by
Loctite Corporation
80
Cure at a fast rate depending on the
substrate. Cure speeds range from several
minutes to 24 hrs
Adhesives catalyzed by the substrate
81
completely formulate the adhesive system,
including resins, fillers, curing agents, etc., in the
liquid state and then converting it into a solid
state that is not completely cured.
(single component)
. Adhesives in solid form (tape, film, powder)
82
hardening process
is usually accompanied by extruding,
calendering, or casting the adhesive formulation
into thin films that are typically 5–10 mils thick
. Adhesives in solid form : tape, film
83
Usually applied to both substrates either by
spray or roll coating.
Contact adhesives
84
Their **tackiness is permanent** and there is no
**optimal time range** when the substrates
must be joined.
Pressure-sensitive adhesives
85
Generally, have relatively high shear and
peel strengths.
Contact adhesives
86
Usually based on elastomer or
thermoplastic solvent solutions.
Pressure-sensitive adhesives
87
Mostly applied to plastic, paper, foil or
fibrous material as suitable backings.
Pressure-sensitive adhesives
88
Also known as solvent activated adhesives.
Reactivatable adhesives
89
Applied to a substrate via solvent coating
and then dried to a non-tacky state
Reactivatable adhesives
90
Labels, nameplates, stamps, etc. are
common applications
Reactivatable adhesives
91
Used for their mechanical interlocking
ability
Resinous solvent adhesives
92
Formulated with a relatively rigid, tough
thermoplastic resin.
Resinous solvent adhesives
93
The **substrate** is generally **porous**. Once applied, the solvent evaporates into the air and through the substrate so that the
**adhesive resin interlocks the pores** of the
substrate together.
Resinous solvent adhesives
94
A type of adhesive that can harden by
cooling from a melt condition
(glue gun)
Hot melt adhesives
95
They are generally thermoplastic adhesives
that soften and melt when heated, and they
harden following subsequent cooling.
Hot melt adhesives
96
ethylene and vinyl
acetate copolymers, polyvinyl acetates,
polyethylene, amorphous polypropylene,
block copolymers (styrene butadiene
rubber), polyamides, and polyester
Hot melt adhesives
97
The difference between paste and liquid
adhesive lies mainly in
viscosity and
method of application
98
free flowing fluids that
can be applied in thin films
Liquid adhesives
99
heavily bodied, often
thixotropic systems that must be applied
with spreading equipment such as a trowel
or caulking gun
Paste adhesives
100
Use organic solvent to reduce viscosity for
easier application
Solvent-based adhesives
101
simply a carrier for the
‘‘solids’’ part of the adhesive
solvent
102
applied by **spraying,
dipping, or brushing,** but the solvent must
be driven off before the joint is assembled
Solvent-based adhesives
103
may be
chemically crosslinked, usually through the
application of a **curing agent and heat**
Solvent-based adhesives
104
Usually emulsions of thermoplastic resins
Water-based adhesives
105
evaporated through the
air or diffused into the porous substrate
water carrier
106
they are
formulated as contact, pressure sensitive,
reactivatable, and resinous adhesive
systems
Water-based adhesives
107
Most widely used emulsion-based adhesive
polyvinyl acetate-polyvinyl alcohol
copolymer
108
known as ‘‘white’’ glue or
wood glue.
polyvinyl acetate-polyvinyl alcohol
copolymer
109
Common forms of ____________ are tape
or film, powder, or solid shape forms.
solid adhesives
110
The main advantages of these single
component adhesives are that _______________ is not required, and they can be
applied uniformly to a substrate with little or
no waste.
metering
and mixing
111
Both thermoplastic and thermosetting
adhesives can be formulated as
solid form
112
used loosely and
interchangeably for adhesives in sheet
form.
Tapes or films
113
Supported on a web of paper, nonwoven
fabric, or on open weave scrim of glass
cotton or nylon.
Tapes or films
114
A single component system that requires
no metering
Tapes or films
115
Must be first heated or solvent-activated to
be made liquid and flowable
Powdered adhesives
115
eliminate
proportioning and mixing errors
Powdered adhesives
116
uniform distribution over large assemblies
is difficult.
Powdered adhesives
117
formulated
with thermoplastic resins
Hot melt forms
118
dependent on development costs and
volume requirements
Adhesive price
119
film or powder form require more ________
than liquid or paste types and are usually more expensive.
processing
120
According to Cost
Efficiency of **coverage**
➢ Ease of application and **processing** equipment needed
➢ Total processing **time**
➢ Cost of **labor** for assembly and inspection of the bonded parts
➢ **Waste** of adhesive contributes to material costs and **environmental** costs for
disposal
➢ Amount of **rejected** material as compared with other methods of joining
121
metal adhesives, wood adhesives, and vinyl adhesives
refer to the _____ to which they will bond
substrates
122
Depending on _______________ can be applied via the
methods
viscosity,
liquid adhesives
123
Heavily bodied adhesive pastes and mastics
are
extrudable
124
Heavily bodied adhesive pastes and mastics
are applied by
syringe, caulking gun, or pneumatic pumping
equipment
125
Depending on viscosity,
liquid adhesives can be applied via the following
methods:
➢ Spraying
➢ Brushing
➢ Trowelling
126
Coating methods include
roller coating
blade/knife coating
flexo-roller
gravure cylinder
127
Laminating adhesives for film and paper structures are
generally required to be applied
over the entire
substrate surface,
127
pressure sensitive adhesives
applied to
label stock
128
heat-seal coating applied
to
lidding stock
129
ability of an adhesive to create a
durable and reliable bond between two
surfaces
Bond Strength
130
There are two important aspects to bond
strength
resistance of the bonded
substrates to being **peeled apart**
resistance to the application of a **shear force**
131
Three key factors significantly impact bond
strength
surface preparation
adhesive properties
substrate material characteristics
132
Contaminants such as oils, grease, dust, or oxides can inhibit
adhesion.
Cleanliness
133
A rough surface provides more area for the adhesive to bond
to, enhancing mechanical interlocking and increasing bond
strength.
Surface Roughness
134
Chemical treatments or primers can modify the surface
properties of substrates to promote adhesion.
Surface Activation
135
Different types of adhesives, such as epoxies, cyanoacrylates,
polyurethanes, or acrylics, have unique chemical compositions that
affect their adhesion mechanisms and bond strength.
Chemical Composition
136
Low-viscosity adhesives penetrate into surface
irregularities ______________, while high-viscosity adhesives
______________ to achieve intimate contact.
more effectively , require more pressure
137
time required for the adhesive to reach its maximum
strength affects the bond formation process.
Cure Time
138
Some adhesives exhibit changes in viscosity, cure rate, or
strength with temperature variations
Temperature Sensitivity
139
e compatibility between the adhesive and substrate materials
influences bond strength
Material Compatibility
140
Substrates with higher surface energy promote better wetting
and adhesion compared to low-energy substrates.
Surface Energy
141
Porous substrates may absorb the adhesive, leading to reduced
bond strength
Porosity
142
applies a pulling force directly opposite the
bonded area, attempting to separate the materials in a
straight line.
Tensile Test
143
maximum force a bond
can withstand before breaking and the elongation
(stretching) that occurs before failure.
Tensile Test
144
ASTM Tensile Test Methods
ASTM Method
D2095
145
applies a force parallel to the bonded area,
trying to make the materials slide past each other.
Shear Test
146
determine the shear strength
of the bond, which is the force required to cause this
sliding fracture
Shear Test
147
Shear Test device
ASTM D1002
148
This test evaluates the bond strength by applying a force
perpendicular to the bonded interface, similar to a tensile
test.
Cleavage Test
149
these tests are
based on adherends that are not deformed significantly
during the measurement.
Cleavage Test
150
test measures the
adhesive strength of the bond, indicating how well the
adhesive itself holds the materials together
Cleavage Test
151
Peel Test device
ASTM D1876.
152
A cleavage tests. However, at least one of the
adherends is made from a flexible material that could be plastically deformed during the measuremen
Peel tests
