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1 min read

What are some advantages of using polymer materials for gears?

By Dave Biering on April 17, 2012

Polymer gears are commonplace in many industries and applications.

Polymer gears are commonplace in many industries and applications. The advantages of a polymer gear include noise reduction, self lubricating features, dramatic weight reduction and cost savings. From paper mill gears to drive gears in copiers, polymer gears have been successfully used for years.

But everything you know about metal gear design gets thrown out the door with polymers. There are many different factors that have to be considered when designing gears out of plastics including thermal expansion and contraction, physical strength, moisture absorption and possible chemical exposure.

Typical polymers for gears are cast nylons, injection molded nylons, polyester and acetal. Various fillers help to strengthen the base polymers such as glass and carbon fiber, aramid fibers and other additives are used to improve lubricity. More recently high end polymers like PEEK and Torlon have been used to make high temperature gears or gears where exceptional strength is required.

No matter what the material, designing polymer gears will require some extra thought and a change from the norm. Tooth profiles and overall height may need to be changed to accomodate bending forces. Contact conditions at the root of the tooth may need modifications from the norm. Flex strength of the polymer will definitely come into play so input and output torque requirements will need to be reviewed closely.

While there are a lot of advantages to polymer gears you can't overlook the basic differences between steel gears and polymer gears. Material choice and adherence to design changes required to address the physical, thermal and wear requirements of the gear must all be looked at closely.

TriStar has several thermoplastic and thermoset materials used frequently for gears and our engineering department can help you in this process. Have more questions? Just ask! 

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Topics: Misc Products
1 min read

Trilon AR

By Dave Biering on October 25, 2011

I recently received a call on Trilon AR, one of our newer materials.  Trilon AR is a modified UHMW compound available in rod or sheet form. It is a good option for chain guides, gears, sprockets and bearings.  Trilon excels in mining, pulp and paper, and timber handling applications.

Other key attributes:

Features:

  • Extreme abrasion resistant
  • Does not absorb moisture
  • Self-lubrication
  • Lowest friction

Benefits:

  • Long wear
  • Low operating cost
  • Machinable
  • Good in all weather
  • UV resistant

 Consult our team to see if Trilon AR would be a good fit for your application.

Topics: Misc Products
1 min read

Torlon is for Punishing Environments

By Dave Biering on June 16, 2010

Torlon® is a high-strength plastic, and is among the most expensive on the market. Torlon can be injection molded, compression molded, and extruded, and is ideally suited for severe service environments. Applications include pump components, valve seats, bearings, rollers, high temperature insulators, electronic equipment, compressor components, and bearing cages.

The main characteristics of Torlon are a high maximum allowable service temperature, excellent mechanical strength and creep resistance over a wide range of temperatures, extremely low coefficient of linear thermal expansion, low flammability, exceptional resistance against high-energy radiation, moderate chemical and hydrolysis resistance, and excellent UV resistance. And Torlon is excellent at maintaining physical properties.

We've got a range of Torlon grades available for your application:

● 4203 and 4503 - structural/insulating grade offering good insulating properties, low thermal expansion, moderate coefficient of friction

● 4301 and 4501 - extrusion most popular - gives excellent wear, reduced coefficient of friction, little to no stick slip, flex modulus over 1 million psi

● 4540 - bearing grade for extreme wear life - insulating materials (primarily structural): aluminum, and stainless steel

● 5530/4XG - excellent electrical insulating properties, good wear resistance, abrasive towards mating surfaces, moderate dynamic coefficient of friction

● 4XCF - another good bearing material in hi-temp applications, high stiffness, lowest coefficient of thermal expansion of any standard polymer shape, non-abrasive

Tell us about your experience with Torlon.

Topics: Misc Products
1 min read

PTFE Slipper Seals

By Dave Biering on March 3, 2010

Our team has seen a spike in interest in slipper seals.

Slipper seals, made from filled PTFE, are designed to act as a low friction interface between a static elastomer expander and the dynamic mating surfaces. i.e shaft or bore. With filled PTFE like our Ultraflon, slipper seals offer exceptional wear life, extrusion resistance, low friction and elimination of stick slip. Slipper seals can be used in both hydraulic and pneumatic applications, lubricated or dry and across a broad temperature range. Since these seals depend on the elastomer for their energizing function, the temperatures will depend on the operating capabilities of that elastomer.

PTFE slipper seals are made in a variety of geometries and cross sections to accommodate the design envelope. There are piston seals, rod seals, wiper seals and a variety of supporting components to make up a complete cylinder design. Tri Star has seal engineers on staff to assist in the design of your slipper seal requirements.

You know the drill - if you have a question, Ask The Experts!

Topics: Misc Products
1 min read

More on Crystallinity of PTFE

By Dave Biering on February 2, 2010

Previous blog addressed importance of crystallinity control on PTFE as it relates to porosity, changes in physical strength and dielectric values. More Tri Star testing has shown better detail on the effects of processing and crystallinity. Specific gravity is the primary gage of crystalline or amorphous stages of polymers. In the case of PTFE the range is generally between 2.1 and 2.3 for unfilled resin. Testing showed that at 2.1 SpG the crystallinity of the molded product was approximately 38%. At 2.13 it was 47%, 2.15- 53%, 2.17 - 60%, 2.2 - 70%. Remember, the higher the crystallinity the lower the flex life, higher compressive stress, lower recovery, more permeability and lower wear life.

Another part of the equation has to do with microvoids as it relates to crystallinity. Microvoids are generally a result of poor attention to preforming conditions and to a lesser extent the sintering process. Microvoids, or porosity, have a direct bearing on crystallinity. As an example, a low microvoid material at 2.13 SpG would be 47% crystalline. However, if processing problems occur and void content grows you could see a substantial increase in crystallinity. At a 1% microvoid level the 2.13 sample at 47% crystallinity would increase to 53%. Doesn't sound like much but could have a great influence on the properties and wear of the material. Additionally, at 1% void content the dielectric strength of the PTFE would drop from it's normal 500 v/mil to 320 v/mil. This is significant when considering PTFE as a dielectric insulator. For more information on the importance of quality in PTFE, contact TriStar via this blog site or our website.

Topics: Misc Products
1 min read

Tivar HOT - High Temperature UHMW

By Dave Biering on December 8, 2009

Tivar HOT is a unique UHMW grade that has a dramatically higher continuous operating temperature (275F) than standard UHMW. Tivar HOT still has excellent wear and abrasion resistance, doesn't absorb moisture, has excellent chemical resistance and meets FDA, USDA and 3A guidelines.

We have found this product to be excellent for higher temperature zones in food processing and packaging equipment but it has also proven to be a great material in down-hole oil drilling applications!

It's a pretty diverse material! If you need excellent abrasion resistance, low friction, self lube bearing material with all of the other attributes mentioned, consider Tivar HOT from TriStar

Our video (below) has some more information about Tivar Hot.

Topics: Misc Products
1 min read

Effect of Crystallinity on Physical Properties of PCTFE at Liquid Oxygen Temperatures (-320F)

By Dave Biering on December 7, 2009

PCTFE has long been the go to material for valve seats, seals and gaskets used in cryogenic applications. But one thing that makes PCTFE unique is that it can be processed to meet a broad molecular state, i.e. crystalline or amorphous. PCTFE is a melt fluoropolymer and when molded in either sheet, rod or tube form it can be set at a specific crystalline state through a unique quenching process. This process is not as easily manipulated with extruded PCTFE rod so if you are looking for controlled molecular values you need to consider molded product.

As an example of some of the differences in physical properties between the amorphous PCTFE and crystalline PCTFE, consider these values:

Property differences between amorphous PCTFE and crystalline PCTFE

Crystalline/amorphous values are monitored by specific gravity and performance in cryogenic service utilizing amorphous grades of PCTFE has been well documented in terms of service life, sealability and property retention.

Ask The Experts at TriStar for more information on how PCTFE can be "custom tailored" to your application through molecular manipulation!

Topics: Material Selection Misc Products
1 min read

Recognizing Quality in PTFE Materials

By Dave Biering on September 29, 2009

Molecular weight and crystallinity are two factors in PTFE that determine many of it's performance qualities. Both of these properties are highly dependant on the sintering operation of the PTFE production. If the material is cooked (sintered) too long or at too high a temperature it can degrade the polymer. Molecular weight is a measure of the polymer chain length and it affects flex life, tensile strength and elongation. As molecular weight increases so do these properties and paying attention to gel temperatures and dwell times during sintering is extra critical.

Crystallinity of PTFE can vary considerably depending on processing. This value can be seen in small variations in the specific gravity although in practice most PTFE materials fall in the 50-60 percent crystalline percentage. Increasing crystallinity decreases flex life, increases compressive stress and decreases recovery values, permeability and wear life. Other properties of PTFE, such as thermal, chemical, electrical and friction, are not generally affected by crystallinity changes.

So, sintering and other processing steps do a make a difference in deterimining the quality of PTFE. If you need to maximize the performance of your PTFE parts, including Rulon, Fluorosint, Ultraflon or even generic products, be sure you contact Tri Star Plastics first. We can help you select the right material and the right process.

Topics: Misc Products Rulon Materials Rulon Plane Bearings