Windscreen Rubber Extrusions: Enhancing Vehicle Safety

The integrity of any vehicle relies on all its components doing their jobs, no matter how small or simple. Windscreen seals are one such small and simply designed part that provides an ingenious benefit, keeping the vehicle in safe working condition. A windshield seal, or gasket, is a rubber strip securing the windscreen, preventing water, air, and debris from entering the vehicle while ensuring a snug, weather-resistant fit. Proper maintenance of the windshield and seal is essential for clear visibility and a protective barrier—crucial for the driver’s safety.

When manufacturing windscreen seals, only one material comes out on top: rubber, specifically extruded rubber. Rubber extrusion is a process made for windscreen seals. In this article, we explain.

The Role of Windscreen Rubber Extrusions

Installed between the windscreen and vehicle body, these extrusions provide a weatherproof seal, insulating the cabin from rain, snow, and external noise and bolstering the windscreen’s structural stability. The evolution of rubber extrusions in automotive applications has focused on improving durability, noise reduction, and, critically, passenger safety.

Early rubber seals have transformed with modern materials like EPDM and silicone to withstand UV, temperature extremes, and environmental stress. For passenger vehicles, quality windscreen seals contribute to the stability needed for airbag deployment. Beyond cars, windscreen seals are essential for boats, aeroplanes, and types of heavy machinery like tractors and excavators, with material selection tailored to meet the specific demands of each vehicle type and usage environment.

Key uses of a rubber windscreen seal:

• Weatherproofing the vehicle from rain, snow, and debris

• Minimising the noise of the road and other external elements

• Supporting the structural integrity of the windscreen

• Protecting the windshield component by absorbing and reducing vibrations by way of vibration-dampening

Cars are not the only vehicles that have rubber windscreens; they’re also needed in boats, aeroplanes, and types of heavy machinery like tractors and excavators.

Rubber in Windscreen Seal Manufacture

Rubber is a popular material for the manufacture of windscreen seals, thanks to its resilience to the varying elements in vehicle climates. Rubber’s high elasticity helps it conform to the shape of the windscreen, assists with installation, and absorbs vibration and noise.

Let’s take a look at the qualities and properties of different types of automotive rubber seals for windscreens.

Silicone

• Resistance to extreme temperatures and UV radiation

• Ensures a long lifespan and reduces the need for frequent replacement

• Easily conforms to the windscreen shape to provide a tight seal and stress-free installation

• Recyclable, reusable, and highly durable

• Silicone rubber extrusions are ideal for more extreme, harsh weather conditions.

EPDM (Ethylene Propylene Diene Monomer)

• Good resistance to weathering and UV radiation in a range of climates

• Generally more affordable than silicone

• Recyclable and performs well in harsh weather conditions

• Can become brittle and stiff over time

Nitrile Rubber

• Highly resistant to chemicals and oils, making it ideal for industrial use

• Known for its resistance to extreme temperatures

• Durable and flexible

• Good resistance to abrasion, heat, and water

Neoprene

• Highly resistant to UV radiation, ozone, and weathering, making it ideal for marine environments

• Good durability and flexibility in all climates

• Highly resistant to hot and cold temperatures compared with nitrile rubber

Benefits of Quality Windscreen Rubber Extrusions

Carefully selecting the best type of material for a windscreen seal depends on its application and the specific environmental conditions it will face. Each material—rubber, PVC, silicone, EPDM, nitrile, neoprene, and even foam—has unique advantages suited to different automotive needs. Silicone and EPDM are ideal for extreme temperatures, with silicone excelling in high-temperature climates due to its durability, heat resistance, and eco-friendly benefits. EPDM offers a more budget-friendly option with solid weather resistance, though it may have a shorter lifespan.

Nitrile and neoprene, on the other hand, are chosen for specific environments. Nitrile’s high resistance to oils and chemicals makes it ideal for industrial applications where exposure to these substances is common, such as in heavy machinery. Neoprene is better suited to marine vehicles

For lighter applications, foam seals are sometimes used. Foam is a lightweight, porous material with good insulation properties, making it suitable for electric vehicles or as a secondary seal in classic cars to maintain design integrity. However, foam is less durable and may need more frequent replacement in high-stress conditions. PVC (Polyvinyl Chloride) is another alternative known for its low maintenance and durability. Resistant to weathering, oils, grease, and petrol, PVC is commonly used in cars, lorries, and buses where rubber may not be ideal. Lightweight and easy to shape, it’s a popular, cost-effective option for vehicles exposed to varying environmental stresses.

A Closer Look at Temperature Impact

Temperature fluctuations significantly impact rubber seals' chemical structure and functional longevity, which are vital for windscreen integrity. Rubber’s elasticity depends on molecular bonds that vary in strength and flexibility, and thermal exposure gradually breaks down these bonds, especially under high temperatures and pressure. Each type of rubber has a specific operational range, beyond which the material’s properties degrade, resulting in brittleness, reduced elasticity, and, ultimately, failure to maintain a secure seal. High temperatures accelerate bond breakage, causing rubber to lose flexibility, while extreme cold increases rigidity, compromising its ability to provide a secure fit.

To withstand these stresses, specific rubber materials are selected based on their thermal endurance to withstand these stresses. Silicone, with a tolerance range of up to 315°C (600°F), resists UV radiation and remains flexible in high-temperature applications, making it ideal for applications such as nuclear plants or heat exchangers. With slightly lower heat resistance, EPDM functions well across varied climates, resisting both UV and chemical exposure, though it may stiffen over time. Nitrile rubber, highly resistant to oils and chemicals, is favoured in industrial applications up to 176°C (350°F), while Viton, noted for its thermal stability and chemical resilience, is commonly used in high-temperature automotive applications like oil seals and water pumps.

Installation Tips for Windscreen Rubber Extrusions

Installing rubber windscreen extrusions correctly ensures the longevity of both the seals and the vehicle.

Top Tips

• Accurate sizing is essential for an effective seal. Measure the window and panel thickness carefully to find the correct profile that will fit snugly, ensuring optimal weatherproofing.

• Always wear gloves and safety glasses when removing or installing seals to prevent injuries, especially when handling glass, which may unexpectedly break or chip.

• Use a flathead screwdriver to carefully pry out the old filler strip, working around the seal to release it fully. This makes it easier to remove the existing window and clean the area.

• Once the old seal is removed, clean any leftover residue or dust from the frame. This ensures the new seal will adhere properly and prevent leaks.

• Rubber seals are easier to work with when warm. Soak them in hot water or leave them in the sun to increase their flexibility, making installation smoother.

• Apply a small bead of silicone sealant around the frame recess before fitting the new rubber seal. This adds extra adhesion and helps secure the seal in place.

• Use a glazing tool to fit the seal’s lip over the glass, working slowly to avoid stretching or damaging the rubber. A glazing tool helps achieve a precise fit.

• Thread the filler strip into the seal's outer groove. Apply lubricant to help slide it into place, ensuring a secure, weatherproof finish around the entire window.

How to Install a Windscreen Seal

1. Ensure the windscreen is completely clean and dry before installation, and ensure it is free of oils. It is recommended that you use a glass cleaning solution and a lint-free cloth.

2. Warm the rubber seal to increase its flexibility. You can do this by soaking it in hot water or laying it in the sun.

3. Apply a good lubricant to the seal, such as KY Jelly or Simple Green cleaner.

4. Physically installing the windscreen seal requires two or three people to work together. Start by installing the seal onto the windscreen to fit snuggly around the glass.

5. Wrap waxed twine around the windscreen seal in the outer groove, leaving 6” extra around each end to use as pull handles. It’s recommended to wrap the twine around twice. This will help get the rubber over the metal lip of the channel when installing the windscreen. Tape both ends of the twine to the glass to keep them out of the way and ensure the twine doesn’t fall out of the groove. Make sure these are taped on the interior side of the glass.

6. Sitting inside the vehicle, place the windscreen on your knees, with the inside part face-down. Let the windscreen sit in the sun for another 10–20 minutes to allow the seal to soften further.

7. Insert any kind of reveal moulding, if needed, before the glass is installed back into the vehicle.

8. Lubricate the outer groove of the seal.

9. One person inside the vehicle should push the glass into the frame. Start by ensuring the bottom of the windscreen is pushed down into the frame first.

10. At the same time, the other person should begin to slowly pull the twine out of the seal at a 90-degree angle to the glass. Keep going until the lip of the seal is completely pulled out over the metal edge.

Common Problems and Solutions

Tips for Cleaning and Care of Windscreen Seals

• To reach difficult areas, wrap a microfibre cloth around a credit card, dampen it with Optimum No Rinse, and slide it along the seal’s edge where it meets the glass.

• For tougher dirt, use an all-purpose cleaner or car shampoo with a soft detailing brush to scrub the seal. Work in small sections, rinsing thoroughly to remove all residue.

• Use a boar’s hair detailing brush with car shampoo for effective yet gentle cleaning. This helps agitate dirt without damaging the rubber surface.

• Use a soft toothbrush or Q-tip for tighter spaces and intricate areas, especially for scrubbing away mould or grime build-up on rubber seals.

• Pressure washing can quickly remove surface dirt, but use it cautiously to avoid damaging the seal. Follow up with soap and a soft brush for a thorough clean.

• If you encounter mould, use a mix of water and white vinegar to clean it and prevent future growth. Avoid harsh chemicals, as they can degrade rubber.

• After cleaning, apply a silicone-based lubricant to keep the rubber flexible and prevent cracking. Avoid petroleum-based products, as they can harm the seal.

• Regularly inspect seals for wear and clean them to remove dirt and prevent deterioration, which helps keep the seals functional and looking new.

Innovations in Windscreen Rubber Extrusions

Continuous development in the manufacturing process of rubber extrusion means design innovations are constantly taking place. Here are some innovations that make rubber windscreen extrusions even better for their intended application.

Multi-Durometer Extrusions

This involves merging two or more materials through a single die in the extrusion process to form a single structure. In doing this, manufacturers can produce a rubber seal with numerous structural benefits, such as a strong attachment base with a softer compound that enables a tighter seal. Multi-durometer extrusions offer exceptional compression set properties, easy installation, and minimised stretch, making them ideal for vehicle windscreen seals.

EPDM Co-Extrusion Technology

This involves co-extrusion of EPDM with different hardness levels within the same profile. This technique combines hard and soft EPDM materials in a single extrusion process, creating a seal with varied properties. The harder segments provide structural integrity and attachment points, while the softer sections ensure a snug fit and effective sealing. This improves the overall performance of the windscreen seal, particularly in maintaining a tight seal against the windshield and car body.

Browse our blog for more details on rubber extrusion applications and the properties of extruded rubber. You can also find out about all the rubber extrusions we produce.