1. POLYMERS Polymer Technology Thermoplastic Polymers
Thermosetting Polymers
Elastomers
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

2. Polymer Long‑chain molecules repeating units connected together
Millions of units in a single polymer molecule
Polymer
derived from the Greek
poly, meaning many
meros (reduced to mer), meaning part
Most polymers are based on carbon
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

3. Types of Polymers Polymers Plastics Rubbers Engineering materials
Thermoplastic polymers
Thermosetting polymers
Elastomers
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

4. Thermoplastic Polymers - Thermoplastics
Solid material at room temperature
Viscous liquids when heated
Injection moulding processes TP
Linear Structure
Branched Structure
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

5. Thermosetting Polymers - Thermosets
Cannot tolerate repeated heating cycles
Elevated temperatures produce a chemical reaction that hardens the material
If reheated, thermosets degrade and char rather than soften TS
Cross-linked or Networked Structure
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

6. Elastomers (Rubbers) Polymers exhibit extreme elastic extensibility
subjected to low mechanical stress
Elastomers can be stretched by a factor of 10
completely recover to their original shape
Elastomer Structure
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

7. Loosely Cross-linked Structure
Stress-Strain Curves
Unstretched
Tensile Stress
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

8. Examples of Polymers Thermoplastics:
Polyethylene, polyvinylchloride, polypropylene, polystyrene, and nylon
Thermosets:
Phenolics, epoxies, and certain polyesters
Elastomers:
Natural rubber (vulcanized)
Synthetic rubbers, which exceed the tonnage of natural rubber
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

9. General Properties of Polymers
Low density relative to metals and ceramics
Good strength‑to‑weight ratios
High corrosion resistance
Low electrical and thermal conductivity
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

10. Polyermerization of Polyethylene
Synthesis of polyethylene from ethylene:
(1) n ethylene monomers yields
(2a) polyethylene of chain length
(2b) concise notation
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

11. Addition Polymerization
Initiation
Rapid addition of monomers
Long chain molecule
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

12. Addition (chain) Polymerization
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

13. Step Polymerization
n‑mer attaching a single monomer to form a (n+1)‑mer
n1‑mer combining with n2‑mer to form a (n1+n2)‑mer
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

14. Step Polyermization
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

15. Possible Arrangements of Atom Groups
Polypropylene
Isotactic
Syndiotactic
Atactic
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

16. Crystalline Polymer Structure
folded chain lamella, the typical form of a crystallized region
long molecules forming crystals randomly mixed in with the amorphous material
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

17. Strength vs. Temperature
Relationship of mechanical properties:
amorphous thermoplastic
100% crystalline (theoretical) thermoplastic
partially crystallized thermoplastic
Tg = Glass transition temperature
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

18. SME Video
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

19. In-class example
A test specimen in a tensile test has a gage length of 2.0 in and an area = 0.5 in2. During the test the specimen yields under a load of 32,000 lb. The corresponding gage length = in. This is the 0.2 percent yield point. The maximum load = 60,000 lb is reached at a gage length = 2.60 in. Determine the following:
(a) yield strength
(b) modulus of elasticity
(c) tensile strength.
fracture occurs at a gage length of 2.92 in
(d) the percent elongation
specimen necked to an area = 0.25 in2
(e) percent reduction in area
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

20. ASSIGNMENT – STUDENT MUST SHOW SOLUTION TO PROFESSOR DURING LAB PERIOD
A tensile test uses a test specimen that has a gage length of 50 mm and an area = 200 mm2. During the test the specimen yields under a load of 98,000 N. The corresponding gage length = mm. This is the 0.2 percent yield point. The maximum load = 168,000 N is reached at a gage length = 64.2 mm. Determine the following:
(a) yield strength
(b) modulus of elasticity
(c) tensile strength
fracture occurs at a gage length of 67.3 mm
(d) percent elongation
specimen necked to an area = 92 mm2
(e) percent reduction in area
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing