UHMW vs. PTFE

There are few questions we dread more than the customer asking about a PTFE truck liner. While the error is understandable – in natural form both UHMW polyethylene and PTFE are white colored plastic, if PTFE were ever used as a truck liner the cost would be many 10s of thousands of dollars and the liner would be worn to bits in short order! Yet, monthly we receive inquiries from customers who simply don’t know any better asking for that. We believe it’s important to discuss the distinction, and some similarities, between the two plastics.

Similarities:

Both plastics in their natural form are white and both are widely stocked by most plastics distributors. Both plastics are known for having a very low coefficient of friction and net zero water absorption. They’re both available in 48″ wide plates and in common thicknesses from 1/8″-2″ (and beyond). Both plastics are FDA/CFIA compliant in their natural form. Both plastics can be modified with a variety of fillers or additives. However, that’s where the similarities end.

Differences:

There are so many differences between the products that a list is the best way to explain:

  • PTFE is substantially much more expensive than UHMW
  • PTFE can only handle about 1/5th the load of UHMW
  • PTFE is more slippery than UHMW (despite both having a low coefficient of friction)
  • UHMW has far better wear properties than PTFE
  • UHMW is typically stocked in 48″ x 120″ sheets where PTFE comes in 48″ x 48″ plates
  • PTFE withstands over 4x the temperature UHMW can in continuous operation

So if UHMW is less expensive, handles more wear, and more load…Where do you use PTFE? The answer is pretty simple: 1.) when it’s spec’d in or 2.) when one of its differing properties from UHMW makes it the better choice. For example, if you’re machining some bushings for use in a 400 degree Fahrenheit environment you would go with a PTFE product vs. a UHMW product which would simply melt. As well, if the application demands bearing pads with dynamic sliding (think telescope mounts) then PTFE is the better choice due to its phenomenal low coeffecient of friction. If in doubt, simply contact Redwood Plastics and Rubber and we’ll lend a hand!

3 Tips For An Easy Rubber Purchase

Purchasing rubber would seem to be a simple thing: everyone knows what “rubber” is and most people think of it as one hegemonic product where even if different rubber types exist, they’re all more or less similar. That is actually untrue and the rubber family is indeed much wider, more extensive, and perhaps complicated than most people might think. The good news is help is available! We are rubber experts here and can carefully guide you through the process of selecting the correct Redco rubber for your application. However, if you feel you have a pretty good handle on rubber and don’t have a need to go through the selection process with us, these three tips will help ensure anyone is satisfied with a hassle-free rubber purchasing experience.

#1 – Know Thy Rubber

Even if you have a pretty good handle on rubber products you do need to make sure you “know enough”. Here is an example, you’ve used SBR rubber before and you know what size and thickness you need it in, perhaps 1/8″. So you email an RFQ “I need one piece of SBR 4′ x 8′ x 1/8″ ” Is that enough information? Actually it isn’t. We offer SBR in both 60A and 80A durometer (hardness) and we need to know which you need. In addition, we offer almost all of our products in a premium grade, which can be provided with certifications, and consumer grade, which cannot be certified beyond a simple compliancy form. Which leads to…

#2 – Know Thy Certifications

One stressful part of the rubber sales process for both the salesperson and the customer, is when certifications are requested after a sale and after the rubber has been shipped. While one may assume that all rubber we sell is certifiable and to any industry spec, this is actually inaccurate. It can lead to annoying situations and even cancelled orders. Our lower-priced consumer grade product offers price savings but cannot be certified for, example, food processing or aerospace requirements. We do offer such grades of rubber! However, those are our premium grade materials. Therefore please always inform us of any certification that is required before purchasing. In addition, we have run into certifications we cannot supply – even with our premium grade materials, which is why it’s best to bring any certs up during the quotation stage of the process.

#3 – Ask and Trust

If you’re unclear at all about what rubber you require, please do not hesitate in asking for help. At times, customers may feel ashamed admitting they need help in picking a product. However, as long as you can get us the information we need on the operational environment of the application we are happy to help make a recommendation. That said, there is a measure of trust involved. Customers tend to be familiar with “neoprene” rubber, for example, but when we’re telling a customer he/she needs Viton P70 rubber to function in the application then trust comes into play.

You can view our rubber line card by clicking here.

For more assistance or a quote on your rubber needs please contact us today.

Three Preparation Steps For Part Design

So, you have a part you want made out of plastic (or rubber). You have a drawing, maybe a CAD file. You know what the part needs to do.

What now?

This is the stage where you need to make the leap from idea to practical. To get the part finalized, material specified, and actually get the part into production. What information do you need to have to finalize everything?

1.) Know Your Operational Environment

This is absolutely critical and something we often need to work through with customers before we make a recommendation. You need to know the complete operational environment for your part. This includes:

  • Min/Max operating temperature
  • Chemical exposure (and how much exposure to each chemical – it matters!)
  • UV-exposure
  • Pressure applied on the part (in PSI)

Depending on the part there may be other critical factors but you should know at least those four.

2.) Know Your Required Tolerances

This is perhaps the most important thing that keeps getting overlooked in part design. Often we’re handed a drawing with metal tolerances (+/- 0.001″) and told to make it (hint: not possible to hold those tolerances). Or, in many cases, customers simply tell us to hold “best” tolerances. Did you know there’s a premium to that? When we work out a quote internally, required tolerances are part of that because of the time and risk involved in hitting our tightest (+/- 0.005″) tolerance. Often a (+/-) 0.03″ is suitable for many applications and since it will save you money, it’s worth it to know the demands of your application.

3.) Know Your Quantities – Buy In Bulk

Quantity usually means price break when it comes to parts. Customers will often send us a drawing and ask that we quote a couple pieces, ostensibly as samples. The issue is that the cost for prototypes will be inflated compared to the prototypes…And sometimes customers just think the price would remain constant. So know an accurate number of how many parts you will need once in production and get both prototypes and production runs quoted at once for a clear picture of your costs.

For more information on how to buy your parts in the most economical way possible, please contact us today.

 

 

 

Plastic Angle

Out of the many parts and plastic profiles requested of Redwood Plastics and Rubber, plastic angle keeps coming up. This is typically plastic bent at a 90 degree angle halfway. This is primarily used for protection of a surface or object if machined out of UHMW or nylon plastic. However, much stronger (more rigid) fiberglass reinforced plastic (FRP) angle is available and stocked by our supplier. A common example of a FRP angle application would be to bolt it in on the edge of a platform at a train station. FRP angle is available in a variety of widths and thicknesses with 1/4″ and 3/8″ thick being the most common. It is available in all three primary EXTREN resin types (general purpose polyester, fire-retardant polyester, and vinyl ester). These angle profiles are more expensive than steel or aluminum angle; however, for certain applications such as those that demand electric or radio non-conductivity, plastic angle may be your only choice.

To get a quote on an angle profile is easy. Firstly, we need to know the width of each side of the angle, they are not always the same! We then need to know both the thickness and the material required. If you need assistance selecting a material, just ask, but me sure to be ready to answer questions about your application such as what the angle is doing, if there is any chemical or high heat exposure, etc. Angle profiles of all plastic types are typically sold by the 10 foot length; however, there are cases where we can supply shorter or longer profiles.

For a quote on your plastic angle needs, please contact us today.

 

Space Shuttle Challenger and Rubber: A Cautionary Case Study

The space shuttle “Challenger” explosion in 1986 was a seminal moment for many Americans. The launch was shown on live TV and there was a high amount of interest in teacher Christa McAullife being on the flight. The shuttle exploded 73 seconds into the flight resulting in the deaths of the entire crew. An immediate investigation was launched and it was determined that a failed rubber o-ring system used as seals on the solid rocket boosters led to the explosion. The launch was on an unusually cold day – the o-ring seals were qualified for use at no less than 40 degrees Fahrenheit but the temperature got as low as 18 degrees Fahrenheit the night before.

Prior to launch several engineers attempted to warn against launching due to this reason. The engineers believed that the cold temperatures would weaken the rubber and also lead to a poor seal, which would allow hot exhaust gases to potentially escape the boosters and cause catastrophic damage. It had already been determined that the o-rings were being damaged even on successful flights. The engineers were forced by NASA management to try to prove that the application would fail at low temperature, something the engineers could not do because of a lack of testing data.

Your application with rubber will likely not be as critical as the space shuttle o-ring seals; however, even with our applications there is much to learn.

Firstly, is you need to pick a rubber that will work within the parameters of your application. You need to know what chemical exposure and temperature range the part will need to operate in.

Secondly, once you get the parts you need to use them within the parameters that you have specified because if you introduce, for example, new chemicals or operate the part outside of the prescribed temperature range, it may fail!

The third and final thing we can learn is to listen to the product experts who helped recommend a rubber solution to you. If they strongly believe a certain material is required and can give you concrete reasons, you should consider this thoroughly before going in another direction. This is particularly a concern where a desired price may be a determining factor for a purchasing decision, rather than if the rubber is actually suitable or not.

Redwood Plastics and Rubber has rubber experts standing by to help recommend the best product for your application so contact us today.

Industry Spotlight: Aggregate

The aggregate industry is defined by the processing and movement of extremely abrasive wet or dry materials, usually by a network of conveyors. This process may also include equipment to pulverize, shape, clean, or otherwise sort the aggregates. Due to the abrasive nature of these materials, wear is a major concern on expensive equipment. Redco products have supplied viable, downtime-reducing, solutions for this industry over many decades. The primary workhorse is Redco polyurethane. This elastomer has extremely high wearing properties and can thrive in abrasive environments involving virtually any wet or dry aggregates.

The applications are too many to name but conveyor and hopper lining are two of the largest. When used as a liner, urethane protects the metal equipment and handles the wear of being in direct contact with the aggregate. However, polyurethane can essentially be used anywhere this wear occurs, including the area the aggregate first contacts the conveyor to any discharge chutes. Contact us with details of your application in order to get a recommendation of the optimal grade of urethane. Some polyurethane products actually exist specifically for aggregate including the innovative Redco Switchblade belt scraper with its replaceable and Redco Green Screens.

A few more notes. Rubber has significant applications in this industry as well, primarily as belt skirting and in areas where constant vibration is a concern. For slurry applications specifically, the Redco VYPUR series of pipe sections and elbows provide exceptional service life above and beyond metal in abrasive or corrosive applications. It’s best if customers reach out directly to us for a consultation, so if you’re involved in the aggregate industry and are looking for some solutions to maintenance costs and downtime, please contact us today.

You can see pictures and read more about our aggregate solutions here: https://www.redwoodplastics.com/industry-solutions/aggregate/

Not Sure What Rubber You Need? Start Here

Ordering rubber products is easy enough when you know exactly what you need and a defined spec is available. However, what if that information has been lost? The answer is to start at “square one” and work your way up to an optimal solution. To that end you need to know five pieces of information:

  • Application – What are you doing with it?
  • Contact with – What aggregates or other materials will contact the rubber?
  • Exposed to – which chemicals?
  • Operating Temp – Lowest and highest?
  • Durometer – What is the hardness (example, 60A)?

The first four pieces of information on the list must be supplied by the customer and should be easy to put together. “Durometer” is a little trickier if not known as that requires a specialized piece of equipment. In that case, a sample of material can be mailed to us and we can test it here. Having this information will help us, help you maximize success in your application.

For assistance with your rubber needs please contact us today.