1 Polymers Chapter 8- Part 1 Manufacturing Processes, 1311 Dr Simin Nasseri Southern Polytechnic...

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PolymersChapter 8- Part 1

Manufacturing Processes, 1311

Dr Simin Nasseri

Southern Polytechnic State University

Manufacturing ProcessesProf Simin Nasseri

POLYMERS

Fundamentals of Polymer Technology Thermoplastic Polymers Thermosetting Polymers Elastomers Guide to the Processing of Polymers


Polymer

A compound consisting of long‑chain molecules, each molecule made up of repeating units connected together

There may be thousands, even millions of units in a single polymer molecule

The word polymer is derived from the Greek words poly, meaning many, and meros (reduced to mer), meaning part

Most polymers are based on carbon and are therefore considered organic chemicals


Natural polymers!

Natural Polymer: Silk fiber is produced by silk worms in a

cocoon, to protect the silkworm while it

metamorphoses in a moth.

The gooey liquid in okra, is a natural polymer used as a food thickener for thousands of years!


A tire is actually one giant network molecule, a molecule so big it takes two hands to pick it up!

A bowling ball contains only one molecule, too.

Polymer


Types of Polymers

Polymers can be separated into plastics and rubbers.

As engineering materials, it is appropriate to divide them into the following three categories:

1. Thermoplastic polymers

2. Thermosetting polymers

3. Elastomers

Plastics

Rubbers


Thermoplastic Polymers - Thermoplastics

Solid materials at room temperature but viscous liquids when heated to temperatures of only a few hundred degrees

About 70% of the tonnage of all synthetic polymers produced

This characteristic allows them to be easily and economically shaped into products

They can be subjected to heating and cooling cycles repeatedly without significant degradation

Symbolized by TP


Thermoplastic polymers

Milk bottleSoft drink bottles

Cafeteria trays


Thermosetting Polymers - Thermosets

Cannot tolerate repeated heating cycles as thermoplastics can

When initially heated, they soften and flow for molding

Elevated temperatures also produce a chemical reaction that hardens the material into an infusible solid

If reheated, thermosets degrade and char rather than soften

Symbolized by TS


Thermosetting Polymers

Plugs, Sockets and lamp holders


Elastomers (Rubbers)

Polymers that exhibit extreme elastic extensibility when subjected to relatively low mechanical stress

Although their properties are quite different from thermosets, they share a similar molecular structure that is different from the thermoplastics

Some elastomers can be stretched by a factor of 10 and yet completely recover

to their original shape!Wow !!


Elastomers

Rubbers, elasticsTire (Synthetic rubber)

Gloves (Natural rubber)


Examples of Polymers

Thermoplastics:

Polyethylene (PE), polyvinylchloride (PVC), polypropylene (PP), polystyrene, and nylon

Thermosets:

Phenolics, epoxies, and certain polyesters

Elastomers:

Natural rubber (vulcanized)

Synthetic rubbers, which exceed the tonnage of natural rubber

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Why are polymers important?


Reasons Why Polymers are Important:

Plastics can be molded into complex part shapes, usually with no further processing Very compatible with net shape

processing

On a volumetric basis, polymers: Are cost competitive with metals Generally require less energy to

produce than metals

Certain plastics are translucent and/or transparent, which makes them competitive with glass in some applications


General Properties of Polymers

Low density relative to metals and ceramics Good strength‑to‑weight ratios for certain (but

not all) polymers High corrosion resistance Low electrical and thermal conductivity


Limitations of Polymers

Low strength relative to metals and ceramics

Low modulus of elasticity (stiffness)

Service temperatures are limited to only a few hundred degrees

Viscoelastic properties, which can be a distinct limitation in load bearing applications

Some polymers degrade when subjected to sunlight and other forms of radiation


Polymer notes! (the first one was made in Australia)

Note Printing Australia (NPA), produced Australia's first polymer banknote in 1988, setting a new world standard in banknote technology.

The numerous benefits of polymer banknotes include improved security, durability, cost effectiveness, processibility and environmental responsibility.


Polymer notes!

By 1996, Australia had issued the world's first complete series of circulating polymer banknotes.

NPA has also produced polymer notes for Thailand, Papua New Guinea, Sri Lanka, Malaysia, Singapore, Brunei, Indonesia, Kuwait, Samoa, New Zealand, Romania, Bangladesh, Solomon Islands, Mexico, Nepal, Vietnam, and Chile.

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