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Durable plastic slides away
For moving components subject to moderately high stresses, the wear properties of common engineering plastics may have stopped your metal replacement efforts dead in their tracks. But a new, hardwearing grade of polyamide-imide (PAI) from Solvay Advanced Polymers could get things moving again.
PAI has long been known for its wear properties-as well as its heat and chemical resistance. But the new grade, TORLON 4435, contains a proprietary lubricant package that bumps the wear performance up a notch, according to Geoff Underwood, a research scientist in the company's TORLON group.
The new grade specifically targets operating environments characterized by a high-PV-a composite measurement of pressure and the moving part's velocity. Based on Solvay's tests, the 4435 grade comfortably covers a PV range from about 50,000 to 100,000 psi-ft/min. Previous TORLON grades, meanwhile, were in a range from about 25,000 to 50,000 psi-ft/min. The new TORLON is also designed to function in these high-PV environments without lubrication-though PAI has enough chemical resistance needed for the material to function as a "back-up" in lubricated systems that could lose their grease.
Solvay has tested TORLON 4435 parts across wear conditions that vary from high pressure/low velocity to low pressure/high velocity (see table). In all cases, the material showed "excellent wear resistance," Underwood reports. That did come with a trade-off in mechanical performance compared to neat PAI. Underwood cites a small-less than 10%-drop in strength properties, though it still has higher stiffness. "That's not really a concern in the applications we're going into," he says.
TORLON 4335 can be injection molded into a variety of sliding and rotating components. Some of the specific applications include bearings, bushings, seal rings, wear pads, and piston rings for everything from cars to industrial machinery.
Solvay Advanced Polymers, www.solvayadvancedpolymers-us.com. Enter 576
|Mechanical and physical properties|
|Tensile strength, 23C||15.5||kpsi||ASTM D 1708|
|Tensile modulus, 23C||1.4||Mpsi||ASTM D 1708|
|Elongation %||6.0||-||ASTM D 1708|
|Specific gravity||1.59||-||ASTM D 792|
|Flexural modulus, 23C||2.2||Mpsi||ASTM D 790|
|Flexural strength, 23C||22||kpsi||ASTM D 790|
|PV (psi-ft/min)||Velocity (ft/min)||Pressure (psi)||Wear factor (x10-10 in3 min/ft lb hr)||Friction Coefficient|
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