1. Engineering Materials and Processes Lecture 20 – Properties of plastics
Prescribed Text:
Ref 1: Higgins RA & Bolton, Materials for Engineers and Technicians, 5th edition, Butterworth Heinemann. ISBN:
Readings:
Callister: Callister, W. Jr. and Rethwisch, D., 2010, Materials Science and Engineering: An Introduction, 8th Edition, Wiley, New York. ISBN
Ashby 1: Ashby, M. & Jones, D., 2011, Engineering Materials 1: An Introduction to Properties, Applications and Design, 4th edition, Butterworth-Heinemann, Oxford UK. IBSN:
Ashby 2: Ashby, M. & Jones, D., 2011, Engineering Materials 2: An Introduction to Microstructures and Processing, 4th edition, Butterworth-Heinemann, Oxford UK. IBSN:
Lecture (2 hrs):
Ref 1, Ch 1: Engineering materials;
Ref 1 Ch 2: Properties of materials.
Laboratory 1 (2 hrs): Hardness test
Callister: Ch 1, 2, 20-21
Ashby 1: Ch 1, 2
Ashby 2: Ch 1 1

2. Properties of plastics
Reference Text
Section
Higgins RA & Bolton, Materials for Engineers and Technicians, 5th ed, Butterworth Heinemann
Ch 20
Reference Text
Section
Callister, W. Jr. and Rethwisch, D., 2010, Materials Science and Engineering: An Introduction, 8th Ed, Wiley, New York.
Ch 4
Engineering Materials and Processes

3. Properties of plastics
Note: This lecture closely follows text (Higgins Ch20)
Blowmoulded Polycarbonate
Engineering Materials and Processes

4. Van der Waals Forces
Why do the alkanes get stiffer as the molecules get longer until eventually becoming a solid? The molecules are held together by weak electrical imbalances in adjacent molecules (caused by electron distribution).
These forces are too weak to hold short molecules together, but when there are hundreds of Carbon atoms in the chains, the Van der Waal molecular forces increase.
This is why HDPE (garbage bin) is harder than LDPE (squeeze bottle).
Alkanes
LDPE bottle
promotionsonly.com.au
HDPE bin
bcsplastics.com.au
Engineering Materials and Processes

5. 20.2 Crystal and glass states
(Higgins 20.2)
READ HIGGINS Ch20.2
In thermoplastics materials, these molecules are attracted to each other by relatively weak van der Waals forces, whilst in thermosetting plastics they are joined to each other by strong, permanent covalent
bonds.
Melting points of polymers
Glass transition temperature
Vicat softening temperature
Wikipedia/CC BY 1.0
Higgins
Engineering Materials and Processes

6. 20.2 Crystal and glass states
(Higgins 20.2)
Amorphous / crystalline structures of Thermoplastics
Periodic Table of Polymers
Reduced version of Periodic Table of Polymers
Copyright: Tangram Technology Ltd. (
The table may be freely reproduced provided full acknowledgement of the copyright is given.
Periodic Table of Polymers
Reduced version of Periodic Table of Polymers
Engineering Materials and Processes

7. 20.3 Mechanical properties (Higgins 20.3)
(i) Low elastic modulus, low yield stress, e.g. PVA and PTFE.
(ii) High elastic modulus, low elongation, e.g. PF, PMMA and PS.
(iii) Low elastic modulus, low yield stress but high elongation and high stress at break, e.g. PE and plasticised PVC.
Higgins
Engineering Materials and Processes

8. 20.3 Mechanical properties (Higgins 20.3)
(iv) High elastic modulus, high yield stress, high tensile strength and low elongation, e.g. rigid PVC and modified PS.
(v) High elastic modulus, high yield stress, high tensile strength and high elongation, e.g. nylons and polycarbonates,
(vi) Very low elastic modulus, low yield stress and low tensile strength but very high elastic elongation, e.g. natural rubber and other elastomers.
Higgins
Engineering Materials and Processes

9. 20.3 Mechanical properties (Higgins 20.3)
Engineering Materials and Processes

10. 20.3 Mechanical properties (Higgins 20.3)
1 Bond bending of the carbon-carbon covalent bonds in the polymer
chain - this is manifested as the ordinary elasticity and is an
instantaneous deformation.
2 Uncoiling of the polymer chains - this gives rise to high elasticity
and is very time dependent.
3 Slipping of polymer chains past each other - this produces
irreversible plastic flow and is also very time dependent.
Engineering Materials and Processes

11. 20.3 Mechanical properties (Higgins 20.3)
Engineering Materials and Processes

12. 20.3 Mechanical properties (Higgins 20.3)
Engineering Materials and Processes

13. 20.3 Mechanical properties (Higgins 20.3)
Hardness tests
Higgins
Engineering Materials and Processes

14. 20.3 Mechanical properties (Higgins 20.3)
Impact tests
Higgins
Engineering Materials and Processes

15. 20.3 Mechanical properties (Higgins 20.3)
Creep
Higgins
Engineering Materials and Processes

16. 20.3 Mechanical properties (Higgins 20.3)
Other mechanical tests
Higgins
Engineering Materials and Processes

17. 20.4 Additives (Higgins 20.4) 20.4.1 Fillers 20.4.2 Anti-static agents
Flame retardants
Friction modifiers
Other additives
Foamed or 'expanded' plastics materials
Higgins
Engineering Materials and Processes

18. 20.5 Shaping plastics (Higgins 20.5)
Calendering
Higgins
Calandered PVC fabric: Wikipedia
Engineering Materials and Processes

19. 20.5 Shaping plastics (Higgins 20.5)
20.S.2 Extrusion
Extruded Plasticised PVC cable:
Higgins
Engineering Materials and Processes

20. 20.5 Shaping plastics (Higgins 20.5)
Moulding
Compression-moulding (Figure 20.11)
Higgins
Compression Moulded Rubber Tyres
news.alibaba.com
Engineering Materials and Processes

21. 20.5 Shaping plastics (Higgins 20.5)
Injection-moulding (Figure 20.12)
PP crate
Higgins
Engineering Materials and Processes

22. 20.5 Shaping plastics (Higgins 20.5)
Transfer-moulding (Figure 20.13)
Higgins
Thermosets: sinotech.com
Engineering Materials and Processes

23. 20.5 Shaping plastics (Higgins 20.5)
Blow moulding (Figure 20.14)
PE bottle:
Higgins
Engineering Materials and Processes

24. 20.5 Shaping plastics (Higgins 20.5)
Blow moulding by preform (PET)
PET bottles:
Injection Moulded Preform:
Blow Moulding explanation
Engineering Materials and Processes

25. 20.5 Shaping plastics (Higgins 20.5)
Film-blowing (Figure 20.15)
Bags? For making film too.
Higgins
Plastic bag recycling?
Engineering Materials and Processes

26. 20.5 Shaping plastics (Higgins 20.5)
Vacuum-forming (Figure 20.16)
Wikipedia
Higgins
Engineering Materials and Processes

27. 20.5 Shaping plastics (Higgins 20.5)
Casting
Slush-moulding
Dip moulding
Roto Moulding
Roto Moulded 34 kL Polyethylene Tank
Dip Moulding:
Engineering Materials and Processes

28. 20.5 Shaping plastics (Higgins 20.5)
Machined Acrylic
Other:
Machining
Engineering Materials and Processes

29. Videos: Engineering Materials and Processes
1.Plastics in manufacturing [videorecording]   Davis, John.   Warriewood, NSW : Classroom Video, c2003.   
1 videodisc (21 min.) : sd., col. ; 4 3/4 in. + teacher's notes.  Explains injection moulding, rotational moulding, and vacuum and pressure forming of plastic products. DVD  /PLAS
2. Forming of plastics. Part A [videorecording]   Scutt, Don.   Chadstone, Vic. : Double D Technical Productions, c2002.   1 videodisc (29 min.) : sd., col. ; 4 3/4 in. This video examines compression and injection moulding of thermosetting materials, physical properties of polymers and how these vary with temperature changes, compounding, extrusion of sheet tube, cross head and co extrusion, blow moulding, blown film and printing, production of fibres and printing on plastics. DVD  /FORM PART A
3. Forming of plastics. Part B [videorecording]   Scutt, Don.   Chadstone, Vic. : Double D Technical Productions, c2002.   1 videodisc (29 min.) : sd., col. ; 4 3/4 in. This video examines the injection moulding process for a range of products, injection blow moulding, using preforms, production of flexible foams, rotational moulding, extrusion compression moulding, thermoforming and the computer modelling and production of stadium seat. DVD  /FORM PART B
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Engineering Materials and Processes 29

30. Resources. Polymers Wikipedia: Plastic
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Engineering Materials and Processes 30

31. Glossary Compounding Extrusion Cross head and co extrusion
Blow moulding
Blown film
Printing on plastics
Production of fibres
Injection blow moulding
Preforms
Flexible foams
Rotational moulding
Extrusion compression moulding
Thermoforming
Injection moulding
Vacuum and pressure forming
Engineering Materials and Processes

32. Complete Quiz 10104 Polymers
QUESTIONS
Higgins Ch20
Moodle XML: Polymers
Complete Quiz Polymers
Explain what crystallinity means in polymers. Outline the effects of increasing crystallinity in thermoplastic polymers.
Describe the differences between blow moulding processes of PET and PE containers. Referring to the properties of each plastic, explain why the processes are different.
Research the cost of an injection moulding tool for a common object of medium to large size: e.g. milk crate, plastic chair, garbage bin.
A nylon gear can be made by machining or injection moulding. Machining setup is $500 with per part / labour costs of $80/hr. Production is 10 per hour. Injection moulding tooling costs $20000 with running costs of $100/hr. Cycle time is 20 seconds. Determine the break-even quantity.
Engineering Materials and Processes 32