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By Joseph Ogando, Senior Editor -- Design News, July 8, 2002
Contact Joseph at jogando@cahners.com
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 | |||
|---|---|---|---|
| Property | Value | Units | Test method |
| 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 |
| Wear properties | ||||
|---|---|---|---|---|
| PV (psi-ft/min) | Velocity (ft/min) | Pressure (psi) | Wear factor (×10-10 in3 min/ft lb hr) | Friction Coefficient |
| 100,000 | 50 | 2,000 | 28 | 0.07 |
| 100,000 | 200 | 500 | 21 | 0.08 |
| 100,000 | 800 | 125 | 49 | 0.09 |
Cast silicone
A cast silicone material processed with a conductive additive can be formulated with resistivity ratings as low as E9 to E12 ohm-cm, and in durometers from 30 to 60 Shore A. Products that can be produced with the Silicone C material include drive rollers for direct thermal printing applications and linerless label rollers. The material can successfully eliminate static buildup problems that may cause periodic machine shutdowns. Mearthane Products Corp., www.mearthane.com. Enter 577
Conductive polymers
Stat-Tech® electrically conductive engineered materials are specifically formulated for protection against static build-up, electrostatic discharge, and electromagnetic or radio frequency interference. The Stat-Tech product line includes formulations in more than 20 rigid and elastomeric thermoplastic base resins. Superior electrical conductivity comes from the use of antistat additives, as well as fillers and reinforcements, such as carbon black, carbon fiber, and metallized fiber. PolyOne Corp., www.polyone.com. Enter 578
Resins
A new version of high heat conductive NORYL GTX® resins for body panels is designed to survive the higher temperatures used in the "e-coat" painting process. The resin helps automotive manufacturers reduce overall system costs, improve body panel performance, and reduce vehicle weight. Its properties include higher flow, heat resistance, and conductivity. GE Plastics, www.geplastics.com Enter 579
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