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Unit-2

Various Polymers

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1

Polymer Structure

Plastics 001

2

Properties:

• medium - high mechanical strength, hardness, rigidity
• high mechanical damping characteristics
• good fatigue strength
• very good wear resistance
• good sliding properties

Polyamide (PA)

Polymer Structure

Plastics 001

Polyamide (Nylon 6-6)

3

• Crystalline – Yes, very flexible
• Hygroscopic – Yes (O and N)
• Glass Transition – Low (135 F)
• Flammability – Varies depending on additives, but will usually self extinguish because of N

Polymer Structure

Plastics 001

4

Applications:

• They are used in the manufacture of rope, thread, belts, brushes, sports equipments etc.
• They are used in the manufacture of rollers, slides, umbrellas, electrical wire jackets.
• used in the manufacture of flexible adhesives for bread wrappers, dried soup packets and book binding

Polymer Structure

Plastics 001

5

Polyimide (PI)

Properties:

• High thermal stability
• Light weight and flexible
• Good chemical resistance
• Excellent mechanical properties
• Characteristic orange/yellow color
• Typical polyimide parts are not affected by commonly used solvents and oils — including hydrocarbons, esters, ethers, alcohols and freons
• They also resist weak acids but are not recommended for use in environments that contain alkalis or inorganic acids

Polymer Structure

Plastics 001

6

Applications:

• They are used in the electronics industry for flexible cables, as an insulating film on magnet wire and for medical tubing
• The semiconductor industry uses polyimide as a high-temperature adhesive
• as an insulating and passivation layer in the manufacture of digital semiconductor and MEMS chips
• The polyimide layers have good mechanical elongation and tensile strength, which also helps the adhesion between the polyimide layers or between polyimide layer and deposited metal layer
• Polyimide powder can be used to produce parts and shapes by sintering technologies

Polymer Structure

Plastics 001

7

Polyamide-imide (PAI)

Properties:

• Good mechanical properties
• High strength
• Melt processibility
• Exceptional high heat capability
• Broad chemical resistance
• Polyamide-imide polymers can be processed into a wide variety of forms – from injection or compression molded parts and ingots – to coatings, films, fibers and adhesives

Polymer Structure

Plastics 001

8

Applications:

• The high temperature and chemical resistance of polyamide-imides make them ideal candidates for membrane based gas separations
• Polyamide-imides are commercially used for coatings as a magnet wire enamel
• They are used for molded articles

Polymer Structure

Plastics 001

Arrangement + Effects

Chlorine is a large atom and tends to separate from the carbon chain when stresses are present like heat and shear.

When it separates from the main chain, the Chlorine forms free radicals that are very flame retardant. Polyvinyl Chloride (PVC) will only burn if a flame is held to it. Once removed, the material will self-extinguish.

The large Chlorine atom also makes the polymer more dense, which is a disadvantage when plastic materials are bought by weight and sold by volume.

The Chlorine is not all bad though, it serves to protect

the main polymer chain from chemical attack, this

is one reason why PVC is used in piping.

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9

Polymer Structure

Plastics 001

10

Polyvinylchloride (PVC)

Properties:

• PVC has high hardness and mechanical properties
• High elastic modulus
• The heat stability of PVC is very poor, when the temperature reaches 140 °C PVC starts to decompose
• Its melting temperature is 160 °C
• PVC is a polymer with good insulation properties

Polymer Structure

Plastics 001

Polyvinylchloride

11

• Crystalline – No, rigid (Cl to big to allow)
• Hygroscopic – No (not O or N)
• Glass Transition – High (185 F)
• Flammability – No (Cl puts out)

Polymer Structure

Plastics 001

12

Applications:

• It is used for sewerage pipes and other pipe applications where cost or vulnerability to corrosion limit the use of metal
• it is a popular material for window and door frames
• By adding plasticizers, it can become flexible enough to be used in cabling applications as a wire insulator
• PVC has become widely used in clothing, to either create a leather-like material
• PVC fabric has a sheen to it and is waterproof so is used in coats, skiing equipment, shoes, jackets, aprons, and bags
• It is also used in medical equipment and flooring

Polymer Structure

Plastics 001

Polystyrene

13

• Crystalline – No (Benzene ring makes it too rigid)
• Hygroscopic – No (not O or N)
• Glass Transition – High (210 F)
• Flammability – Yes only C-H bonds

Polymer Structure

Plastics 001

Arrangement + Effects

Chain Flexibility – Side Groups

Having a Benzene ring attached to one side of the chain will greatly affect the stiffness. Polystyrene is very stiff to the point of being brittle (CD cases)

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14

Polymer Structure

Plastics 001

Polyethylene terephthalate (PET)

15

• Crystalline – Yes, flexible enough
• Hygroscopic – Yes (O)
• Glass Transition – Low (155 F)
• Flammability – Yes (only C-H and C=O bonds)

Polymer Structure

Plastics 001

Arrangement + Effects

Chain Flexibility – Types of Bonds

Having a benzene ring in the main chain can add stiffness to it. It depends a lot on what else is present in the monomer.

For example: Polycarbonate has two benzene rings in the main chain separated by a Carbon with two methyl groups (CH3) attached. This structure is very rigid. Polyester Has a benzene ring in the main structure, but also has an Oxygen and a few Carbon-Hydrogen bonds to allow it to be flexible when there is adequate room to move.

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16

PC

Rigid

PET

Flexible

when hot

Polymer Structure

Plastics 001

17

Properties:

• The most important mechanical properties of ABS are impact resistance and toughness
• ABS polymers are resistant to aqueous acids, alkalis, concentrated hydrochloric and phosphoric acids, alcohols and animal, vegetable and mineral oils,
• They are swollen by glacial acetic acid, carbon tetrachloride and aromatic hydrocarbons and are attacked by concentrated sulfuric and nitric acids.
• They are soluble in esters, ketones, ethylene dichloride and acetone
• ABS is flammable when it is exposed to high temperatures, such as a wood fire

ABS is also damaged by sunlight

Acrylonitrile butadiene styrene (ABS)

Polymer Structure

Plastics 001

18

Applications:

• Musical instruments (recorders, plastic clarinets, and piano movements), golf club heads (due to its good shock absorbance)
• Automotive trim components, automotive bumper bars
• Medical devices for blood access
• Enclosures for electrical and electronic assemblies
• Household and consumer goods are the major consumers of acrylonitrile butadiene styrene
• ABS is also commonly used in rapid prototyping extrusion-based 3D printers.

Polymer Structure

Plastics 001

19

Poly(p-phenylene oxide) (PPO) or poly(p-phenylene ether) (PPE) 

Properties:

• PPE is an amorphous high-performance plastic
• It is rarely used in its pure form due to difficulties in processing
• The glass transition temperature is 215 °C, but it can be varied by mixing with polystyrene
• Through modification and the incorporation of fillers such as glass fibers, the properties can be extensively modified
• High-temperature resistant plastic.

Applications:

PPE blends are used for structural parts, electronics, household and automotive items that depend on high heat resistance, dimensional stability and accuracy

 They are also used in medicine for sterilizable instruments made of plastic

Polymer Structure

Plastics 001

20

Poly(p-phenylene sulfide) (PPS)

Properties:

• Resists chemicals
• Resists thermal attack
•  PPS has not been found to dissolve in any solvent at temperatures below about 200 °C 
• Resists dyeing
•  PPS can be molded, extruded, or machined to high tolerances
• In its pure solid form, it may be opaque white to light tan in color

Applications:

• PPS is used to make filter fabric for coal boilers,papermaking felts, electrical insulation, specialty membranes, gaskets, and packings
•  PPS is used in applications ranging from automotive engine mounts to hair straightener housings, and hard disk drive components to chemical pumps

Polymer Structure

Plastics 001

21

Properties:

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PEEK is a semicrystalline thermoplastic with excellent mechanical and chemical resistance properties

 It is highly resistant to thermal degradation as well as attack by both organic and aqueous environments

It is attacked by halogens as well as some halogenated compounds and aliphatic hydrocarbons at high temperatures

 It dissolves completely in concentrated sulfuric acid at room temperature 

Polyether ether ketone (PEEK)

Polymer Structure

Plastics 001

22

Applications:

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Because of its robustness, PEEK is used to fabricate items used in demanding applications, including bearings, piston parts, pumps, compressor plate valves, and cable insulation

 It is one of the few plastics compatible with ultra-high vacuum applications

PEEK is considered an advanced biomaterial used in medical implants

 It is finding increased use in spinal fusion devices and reinforcing rods

 It is extensively used in the aerospace, automotive and chemical process industries

Polymer Structure

Plastics 001

23

Polytetrafluoroethylene (PTFE)

Properties:

• PTFE is a thermoplastic polymer, which is a white solid at room temperature
•  It maintains high strength, toughness and self-lubrication at low temperatures down to 5 K 
• The only chemicals known to affect these carbon-fluorine bonds are certain alkali metals and most highly reactive fluorinating agents
•  PTFE is so slippery that they can be used to prevent insects climbing up surfaces painted with the material

Polymer Structure

Plastics 001

24

Applications:

• The major application of PTFE, consuming about 50% of production, is for wiring in aerospace and computer applications
• Another major application is for fuel and hydraulic lines, due to its low resistance against flowing liquids
• In industrial applications, owing to its low friction, PTFE is used for applications where sliding action of parts is needed: plain bearings, gears,slide plates, etc
• PTFE (Teflon) is best known for its use in coating non-stick frying pans and other cookware, as it is hydrophobic and possesses fairly high heat resistance
• PTFE membrane filters are among the most efficient used in industrial air filtration applications

Polymer Structure

Plastics 001

25

Urea

Properties:

•  It is a colorless, odorless solid, highly soluble in water and practically non-toxic
• By virtue of its tendency to form a porous frameworks, urea has the ability to trap many organic compounds
• Urea can be irritating to skin, eyes, and the respiratory tract
• The substance decomposes on heating above melting point, producing toxic gases, and reacts violently with strong oxidants, nitrites, inorganic chlorides, chlorites and perchlorates, causing fire and explosion

Polymer Structure

Plastics 001

26

Applications:

• Urea is widely used in fertilizers as a convenient source of nitrogen.
• Urea is a raw material for the manufacture of many important chemical compounds, such as various plastics, especially the urea-formaldehyde resins and various adhesives, such as urea-formaldehyde or the urea-melamine-formaldehyde used in marine plywood
• Urea can be used to make urea nitrate, a high explosive that is used industrially and as part of some improvised explosive devices
• Urea is used to reduce the NO_x pollutants in exhaust gases of combustion from Diesel, dual fuel, and lean-burn natural gas engines
• An ingredient in many tooth whitening products
• An ingredient in dish soap
• As a solubility-enhancing and moisture-retaining additive to dye baths for textile dyeing or printing

Polymer Structure

Plastics 001

27

Phenol Formaldehyde resin

Properties:

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•  It is smooth and has lustrous surface.
• Usually it seems hard and rigid, with good dimensional stability.
• It may be brittle in thin sections with low impact strength.
• It is very easy to mould.
• Phenolic resin retains its properties at freezing temperatures.
• Phenol formaldehyde have Improved strength and Improved impact resistance
• Good flame resistance
• Produces less smoke
• High strength-to-weight ratio
• It is creep resistant
• It is resistant to corrosion

Polymer Structure

Plastics 001

28

Applications:

• Space, Aerospace & Defense Composites in ablative liners
• Carbon-Carbon Composites
• Prepregging applications
• Phenolic resins are mainly used in the circuit board production
• Used in engine ignition equipment

Polymer Structure

Plastics 001

29

Polymer Structure

Plastics 001