Effects of Process Variables

Question 1

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

Answer 1

increases, increases, expand

Question 2

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

Answer 2

Polymers, temperature

Question 3

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

Answer 3

high temperatures

Question 4

Solid polymers that tend to form
ordered regions are termed

Answer 4

crystalline polymers

Question 5

Polymers that have no crystals at
all are called

Answer 5

amorphous

Question 6

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

Answer 6

never completely ; percentage of crystallinity

Question 7

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.

Answer 7

glassy state

Question 8

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

Answer 8

glass

Question 9

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

Answer 9

glassy state

Question 10

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.

Answer 10

rubbery state

Question 11

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

Answer 11

glass transition temperature Tg

Question 12

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

Answer 12

flow temperature, tf

Question 13

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

Answer 13

glass transition temperature
melting point temperature

Question 14

Polymer with highest Tg; lowest

Answer 14

Polycarbonate, LDPE

Question 15

The glass transition temperature depends on the

Answer 15

mobility and flexibility of the polymeric chains

Question 16

ease of the chain segment to rotate along
the chain backbone

Answer 16

flexibility

Question 17

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 ________

Answer 17

lower temperature, lower

Question 18

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.

Answer 18

stable; more energy

Question 19

Factors Affecting the Glass
Transition Temperature

Answer 19

intermolecular forces
chain stiffness
cross linking
pendant groups
plasticizers
molecular weight

Question 20

Strong intermolecular forces cause _______ Tg

Answer 20

higher

Question 21

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

Answer 21

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

Question 22

restrict
rotational motion and raise the glass transition
temperature.

Answer 22

cross linking

Question 23

The presence of __________ can change
the glass transition temperature.

Answer 23

pendant groups

Question 24

types of pendant groups

Answer 24

bulky
flexible

Question 25

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

Answer 25

flexible pendant groups

Question 26

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

Answer 26

bulky pendant groups

Question 27

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

Answer 27

plasticizers

Question 28

Plasticizers reduce ________ between polymer chains, which ________ Tg

Answer 28

intermolecular cohesive forces, decrease

Question 29

Tg is _______________with the molecular weight.

Answer 29

increased

Question 30

The modulus of a polymer __________ with increasing temperature.

Answer 30

decreases

Question 31

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

Answer 31

pressure; density

Question 32

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

Answer 32

polymer and the conditions

Question 33

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

Answer 33

hydrostatic pressure

Question 34

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

Answer 34

proportional; increases

Question 35

is the pressure exerted by a liquid on a solid surface

Answer 35

Hydrostatic pressure

Question 36

Effect of Pressure on the Mechanical Properties of Polymers

Answer 36

elastic modulus Yield strength Fracture properties

Question 37

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

Answer 37

elastic modulus

Question 38

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

Answer 38

elastic modulus

Question 39

Elastic modulus describes the ratio of

Answer 39

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

Question 40

A stiffer material will have a ________elastic modulus.

Answer 40

higher

Question 41

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

Answer 41

stress

Question 42

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

Answer 42

strain

Question 43

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

Answer 43

Young modulus

Question 44

Young modulus is defined as the ratio of __________

Answer 44

tensile stress to tensile strain

Question 45

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

Answer 45

Shear modulus/ Modulus of rigidity

Question 46

Shear modulus is defined as

Answer 46

shear stress over shear strain

Question 47

Types of elastic modulus

Answer 47

Bulk Flexural

Question 48

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

Answer 48

bulk modulus K

Question 49

extension of Young's modulus to three dimensions

Answer 49

Bulk modulus K

Question 50

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

Answer 50

volumetric stress over volumetric strain ; compressibility

Question 51

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

Answer 51

flexural modulus

Question 52

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

Answer 52

increases

Question 53

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

Answer 53

finite deformations on the polymer

Question 54

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

Answer 54

High

Question 55

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

Answer 55

yield strength or yield stress

Question 56

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.

Answer 56

yield strength

Question 57

The yield strength of polymers also ___with applied hydrostatic pressure

Answer 57

increases

Question 58

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

Answer 58

fracture

Question 59

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

Answer 59

fracture of a solid

Question 60

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

Answer 60

normal tensile crack/crack

Question 61

If a displacement develops tangentially, it is called a

Answer 61

shear crack, slip band, or dislocation

Question 62

stress at which a specimen fails via fracture.

Answer 62

fracture strength

Question 63

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

Answer 63

tensile test; fracture strength

Question 64

of the polymers always increased with increasing hydrostatic pressure.

Answer 64

ultimate tensile strengths

Question 65

The fracture strength increased proportionally to the

Answer 65

yield strength

Question 66

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

Answer 66

tensile strength

Question 67

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

Answer 67

brittle-ductile transition

Question 68

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

Answer 68

catalyst

Question 69

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

Answer 69

catalysts

Question 70

quantity that measures the extent to which the reaction has proceeded

Answer 70

extent of reaction

Question 71

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

Answer 71

extent of reaction

Question 72

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

Answer 72

cross linking; extent of bonding

Question 73

The extent of the reaction can be controlled through

Answer 73

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

Question 74

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.

Answer 74

Carother's equation

Question 75

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

Answer 75

Extent of Reaction

Question 76

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

Answer 76

Average degree of polymerization

Question 77

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

Answer 77

gelation

Question 78

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

Answer 78

gel; sol

Question 79

soluble in all non degrading solvents

Answer 79

gel

Question 80

soluble and can be extracted from the gel.

Answer 80

sol

Question 81

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 ______________

Answer 81

increases; infinite viscosity

Question 82

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

Answer 82

Carother’s reaction

Question 83

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

Answer 83

gelation.

Question 84

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.

Answer 84

theoretical extent of reaction