Tech Talk Blog

All of us in the fluoropolymer business are suffering what could be called a perfect storm of bad news! First, the raw material situation. One of the key ingredients in the processing of fluoropolymers is a mineral called fluorspar. This is a material that is critical in the production of not only fluoropolymers but pharmaceuticals, hydrofluoric acid, refrigerants and any other product that requires a fluorine based stock. China controls most of the worlds resources on this mineral and it became part of a war of words and ultimately manipulation in the world market. Countries, including the USA, are now scrambling to reopen old or open new mining resources of this critical mineral. So this shortage, as well as a worldwide surge in demand for fluoropolymers and a reduction in processors of the PTFE resin, all leads  to this very difficult situation. The bad news is there is no end in sight. The EU has declared fluorspar to be on it’s worldwide shortage list until 2030. So we all  will have to deal with this out of control pricing escalation for years to come. Best if you call Tri Star and place blanket orders for your requirements for the future!!

Tivar® HOT is a good alternative when standard UHMW is unable to withstand your operating temperature.  As the name implies, it is engineered to withstand high operating temperatures up to 220°F.  It is a diverse material that can be modified to fit a broad scope of applications.

Tivar HOT has near-zero water absorption, so it can be used in scalding and submerged applications.  It gives superior wear and chemical resistance, offers good impact strength, low friction, and is self-lubricating. It is also incredibly abrasion-resistant.

Tivar is a good solution for food processing and packaging equipment.  It meets FDA/USDA guidelines and is 3A Compliant.  We see it used in the production of sugar and candy.  Also many industrial applications such as pipe saddles, hopper liners, and conveyor guides.

It is available in sheet, rod or tube form, can be made to order, and is easily machined.  We can custom fabricate a part to match your print.

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.

Here’s a quick review of the different categories of plastics:

Plastics are classified into two categories:

1)      Thermoset – is any material that, once heated, cannot be reheated or reformed (Examples: Bakelite, Melamine, Teflon, Torlon, Celazole, glass epoxy systems, phenolic, Micarta

2)   Thermoplastic – any material that can be heated and reheated to make a finished part or stock shape (Examples: PVC, PEEK, polyethylene, nylon, acetal, acrylic)

Plastics also break down into two subcategories:

1)      Amorphous – Which is see-through or

2)      Crystalline – Not see-through.

The molecular structure is very important to the performance properties of any plastic material.

In processing, thermoset materials can only be compression or transfer molded. The process usually requires extremely high pressures and elevated temperatures. Thermoset materials usually require some form of reinforcement for stability and strength.

Thermoplastics can be extruded, injection molded, compression molded, blow molded, thermo formed, bonded to substrates, stamped and machined. And with thermoplastics, we have the ability to include additives to enhance properties like wear, fire resistance, electrical properties, and improvements in impact strength.  We can also reinforce with additives like glass fibers, carbon fibers, Kevlar, graphite, calcium carbonate.

We also classify by temperature:

1)      Commodity Plastics – lower cost and performance, typically doesn’t work above 200° F, good chemical resistance

2)      Engineering Plastics – 300° F limit, generally more versatile, used in structural and wear applications, available with enhancements

3)      High Performance Plastics -  most expensive, handle high temperatures over 300° F, associated with the most extreme operating conditions – thermally stable, excellent inherent wear properties, broad chemical resistance.

Our team is always looking at new alloys, new fillers, and extending chemistries to make new polymers.

Did you realize there are probably over 300 types of Rulon? Rulon is a self-lubricating material that can almost be considered “generic” in some ways.  It is a PTFE material with various fillers; it is the type and amount of filler that makes each variation of Rulon unique.

When choosing Rulon, we ask:

1) What is the application function – bearing? Seal? Gasket? Some materials can be used for all applications.

2)  What is the temperature? -400 to +550 is the general range Rulon can accept. For design purposes, we need to know how much press fit and close in to account for in the gradient.

3)  What is the environment? Some types are made for FDA or USDA environments or for resisting abrasion. Most PTFE materials don’t do well in water, but a few do.

4)  What is the speed? All types of Rulon can take 400/500 feet per minute without lubrication; but we need the load to be a bit more accurate. Rotating? Oscillating? Linear?

5)  What are the loads on that bearing? Most can handle 1000 psi, but others can withstand higher levels.

6)  What type of hardware (consider temperature)? Only a few types of Rulon can work with stainless steel.

7)  What is the surface finish? 8-16 rms on the shaft is recommended, but for holding purposes, we would suggest 32 rms.

We can help you choose the right Rulon for your application.

We see this question often.  Plane bearings offer many advantages; a simple design, self-lubrication, a wide range of operating parameters, and lower cost.

When selecting a plane bearing, consider:

Load – this can be the most difficult attribute to define. What is the pressure? Multiply the ID times the length, and then divide the load by that number. Pressure (P) is expressed in PSI.

Speed – you may know what your shaft speed is, but you need to find the velocity (v). Take the diameter multiplied by pi, then multiply by the RPM. Divide this number by 12, because V is measured in surface feet per minute (SFPM). Every material is rated for a maximum velocity.

P and V – these must always be considered in tandem. The combination of load and speed generates frictional heat. Always review P x V or PV. Every material has a maximum PV rating.

Material Rating – look at all the values for each individual project. Plastics are insulated in nature, and heat will kill a plastic bearing faster than anything else.  Be sure to stay within the known limits to understand what materials are capable of taking.

Temperature – this is critical to getting the proper “press fit”.  Be certain there is no loss of tolerance or close-ins.

You can also visit our Plane Bearing Design Worksheet for guidance, or contact us directly.

Plane bearings are straightforward; two surfaces moving against each other without the aid of a rolling element. A shaft turning in a bushing, a slide pad damping vibration, a bridge joint expanding, and a chain running through a channel are all examples of plane bearings. Sleeve or flange bushings, thrust washers, linear-slide plates, friction bearings, and wear pads all fall into the plane-bearing category. If there are no balls, needles, retainers, or races, it’s a plane bearing.

Plane bearings stand up to most industrial and outdoor applications. They are self-lubricating and offer superior resistance to fresh water, saltwater, deionized water, slurries, acids, or bases. And because they have few moving parts, most plane bearings are not adversely affected by particulates like coal dust, quartz debris, sand, and road ballast. Plane bearings are safe for clean rooms, too, because they produce minimal debris and won’t attract dirt. Many materials also meet FDA, USDA, 3A, or NSF standards.

Our team can walk you through our complete selection to make sure you get the right fit for your application.

Moly filled cast nylon bearings have been used very successfully for many years. The known drawbacks of nylon has always been it’s inherent tendancy to absorb moisture over time and thus causing swelling of the material. More than that, the constant absorption and drying cycle leads to fatigue failure over time. The CJ bearing has zero absorption in moisture, is stronger in terms of compressive strength and resistance to deformation, has a thermal expansion rate the same as steel and has a very low friction. Since the CJ requires no lubrication, it is as close to maintenance free as you can get. In independant testing it was shown that wear life of the CJ is significantly better as well. In rotary wear tests we found that the Nylon/MOS2 had a weight loss of over 180mg after 50 hours. The CJ had 100.5 mg of loss in the same test. Load for the test was 2000 psi at 25 sfpm and temperatures and humidity were controlled in the lab at 78F and 50% humidity. For more information on the CJ Bearing products visit www.tstar.com and check out the Video Library and our on line catalog.

We’ve received a request for a quick review of plasma, so I present Plasma 101…

Simply put, plasma is an ionized gas, a gas into which sufficient energy frees electrons from atoms. Plasma is the fourth state of matter.  With plasma, positive ions, negative ions, electrons and radicals coexist in a concert of reactions and collisions — as long as an electric potential exists.

Plasma systems control the treatment conditions by controlling the gas type, flow, pressure, and concentration.  Plasma also dictates the energy, frequency, wattage, and electrode configuration.

Vacuum plasma technique is one form of surface modification our team provides.  Plasma has the unique ability to treat a material three dimensionally to prime any surface for adhesion, painting, coating or printing.  And plasma is recognized as a “green” process that releases no hazardous byproducts.

As always, if you still need some clarification – don’t hesitate to Ask The Experts!

Now that we’ve established the importance of bag selection in accelerated aging, let’s move on to temperatures.

The aging process subjects samples to elevated temperatures for specific periods of time to simulate the effects of real-time aging.  It is usually required in the testing of medical equipment such as diagnostic devices and surgical implements, and also in aerospace applications.

We’ve noticed the tendency for keeping testing temperatures too high.  By maintaining too high of a temperature, unintended physical changes such as melting may occur.  One must consider the most likely temperature extremes a device would see in practical use and test the device at that temperature.  Another temperature guideline is the Arrhenius reaction rate function, or “10-degree rule.”  This function states that a 10° C increase or decrease in the temperature of a homogenous process results in approximately a two times or ½ time change in the rate of a chemical reaction.

Share with us your experience with temperature testing.