Transcript Chapter 7 - Loy Research Group

Chapter 7
Polymer Additives & Fillers &
Blends & Composites
Polymer-Polymer Solutions:
Polymer Blends
• Miscible blends-averaging of properties of two different
materials. Raising the Tg or strength or toughness of a cheap
polymer.
• Immiscible Blends: Composite structures-properties may be
synergistically greater than those of constituent materials
Blends: Thermodynamics
Combinatorial entropic
contribution (usually
can be ignored)
Enthalpic
difference in
solubility:  ≥ 0
Minimize difference in solubility parameters ()
But even small positive  will cause G > 0
Polymer Solubility
• When two hydrocarbons such as dodecane and 2,4,6,8,10pentamethyldodecane are combined, we (not surprisingly)
generate a homogeneous solution:
• It is therefore interesting that polymeric analogues of these
compounds, poly(ethylene) and poly(propylene) do not mix, but
when combined produce a dispersion of one material in the
other.
n
n
Extremely low probability of matching solubilities
Polymer Miscibility (Temp-Composition)
Phase Diagrams
Upper critical solution temperature
Heat up mixture
& entropy rules
This is for Hildebrant
interactions only: No
strong non-bonding
interactions & theta
solvent
Polymer Miscibility (Temp-Composition)
Phase Diagrams: Free Energy
Single Phase Region
Free Energy
Phase separation would
result in a net increase in
energy
Polymer Miscibility (Temp-Composition)
Phase Diagrams: Free Energy
Two Phase Region Free
Energy
Anywhere between 30 & 70%
leads to decomposition to two
phases with 30 & 70% comps.
More phase diagrams:
Between spinoidal limits: spontaneous phases sep.
Between ' and spinoidal limit: kinetics (nucleation) rules
Result of
thermodynamics vs
kinetic control
UCST Plot with spinoidal lines
Effects of Mw (# monomer repeat units)
On Phase Separation
Polymer Miscibility (Temp-Composition)
Phase Diagrams: Strong Non-bonding
Interactions
A new term needs to be added
to free energy equation to
account for non-bonding
interactions
Lower critical solution temperature (LCST)
More Thermodynamics
If we ignore the combinatorial entropic
contributions (ok) then the equation simplifies to:
For solubility GH ≤ 0
or
≥0
Repulsive
Attractive
Lower critical solution temperature
(LCST) Plot for Polystyrene with
Polyvinyl-methyl ether
Miscible Blend based on weak
interactions
Noryl
Some others: PMMA-PEO; PVAPEO, PS-PVME
Some miscible blends
Mini Cooper / Cooper S, radiator grille
& PETE
Miscible Blend
PMMA
PVF
PVF is blended into PMMA to make the latter more resistant to UV
Blends with:
PVA
PMMA
PC
Effects of Blends on Tg
Blends
Immiscible Blends
Controlling Phase segregation
Compositional quenching
Surfactants
block polymers
Compatibilizers (usually a smalll amt of block copolymer)
Nature Materials, 2002, 1, 8 - 10
LCST
SAN-PMMA
Blends composed of separate polymers:
Compositional Quenching
Optical Phase Contrast Microscope
The dark, continuous phase is polymethyl
methacrylate (PMMA). The lighter, irregular regions
are PS. The dark particles inside the PS are PB
PP-NBR Blend
Immiscible
Blends
Using Immiscibility to an Advantage
Completely immiscible
High Impact Polystyrene
Best if the polymers are connected into a block-copolymer
Using Immiscibility to an Advantage
Lining of PET soda bottles
lamellar morphology
1:2 (PTV:PCBM)
1:3 (PTV:PCBM)
1:4 (PTV:PCBM)
1:6 (PTV:PCBM)
1:10 (PTV:PCBM)
C12H25
S
n
Blends are not easy to make:
• Blends are not easy to discover-often copolymers are needed to
make blend with another homopolymer
• Phase separation gets out of hand in immiscible systems
without compatibilizers.
• Some blends must be made with solvent.
Immiscible Blends with 2 homopolymers
HDPE + 30 wt% Nylon 6
EPR + 30 wt% PP
Immiscible Blends with 2 homopolymers can be mixed
But with time coalescence coarsens featues
Immiscible Blends with 2 homopolymers & compatiblizer
LDPE/PS blend without a
compatibilizer
LDPE/PS blend with a
compatibilizer
Block Copolymers
Block Copolymers
Making Hybrid Materials: Class 1E
(Interpenetrating network or IPN)
•Two lightly crosslinked
• Together they are
networks
stronger, tougher than
•Cannot be untangled.
sum of the individual
•Each network has different
polymers = synergistic
mechanical
Properties. All organic IPN adhesives & coatings
POLYMERICS IPNS
Conventional epoxy Networks
Interpenetrating Networks
http://www.polymerics.de/technology/ipn_en.html#vorteile
Simultaneous Interpenetrating network
polymers
•The two networks assembled at the same time
•Phase separation of hard colloidal particles would
ruin IPN
Sequential Interpenetrating networks
•The two networks are not
assembled at the same time
•In this case the inorganic
network is assembled before
the organic
Synthesis of poly(methylphenylsiloxane)/phenylenesilica hybrid material with interpenetrating networks
and its performance as thermal resistant coating
Gao, D. and Jia, M. J. Appl. Polym. Sci. 2012.
Synthesis of poly(methylphenylsiloxane)/phenylenesilica hybrid material with interpenetrating networks
and its performance as thermal resistant coating
Stable > 300 °C
Gao, D. and Jia, M. J. Appl. Polym. Sci. 2012.
doi: 10.1002/app.38372
Tensile
10-20 MPa
Organic–inorganic polymer hybrids based
on unsaturated polyester
•Sol-gel polymerization of phenyltriethoxysilane in
presence of Linear organic polymer
•Photochemical cure of organic network
Journal of Non-Crystalline Solids, 2002, 311, 195–198
Simultaneous Interpenetrating networks:
"Inverse" organic-inorganic composite materials.
Monomer containing
both silica and
organic components
splits apart
Macromolecules, 1991, 24 (19), pp 5481–5483
Simultaneous Interpenetrating networks:
"Inverse" organic-inorganic composite materials.
For a hybrid to be an IPN,
there must be a nonlinear, synergistic effect
on the mechanical
properties
Macromolecules, 1991, 24 (19), pp 5481–5483
Composites
The essence of the concept of composites is that the load is applied
over a large surface area of the matrix. Matrix then transfers the load
to the reinforcement, which being stiffer, increases the strength of the
composite. It is important to note that there are many matrix materials
and even more fiber types, which can be combined in countless ways
to produce just the desired properties.
In the United States, composites manufacturing is a 25 billion dollar
a year industry. There are about 6000 composites related
manufacturing plants and materials distributors across the U.S. The
industry employs more than 235,000 people. An additional 250,000
people are employed in businesses that support the composites
industry, including materials suppliers, equipment vendors, and other
support personnel.
About 90% of all composites produced are comprised of glass fiber and
either polyester or vinylester resin. Composites are broadly known as
reinforced plastics.
Composites
A composite is:
Two or more distinct materials
that interface on a
macroscopic scale
To achieve best
properties not
possessed by any one
acting alone.
56
Composites – Polymer Matrix
Polymer matrix composites (PMC) and fiber reinforced plastics (FRP)
are referred to as Reinforced Plastics. Common fibers used are glass
(GFRP), graphite (CFRP), boron, and aramids (Kevlar). These fibers
have high specific strength (strength-to-weight ratio) and specific
stiffness (stiffness-to-weight ratio)
Matrix materials are usually thermoplastics or thermosets; polyester,
epoxy (80% of reinforced plastics), fluorocarbon, silicon, phenolic.
Composites are all around us
58
Composites have a long use in military
59
A composite has three elements
Reinforcement:
Makes up the ‘skeleton’
which provides
mechanical strength
Matrix:
Binds the
reinforcing fibers
and distributes the
load
Additives / Fillers:
Provide special
attributes not in the base
materials
PETE
HDPE
PP
PS
PVC
PEEK
Wet Out
Sizing
Talc
Chalk
Flowablility
Fire Retardant
60
What makes composites attractive
Reduced weight
Corrosion resistance
High specific strength
and stiffness
High resistance to
chemicals and weathering
(UV)
Good fatigue strength
Functional integration
Energy absorbing
Design flexibility
Durability:
61
Main limitations of composites
Initial expense
Impact strength
High temperature
62
Reinforcement Forms
Woven
perpendicular warp and weft yarns
Glass fiber
E-glass
C-glass
S-glass
Polymer:
Kevlar
Nomex
Carbon (PAN or Pitch)
Ceramic: Si-C, Si3N4, or BN
63
Typical properties of fibers
64
Wood-Polymer Composites
Oriented strand board
Particle Board
Masonite
Pegboard
Composites are used in Commercial Aircraft
66
Application of Composites in
Aircraft Industry
20% more fuel efficiency
and 35,000 lbs. lighter
Properties of Reinforced Plastics
The mechanical properties of reinforced plastics
vary with the kind, shape, relative volume, and
orientation of the reinforcing material, and the
length of the fibers.
Effect of type, length, % volume, and orientation
of fibers in a fiber reinforced plastic (nylon)
Advantages of Composites
Higher Specific Strength (strength-to-weight ratio)
Composites have a higher specific strength than many other
materials. A distinct advantage of composites over other materials is
the ability to use many combinations of resins and reinforcements,
and therefore custom tailor the mechanical and physical properties
of a structure.
The lowest properties for each material are associated with simple
manufacturing processes and material forms (e.g. spray lay-up glass fibre),
and the higher properties are associated with higher technology manufacture
(e.g. autoclave moulding of unidirectional glass fibre), the aerospace industry.
Advantages of Composites
Design flexibility
Composites have an advantage over other materials because they can
be molded into complex shapes at relatively low cost. This gives
designers the freedom to create any shape or configuration. Boats are a
good example of the success of composites.
Corrosion Resistance
Composites products provide long-term resistance to severe chemical
and temperature environments. Composites are the material of choice
for outdoor exposure, chemical handling applications, and severe
environment service.
Advantages of Composites
Low Relative Investment
One reason the composites industry has been successful is because of
the low relative investment in setting-up a composites manufacturing
facility. This has resulted in many creative and innovative companies in
the field.
Durability
Composite products and structures have an exceedingly long life span.
Coupled with low maintenance requirements, the longevity of composites is a
benefit in critical applications. In a half-century of composites development,
well-designed composite structures have yet to wear out.
In 1947 the U.S. Coast Guard built a series of forty-foot patrol boats,
using polyester resin and glass fiber. These boats were used until the
early 1970s when they were taken out of service because the design was
outdated. Extensive testing was done on the laminates after
decommissioning, and it was found that only 2-3% of the original strength
was lost after twenty-five years of hard service.
Disadvantages of Composites
Composites materials are difficult to inspect with conventional
ultrasonic, eddy current and visual NDI methods such as radiography.
American Airlines Flight 587, broke apart
over New York on Nov. 12, 2001 (265 people
died). Airbus A300’s 27-foot-high tail fin
tore off. Much of the tail fin, including the
so-called tongues that fit in grooves on the
fuselage and connect the tail to the jet,
were made of a graphite composite. The
plane crashed because of damage at the
base of the tail that had gone undetected
despite routine nondestructive testing and
visual inspections.
Disadvantages of Composites
Composites are heterogeneous
properties in composites vary from point to point in the material. Most
engineering structural materials are homogeneous.
Composites are highly anisotropic
The strength in composites vary as the direction along which we
measure changes (most engineering structural materials are isotropic).
As a result, all other properties such as, stiffness, thermal expansion,
thermal and electrical conductivity and creep resistance are also
anisotropic. The relationship between stress and strain (force and
deformation) is much more complicated than in isotropic materials.
The experience and intuition gained over the years about the behavior of
metallic materials does not apply to composite materials.