Amorphous Polymer

Polymer chains with branches or irregular pendant groups cannot pack together regularly enough to form crystals. These polymers are said to be amorphous. A two-dimensional schematic of an amorphous polymer is shown at the right.

Amorphous regions of a polymer are made up of a randomly coiled and entangled chains. They have been compared to a bucket containing a large number of entangled worms - each one 20-feet long and of 1/4-inch thickness1. The worms are so tangled that an entire worm cannot slide past the others, but small portions of the worms can twist around within the mass.

Amorphous polymers are softer, have lower melting points, and are penetrated more by solvents than are their crystalline counterparts.

Overview

Pro's

Good Clarity

High Impact

Good Low Temperature Performance

Good Surface Appearance

High Stiffness

Little Shrinkage

No Warpage

Wide Processing Window

Cons

Poor Chemical Resistance

Poor high Temperature Performance

Flows Under its Own Weight Above Tg

Poor Creep

Little Memory (Not For Living Hinges)

Solvent Bondable

Easily Painted or Plated

Good Cooling Needed

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Polymer Advantages Drawbacks Some Typical Applications
PAI High heat, High wear Very hard to process Bearings, Aerospace
PEI Impact, Heat, Sterilization, Microwave Benzene, Gasoline Engine internals
PSU Alcohol, Salt, Hot water, Plumbing Benzene, Gasoline Hot water pipes
PUR Gasoline, Acids, Oil, Plating Boiling water Fuel bowls
PPO Hot water, Solvent bondable, Easy FR Oil, Gasoline, Grease Pump housings
PC Impact, Stiffness, Optical Oil, Gasoline, Grease, Chemicals Safety glass lenses
ASA Weatherable, Oil, Grease, Salt Benzene, Alcohol Auto trim, Signage
PMMA Weatherable, Clarity, Lenses, Scratch resistance Low temperature impact, Dishwater Signs, Reflectors
COPOLYESTER Some oil, Gas, Detergents, Scratch resistance Temperatures, Inadequate cooling Shampoo equipment
SMMA Practical Toughness, Sterilization High impact strength Medical, Vacuum equipment
ABS Impact, Stiffness, Economical Oil, Gasoline, Grease, Esters Housings, Auto interior
SAN Clarity, Stiffness, Improved chemical resistance Many chemicals, Impact Tumblers, Cosmetics
PVC Weatherability, Good impact, Water resistance Environmental, Corrosion Outdoor drains, Pools
PS/HIPS Economical, Impact, Stiffness Moderate Chemicals Disposable housings