ENMAT101A Engineering Materials and Processes
Associate Degree of Applied Engineering
(Renewable Energy Technologies)
Lecture 20 – Properties of plastics
www.highered.tafensw.edu.au
TAFE NSW -Technical and Further Education Commission
Properties of plastics
Reference Text
Section
Higgins RA & Bolton, 2010. 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
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Properties of plastics
Note: This lecture closely follows text (Higgins Ch20)
Blowmoulded Polycarbonate
http://www.kautex-group.com
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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).
LDPE bottle
promotionsonly.com.au
HDPE bin
bcsplastics.com.au
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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.
Wikipedia/CC BY 1.0
20.2.1 Melting points of polymers
20.2.2 Glass transition temperature
20.2.3 Vicat softening temperature
Higgins
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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. (www.tangram.co.uk).
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
EMMAT101A Engineering Materials and Processes
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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
EMMAT101A Engineering Materials and Processes
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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
EMMAT101A Engineering Materials and Processes
TAFE NSW -Technical and Further Education Commission
20.3 Mechanical properties (Higgins 20.3)
Higgins
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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.
EMMAT101A Engineering Materials and Processes
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20.3 Mechanical properties (Higgins 20.3)
Higgins
EMMAT101A Engineering Materials and Processes
TAFE NSW -Technical and Further Education Commission
20.3 Mechanical properties (Higgins 20.3)
Higgins
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20.3 Mechanical properties (Higgins 20.3)
20.3.2 Hardness tests
Higgins
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20.3 Mechanical properties (Higgins 20.3)
20.3.3 Impact tests
Higgins
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20.3 Mechanical properties (Higgins 20.3)
20.3.4 Creep
Higgins
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20.3 Mechanical properties (Higgins 20.3)
20.3.5 Other mechanical tests
Higgins
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20.4 Additives (Higgins 20.4)
20.4.1 Fillers
20.4.2 Anti-static agents
20.4.3 Flame retardants
20.4.4 Friction modifiers
20.4.5 Other additives
20.4.6 Foamed or 'expanded' plastics materials
Higgins
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20.5 Shaping plastics (Higgins 20.5)
20.5.1 Calendering
Higgins
Calandered PVC fabric: Wikipedia
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20.5 Shaping plastics (Higgins 20.5)
20.S.2 Extrusion
Extruded Plasticised
PVC cable:
Higgins
www.diytrade.com
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20.5 Shaping plastics (Higgins 20.5)
20.5.3 Moulding
Compression-moulding (Figure 20.11)
Higgins
Compression Moulded Rubber Tyres
news.alibaba.com
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20.5 Shaping plastics (Higgins 20.5)
Injection-moulding (Figure 20.12)
http://www.custompartnet.com/estimate/injection-molding/
PP crate
www.woolworths
Higgins
EMMAT101A Engineering Materials and Processes
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20.5 Shaping plastics (Higgins 20.5)
Transfer-moulding (Figure 20.13)
Thermosets: sinotech.com
Higgins
EMMAT101A Engineering Materials and Processes
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20.5 Shaping plastics (Higgins 20.5)
Blow moulding (Figure 20.14)
PE bottle:
http://www.kautex-group.com
Higgins
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20.5 Shaping plastics (Higgins 20.5)
Blow moulding by preform (PET)
Injection Moulded Preform:
www.kenplas.com
PET bottles: www.kenplas.com
Blow Moulding explanation
http://www.kenplas.com/project/pet/petblow.aspx
EMMAT101A Engineering Materials and Processes
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20.5 Shaping plastics (Higgins 20.5)
Film-blowing (Figure 20.15)
Bags? For making film too.
Higgins
Plastic bag recycling?
http://www.occupyforanimals.org
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20.5 Shaping plastics (Higgins 20.5)
Vacuum-forming (Figure 20.16)
Wikipedia
http://czjinlibao.en.made-in-china.com
Higgins
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20.5 Shaping plastics (Higgins 20.5)
20.5.4 Casting
Slush-moulding
Dip moulding
Roto Moulding
Dip Moulding:
Roto Moulded 34 kL Polyethylene Tank
http://www.plasticmouldings.com
http://www.watertankfactory.com.au
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20.5 Shaping plastics (Higgins 20.5)
Machined Acrylic
Other:
Machining
http://www.dotmar.com.au
EMMAT101A Engineering Materials and Processes
TAFE NSW -Technical and Further Education Commission
Videos:
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 668.412/PLAS 35555076215658
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 668.412/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 668.412/FORM PART B
EMMAT101A Engineering Materials and Processes
TAFE NSW -Technical and Further Education Commission
Resources.
Polymers
Wikipedia: Plastic
http://www.kenplas.com/project/pet/petblow.aspx
http://www.dotmar.com.au/engineered-plastics-products.html
http://www.adelaideplastics.com.au/glossary.htm
EMMAT101A Engineering Materials and Processes
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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
EMMAT101A Engineering Materials and Processes
TAFE NSW -Technical and Further Education Commission
QUESTIONS
Higgins Ch20
Moodle XML: 10104 Polymers
1. Complete Quiz 10104 Polymers
2. Explain what crystallinity means in polymers. Outline the effects of increasing
crystallinity in thermoplastic polymers.
3. 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.
4. 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.
5. 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.
EMMAT101A Engineering Materials and Processes
TAFE NSW -Technical and Further Education Commission