Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Polymer engineering > Effects of Process Variables > Flashcards

Effects of Process Variables Flashcards

1
Q

As temperature__________, the molecules of
the polymer move faster and their kinetic
energy ______________. This can cause the
polymer to _____, and its shape to change

A

increases, increases, expand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Substances that are made up
of long chains of repeating molecules. The
behavior of polymers can be affected by
__________ changes

A

Polymers, temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

At _____________, certain polymer chains
may break down and degrade, resulting in a
loss of material

A

high temperatures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Solid polymers that tend to form
ordered regions are termed

A

crystalline polymers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Polymers that have no crystals at
all are called

A

amorphous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

A real polymer is ___________
crystalline, and the extent of
crystallization is characterized by
the ____________.

A

never completely ; percentage of crystallinity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

In the amorphous region of the polymer,
at lower temperature, the molecules of
the polymer are in frozen state, where the
molecules can vibrate slightly but are not
able to move significantly.

A

glassy state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

In __________ state, the polymer is brittle, hard, and rigid analogous to glass

A

glass

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

shows hard, rigid, and
brittle nature analogous to a crystalline
solid with molecular disorder as a liquid.

A

glassy state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

When the polymer is heated, the polymer
chains are able to wiggle around each
other, and the polymer becomes soft and
flexible similar to rubber.

A

rubbery state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

The temperature at which the glassy
state makes a transition to rubbery state
is called the

A

glass transition temperature Tg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

There is a diffuse transition zone between
the rubbery and liquid states for
crystalline polymers; the temperature at
which this occurs is called the

A

flow temperature, tf

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

______________is the
property of the amorphous region of the
polymer, whereas the crystalline region is
characterized by the ________________

A

glass transition temperature
melting point temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Polymer with highest Tg; lowest

A

Polycarbonate, LDPE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

The glass transition temperature depends on the

A

mobility and flexibility of the polymeric chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

ease of the chain segment to rotate along
the chain backbone

A

flexibility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

If the
polymeric chains can move easily, then the glassy state
can be converted to the rubbery state at _________, that is the glass transition temperature is ________

A

lower temperature, lower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

If somehow the mobility of the chains is restricted, then
the glassy state is more __________ and it is difficult to break
the restriction causing the immobility of the polymer
chains at the lower temperature, because ______ is
required to make the chains free.

A

stable; more energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Factors Affecting the Glass
Transition Temperature

A

intermolecular forces
chain stiffness
cross linking
pendant groups
plasticizers
molecular weight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Strong intermolecular forces cause _______ Tg

A

higher

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

The presence of the stiffening groups such as ______ in the polymer chain reduces the _________ of the chain

A

amide, sulfone, carbonyl, p-phenylene; flexibility, higher Tg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

restrict
rotational motion and raise the glass transition
temperature.

A

cross linking

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

The presence of __________ can change
the glass transition temperature.

A

pendant groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

types of pendant groups

A

bulky
flexible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

limits the packing of the chains and hence
increases the rotational motion, tending to less Tg
value

A

flexible pendant groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

can
restrict rotational freedom, leading to higher
glass transition temperature.

A

bulky pendant groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Low molecular weight
and non-volatile materials added to
polymers to increase their chain
flexibility

A

plasticizers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Plasticizers reduce ________ between polymer chains, which ________ Tg

A

intermolecular cohesive forces, decrease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Tg is _______________with
the molecular weight.

A

increased

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

The modulus of a polymer __________ with
increasing temperature.

A

decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

When _______ is applied to a polymer, it can cause the chains to
become more tightly packed together, leading to an increase in
___________

A

pressure; density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

The specific effects of pressure on a polymer depend on the type of ___________ which it is subjected to pressure

A

polymer and the conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

defined
as the pressure exerted by a fluid
at equilibrium at any point of time
due to the force of gravity.

A

hydrostatic pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Hydrostatic pressure is
____________ to the depth
measured from the surface as the
weight of the fluid ___________
when a downward force is
applied.

A

proportional; increases

35
Q

is the
pressure exerted by a liquid on a
solid surface

A

Hydrostatic pressure

36
Q

Effect of Pressure on the
Mechanical Properties of Polymers

A

elastic modulus
Yield strength
Fracture properties

37
Q

is the unit of measurement of an
object’s or substance’s resistance to being
deformed elastically

A

elastic modulus

38
Q

measure of a material’s
stiffness or resistance to deformation under an
applied load.

A

elastic modulus

39
Q

Elastic modulus describes the ratio of

A

change in length or volume of a material to the
change in length or volume of the applied load.

40
Q

A stiffer material will have a ________elastic
modulus.

A

higher

41
Q

force causing the
deformation divided by the area to which the
force is applied

A

stress

42
Q

ratio of the
change in some parameter caused by the
deformation to the original value of the
parameter

A

strain

43
Q

ensile and compressive
elasticity, or the tendency of an object to deform along an axis
when opposing forces are applied along that axis

A

Young modulus

44
Q

Young modulus is defined as the ratio of __________

A

tensile stress to tensile strain

45
Q

describes an
object’s tendency to shear (the deformation of shape at
constant volume) when acted upon by opposing forces

A

Shear modulus/ Modulus of rigidity

46
Q

Shear modulus is defined as

A

shear stress over shear strain

47
Q

Types of elastic modulus

A

Bulk
Flexural

48
Q

describes volumetric elasticity, or the
tendency of an object to deform in all directions when
uniformly loaded in all directions

A

bulk modulus K

49
Q

extension of Young’s
modulus to three dimensions

A

Bulk modulus K

50
Q

Bulk modulus is defined as _______________ and is the inverse of ____________

A

volumetric stress over volumetric strain ;
compressibility

51
Q

describes the object’s tendency to flex
when acted upon by a moment.

A

flexural modulus

52
Q

Elastic modulus of polymers ___________with increasing hydrostatic pressure in tension, compression, and shear

A

increases

53
Q

One of the main reasons for the increase in the elastic modulus with increasing pressure is the effects of

A

finite deformations on the polymer

54
Q

_______ hydrostatic pressure can also cause the glass
transition in a polymer to shift to higher temperatures.

A

High

55
Q

a material property and
is the stress corresponding to the yield point at which the
material begins to deform plastically

A

yield strength or yield stress

56
Q

often used to determine the maximum
allowable load in a mechanical component, since it
represents the upper limit to forces that can be applied
without producing permanent deformation.

A

yield strength

57
Q

The yield strength of polymers also ___with
applied hydrostatic pressure

A

increases

58
Q

appearance of a crack or complete
separation of an object or material into two or more pieces
under the action of stress.

A

fracture

59
Q

occurs due to the development
of certain displacement discontinuity surfaces within the solid

A

fracture of a solid

60
Q

If a displacement develops perpendicular to the surface, it is
called a

A

normal tensile crack/crack

61
Q

If a displacement develops tangentially, it is called a

A

shear crack, slip band, or dislocation

62
Q

stress at
which a specimen fails
via fracture.

A

fracture strength

63
Q

Fracture strength is
usually determined for a
given specimen by a ______, where the final recorded point is the _________

A

tensile test; fracture strength

64
Q

of the polymers always increased
with increasing hydrostatic pressure.

A

ultimate tensile strengths

65
Q

The fracture strength increased
proportionally to the

A

yield strength

66
Q

The ___________ tends to
increase for ductile polymers
but decrease for some brittle
polymers

A

tensile strength

67
Q

In some brittle polymers like
PS, ______________________
is induced beyond a certain
critical pressure

A

brittle-ductile transition

68
Q

substance that accelerates
chemical reactions without being consumed in
the process.

A

catalyst

69
Q

can help to speed up the
polymerization process, reduce the
temperature required for polymerization, or
control the structure of the resulting polymer.

A

catalysts

70
Q

quantity that measures
the extent to which the reaction has proceeded

A

extent of reaction

71
Q

the degree of crosslinking or bonding between
the monomers in a polymer chain

A

extent of reaction

72
Q

________ increases the rigidity and strength of
the polymer, while the ___________ can
affect its flexibility and solubility.

A

cross linking; extent of bonding

73
Q

The extent of the reaction can be controlled
through

A

temperature, time, and the type and
concentration of the crosslinking agents used.

74
Q

general expression, relating
average functionality (f),extent of reaction (p), and average
degree of polymerization ത 𝑋𝑛for polycondensation reaction
carried out for a period t.

A

Carother’s equation

75
Q

s defined as the fraction of
functional groups/monomers that have reacted at time t.

A

Extent of Reaction

76
Q

defined as equal to
the total number of bifunctional initially added, No, divided by
the remaining number of molecules Nafter time t.

A

Average degree of polymerization

77
Q

implied the formation of essentially infinitely large
polymer network in the reaction mixture.

A

gelation

78
Q

The sudden onset of gelation marks the division of the
mixture into two parts

A

gel; sol

79
Q

soluble in all non
degrading solvents

A

gel

80
Q

soluble and
can be extracted from the gel.

A

sol

81
Q

As polymerization proceeds beyond the gel point, the
amount of gel ___________ at the expense of the sol, and the
mixture rapidly transforms from a viscous liquid to an
elastic material of ______________

A

increases; infinite viscosity

82
Q

can help in determining the critical
extent of reaction at which gelation or cross-linking would
commence

A

Carother’s reaction

83
Q

It is thus essential to
stop the polymerization reaction before the onset of
________

A

gelation.

84
Q

It can be clearly seen that at the point of a _______, when the reaction is complete, the
polymer being formed in the polycondensation system gets
cross-linked and, hence, turns into insoluble, infusible gelled
mass.

A

theoretical extent of reaction

Polymer engineering (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions