EFFECT OF PROCESS VARIABLES

Question 1

As temperature increases, the molecules of the polymer move faster and their kinetic energy ______.

Answer 1

increases

Question 2

Solid polymers that tend to form ordered regions are termed ______ polymers.

Answer 2

crystalline

Question 3

Polymers that have no crystals at all are called ______.

Answer 3

amorphous

Question 4

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. This state is referred as the ____.

Answer 4

Glassy state

Question 5

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. This state is called the _____.

Answer 5

Rubber state

Question 6

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

Answer 6

Glass transition temperature

Question 7

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 7

Flow temperature

Question 8

The glass transition temperature is the
property of the amorphous region of the polymer, whereas the crystalline region is characterized by the ______.

Answer 8

Melting point temperature

Question 9

Strong intermolecular forces cause ____ Tg

Answer 9

higher

Question 10

The presence of the stiffening groups in the polymer chain reduces the flexibility of the chain, leading to _____ glass
transition temperature.

Answer 10

higher

Question 11

Higher cross-linked molecule will show _____ Tg

Answer 11

higher

Question 12

The presence of bulky pendant group, such as a benzene ring, can restrict rotational freedom, leading to _____
glass transition temperature.

Answer 12

higher

Question 13

The presence of flexible pendant groups, for example, aliphatic chains, limits the packing of the chains and hence increases the rotational motion, tending to _____ Tg value.

Answer 13

decrease

Question 14

Plasticizers are low molecular weight
and non-volatile materials added to
polymers to increase their chain
flexibility. They reduce the
intermolecular cohesive forces
between the polymer chains, which in
turn ______ Tg

Answer 14

decrease

Question 15

The glass transition temperature is
also affected by the molecular weight of the of the polymer. Tg is _____ with
the molecular weight.

Answer 15

increased

Question 16

The modulus of a polymer _____with increasing temperature.

Answer 16

decreases

Question 17

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

Answer 17

Hydrostatic pressure

Question 18

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

Answer 18

Elastic modulus

Question 19

A stiffer material will have a _____ elastic modulus

Answer 19

higher

Question 20

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

Answer 20

Stress

Question 21

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

Answer 21

Strain

Question 22

Describes the tendency of an object to deform along an axis when opposing forces are applied along that axis; it is defined as the ratio of tensile stress to tensile strain.

Answer 22

Young’s modulus / elastic modulus

Question 23

Describes an object’s tendency to shear (the deformation of shape at constant volume) when acted upon by opposing forces; it is defined as shear stress over shear strain.

Answer 23

shear modulus / modulus of rigidity

Question 24

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

Answer 24

bulk modulus

Question 25

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

Answer 25

Flexural modulus

Question 26

Elastic modulus of polymers _____ with increasing hydrostatic pressure in tension, compression, and shear.

Answer 26

increases

Question 27

High hydrostatic pressure can also cause the glass transition in a polymer to shift to _____ temperatures

Answer 27

higher

Question 28

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

Answer 28

Yield strength / yield stress

Question 29

The yield strength of polymers ____ with
applied hydrostatic pressure.

Answer 29

increases

Question 30

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

Answer 30

Fracture

Question 31

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

Answer 31

normal tensile crack

Question 32

If a displacement develops tangentially, it is called ______

Answer 32

shear crack / slip band / dislocation

Question 33

Also known as breaking strength, is the stress at which a specimen fails via fracture.

Answer 33

Fracture strength

Question 34

The ultimate tensile strengths maximum stress) of the polymers always ______ with increasing hydrostatic pressure.

Answer 34

increased

Question 35

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

Answer 35

catalyst

Question 36

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

Answer 36

extent of the reaction

Question 37

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

Answer 37

Carother’s Equation

Question 38

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

Answer 38

Extent of Reaction

Question 39

Is defined as equal to the total number of bifunctional initially added, divided by the remaining number of molecules after time t.

Answer 39

Average degree of polymerization

Question 40

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

Answer 40

Gelation

Question 41

As polymerization proceeds beyond the gel point, the amount of gel increases at the expense of the sol, and the mixture rapidly transforms from a viscous liquid to an _____

Answer 41

elastic material