HDPE vs UHMW: When to Use High-Density Polyethylene
HDPE and UHMW are popular and well known types of plastics across many different industries for their reliability, so much so that many people have started to use them interchangeably. However, their uses don’t coin cide nearly as often as many think–HDPE has different qualities that lend well to different applications. While both materials are very light, with a density of .94 – which means they both float in water.
When best to use HDPE
High-Density Polyethylene or HDPE is known for its versatility and low moisture absorption, which result from its high-density chemical makeup. Its chemical composition also makes it highly chemical resistant, so it’s excellent for applications that involve moisture or mild chemicals.
HDPE is also very easy to machine and shape. As a result, it has been used successfully to make plastic lumber, milk jugs, containers, cutting boards, and many other products.
In addition to being easy to machine, HDPE sheet and rod are also relatively lightweight, and can be NSF and FDA compliant. This very durable material can not be glued or bonded, and thus must be heat welded together or attached with mechanical fasteners. HDPE is excellent for applications where reduced weight and low costs are paramount. This, combined with its easy machinability, allows HDPE to be cut, drilled, routed and shaped for many different end uses. Food cutting boards, piping, storage vessels, marine components, and many more benefit from HDPE. It’s also been successful in outdoor furniture, signage, playground equipment, structural tanks, food processing equipment, vacuum-formed parts, transfer boards, tank liners–and this is just a small number of its applications.
When not to use HDPE
While HDPE and UHMW have similar properties, they are often better suited to different tasks. Both plastics do have high impact resistance, but UHMW (Ultra-High Molecular Weight Polyethylene) performs better in applications where friction and constant impact are present. The UHMW molecular chain is much longer, thus giving UHMW the extreme wear resistance. This results in UHMW being used more often in functional components, like conveyor systems, concrete chute liners, mated parts, bumpers, and bearing applications. HDPE does not perform as well as UHMW under constant friction, making HDPE better for food processing surfaces, chemical resistant parts, decorative products, or components that will not experience constant friction. If a reduced friction application is needed, the use of UHMW with a coefficient of friction of just 0.08 (compared to HDPE with a coefficient of friction of 0.20) is much more suitable.
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UHMW (Ultra High Molecular Weight Polyethylene) and PTFE Sheet(PolyTetraFlouroEthylene) are very similar materials, and yet very different at the same time. They both possess certain characteristics that make them similar to each other. For instance, they both have a very low co-efficient of friction, which means they are great for sliding applications and are easy to machine.
Both of these materials are very resistant to chemicals such as chlorine and some acids and have great wear resistance. They have low to no water absorption. They also are FDA approved for handling food. PTFE and UHMW Polyethylene are both nearly impossible to bond (without treatment) and are susceptible to sagging under tensile load which is called ‘creep’. These both have very low coefficient of friction and work well for wear strips, slide pads and truck liners to make it easy to empty. These two materials are different in many ways also, and choosing between the two materials for a specific job is critical.
Below are a few examples of how these two materials are different.
1. UHMW is a polyolefin and PTFE is a fluoropolymer. Polyolefins are double bonded carbon while Fluoropolymers are carbon and fluorine bonded. UHMW is a monomer which is consisted of one atom that will bond with another to form a polymer. PTFE is a polymer which is made up of a repeating chain of monomers.
2. PTFE has a higher temperature range than UHMW. The PTFE has a continuous use temperature of 500 degrees F. UHMW is much lower with a continuous use temperature of 200 degrees F and a melting point of 271 degrees F. The UHMW starts to become become soft at higher temperatures while the PTFE is much more resistant and with a melting point of 621 degrees F.
3. UHMW has higher abrasion resistance than PTFE. Both have great impact and wear resistance but because of UHMW having a molecular weight between 2-6 million making it the best wear resistance material in the plastic family, it makes it ideal to take wear and impact over a wider range and longer period of time without losing its properties.
4. UHMW has a much lower density than PTFE. This makes UHMW able to float in water while Fluoropolymers are significantly heavier (almost twice the density of UHMW) and would sink.
5. PTFE has excellent electrical and thermal properties. The virgin grade of PTFE is a better insulator and exhibits better electrical properties which can be used in radio frequencies, cables and circuit boards while UHMW cannot.
6. UHMW is much less expensive than the Fluoropolymers. Especially recently, PTFE has become harder to come by, and during the last 18 months there has been a global shortage of a key raw material called fluorspar that is used to make all Fluoropolymer materials. The ability to take lots of wear and tear and requiring low long term maintenance makes UHMW more cost effective.
7. The standard color of PTFE is Natural, which is a dense white. The UHMW comes in Natural (a deep milky white) or Black. The UHMW can be produced in many colors, and minimums are rather low. To obtain PTFE in colors is much more difficult, and would also have large minimum orders.
Click here for data sheet comparisons for each material…
Both the UHMW and the PTFE are available as sheet, sheets, sheeting, slab, bar, strip, panels, film, round rod, rods and block. Contact us for assistance with these or other shapes.
PTFE Sheeting Properties
Specific Gravity D792 2.14 – 2.24
Tensile Strength Yield D638 2,500 – 6,000
Tensile Modulus D638 80,000
Izod Impact – Notched D256 3.0
Hardness – Rockwell D785 D50 – D65
Deflection Temp @ 264psi D648 150
Deflection Temp @ 66 psi D648 250
Co. Thermal Expansion D696 5.5X10-5
UHMW Sheeting Properties
Specific Gravity D792 .93 – .94
Tensile Strength Yield D638 6,800
Coefficient of Friction – Static D1894 .25
Izod Impact – Notched D256 No Break
Hardness – Rockwell D785 R64
Vicat Softening Temp D1525 260
Deflection Temp @ 66 psi D648 174
Co. Thermal Expansion D696 11.0X10-5
These are just some examples of plastic materials being similar, and yet having very different properties. The PTFE Sheet and UHMW Sheet may appear very similar in color and can be used for some of the same applications, but when needed for a specific use or property needed, one might be dramatically better than the other. As the old saying goes, “You should never judge a book by its cover” and the same is true with plastic. Review the properties and test prior to choosing a final material for your application.