PGCE The polymer science 2011 question paper

1. 1
Engineering Thermoplastics
Polyamides (PA) / Nylons
Polyoxymethylene(POM)/ Acetals
Polyesters (PBT and PET)
Polycarbonate (PC)
Poly phenylene oxide (PPO)

2. 2
Polyamide
• PA is considered the first engineering thermoplastic
• PA is one of many heterochain thermoplastics, which has
atoms other than C in the chain.
• PA was created when a condensation reaction occurred
between amino acids, dibasic acids, and diamines.
• Nylons are described by a numbering system which indicates
the number of carbon atoms in the monomer chains
– Amino acid polymers are designated by a single number,
as nylon 6
– Diamines and dibasic acids are designated with 2
numbers, the first representing the diamine and the second
indicating the adipic acid, as in nylon 6,6 or nylon 6,10
with sebacic acid.

3. Preparation of Nylon 66
NH2(CH2)6NH2 + COOH(CH2)4COOH
hexamethylene diamine Adipic Acid
(heat)
n[NH2(CH2)6NH . CO (CH2)4COOH ]
nylon salt
[NH2(CH2)6NH . CO (CH2)4CO ]n + nH2O
Nylon 6,6 polymer chain byroduct
3

4.  Polyamides are heat sensitive materials.
 The Polyamide 66 is processed in the temperature
range of 260-320°C.
 The material has to be predried at 80°C for 2 - 4 hours
 The annealing temperature of Polyamide 66 part is 149
– 177°C.
 Injection moulding, Extrusion techniques, Compression
moulding, Foam moulding and Rotomoulding
techniques are used for processing the materials.
4
Processing considerations for PA 66

5. 5
 Polyamide 6 is prepared from  caprolactam in the presence of
water (which acts as a catalysts) and acetic acid as a molecular
weight regulator.
 The typical combination is charged into the vessel and reacted
under a nitrogen blanket at 250°C for about 12 hours.
Preparation of Nylon 66

6. 6
Characteristics of Polyamide 6 & 6,6 (For
identification)
• The material is semicrystalline and having high water absorption
capacity.
 It is milky white - yellow colour
 It is identified by the smell of burnt horn when burned, yellow
flame with a blue halo, can be formed into a filament.
 Its melting point is 215°C (PA6) & 264°C(PA66)
 Its short term and long term service temperature are respectively
140 - 160°C(For PA6,6 10°C more) and 80 - 100°C.

7. Nylon 6
7
Monomer Structure
 caprolactam
Polyomer Structure

8. 8
Synthesis of Nylon 6

9. 9
Relations of Structure and properties of Polyamide 6
 The following structural variables affect the
properties.
 The distance between the repeating –
CONH- group
 The number of methylene groups in the
intermediates
 The molecular weight
 N- substitution
 Co-polymerization

10. • The Polyamide 6 is available in various grades
 Injection molding grade
 Extrusion grade
 Rotational Molding grade
 Fluidized bed coating grade
10
Grades of Polyamide 6

11. Processing considerations for PA 6
11
The material has to be predried at 80°C for 2 - 4 hours
 While molding Polyamide attention on the following
points is essential.
 High Injection speed of the molding machine
 Control of shot or size
 Minimizing drooling by nozzle of reverse tapper type.
 Shrinkage of the part
 Annealing at 130° to 149°C for 10 - 20 hrs.

12. PA: Applications
Appliances
 Automotive
 Business equipment
 Consumer Products
 Electrical
 Hardware
 Machinery and packaging
12

13. Applications
13
Machinery
Agricultural
Mining and oil drilling
Food processing
Printing
Textile processing
Engine parts
Pumps/valves/meters/filters
Air blowers
Material handling equipment
Standard components
Gears
Cams
Sprockets
Bearings
Gaskets
Pulleys
Brushes

14. 14
Applications for Polyamides
• Fiber applications
– 50% into tire cords (nylon 6 and nylon 6,6)
– rope, thread, cord, belts, and filter cloths.
– Monofilaments- brushes, sports equipment, and bristles (nylon 6,10)
• Plastics applications
– bearings, gears, cams
– rollers, slides, door latches, thread guides
– clothing, light tents, shower curtains, umbrellas
– electrical wire jackets (nylon 11)
• Adhesive applications
– hot melt or solution type
– thermoset reacting with epoxy or phenolic resins
– flexible adhesives for bread wrappers, dried soup packets, bookbindings

15. 15
Comparison between different polyamides
Polyamide 6 Polyamide 66
processing easy easy
Strength good better
Abrasion resistance Low High
Toughness Low higher
Water absorption high high
cost less Little High

16. Comparison Performance Properties
16

17. 17
Chemistry Name of linear polyamides
• Nylon 6, 10 - polyhexamethylenesebacamide
[NH2(CH2)6NH . CO (CH2)8CO]n
• Nylon 11 - Poly(11-amino-undecanoic-amide
[NH(CH2)10CO ]n
• Nylon 12 - Poly(11-amino-undecanoic-amide
[NH(CH2)11CO ]n
• Other Nylons (Nylon 8, 9, 46, and copolymers
from other diamines and acids)

18. Nylon 11 or Polyamide 11
• It is a bioplastic and is an odd nylon.
• It is produced by the polymerization of 11-
aminoundecanoic acid. It is produced
from castor beans by Arkema under the trade
name Rilsan.
18

19. Advantages
• Low water absorbing nylon
• Good chemical resistance
• Ability to accept high loading of fillers
Limitations
• High cost relative to other nylons
• Minimal heat resistance
19
Nylon 11 or Polyamide 11

20. • It is made from ω-aminolauric acid.
• It is also made from ring-opening
polymerization of laurolactam at 260-300˚C.
• Melting point: 178 to 180 °C (352 to 356 °F; 451 ...
• Density: 1.01 g/mL
20
Nylon 12 or Polyamide 12

21. Advantages
• Low water absorbing nylon
• Good chemical resistance
• Ability to accept high loading of fillers
Limitations
• High cost relative to other nylons
• Minimal heat resistance
21
Nylon 12 or Polyamide 12

22. 22
Mechanical Properties of Nylon
Nylon 6 Nylon 6,6 Nylon 6,10 Nylon 6,12
Density, g/cc 1.13-1.15 1.13-1.15 1.09 1.06-1.10
Crystallinity 30-% - 50% 30-% - 50% 30-% - 50% 30-% - 50%
Molecular Weight 10,000–30,000 10,000–30,000 10,000–30,000 10,000–30,000
Tensile Strength,
psi
6,000 – 24,000 14,000 8,500 – 8,600 6,500 – 8,800
Tensile Modulus,
psi
300K 230K – 550K 250 K 220 - 290 K
Tensile
Elongation, %
30% - 100% 15%-80% 70% 150%
Impact Strength
ft-lb/in
0.6 – 2.2 0.55 – 1.0 1.2 1.0 –1.9
Hardness R80 - 102 R120 R111 M78

23. 23
Physical Properties of Polyamide
Nylon 6 Nylon 6,6 Nylon 6,10 Nylon 6,12
Optical Translucent to
opaque
Translucent to
opaque
Translucent to opaque Translucent to opaque
Tmelt 210C -220 C 255C – 265C 220 C 195 -219 C
Tg
H20
Absorption
1.3-1.9% (24h)
8.5-10 (Max)
1.0-2.8% (24h)
8.5% (Max)
1.4% (24h)
3.3% (Max)
0.4 – 1.0% (24h)
2.5 –3 % (Max)
Oxidation
Resistance
good good good good
UV Resistance Poor Poor Poor Poor
Solvent
Resistance
Dissolved by
phenol &
formic acid
Dissolved by
phenol & formic
acid
Dissolved by phenol &
formic acid
Dissolved by phenol &
formic acid
Alkaline
Resistance
Resistant Resistant Resistant Resistant
Acid
Resistance
Poor Poor Poor Poor
Cost $/lb $1.30 $1.30 $3.00 $3.10

24. 24
Advantages of Polyamide
Tough, strong, impact resistant
Low coefficient of friction
Abrasion resistance
High temperature resistance
Processable by thermopalstic methods
Good solvent resistance
Resistant to bases

25. Disadvantages of Polyamide
–High moisture absorption with
dimensional instability
– Subject to attack by strong acids and oxidizing
agents
– Requires UV stabilization
– High shrinkage in molded sections
– Electrical and mechanical properties
influenced by moisture content
– Dissolved by phenols
25

26. 26
Polyester
• Polymers used for films and fibers.
• Polyesters includes unsaturated
(thermosets), and saturated
thermoplastic polyesters.
• In thermoplastic polyesters there are
2 polymers PET and PBT

27. Synthesis of PET and PBT
27
• Thermoplastic polyesters have ester(-C-O) repeating link
• Polyester (linear) PET and PBT
O

28. 28
PET Properties
• The flexible, but short, (CH2)2 groups tend to leave the
chains relatively stiff.
• PET is known for its very slow crystallization. If cooled
rapidly from the melt to a Temp below Tg, PET solidifies
in amorphous form.
• If PET is reheated above Tg, crystallizaiton takes place to
up to 30%.
• In many applications PET is first pre-shaped in amorphous
state and then given a uniaxial (fibers or tapes) or biaxial
(film or containers) crystalline orientation.
• In Injection Molding PET can yield amorphous transparent
objects (Cold mold) or crystalline opaque objects (hot
mold).

29. 29
PBT Properties
• The longer, more flexible (CH2)4 groups
allow for more rapid crystallization than PET.
• PBT is not as conveniently oriented as PET
and is normally injection molded.
• PBT has a sharp melting transition with a
rather low melt viscosity.
• PBT has rapid crystallization and high degree
of crystallization causing warpage concerns

30. 30

31. 31
PET PBT LCP Polyester
Optical Transparent to
Opaque
Opaque Opaque
Tmelt 245C -265 C 220C – 267C 400 C - 421 C
Tg 73C - 80C
H20
Absorption
0.1 - 0.2% (24h) 0.085% (24h)
0.45% (Max)
<0.1% (24h)
<0.1% (Max)
Oxidation
Resistance
good good good
UV Resistance Poor Poor none
Solvent
Resistance
Attacked by
halogen
hydrocarbons
good good
Alkaline
Resistance
Poor Poor Poor
Acid
Resistance
Poor Poor fair
Cost $/lb $0.53 $1.48 $7.00 - $10.00

32. 32
Advantages of Polyesters
– Tough and rigid
– Processed by thermoplastic operations
– Recycled into useful products as basis for
resins in such applications as sailboats,
shower units, and floor tiles
– PET flakes from PET bottles are in great
demand for fiberfill for pillows and sleeping
bags, carpet fiber, geo-textiles, and regrind
for injection and sheet molding
– PBT has low moisture absorption

33. Disadvantages of Polyesters
–Subject to attack by acids and bases
–Low thermal resistance
–Poor solvent resistance
–Must be adequately dried in
dehumidifier prior to processing to
prevent hydrolytic degradation.
33

34. 34
PC Structure

35. KEY PROPERTIES
• high impact strength,
• transparency,
• excellent creep resistance
• temperature resistance
35

36. Synthesis of PC
36

37. 37
Applications for PC
- lenses, films, windshields, light fixtures,
containers, appliance components and tool
housings
– hot dish handles, coffee pots, popcorn
popper lids, hair dryers.
– Pump impellers, safety helmets, beverage
dispensers, trays, signs
– aircraft parts, films, cameras, packaging

38. 38
Advantages
– High impact strength, excellent creep resistance,
– Very good dimensional stability
– continuous temp over 120 C
Disadvantages
– High processing temp,UV degradation
– Poor resistance to alkalines
– subject to solvent cracking

39. 39
PPO (Poly Phenylene oxide)

40. 40

41. 41
PPO/PPE
• Poly(p-phenylene oxide) or poly(p-phenylene
ether) (PPE) is a high-temperature thermoplastic.
• It is an amorphous high-performance plastic.
• It is rarely used in its pure form due to difficulties in
processing and mainly used as blend with PS, HIPS or
PA.
• It can be used in applications upto 110 C temperature
intermittently.

42. 42

43. Preparation of PPO
43

44. 44

45. 45

46. 46

47. 47

48. 48

49. 49

50. 50

51. 51

52. 52

53. 53

54. Polyoxymethylene POM
• Polyoxymethylene (POM), also known
as acetal,[2] polyacetal, and polyformaldehyde.
• It is an engineering thermoplastic used in precision
parts requiring
– high stiffness,
– low friction,
– and excellent dimensional stability.
54

55. Synthesis of POM
55

56. Relations of Structure and Properties of POM
 Due to structural similarity properties of acetal polymers are compared
with those of polyethylene.
 Both polymers are linear with a flexible chain backbone and are thus
both thermoplastic.
 Both the structures are regular and since there is no question of tacticity
arising both polymers are capable of crystallization.
 In the case of both materials polymerization conditions may lead to
structures which slightly impede crystallization; with the polyethylene, this
is due to a branching mechanism, whilst with the polyacetals this may be
due to co-polymerization.
 The acetal polymer molecules have a shorter backbone (-C-O-) bond
and they pack more closely together than those of polyethylene. The
resultant polymer is thus harder and has a higher melting point.

57. Characteristics of POM
 Good appearance
 Homopolymer is resistant to mid acids and bases
 Good electrical properties but affected by moisture
 Stiff and rigid
 Good toughness
 Notch sensitive
 Excellent fatigue resistance under repeated load
Excellent creep resistance under continuous load
 Low coefficient of friction
 Good abrasion resistance
 Maintains the mechanical, chemical and electrical
properties over broad temperature range and time

58. Characteristics of POM
High resistance to thermal and oxidative degradation
 Very good resistance to stress relaxation
 Excellent dimensional stability
 Good processability
 Copolymers have better thermal stability
 Burn slowly without smoke generation
 Susceptible to UV degradation
 Attacked by phenol and aniline
 Difficult to electroplate
 Degradation at high processing temperature and liberate
formaldehyde
 It is identified by the strong smell of formaldehyde, when burned,
faint color flame, melt and drips
 Its melting point is 165-175°C

59. Structural difference between homopolymer /&
copolymer

60. 60

61. 61

62. Properties of Polyacetal
Properties Values
Units Homopolymer Copolymer
Specific gravity ---- 1.42 1.41
Tensile strength MPa 69 61
Tensile modulus MPa 3100 2829
Flexural modulus Mpa 2620-2960 2588
Elongation at break % 27-75 40-75
Impact strength izod, Notched, J/m 69-123 53-80
Hardness M92-94 M78-80
Deflection temperature under load
0
C 136 110
(1.82 Mpa)
Vicat softening temperature
0
C 185 167
Coefficient of linear expansion mm/mm/
0
C 10-15 x 10
-5
8.5 x 10
-5
Water absorption, 24hrs % 0.25-0.32 0.22
Dielectric strength KV/mm 20 20
Dielectric constant 10
-6
Hz 3.7 3.7
Power factor 0.005 0.006
Volume resistivity Ohm.m 10
-13
- 10
-14
-
Melting point
0
C 175 165

63. Grades of POM
The polyacetals are available in the following grades.
 Injection grade
 Extrusion grade
 Extrusion blow grade
rotational grade
In addition to that the following special grades are
available,
 Improved processability grade.
 Low friction grade.
 Glass filled grade
 Mineral filled grade
 UV-Stabilized grade

64. Processing considerations of
Polyacetals
While processing polyacetal following precautions to be taken.
1. Stepwise thermal or based catalyzed hydrolytic
depolymerization initiated from the hemiformal chain end with
the evolution of formaldehyde.
2. Oxidative attack at random along the chain leading to chain
scission and subsequent depolymerization.
3. Acid catalysed cleavage of the acteal linkages.
4. Thermal depolymerization through scission of C-O bonds can
occur catastrophically above 270°C and care must be taken not
to exceed this temperature during processing.
The homopolymer is moulded at melt temperature of 200-210°C while the
copolymer would be moulded at melt temperature of 190-205°C.
 Therefore end capping is done during polymerization and antioxidants and acid
acceptors are added

65. Applications of Polyacetal
 Appliances
 Agriculture & Irrigation
 Consumer Products
 Industrial
 Electrical
 Plumbing & Hardware

66. Appliances: Housing for business machine,
gears, cams, friction pads, rollers, pulleys, nuts,
chain links and shelf support brackets, detergent
pumps, refrigerator clips, brackets, bearing, wear
strips and instrument housing in washers and
dryers, spray nozzies and soap dispensers in
dishwares , bowls, mixing blades and bearings
in counter-top appliance bodies, tops and cups in
water boilers.
Applications of Polyacetal
Agriculture & Irrigation: Pop-up sprinklers
(nozzles arms, gears, housing and water ways),
pumps(housing, impellers, pistons) metering
valves, tractor components (shift lever housing,
hydraulic connectors, seed applicators, bearings
and gears)

67. Automotive: Fuel level indicators, pump
components, gas caps, cooling fans, trip clips,
colour co-ordinated bucket housings, window
cranks, shift lever handles, knobs, lever and
mounting brackets, instrumental cluster gears,
bearings, housing and dials, exterior door pulls,
mirror housing and brackets
Applications of Polyacetal
Industrial: Valves, springs, bearings, cams,
material handling components such as
conveyors, chain links gears, pumps and hose
connectors

68. Applications of Polyacetal
Electrical: Key tops pluggers, switches, buttons,
cassette tape rollers and hubs, base plates in computer
keyboards, springs in telephones and connectors in
modular components.
Laser mark part HVAC Control