Transcript Further material properties 1

Further material properties 1
BADI 1
J. L. Errington MSc
Important kinds of engineering materials
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Metals
Ceramics
Polymers
Composites
Properties of materials 1:Metals
Metal
Density
Young’s
modulus
Shear
modulus
Poisson’s
ratio
Yield Stress
Ultimate
Stress
Elongation
Alumimium
2.7
70
26
0.33
20
70
60
Al Alloy
2.7
80
28
0.33
35 - 500
100-550
1 - 45
Brass
8.6
100
39
0.33
70 - 550
200-600
4 - 60
Bronze
8.2
110
40
0.33
80 - 690
200-830
5 - 50
Cast Iron
7.2
80 - 170
60
0.2 – 0.3
120 -290
70-480
0-1
Mag Alloy
1.7
45
17
0.35
80 - 280
140-340
2 - 20
Solder
9
20 - 30
12 - 54
5 - 30
Steel
7.8
200
80
0.3
340-1900
3 - 40
Ti Alloy
4.5
110
40
0.33
960
10
280-1600
Properties of materials 2: non-metals
Material
Density
Mg/m3
Young’s modulus
GPa
Poisson’s
ratio
Brick (compression)
1.8 – 2.4
10 - 24
Concrete
2.4
18 - 30
0.1 – 0.2
Glass
2.6
48 - 83
0.2 – 0.27
Nylon
1.1
2.1 – 2.8
0.4
Stone: Granite
(compression)
2.6
40 - 70
0.2 – 0.3
70 – 280
Stone: Marble
(compression)
2.8
50 - 100
0.2 – 0.3
50 - 180
Wood: Ash
(Bending)
0.6
10 - 11
40 - 70
50 - 100
Wood: Oak
(Bending)
0.7
11 - 12
40 - 60
50 - 100
Wood: Pine
(Bending)
0.6
11 - 14
40 - 60
50 - 100
Yield Stress MPa
Ultimate Stress
MPa
7 - 70
230 - 380
40 - 70
1. flexible thermoplastics
• Polyethylene
• Polypropylene
• Capable of large
plastic deformations
2. rigid thermoplastics
• Polystyrene
• Polyvinyl chloride
• Polycarbonate
3. rigid thermosets
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Epoxies (EP)
Phenolics e.g. PF
Polyimides
Hard and stiff due to
cross-linking
• Doesn’t soften with heat
• Resistant to chemicals
4. elastomers or rubbers
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Polyisoprene
Polybutadiene
Polyisobutylene
Polyurethanes
Impact resistance
The first elastomer
There was a time long past when the only rubber we had was natural rubber
latex, polyisoprene. Straight out of the tree, natural rubber latex isn't good for
much. It gets runny and sticky when it gets warm, and it gets hard and brittle
when it's cold. Tires made out of it wouldn't be much good unless one lived in
some happy land where the temperature was seventy degrees year round. A
long time ago...how long, you ask? It was about a hundred and sixty years ago,
1839 to be exact. This was before there were any cars to need tires, but the
idea of a useable rubber was still attractive. One person trying to make rubber
more useful was named Charles Goodyear, a tinkerer and inventor, and by no
means a successful one at this point. While goofing around in his kitchen with a
piece of fabric coated with a mixture of rubber latex, sulfur and a little white
lead, he accidentally laid it on a hot stove top. It began sizzling like a mass of
really smelly bacon or (strangely enough) burning rubber. Wouldn't you know,
when he took a look at this mass of rubber, he found it wouldn't melt and get
sticky when it was heated, nor would it get brittle when he left it outside
overnight in the cold Massachusetts winter. He called his new rubber
vulcanized rubber.
Tying it All Together
What had happened here? What did the sulfur do to the rubber? What it did was it
formed bridges. Which tied all the polymer chains in the rubber together. These are
called crosslinks. You can see this in the picture below. Bridges made by short
chains of sulfur atoms tie one chain of polyisoprene to another, until all the chains
are joined into one giant supermolecule.
Yes, folks, this means exactly what you think it does. An object made of a
crosslinked rubber is in fact one single molecule. A molecule big enough to pick
up in your hand.
These crosslinks tie all the polymer molecules together. Because they are tied
together, when the rubber gets hot, they can't flow past each other, nor around
each other. This is why it doesn't melt. Also, because all the polymer molecules are
tied together, they aren't easily broken apart from each other. This is why the
Charles Goodyear's vulcanized rubber doesn't get brittle in when it gets cold.
We can look at what's going on conceptually, and take a look at the bigger picture.
The drawing below shows the difference between a lot of single uncrosslinked
polymer chains, and a crosslinked network.
Polymerization of isoprene
Other elastomers
• Other kinds of rubber, which chemists
call elastomers that are crosslinked
include:
• Polybutadiene
• Polyisobutylene
• Polychloroprene
Crosslinked polymers - thermosets
Plastics are also made stronger by crosslinking. Formica is a crosslinked
material.
Crosslinked polymers are molded and shaped before they are crosslinked.
Once crosslinking has taken place, usually at high temperature, the object can
no longer be shaped. Because heat usually causes the crosslinking which
makes the shape permanent, we call these materials thermosets. This name
distinguishes them from thermoplastics, which aren't crosslinked and can be
reshaped once molded.
Interestingly, the first thermoset was again polyisoprene. The more sulphur
crosslinks you put into the polyisoprene, the stiffer it gets. Lightly crosslinked,
it's a flexible rubber. Heavily crosslinked, it's a hard thermoset.
Other crosslinked thermosets include:
Epoxy resins
Polydicyclopentadiene
Polycarbonates
Cross-linking
Environmental Stress Cracking and Crazing (ESC)
Some polymers, when stressed, are affected by contact
with certain chemical substances.
ESC describes a slow brittle failure in stressed polymers by
organic substances. For example PVC exposed to certain
hydrocarbon impurities may crack and PS in contact with
organic liquids may develop crazes.
Crazed materials retain considerable strength but crazing
may precede cracking.
In both ESC and crazing, damage arises from
simultaneous action of a substance and environmental
stress. The resistance of a polymer to ESC failure depends
on structural factors; for example, PE's resistance varies
with molar mass, melt flow index, crystallinity and density.
Common engineering polymers
XPS
HIPS
SAN
ABS
PMMA
MBS
RPVC
CPVC
PVDC
PB
LDPE
LLDPE
HDPE
HMWHDPE
LCP
PAS
PAEK
PC/ABS
PEEK
PEI
PEKEKK
PES
POM
PPA
Polystyrene Crystal
High Impact Polystyrene
Styrene Acrylonitrile Copolymer
Acrylonitrile Butadiene Styrene
Polymethylmethacrylate (Acrylic)
Polymethacrylate Butadiene Styrene
Rigid Polyvinyl Chloride
Chlorinated Polyvinyl Chloride
Polyvinylidene Chloride
Polybutylene
Low Density Polyethylene
Low Linear Density Polyethylene
High Density Polyethylene
High Molecular Weight HDPE
Liquid Crystal Polymer
Polyarylsulfone
Polyaryletherketone
Polycarbonate/ABS Alloy
Polyetheretherketone
Polyetherimide
Polyetherketoneetherketoneketone
Polyethersulfone
Acetal
Polyphtalamide
PPE
Phenylene Ether Copolymer
PPS
Polyphenylene Sulfide
PSO
Polysulfone
PUR
Polyurethane Plastic Rigid
TPI
Polyimide
PP
Polypropylene Homopolymer
PP/Co
Polypropylene Copolymer
PP/Talc Polypropylene 40% Talc Filled
PP/Glass f Polypropylene 30% Glass Filled
EVA
Ethylene Vinyl Acetate
In
Ionomers (Surlyn)
CP
Cellulose Acetate Propionate
TPU
Thermoplastic Polyurethane
TPO
Thermoplastic Elastomer Polyolefin
TP
Thermoplastic Elastomer Polyester
PA6
Polyamide (Nylon) 6
PA66
Polyamide (Nylon) 66
PA11
Polyamide (Nylon) 11
PA12G Polyamide 12, 30% glass filled
PA66M Polyamide 66, 40% mineral filled
PBT
Polybutylene Terephtalate
PET
Polyethylene Terephtalate
PETG
Polyethylene Terephtalate Glycol
PC
Polycarbonate
PVDF
Polyvinyldene Fluoride
Resources
http://www.pslc.ws/mactest/maindir.htm
Macrogalleria - all about polymers!
http://www.plasticstechnology.com/dp/materials/ polymer database
http://www.matweb.com/ searchable database of materials (includes articles)
http://www.azom.com/default.asp searchable database of materials
http://www.goodfellow.com/csp/active/gfHome.csp periodic table of elements
with links to properties
http://www.goodfellow.com/csp/active/gfMaterials.csp alphabetic access by
name to properties of materials of all descriptions
http://www.bpf.co.uk/bpfindustry/plastics_materials.cfm?printable=yes
Good resource about different plastics
http://www.theotherpages.org/abbrev.html abbreviations for plastics
http://mysite.freeserve.com/designandtech/Materials_Database.xls