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Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials...

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POLYMERS Prof. Amita Chaudhary
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Page 1: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

POLYMERS

Prof. Amita Chaudhary

Page 2: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more
Page 3: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

Molecular Structure of Polymers• Linear

• High Density Polyethylene (HDPE), PVC, Nylon, Cotton

• Branched

• Low Density

Polyethylene (LDPE)

• Cross-linked

• Rubber

• Network

• Kevlar, Epoxy

Page 4: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

COPOLYMERS

Page 5: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

TACTICITY(Arrangement Of Side groups)

Page 6: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

Geometrical isomerism of Polymers

• Configuration

The two types of polymer configurations are cis and trans.

These structures can not be changed by physical means (e.g. rotation).

The cis configuration arises when substituent groups are on the same side of a

carbon-carbon double bond.

Trans refers to the substituents on opposite sides of the double bond.

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Conformation

• Conformation refers to order that arises from the rotation of molecules

about the single bonds:

• thermal fluctuation of the bond length (3%) and bond angle (3-5°) are small

at room temperature

• rotations around the bonds are well possible

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COORDINATION POLYMERISATION

(Insertion polymerisation)

Zeigler – Natta catalyst

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Ziegler-Natta Catalysis

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Polymerization of propylene through action of the titanium

catalyst gives an isotactic product; whereas, a vanadium

based catalyst gives a syndiotactic product.

Page 12: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

BIOPOLYMERS1. Starch

• Starch or amylum is a carbohydrate consisting of a large number of glucose units joined by

glycosidic bonds.

• It is a polysaccharide comprising glucose monomers joined in α 1,4 linkages.

• A white, granular, organic chemical that is produced by all green plants.

• A soft, white, tasteless powder that is insoluble in cold water, alcohol, or other solvents.

• The basic chemical formula of the starch molecule is (C6H10O5)n.

• The simplest form of starch is the linear polymer amylose; amylopectin is the branched

form.

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α-1,4-glycosidic bonds

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2. Cellulose- A polysaccharide consisting of a linear chain of several hundred to many thousands of β

linked D-glucose units.

- Formula: (C6H10O5)n

- Non- reducing carbohydrate.

- Insoluble in water.

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Polymer Composite materials

Chapter-4

Page 16: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

COMPOSITES

-Composite materials are engineered materials made from two or more

constituent materials that remain separate and distinct while forming a single

component

-Generally, one material forms a continuous matrix while the other provides the

reinforcement.

- The two materials must be chemically inert with respect to each other so no

interaction occurs upon heating until one of the components melts, an exception

to this condition is a small degree of inter diffusion at the reinforcement-matrix

interface to increase bonding

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COMPOSITES

Can you think of any examples of where composites are used?

Page 18: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

COMPOSITES

Composites can be found in:

-Boat hulls

-The aerospace industry (structural components as well as engines and motors)

-Automotive parts (panels, frames, dashboards, body repairs)

-Sinks, bathtubs, hot tubs, swimming pools

-Cement buildings, bridges

-Surfboards, snowboards, skis

-Golf clubs, fishing poles, hockey sticks

-Trees are technically composite materials, plywood

-Electrical boxes, circuit boards, contacts

-Everywhere

Page 19: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

CONSTITUENTS OF COMPOSITES• Composite materials consist of two phases:

(i) Body constitutes or matrix phase

(ii) Structural constituents or dispersed phase or reinforcing materials

I. The properties of the constituents phases.

II. Concentration of constituents.

III. Their distribution and orientation.

For example:

Fibre glass reinforced plastic : Matrix- Plastic

Dispersed phase- fibre glass

Dispersed phase

Matrix

(continuous phase)

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COMPOSITES

Composites can be classified by their matrix material which include:

-Metal matrix composites (MMC’s)

-Ceramic matrix composites (CMC’s)

-Polymer matrix composites (PMC’s) or sometimes referred to as organic

matrix composites (OMC’s)

(Polyamide(nylons), phenolics, epoxy, polysulphones and silicons)

Page 21: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

Functions of matrix phase

Binds the reinforcing material

Protect the dispersed phase

Acts as a medium by which an externally applied load is transmitted and

distributes through the dispersed phase

Prevent from propagation of cracks by virtue of its relative softness and

plasticity

Properties of good matrix

Should be ductile

High bonding Strength with dispersed phase

Elastic modulus should be lower than dispersed phase

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The dispersed phase (reinforcement)

Dispersed Phase

Fibre Particulate Flakes Whiskers

Glass Fibres Carbon Fibre Aramid Fibre

Page 23: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

TYPES OF FIBERS

Some commonly used fibers for polymer matrix composites:

-Glass fibers

-Carbon fibers

-Aramid fibers

Fibre: Any polymer metal or ceramic that is drawn into long and thin filament.

Characterstics:

• High length to diameter ratio ( aspect ratio)

• High tensile strength and stiffness.

Page 24: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

GLASS FIBERS

Produced by forcing out a melt glass through a small orifices and rapidly

pulling with subsequent cooling. Individual glass fiber called

monofilaments having diameter around 10µm.

Characteristics:

1. Chemically inert.

2. Very high strength.

3. Can be easily drawn into fibre.

4. Readily available and low cost.

5. Used in continuous form in catalyst activated thermosetting resins.

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CARBON FIBERS-Carbon fibers are produced by pyrolysis of organic polymers such as about 90%

of the carbon fiber produced are made from polyacrylonitrile (PAN) and remaining

10% are made from rayon or petroleum pitch in an inert atmosphere.

monofilaments have diameter in the range of 5-10µm.

-High specific strength and stiffness

-Good resistance to moisture, acids, bases

“Carbon fiber composites are five times stronger than 1020 steel yet five times

lighter. In comparison to 6061 aluminum, carbon fiber composites are seven times

stronger and two times stiffer yet still 1.5 times lighter”

-Initially used exclusively by the aerospace industry they are becoming more and

more common in fields such as automotive, civil infrastructure, and paper

production.

Page 26: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

ARAMID FIBERS

They are aromic polyamides (aramides) i.e. Nomex and

Kevlar.

Kevlar is p-phenylene terephthalamide. It is spun from a nematic liquid crystalline solution

using a jet wet spinning technique using sulphuric acid as solvent and cold water as

coagulant.

-They have the highest level of specific strength of all the common fibers.

- Retain mechanical properties in a wide temperature range (-200 to +200 0C).

-They are commonly used when a degree of impact resistance is required such as in ballistic

armour

- High tensile strengths and tensile moduli

- Resistant to combustion and stability at high temperature

- But prone to degradation by strong bases and acids.

- Weak in compression.

Page 27: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

Particulates

Dispersed phase in particulate composites consists of particles

(metallic and non metallic)

- Improved performance at high temperature

- Wear and abrasion resistance

- Improved thermal and electrical conductivities

- Surface hardness is increased.

- Reduction in cost, shrinkage and friction.

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Flakes

Two dimensional geometry.

Provide equal strength in all directions in their plane.

Mica flakes are used in electrical and heat insulating applications.

Whiskers

Very thin single crystals with high aspect ratio.

Show a high degree of crystalline perfection

High strength

Graphite, silicon carbide, silicon nitride and aluminium oxide.

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COMPOSITES

PARTICLE REINFORCED

LARGE PARTICLE

DISPERSION STRENGTHENED

FIBRE REINFORCED

CONTINUOUS

GLASS FIBRES

CARBON FIBRES

ARAMID FIBRES

DISCONTINUOUS

ALIGNGED

RANDOMLY ORIENTED

STRUCTURAL

LAMINAR

SANDWICH PANELS

Page 30: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

FIBRE REINFORCED COMPOSITES

(FRC)Property of FRC are affected by:

Length of fibers

Orientation of fibers

Concentration of fibers

1. Fibers length:

𝑙𝑐 = 𝑑𝜎𝑓

𝑇𝑐

Where:

𝑙𝑐 = Critical length of fiber

d = Fiber diameter

𝜎𝑓 = Tensile strength

𝑇𝑐 = Bond strength of matrixNote:

If 𝑙 >> 𝑙𝑐 or 𝑙 > 15𝑙𝑐 then the fibers are continuous fibers

If 𝑙 < 𝑙𝑐 , discontinuous or short fibers.

Generally length of the fiber is in the range of 20-150 time its diameter

The minimum length at which the center of the

fiber reaches the ultimate (tensile) strength sf,

when the matrix achieves the maximum shear

strength tm:

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Laminar composite structure – conventional

Sandwich structure

Honeycomb sandwich structure

Structural Composite

Page 33: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

ADVANCED POLYMERIC MATERIALS1. Polythene or polyethylene

- Low density polythene (LDPE)

It has branched structure

- High density polythene (HDPE)

It has a linear structure.

2. Saran:

- It is a copolymer of vinylidene chloride and vinyl chloride.

- As protective wrap for food.

Page 34: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

Polyethylene or polytheneLow Density Polythene (LDP)

• Reaction involved:

n CH2=CH2

• Chemically inert, flexible, and poor

conductor of electricity.

• Used in insulation of electric wires, for

making squeeze bottles, toys and pipes.

High Density Polythene (HDP)

• Reaction involved:

n CH2=CH2 -(CH2-CH2-)n

• Chemically inert, tough and hard, high

tensile strength.

• Used in the manufacture of container,

bottles, housewares, etc.

350 – 570 K

1000 – 2000 atm,

traces of O2

330-350K

Zeigler – Natta

catalyst

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3. Polyamide – Kevlar- Heating 1,4-benzenediamine and the acylchloride of benzene-1,4-dicarboxylic acid gives

the aramid Kevlar with loss of HCl.

- Used to make bullet-proof vests, protective helmets.

Page 36: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

4. Polycarbonates – Lexan- Clear transparent, strong, and impact-resistant plastic

- Used

- Protective and everyday eye glasses

- CDs and DVDs

- Mobile phones

- Automobile dash panels and headlight and taillight lenses

- Helmets of Apollo-11 astronauts

Page 37: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

6. Polyethylene Terephthalate (PET)- A linear thermoplastic polyester

- Formed from monomers terephthalic acid and ethylene glycol

- Used in food packaging, soft-drink bottles, photographic films, audio tapes, video tapes

- PET + cotton/wool give better wash/wear and crease-resistant properties to textiles.

Page 38: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

Cyclist wearing a pair of spandex shorts and a cycling jersey

Polyurethanes:(-NHCOO-)- A major use in spandex fibers

- In athletic wear, paints, adhesives and foams.

Page 39: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

Conductive Polymers

- Electrically conductive polymer contain electron donor and

electron acceptor groups.

- First conductive polymer- Polyacetylene

- Polyaniline (PAN), polypymole, polythiophene and poly(p-

Phenylene)

- Used in sensors, laser printing, solar cells, batteries etc.

Page 40: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

Uses of Conductive polymers

1.Electrochromic displays

2.Polymeric electrodes for light weight batteries.

3.Coating

4.Sensors

5.Polymeric ferroelectric RAM

6.Artificial nerves, Brain cells.

7.Laser printing

8.Conductive adhesives.

Page 41: Polymer Composite materials - WordPress.com · 2016. 10. 21. · Polymer Composite materials Chapter-4. COMPOSITES-Composite materials are engineered materials made from two or more

8. Liquid Crystal Polymers (LCP)- Have highly aromatic structures. Ex: Vectra

- Used in electronic components, aerospace applications.

9. Epoxy Resins- basically polyether

- Obtained by condensation of epichlorohydrin with diphenylol propane.

- Used in surface- coating materials.

10. Thermocole It is a foamed-plastic, obtained by blowing air or gas through molten polystyrene or

polyurethane.

Light, strong and chemically inert.

Used as shock-proof material.

Compressive strength is 117-145 kg/cm2.

Can be used up to 55 0C.

Used for packing materials, insulation, protecting screens in radar and decorative

purposes

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