Low Wear and Friction

Low wear and friction Delrin® acetal for injection moulding and extrusion

Delrin® is well-known for its industry-leading mechanical properties, of which low wear and low friction are key. These features can also be enhanced with additional additives such as PTFE, siloxane and specialised lubrication oils. Many mechanical assemblies involve moving parts where surfaces rub against each other, for example in gear trains. Using standard polymers without any form of advanced lubrications would demand higher forces to turn the gears and, over time, the surfaces would wear, deteriorate and potentially cause product failure.

Leveraging the innate low wear and friction attributes of Delrin® can combat common issues of wear, high friction, frictional heat and noise.

Wear

Wear refers to the progressive loss of material from interacting surfaces when the parts are in motion against each other. A common test for this is the steel thrust washer test. This involves spinning a polymer sample against a stationary steel washer. Friction is created between the metal washer and polymer sample, and after 100 hours the plastic is measured for signs or wear and erosion.

Two common types of wear in polymers are adhesive wear and abrasive wear.

Adhesive wear occurs when frictional heat causes the transfer of one material onto another.  

Abrasive wear occurs when a hard polymer or metal causes damage by scratching or gouging the other polymer material.

Friction

Friction is the resistance created in the motion between two interacting surfaces. This usually results in heat and damage to the polymers involved. The coefficient of friction (µ) is a measure of the amount of friction existing between two surfaces.

Noise

Sliding interacting surfaces can create noise, which may not be desirable in certain applications. Mechanical noise and squeaking are two common noise issues.

Mechanical noise is the fault of impact between two mating parts, for example gear teeth on acetal gears hitting each other. In fast moving parts, this can sound like squeaking. In this case, an improvement to the design will help, for example, changing the gear teeth rake and angle. In some cases, it will require a softer polymer such as Hytrel® TPC-ET to add a dampening effect between the Delrin® acetal gears.

Squeaking is usually created by friction between two parts and is directly linked to the coefficient of friction. Sometimes we see this when one part is static against a dynamic part. As a basic rule, if the coefficient of friction is higher in the dynamic part than the static part, the movement judders as the parts stick and then slip. This results in a squeak type of noise.

Understanding the working environment for Delrin® acetal to get the right low wear and friction solution

So that Distrupol can help you choose the optimal low wear and friction Delrin® solution, it is important to understand the whole environment and all factors that influence friction:

• Contact pressure and contact force between the two components
• The velocity of the two surfaces
• Temperature of the surfaces
• The type of motion (rolling like two opposing gears, sliding surfaces or vibration type motion known as fretting)
• Finish of the two mating surfaces (rough or polished)
• Lubrication environment (running dry, continuous lubrication or parts are wet)

Why choose Delrin® to solve your wear and friction issues?

Mechanically engineered to combat the common wear and friction issues in polymer processing, Delrin® and its associated suite of tailor-made solutions are first choice for designers and engineers across all industries. Additional lubricating systems are also available for Delrin®, including PTFE, advanced lubricating oils, PTFE micropowders, chemical lubricants, Kevlar®, aramid fibres and siloxane oils.

Each one of these provides a unique low wear and friction attribute. Depending on your surface combinations, we can select the ideal Delrin® solution for your application.

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