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Know your materials: UHMW

Polyethylene is a thermoplastic with a variable crystalline structure. This popular material is used in everything from shopping bags, to pipes, to prostheses and other medical devices. With several grades, types, and formulations of polyethylene available, it’s essential to learn about each material’s properties, advantages, and disadvantages before deciding which type to use for your product. Here’s everything you need to know about ultra high molecular weight polyethylene (UHMW or UHMWPE) from its molecular structure to its many uses.

What is UHMW?

An extremely dense form of polyethylene, UHMW is a semi-crystalline thermoplastic composed of long chains. UHMW forms when ethylene molecules bond, and the resulting UHMW molecules are much longer than the molecules found in other forms of polyethylene thanks to the presence of metallocenes. These compounds can serve as a catalyst and usually consist of positively charged metal ions located between negatively charged cyclopentadienyl anions.

With compression molding, sintering, ram extrusion, or gel spinning, UHMW can be produced as a sheet, rod, strip, or tube. Though the polymerization of UHMW wasn’t commercialized until the 1950s, it was quickly recognized as a versatile material suitable for many applications.

UHMW’s properties and mechanical specifications

UHMW plastic is very strong thanks to each molecule’s impressive length and high molecular orientation. In fact, UHMWPE fibers are among the strongest and lightest on the market today. UHMW is tough, slick, and durable with high tensile strength. It’s also highly resistant to corrosive chemicals, wear, abrasion, impact, moisture, and cold temperatures.

As the name suggests, UHMWPE has a very high molecular weight between 3.1 and 100 million grams per mole. Some of UHMW’s mechanical properties include:

  • Tensile strength, yield: 18.9 – 5800 psi
  • Tensile strength, ultimate: 2030 – 102000 psi
  • Flexural strength at yield: 2000 – 5800 psi
  • Flexural modulus: 58.0 – 210 ksi
  • Compressive strength: 580 – 12000 psi
  • Compressive modulus: 42.0 – 100 ksi
  • Hardness, shore D: 57 – 120

When considering using UHMW plastic for your next project, you should know that UHMWPE fibers are less resistant to heat than other high-strength plastics. UHMW polyethylene fibers have a melting point between 144 °C and 152 °C and shouldn’t be used for extended periods at temperatures above 80 °C to 100 °C. Also, even though UHMW plastic is known for its ability to withstand cold temperatures, it will become brittle at temperatures below -150 °C (or -240 °F).

 With compression molding, sintering, ram extrusion, or gel spinning, UHMW can be produced as a sheet, rod, strip, or tube.

Popular UHMW applications

Due to its strength and durability, UHMW is often used in belt scrapers, chain guides, idler rollers, sprockets, packaging machinery components, and gears. Other UHMW plastic uses include bearings, conveyor systems’ star wheels, guard rails, and food processing machining parts.

UHMWPE’S strong and light fibers make it an ideal material for body armor. It provides increased ballistic protection and resistance to cuts while remaining comfortable to wear. Many prostheses also contain UHMW due to its biocompatibility, strength, and wear resistance. UHMW’s abrasion and moisture resistance make it a popular choice for building docks, and its resistance to cold temperatures makes it an ideal material for snowplow blades, snowmobile skis, skid steers, and truck bed liners.

Why choose UHMW?

It’s challenging for many product teams to decide between HDPE and UHMWPE. After all, high-density polyethylene (HDPE) and ultra high molecular weight polyethylene (UHMWPE) are both linear versions of polyethylene plastic that are affordable as well as resistant to abrasion, chemicals, and impact.

HDPE is well suited for use in fuel tanks, piping, and outdoor furniture, and unlike UHMW, it is ideal for injection molding. However, it may crack under stress. In contrast, UHMW is incredibly dense and strong — in fact, its strength rivals steel. UHMW’s combination of high tensile strength, wear resistance, impact resistance, and self-lubrication make it an ideal material for industrial applications as well as high-performance equipment.

Getting started with UHMW

UHMWPE is a strong, water-resistant, and biocompatible plastic that’s suitable for a wide range of applications, from docks to orthopedic implants. It’s highly versatile, durable, and easy to fabricate, making it an ideal choice for many projects. Choosing the right material for your project is essential, but it’s not as simple as reading a data sheet. Working with an experienced manufacturing partner when selecting materials can simplify the process and elevate your final product.

When you partner with Fast Radius, we’ll work with you and offer in-depth information to help you navigate the manufacturing process. Backed up by years of manufacturing experience with a wide range of materials, we can guide you to the best material that will help you achieve your manufacturing goals. Ready to get started? Contact us today.

Check out our resource center to learn more about plastics manufacturing, including hydrolysis- and UV-resistant plastics and how to select the right plastic manufacturing process for your application.

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