The science and ingenuity behind the humble wiper blade

Have you ever wondered what goes into the wiper blade? How they are made and how manufacturers juggle performance and durability and cost?

If you’ve ever been caught in a heavy downfall in your car, or been met with a windscreen of snow when you’re about to head out, chances are you’ve thanked your wiper blades for clearing the way forward. 

And while they may seem to be a simple accessory, there is more than meets the eye – a great deal of thought and science is behind the construction and design of the humble wiper blade.

Of course, the moment of truth for any wiper blade is when you really need them, when the rubber hits the windscreen so to speak. The performance of your wiper blades at this moment will depend on all the decisions that were made about their construction. Specifically: what are they made of? And, what coating was used?

Natural or synthetic?

Despite its many strengths, natural rubber is not ideal for windshield wipers. As they spend most of their life stationary in standby mode, natural rubber wiper blades tend to permanently ‘set’ to one side. But to be effective, windscreen wipers need to flip as the wiping mechanism switches direction. A ‘set’ blade can’t flip, and the result is squeaking blades that don’t clear the windscreen.

Synthetic (ethylene propylene diene methylene, or EPDM) rubbers don’t set, and they also perform better than natural rubbers in regard to thermal aging, and overall resistance to UV, ozone and tearing.

Natural rubber does, though, perform better than synthetic rubbers in cold conditions.

As a result, manufacturers have begun combining natural and EPDM rubber materials through a coextrusion process for superior performance in all conditions.

Coating – the vital layer

Whatever the choice of material, both natural and synthetic rubbers slowly deteriorate over time as a result of heat, UV radiation, oxygen and ozone.

One way manufacturers have dealt with this is by the addition of coatings. Not only do coatings reduce friction between the blade and the windscreen, they preserve wipe quality over the life of the blade and reduce noise.

Some manufacturers like French company Valeo are using graphitized coatings to maximize friction performance and durability.

The extrusion process

Unlike moulding, extrusion is a continuous process that can be adapted to produce a wide variety of products such as pipes, profiles and sheets.

Extrusion plays a prominent part in the plastics industry as it allows to production of objects of a fixed cross-sectional profile. It is also an efficient and highly productive form of construction, making it perfect for wiper blade production.

A production line for wiper blades extrusion is commonly a 130-metre length machine consisting of sections for:

• Extrusion
• Vulcanization
• Bromation
• Coating
• Finishing (brushing, printing, slitting) 

Check your blades

Major manufacturers like Valeo recommend replacing wiper blades as soon as they show any sign of wear that results in a loss of wiping effectiveness, or at least every 12 months.