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CHEMISTRY > POLYMERS > Flashcards

POLYMERS Flashcards

1
Q

Polymer

A

Long molecule formed by the joining togethor of thousands of small molecular units by chemical bonds.

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2
Q

Macromolecules

A

Due to their large size polymers are also sometimes called macromolecules

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3
Q

Polymer

A

Any substance made up of many repeating units building blocks called mers

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4
Q

Resins

A

when in form ready for further working polymers are called resins

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5
Q

polymerisation

A

chemical process leading to the formation of polymers is called polymerisation

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6
Q

degree of polymerisation

A

number of monomeric units contained in the polymer is known as degree of polymerisation

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7
Q

monomers

A

small molecules which combine with each other to form polymer molecules are known as monomers

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8
Q

greek translation of poly and mers

A

poly : many
mers : units or parts

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9
Q

Functionality

A

number of bonding sites in a monomer

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10
Q

significance of functionality

A

1) when the functionality of monomer is two, linear or straight chain polymer molecule is formed. Ex : All vinyl monomers, ethylene glycol, amino-acid

2) when functionality is three, 3-D network polymer is formed. Ex: phenol, melamine, etc

3) when a trifunctional monomer is mixed in small amounts with a bifunctional monomer, a branched chain polymer is formed

4) when a bifunctional monomer is mixed in small amounts with a trifunctional monomer, a 3-D network polymer is formed

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11
Q

functionality of monomer

A

number of bonding sited in a given molecule. The number of reactive functional groups per molecule of compound defines its functionality

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12
Q

why all single organic compounds cannot act as monomer during polymerisation process

A

because for a substance to act as a monomer it must be at least bi-functional. thus organic compounds like acetic acid and benzoic acid cannot act as monomer since they are monofunctional

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13
Q

Explain characteristics of polymers

A

1) they are macromolecules
2) they have both amorphous and crystalline regions
3) intermolecular forces in polymers can be van der waals, dipole-dipole or or hydrogen bonding.
4)they show time-dependent properties
5)they are combustible
6) they have low densities and excellence resistance to corrosion
7) they are thermal and electrical insulators

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14
Q

Advantages of polymers

A

low density
low absolute strength and stiffness but favourable specific strength and specific stiffness
resistant to corrosion
great electrical and thermal insulators
some polymers are inherently flexible
easily mouldable
ability to take various colours and shades
they are tailor made

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15
Q

crystallites

A

polymers have regions of crystallinity called crystallites embedded in amorphous regions.
crystallites provide strength and hardness
amorphous regions provide flexibility

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16
Q

Drawbacks of polymers

A

lower strength and stiffness, easily deformed under load
temperature limitations
time-dependent properties
combustible nature

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17
Q

classification of polymers based on structure or shape

A

linear
branched
cross linked

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18
Q

linear polymers

A

monomeric units that are joined in the form of long straight chains
high MP density and tensile strength

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19
Q

Branched polymers

A

polymers which are mainly linear in nature but also possess some branches along the main chain
low MP, density and tensile strength

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20
Q

Cross-linked polymers

A

3-D network polymers which contain cross-links in the form of strong covalent bonds btw polymer chains
Hard, rigid, do not melt on heating

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21
Q

PVC is soft and flexible as compared to bakelite

A

PVC is a linear polymer so it is soft and flexible. Bakelite is cross-linked polymer in which polymeric chains are bonded togethor by strong covalent bonds. thus no deformation can take place in its molecule as cross-links restricts the motion of polymer chains

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22
Q

classification of polymers based on physical state

A

amorphous
semi-crystalline

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23
Q

Amorphous polymers

A

polymer chains tend to be flexible and easily entangled or folded; tend to be disordered and are hard to crystallize.
Ex: LDPE, Rubbers

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24
Q

Crystalline polymers

A

Polymer chains that exhibit ordered structures. Degree of crystallinity depends upon amount of ordering in a polymer
Ex: HDPE, Nylon

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25
Q

classification of polymers based on number of monomers

A

Homopolymers
copolymers

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26
Q

homopolymers

A

polymers which are obtained by the repeated combination of only one type of monomer molecules
Ex: PE,PP,PVC

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27
Q

copolymers

A

polymers which are obtained by repeated combination of two or more types of monomers
Ex: styrene acrylonitrine copolymer, SAN

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28
Q

classification of polymers based on end use

A

Fibers
elastomers
adhesive
membranes
plastics
films
paints

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29
Q

Fibers

A

polyester Nylon

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30
Q

Plastics

A

thermoplastics and thermosets

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31
Q

elastomers

A

Rubber, Buna-S, Polyurethane

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32
Q

Films

A

PP, LDPE, PET, HDPE

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33
Q

Adhesives

A

PVA, Epoxy resin

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34
Q

Paints

A

epoxy

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35
Q

Membranes

A

polyacetylene, Polyaniline

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36
Q

classification of polymers based on tacticity or configuration

A

isotactic
syndiotactic
atactic

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37
Q

Tacticity

A

orientation of side groups around the main backbone chain in three-dimensional structure of a polymer

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38
Q

Isotactic polymers

A

side groups are all on the same side

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39
Q

Syndiotactic polymers

A

Arrangement of side groups is in alternating fashion

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40
Q

Atactic polymers

A

arrangements of side groups is random around the main chain

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41
Q

classification of polymers based on origin

A

Natural
Synthetic

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42
Q

Synthetic polymers

A

polymers which are synthesised in the laboratory are called synthetic polymers
Ex: rubber, fibers

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43
Q

Natural polymers

A

Polymers which can be found in nature
Ex: Carbohydrate and proteins

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44
Q

Conductance polymers

A

insulating polymers
conducting polymers

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45
Q

conducting polymers

A

polymers which conduct heat
Ex: polyaniline , Polypyrrole

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46
Q

classification of polymers based on environment friendly nature

A

durable
Biodegradable

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47
Q

biodegradable polymer example

A

Starch based PE

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48
Q

classification of polymers based on based on polarity of monomers

A

polar
non-polar

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49
Q

Polar monomers

A

PET, Nylon

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50
Q

non-polar monomers

A

PE, PP

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51
Q

classification of polymers based on their behavior when heated to processing temperature

A

thermoplastics
thermosets

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52
Q

Difference btw thermoplastics and thermosets

A

Book pg. 170

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53
Q

Polymerization

A

synthesis of large molecular weight polymers is termed as polymerization

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54
Q

Different ways for doing polymerization

A

by opening double bond
by opening a ring
by using molecules having 2 functional groups

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55
Q

addition polymerization

A

polymer synthesized by addition polymerization has the same empirical formula as that of monomer . No molecule is evolved during polymerization and the polymer is an exact multiple of original monomeric molecule

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56
Q

substituent groups:
-H
-CH3
-Cl
-C6H5

A

Polymer
Polyethene
polypropylene
polyvinyl chloride
Polystyrene

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57
Q

condensation polymerization

A

It takes place by condensation of two different bi- or poly functional monomers having functional groups which have affinity for each other.

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58
Q

Difference btw condensation and addition polymerization

A

Book pg 172

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59
Q

Copolymerization

A

polymerization of two or more monomeric species together

resultant polymer possesses some advantageous properties from both monomers Ex: styrene-butadiene rubber (SBR)

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60
Q

Different types of copolymers

A

Alternate
Block
Random
Graft

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61
Q

Alternate copolymers

A

monomers are arranged in regular alternate fashion

62
Q

Block copolymers

A

A block of repeating unit of one kind of monomer is followed by block of another kind of monomer

63
Q

Random copolymers

A

monomers are randomly distributed along the polymer chain

64
Q

Graft copolymers

A

they have branched structures in which the monomer segments on the backbone and branches differ

65
Q

Reaction mechanism of free-radical polymerization

A

monomer is activated by its transformation into radical by the action of light, heat, ionizing radiation, or by adding chemicals

66
Q

Initiators

A

compounds which readily decompose into free-radical so that monomer molecules can interact with these free-radicals for their activation
Ex: benzoyl peroxide, AIBN

67
Q

Initiation by oxygen

A

Oxygen is known to initiate some free radical ethylene polymerization reactions It occurs at higher temperatures by the thermal decomposition of peroxides and hydroperoxides formed from the monomer

68
Q

Mechanism of free radical polymerization

A

1) Chain initiation- it involves 2 steps decomposition of initiator and the addition of first vinyl monomer molecule to free radical leading to the formation of intermediate

2)Chain propagation- addition of monomer molecules to leading to the formation of macro-radicals.

3)Chain termination- Growing polymer chain can be terminated by :
(I)Recombination
(II)Disproportionation
(III)Reaction with polymerization inhibitors
(IV)Reaction with Solvent Molecules

69
Q

Chain propagation helps determine:

A

1) rate of polymerization
2) molecular weight of polymer
3) structure of polymer chain
4)mode of monomer addition

70
Q

Head-to-tail placement of monomer units

A

in final polymer monomer units are linked together in such a manner that they have substituents on alternate carbon atoms. This H-T placement is favored on both steric and resonance grounds

71
Q

Chain transfer reactions

A

in these reactions the original growing free radical chain is terminated by reaction with the monomer molecule and a new chain is initiated

72
Q

how do chain transfer reactions decrease molecular weight of polymer

A

there will be no change in the overall rate of polymerization but the avg molecular weight of polymer will decrease

73
Q

Explain branching and cross-linking during the free-radical addition polymerization

A

once a macroradical is formed by the propogation of free-radical polymerisation reaction, back-biting can take place, leading to the abstraction of hydrogen atom from the growing end of the polymer chain to the middle of the chain. Now propogation of reaction from middle centres will create branches .
There will also be the possibility of reaction between 2 molecules of type II leading to the formation of cross-linkages

PG 176-177

74
Q

Monomers which can be polymerized by free radical polymerization

A

ethylene and other vinyl derivatives
Acrylic acid derivatives
Butadiene , isoprene and chloroprene

75
Q

Cationic polymerization

A

Monomers with electron releasing substituents undergo cationic polymerization in the presence of lewis acids and friedel-craft catalysts. They add on to the monomer forming a carbonium ion. Electron releasing substituents such as alkyl , alkyloxy and phenyl increase the e- density at C-C double bond and facilitate its bonding to cationic species
The mechanism can be explained by polymerization of styrene

76
Q

polymerization of styrene

A

PG NO 178

77
Q

Anionic polymerization

A

Monomers with electron attracting substituents undergo anionic polymerization in the presence of sodium or potassium amide and grignard reagent as catalysts.
In anionic polymerization catalysts interact with monomer to generate a carbanion as the active centre for chain growth . As the intermediate carbanion is stabilized by electron withdrawing substituens hence anionic polymerization is favourable with the monomers having such substituents.
The mechanism can be explained by formation of PMMA

78
Q

Formation of PMMA

A

Book pg 179

79
Q

Conclusions from generalized anionic mechanism for the formation of PMMA

A

(1) in Anionic polymerization end group posseses high activity and good stability. Polymerization process continues till available monomers are consumed.

(2) Its possible to produce very high molecular weight polymers by anionic polymerization

(3) block copolymers can also be made by anionic polymerization by carefully adding alternatively the required monomers with pre-determined concentration

80
Q

Killed polymers

A

polymers which are produced by stopping the polymerization process at predetermined stage with the help of a sutaible terminating agent like water

81
Q

Difference btw radical and ionic polymerization

A

Pg 180

82
Q

Types of PVC

A

rigid PVC
Plasticized PVC

83
Q

Manufacturing of PVC

A

PVC can be made from vinyl chloride by emulsion polymerisation. Vinyl chloride is mixed with water in equal parts, small amount of catalyst and an emulsifier. Mixture is vigorously stirred and then senf to autoclave at temp. of 40-45°C. The polymer is then coagulated by acid and dried. The desired properties in PVC can be achieved by using plasticizers , stabilizers , lubricants and fillers.

Equation: PG187

84
Q

Properties of PVC

A

1) stronger and tougher than polyethylene
2)colourless, odourless, and non-inflammable
3)it has superior chemical resistance but dissolves in ethyl chloride and hydro furan
4)excellent oil resistance

85
Q

Applications of PVC

A

In acid recovery plants to handle hydrocarbons
in pipes for drainage and guttering
making bottles

86
Q

PVC is tougher and stronger than polyethylene

A

presence of chlorine atom on alternate carbon atoms of pvc with C-C dipole causes an increase in interchain attraction. These strong dipole-dipole attractive forces make PVC tougher and stronger than polyethylene which has weak van der waals forces of attraction between different PE chains

87
Q

Prepartion of Plasticized PVC

A

it is obtained by adding plasticizers such as DOP, dibutyl phthalate to rigid PVC

88
Q

Properties of plasticized PVC

A

It is good insulator for direct current and low frequency AC current

89
Q

Uses of Plasticized PVC

A

car applications
kitchen upholstery
ladies handbags
plastic rainwear
baby pants
garden hose

90
Q

Polymethyl Methacrylate (PMMA) preparation

A

polymerization of methyl methacrylate in the presence of acetyle peroxide or hydrogen peroxide as catalyst

91
Q

Polymethyl Methacrylate (PMMA) aka

A

plexiglass or lucite

92
Q

properties of PMMA

A

1)amorphous, colourless, transparent thermoplastic
2)hard
3)polar polymer hence no electrical insulation properties
4)high softening point due to intermolecular dipole forces
5)critical angle for polymer air boundary is 42 degree. A wide light beam mat be transmitted through long lengths of solid polymer

93
Q

Applications of PMMA

A

Display signs
light fittings
motorcycle windscreen
wash basins
optical fibres

94
Q

Preparation of Nylon 6

A

pg no 192-193

95
Q

properties of Nylon-6

A

fibres are tough, they own high tensile strength elasticity and lustre
they are wrinkleproof
highly resistant to abrasion and chemicals
they can absorb upto 2.4% of water
easily dyeable

96
Q

applications of Nylon-6

A

as thread in bristles for toothbrushes, surgical sutures and strings for musical instruments
used in hosiery and knitted garments
glass fibre reinforced Nylon-6 is used in gears, bearings and fittings

97
Q

preparation of Nylon-66

A

pg no 194-195

98
Q

properties of Nylon-66

A

high crystallinity which imparts high strength, high melting point, elasticity and toughness
they are sterilisable
good hydrocarbon resistance

99
Q

Applications of Nylon-66

A

used in fibres
in gears, bearings, bushes etc. they can run without much lubrication
for jacketing electrical ware

100
Q

Preparation of Polytetrafluoroethylene (PTFE)

A

It is prepared by polymerisation of tetrafluoroethylene under pressure in the presence of benzoyl peroxide as catalyst

101
Q

PTFE is aka

A

Teflon

102
Q

Properties of Teflon

A

High density
excellent electrical insulation properties
chemical inertness over wide temperature range
non-adhesive characteristics
excellent toughness and heat resistance

103
Q

Application of Teflon

A

Wire and cable insulation
laminates for printed circuitry
coating of frying pans
non-lubricating bearings
insulators for motors, generators, etc

104
Q

Structure of Teflon

A

it has a twisted zig-zag structure with fluorine atoms packing tightly in a spiral around the C-C skeleton. Due to presence of highly electronegative fluorine atoms there are very strong attractive forces between different chains

105
Q

Polyacrylonitrile preparation

A

it is prepared by polymerization of vinyl cyanide (Acrylonitrile)

106
Q

Polyacrylonitrile is aka

A

Orlon

107
Q

properties of polyacrylonitrile

A

does not dissolve in its monomer
it dissolves in dimethylformamide and tetramethylenesulphone
resistant to water and quick drying
more resistant to acid and gases than nylon

108
Q

Applications of polyacrylonitrile

A

in manufacturing window shades
as wool-like fibre in suits, sweaters etc

109
Q

Polyvinyl acetate (PVA) preparation

A

Catalyst used is either benzoyl peroxide or acetyl chloride. A solution of vinyl acetate and catalyst is prepared in benzene.

110
Q

Properties of Polyvinyl acetate

A

It is clear, colourless and transparent material
amorphous polymer
they become gum-like when masticated
fairly soluble in organic solvents

111
Q

applications of polyvinyl acetate

A

production of water-based emulsion paints
chewing gums
making records
bonding of paper

112
Q

Phenol formaldehyde resin preparation

A

Book pg 196-197

113
Q

Phenol formaldehyde resin aka

A

bakelite

114
Q

Phenol formaldehyde resin properties

A

they are hard rigid and strong materials
they have excellent heat and moisture resistance
good chemical resistance
good abrasion resistance
good electrical insulation characteristics
usually dark coloured, pinkish brown

115
Q

Applications of Phenol formaldehyde resin

A

domestic plugs and switches
distributor heads of cars
adhesive
impregnating word,paper and other fillers for producing decorative laminates
electrical insulation and protective coating

116
Q

Urea formaldehyde resins preparation

A

book pg no 198

117
Q

Urea formaldehyde resins properties

A

clear and colourless
better hardness and tensile strength
good solvent , grease and moisture resistance
good adhesive characteristics

118
Q

Urea formaldehyde resins applications

A

as adhesives for plywood etc
for finishing of cotton textiles
for making buttons, vacuum flask cups etc
for bottle caps
for coloured toilet seats

119
Q

Biopolymerization

A

a polymerization process for the production of biopolymers

120
Q

Types of biopolymerization

A

using microbes
using fermentation

120
Q

Biopolymers using microbes

A

biopolymers made using microbes. they are produced by a range of micro-organisms cultivated under various nutrient and growth conditions

120
Q

Production of biopolymers

A

biopolymers are made from a compound called poly-hydroxy-alkanoate (PHA). bacteria accumulate PHA in the presence of excess carbon source.
Example of bacteria useful for bio-polymerization:
archaebacteria, bacillus megaterium, ralstonia eutropha , bacillus mycoides

121
Q

fermentation

A

it is the use of micro-organisms to break down organic substances usually in the absence of oxygen

121
Q

Bacterial polyester fermentation

A

ralstonia eutropha bacteria use the sugar of harvested plants to fuel their cellular processes. The by-product of this cellular process is polyester which is then separated from the bacterial cells

122
Q

Lactic acid fermentation

A

Lactic acid is fermented from sugar using bacteria. After the lactic acid is produced by fermentation process it is converted to polylactic acid using traditional polymerization processes

polymer formed is called PLA

123
Q

Growing plants using plants

A

A genetically engineered plant ( Arabidopsis thaliana) contains enzymes used by bacteria. bacteria create plastic through the conversion of sunlight. Through transfer of gene codes for this enzyme production into the plant we are able to produce the plastic through the cellular processes of plant. Plant is harvested and plastic is extracted from it using a solvent. Subsequently using distillation plastic is separated from the solvent

124
Q

Advantages of biopolymerization

A

1) eco friendly synthetic process
2)bio-polymers are biodegradable
3) biopolymer is derived from renewable resources and possesses good mechanical properties

125
Q

Shortcoming of biopolymerization

A

1) prone to thermal degradation
2) brittle
3) reactive groups and not present in biopolymers so they interact poorly with additives
4) processing is difficult

126
Q

Biodegradation

A

process carried out by biological systems wherein a polymer chain is cleaved via enzymatic activity

127
Q

Biodegradable polymers

A

those polymers which get decomposed by the process of biodegradation

128
Q

Requirements of biodegradation

A

Micro-organisms
Environment
Substrate

129
Q

Microorganisms in biodegradation

A

they must exist with the appropriate biochemical machinery to synthesize enzymes specific for the target polymer to initiate the depolymerization process

130
Q

Environmental factor in biodegradation

A

following enviornmental factors must be tuned in a given enviornment within the window of acceptibility for the organisms producing the appropriate enzymes to degrade the target polymer:
1) temperature
2) pressure
3) moisture
4) oxygen
5) type and concenteration of salts
6) light
etc

131
Q

substrate factor in biodegradation

A

polymer must have following essential features for biodegradation process to be successful
1) suitable functional groups (like ester)
2) hydrophilicity (should be greater)
3) low molecular weight
4) less crystallinity

132
Q

Types of biodegradable polymers

A

Natural- natural rubber, collagen, lignin,
Synthetic - polyvinyl alcohol, polyanhydrides, PHBV

133
Q

Need for biodegradable polymers

A

solid waste problem
Litter problem
Entrapment

134
Q

Applications of biopolymers

A

PHB is used in shampoo bottles
HB-HV is used as matrices for controlled release of drugs
PLA is used in sutures, drug-delivery-systems and wound clips

135
Q

Limitations of biopolymers

A

Not easily recyclable
expensive
not easily available

136
Q

Drawbacks of raw rubber

A

1)soft & sticky in hot summer and hard & brittle in cold winter
2)low tensile strength
3)attacked by oxidising agents
4)in organic solvents it undergoes swelling and disintegration
5)oxidises in air

137
Q

Compounding

A

incorporation of suitable substances in the polymer so as to impart the desired properties in it

138
Q

Compounding of rubber includes

A

vulcanizers
accelerators
antioxidants
reinforcing agents
plasticizers
colouring agents
inert fillers

139
Q

Vulcanization of rubber

A

Book pg 203

140
Q

Advantages of vulcanization

A

1) increase in tensile strength
2) excellent resilience
3) broader temperature range
4) better resistance to moisture, oxidation and abrasion
5) resistance to organic solvents
6) slight tackiness
7) low elasticity

141
Q

Styrene rubber

A

Book pg 204

142
Q

Properties of styrene rubber

A

high abrasion resistance
high load bearing capacity
resilience
swells in oil
low oxidation resistance

143
Q

applications of styrene rubber

A

motor tyres
shoe soles
insulation of wires
carpet backing
gaskets
adhesives
tank-lining

144
Q

nitrile rubber

A

Book pg 205

145
Q

properties of nitrile rubber

A

less resistant to alkalis
increased resistance to oils,salts, solvents and acids
more heat resistant
good abrasion resistance

146
Q

applications of nitrile rubber

A

conveyor belts
lining of tanks
gaskets
printing rollers
oil-resistant foams
automobile parts
hoses
adhesives

147
Q

Monomers of all thermoplastic polymers

A

Book pg 207

CHEMISTRY (3 decks)

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