NVH Reduction Solutions Improve Driving Experience

Today's automotive consumer has high expectations when it comes to handling, ride and comfort of a vehicle. And as autonomous driving evolves, sensitivity to noise, vibration and harshness (NVH) will continue to increase as the driver becomes the passenger and vehicle operation takes a backseat.

Automakers are seeking new solutions for a smoother, quieter driving experience, but can't solve the issue with materials that compromise overall vehicle weight. After all, reducing NVH can be just as important as improving fuel economy.

Through advanced chemistry, BASF has developed a selection of materials with properties that are not only lighter in weight than many conventional solutions, but provide a smooth, solid and quiet ride. These materials have varied applications from hood liners, engine covers and dashboard insulators for the engine compartment to interior solutions such as carpeting and headliners and come in a range of densities.

The ideal material for vehicle sound-proofing

Basotect® is an open-cell foam made from melamine resin. This material structure enables engine sound waves to enter the foam, where their energy is absorbed through friction with the foam cell walls. This makes Basotect an extremely efficient sound absorber to increase vehicle interior sound quality.

Commonly used for engine covers, hood liners, transmission covers and dashboard insulators, parts made of Basotect are lighter weight as the foam has a significantly lower density (down to only 9 g/m³ or 0.56 pcf) than any other materials employed in similar parts to reduce engine noise.

Its ability to withstand excessive heat is also of particular importance as automakers trend toward using smaller, more fuel-efficient engines equipped with direct injection and turbocharger technologies. These engines not only maximize performance, but increase noise and temperatures under the hood.

And because of its excellent sound absorption, lightweight nature and flame retardant properties, this technology is reducing weight and noise across the mobility segment in automobiles, trains, subways, buses as well as in aircraft.

"Basotect was developed with the primary purpose of sound absorption, and because it's a 100 percent open-cell foam, it does that very well," said Holli Woodard, Basotect market development manager for BASF's Performance Materials Division. "But when you consider it can withstand temperatures of up to 400 degrees Fahrenheit, is flame retardant as well as provides a lightweight alternative to other materials, it provides a real value for automakers."

Minimize road noise and vibration

Offering superior durability and driving dynamic properties, 90 percent of all car manufacturers use components made from Cellasto® to isolate and dampen vibrations.

From jounce bumpers, top mounts and coil spring isolators for the chassis, to powertrain applications such as mounts for electric motors or battery packs, Cellasto is used to create a number of microcellular polyurethane elastomer components. It can also be customized to meet the NVH needs of automakers while offering superior performance.

Compared to rubber components, Cellasto provides high-volume compressibility because it's a foam and therefore there's no need for a wider package. The jounce bumper can be compressed by up to 40 percent of original height without lateral expansion. It also allows for producing components that are about 30 percent lighter than those made from more traditional materials, as well as resistance to heat, cold, moisture, oil and grease.

"With Cellasto, even the toughest chassis loads experienced drastically minimized noise, vibrations and harshness," said Marc Ingelmann, head of new NVH for BASF's Performance Materials Division. "By ensuring a smoother ride, Cellasto components and modules offer improved comfort, as well as greater safety and better vehicle dynamics that are significant to premium automakers and especially in autonomous and electric vehicles."

Lightweight acoustic solution 

BASF's Elastoflex® is a polyurethane foam that not only serves as a lightweight acoustic solution, but has multiple grades that can be used in a variety of applications to reduce NVH levels.

In contrast to other acoustic materials, flexible foam systems can be adjusted to serve as sound absorbing foam and as a sound dampening material lowering the level of road, wind and engine noise in the cabin.

Elastoflex can be injected into the vehicle's body in white structure during the manufacturing process, quickly expanding to fill cavities such as pillars and sills. Elastoflex® E and Elastoflex® W grades are used to support these applications.

"It's completely customizable based on the cavity size," said Brian Shaner, market segment manager for automotive BIW, chassis and exterior for BASF's Performance Materials Division in North America. "The polyurethane foam shot size can be adjusted to the necessary volumes easily and allows automakers to make changes quickly during the development phase."

Elastoflex is a sound absorbing foam and a sound dampening material lowering the level of road, wind and engine noise in the cabin.

Elastoflex® W can also be found under the vehicle's interior carpet or behind the dashboard. The material can be designed to meet specific acoustic requirement profiles, by triggering viscoelastic and energy dissipating properties, and match desired interior sound sensations.

Special developments in the material have also resulted in resistance to very high temperatures and, in some cases, flame-retardant parts for engine covers or NVH active technical parts in the engine compartment. These properties have made polyurethane flexible foams the most widely used of acoustic solutions by the auto industry.

While Elastoflex flexible foam systems are widely used as an NVH solution for engine covers, these systems are not sufficient as a decorative part and are therefore surrounded by a hardcover made mostly from a polyamide. Although this combination offers a good fit in terms of design and function, BASF introduced Elastofoam®I as a one-shot process for acoustic parts that have an attractive surface skin.

Elastofoam®I has an open-cell foam core that offers sound absorption and an integral compact skin that is scratch resistant and attractive. This eliminates the need for a secondary hard cover and a step in the manufacturing process, reducing costs and parts. It also provides added pedestrian safety because it is softer than other materials typically used to create engine covers.

Aside from flexible or semi-rigid polyurethane foam solutions, BASF also offers thermoformable polyurethanes under the product family Elastoflex E 3943. These fully open-cell block foam systems can be sliced and cut to the right dimensions, assembled with glass mats and decorative surfaces, and thermoformed to 3D acoustic parts widely used for interior headliners or hood liners. Again, the open cell structure guarantees extreme sound absorption properties at very low density and part thickness. These BASF foam systems come with the adhesive series Iso116, which is designed specifically for the assembly process. The hood liners are also equipped with flame retardants allowing for UL94 V0 properties.

Reduce weight without compromising performance 

The automotive industry has used steel or die-cast aluminum for a number of years to achieve the necessary stiffness to reduce NVH in the cabin.

But BASF's glass-fiber filled polyamide, Ultramid®, has the strength and stiffness automakers are looking for, with the ability to reduce overall vehicle weight. This is following the trend set by the air intake manifold market where polyamide has replaced die-cast aluminum to become the incumbent material in this market. Acting as if there's a shock absorber built into the material because of the fiber reinforcement and polyamide matrix, Ultramid® offers 20 to 30 times the dampening effect of the die-cast aluminum in working range of automotive temperatures (80 to 100 degrees Celsius). The 50 percent glass fiber-filled material (Ultramid A3WG10 CR) is 40 percent less dense than the die-cast alumni and has anti-corrosion benefits.

Ultramid is a lightweight solution for manufacturing structural parts with NVH benefits.

This Ultramid grade today is being used in top mounts, torque rods, engine/transmission brackets, transmission adaptors, engine/sub-frame mounts and sub-frame brackets.

"Ultramid in mounting applications reduces the amount of energy that is transported to the body because of the high level of damping," said Christopher Korson, market segment specialist for chassis and exterior for BASF's Performance Material Division in North America. "And it's the type of lightweight solution with proven performance that offers automakers the ability to manufacture a structural part with NVH benefits that they're looking for."

Improve vehicle dynamics and driving comfort 

While providing significant advantages on their own, BASF has also found success by combining two of its NVH reduction solutions to create the world's first top mount with polyurethane bearing made of Cellasto® and a plastic housing made of Ultramid®.

The Ultramid and Cellasto Top Mount is lighter than traditional aluminum die-cast and rubber top mounts and contributes to a comfortable, quiet ride.

The end result was a solution that is 25 percent lighter than an aluminum die-cast version with rubber.

"Since top mounts link the shock absorber to the chassis, they can have a direct impact on passenger comfort, as well as the overall driving dynamics," Ingelmann said. "By using Cellasto, the top mount has excellent static and dynamic behavior while only requiring a small amount of space. Ultramid, meanwhile, is reinforced with 50 percent glass fibers, making it exceptionally rigid and solid."

To learn more about BASF's NVH reduction solutions, please contact BASFAutomotiveSolutions@basf.com.