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Choose the Right Plastic for Your Manufacturing or Fabrication Project

10/8/21
Grainger Editorial Staff

There are many plastics to choose from when you're planning a manufacturing or fabrication project. To find the best material, start by thinking about the application and environment. What does the plastic part or product need to do? And where will it be doing it? These questions can help you better understand what plastic characteristics you need:

  • What range of temperatures does it need to withstand?
  • Will it be exposed to chemicals or other harsh conditions?
  • Will it be used outdoors and exposed to UV light?
  • Is it a structural piece requiring strength and dimensional stability?
  • Is it for a bearing-and-wear application requiring a low-friction surface and high wear resistance?
  • What is its expected lifespan?
  • What kind of load does it need to withstand?

The Polymer Pyramid

The polymer pyramid (also called the plastics pyramid) is a common way of thinking about the range of plastic materials and their general characteristics. These are the three levels of the pyramid, beginning with the base.

Standard plastics, also called commodity plastics, are relatively inexpensive and are good for noncritical applications that don't require outstanding thermal or mechanical properties. 

Engineering plastics have better thermal or mechanical properties and are generally suitable for bearing-and-wear applications.

Advanced engineering plastics, also called high-performance plastics, have even better thermal or mechanical properties and are suitable for more demanding applications. Imidized plastics such as PAI offer the best performance.

The plastics on the left side of the pyramid are amorphous polymers, while those on the right side are semi-crystalline polymers. This distinction is based on whether the molecules that make up the plastic are arranged in a more random or in a more orderly way. The chart below summarizes the general properties of amorphous and semi-crystalline plastics.

Key Characteristics of Amorphous vs. Semi-Crystalline Plastics

Amorphous

Semi-Crystalline

Not suitable for bearing-and-wear applications

Suitable for bearing-and-wear as well as structural applications

Tend to be translucent in thicker sections

Tend to be opaque in thicker sections

Not resistant to fatigue or stress cracking

Resistant to fatigue and stress cracking

Bond well with adhesives and solvents

Bond poorly with adhesives and solvents

Soften at a broad range of temperatures; easy to thermoform

Melt at a distinct melting point; challenging to thermoform

Less chemical resistant

More chemical resistant

Plastic Selection Guide Chart

This table gives information on common applications and characteristics for some of the most widely used plastics.

Plastic Type Common Uses Characteristics
Acetal Precision gears, bearings, bushings, rollers Available as acetel comopolymer sheets and bars and acetel copolymer rods
Naturally slippery surface
Wear resistant
Easy to machine to close tolerances because they don't expand with exposure to heat or moisture
Low moisture absorption; better than nylon and other similar materials in high moisture or when submerged
High strength, stiffness and dimensional stability
For replacing metal parts and other higher performance needs, consider acetal homopolymer sheets and bars or acetal homopolymer rods
Polycarbonate Machine guards, windows, windshields, safety shields, sports equipment, instrument gauge covers, display racks Available as polycarbonate sheets and bars and polycarbonate tubes
Stronger and lighter than glass
Stronger than acrylic
Excellent impact resistance and good clarity
Can be clear or colored
UHMW Polyethylene Food handling solutions, conveyance mechanisms, material handling, packing solutions Available in UHMW Polyethylene films and rolls, UHMW Polyethylene sheets and bars and UHMW Polyethylene rods.
Durable, wear-resistant, low-friction surface
Does not absorb moisture
Good electrical insulating properties
Moderate mechanical strength and stiffness
Excellent machinability
Some products have an adhesive side for easier application
Nylon Bearings, bushings, food handling solutions Available in nylon sheets and bars and nylon rods.
Wear resistant for high-friction applications
Can reduce weight, noise and wear when replacing metal parts
Products filled with molybedenum disulfide (MDS) or other lubricant eliminate need for additional lubrication
Polytetrafluoroethylene (PTFE) Slide plates, gears and bearings; circuit board insulation Available in PTFE sheets and bars and PTFE films and rolls.
Withstand chemicals and solvents better than most plastics
Remain stable at high temperatures
Naturally slippery surface useful for applications that require sliding action
Nonconducting
Suitable for food contact
Some bars have an adhesive side for easy application
Acrylic Signs, displays, skylights, and conveyor shields Available in acrylic sheets and bars and acrylic tubes
Excellent strength and stiffness
Excellent optical clarity with more durability than glass
Easily fabricated and thermoformed
Bonds well with adhesives or solvents
Suitable for outdoor use and withstands outdoor conditions better than polycarbonate
Maintains clarity over time
Cast acrylic is available for easier machining
High-density polyethylene (HDPE) Plugs, seals and containers Available in HDPE sheets and bars and HDPE rods
Excellent moisture resistance
High chemical resistance against basic solvents, greases, waxes and acids
Excellent smoothness and anti-adhesive properties
Marine-grade HDPE is available for use around water
Garolite Medical, aerospace and marine applications Available in garolite sheets and bars and garolite rods and disks
Strong and machinable
Lightweight
Electrically insulating
High dimensional stability
Highly resistant to moisture
Flame-retardant garolite is also available
PVC Valve parts, fittings, piping systems, welded chemical tanks and manifolds Available in PVC sheets and bars and tubes
Resistant to chemicals and oxidizing media
Easily fabricated and thermoformed
Can be joined with solvents or adhesives
CPVC is available for additional heat resistance

Other plastics for fabrication and manufacturing include ABS, carbon fiber, HIPS, LDPE, PAI, PEEK, PEI, PETG, polypropylene. 

Selecting by Form

You can also select a plastic by thinking about the form as a starting point. Rods, sheets, tubes and films are among the most commonly used shapes, but there are many other plastic forms.

The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.

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