QwikConnect April 2008

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The Future is Here, and It’s Made of Plastic

or many people, “plastic” means “cheap and

breakable.” But when engineers search for new

ways to enhance weight savings, corrosion

resistance, shock and vibration dampening and

stealth they immediately turn to plastic—the only

alternative material capable of meeting, and beating,

the established performance levels of aluminum,

brass, titanium and steel.

The name “plastic” refers to the ability to

form or shape a material, or to the moldability a

material adopts under forces such as pressure or

heat. Engineers often use the term “polymer” when

referring to plastic materials, because it more clearly

describes how many (poly) chemical units (mers)

form up in complex chains to create modern plastic

resins. “Thermoplastics” are polymer materials that

melt to a liquid when heated and form into a hard,

dimensionally stable shape when cooled.

Thermoplastic polymers are created by

subjecting various chemical and petroleum-based

ingredients to heat and pressure in sealed vessels.

Speciﬁ c chemical additives control how the polymer

is formed and contribute to its performance in such

areas as surface hardness and ﬂ ame resistance.

The process of mixing base materials with chemical

additives to create speciﬁ c types of plastic resins

is called “polymerization.” The resulting plastic

materials can be classiﬁ ed in various ways—by

chemical or physical structure, by strength or thermal

performance and by optical or electrical properties.

Resin Morphology

When polymer resins are combined with glass

ﬁ bers, or other structural materials, the resultant

“composite” material can deliver truly amazing levels

of performance. Since over sixty thermoplastic

base-resins can be used to produce composites, it

is helpful to understand a little about resin chemistry

and morphology as a baseline for understanding

the properties of the different grades of composite

plastics. Although “morphology” sounds complicated,

it can simply be viewed as the orientation the

molecules take when they go from the liquid to solid

state during processing, such as injection molding.

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A thermoplastic resin is either amorphous, having

a random molecular orientation, or semi-crystalline,

having ordered or crystalline regions of molecules

dispersed within the random amorphous molecules.

Morphology choice depends on application, as there

are advantages for each material type.

The most signiﬁ cant structural classiﬁ cation for

polymers has to do with their shape at the molecular

level. Polymers whose long, linear shaped molecules

fold tightly together into packed and ordered areas

Thermoplastic polymers are created by subjecting various

chemicals and petroleum-based ingredients to heat and

pressure in sealed vessels. The materials shown here have

been formed into shapes suitable for machining.

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