For more than two decades, automakers have consolidated accessory drive components into one belt, known as the stretch belt, that offers less tension and fewer noise and vibration issues. To improve engine efficiency, more OEMs are switching from polyester stretch belts used in traditional ICE to elastic options designed for next-generation front-end accessory drive (FEAD) systems.

Due to their low-friction performance and better power transfer capabilities, elastic stretch belts offer considerable fuel savings and improve vehicle range. This approach also enables engine designers to remove several belt drive components, including alternator overrunning pulleys and auto-tensioners prone to wear that may lead to harsh noise and engine failure. In addition to design simplification, the shift to elastic stretch belts provides cost savings of €10 to €15 per vehicle.

Yet, polyamide 66 (PA66), which is commonly used to manufacture elastic stretch belts, tends to lose the tension required to optimize belt performance over time. Due to PA66’s limited ability to hold belt tension, stretch belts made with the material need to be installed at higher tension levels, which leads to a higher load on the alternator and waterpump bearings. This decreases power transfer from the belt and takes an immediate toll on the fuel economy of the vehicle.

Faster loss of tension also increases the risk of the belt slipping on a pulley. This manifests itself as a squeaking noise and heats up the belt. It can lead to premature part failure, which causes the engine to suddenly stop working and leaves drivers and passengers stranded – potentially damaging your brand’s reputation. As a result, more manufacturers are searching for an alternative polyamide cord material that enables them to offer OEMs a more reliable elastic stretch belt.

Envalior’s advanced elastic drive belt solution

Our Stanyl® PA46 is an industry-leading aliphatic polyamide optimized for under-the-hood automotive components. The material’s inherent high stiffness and durability provides excellent wear and friction performance required for engine parts built to withstand extreme heat and torque levels. In stretch belts, Stanyl PA46 offers 30 to 50% better stress retention performance compared to PA66. This allows OEMs to install the part under less tension, which reduces strain, improves noise, vibration and harshness (NVH) characteristics, increases fuel efficiency, and extends belt lifetimes.

Outperforming the competition

To achieve consistent tension after stress relaxation, PA66 stretch belts need to be installed with high pre-tension levels across each belt rib. Added strain on the belt creates high bearing hub loads at the alternator and AC compressor, leading to increased friction levels that generate excess heat. This results in the AC and alternator parts wearing out faster and it decreases overall engine efficiency. Due to Stanyl PA46’s superior mechanical properties, stretch belts made from the material can be installed with pre-tension levels 50N lower per rib. Tests comparing PA66 and PA46 belts running at 2,000 RPMs determined that the PA46 option achieved friction approximately 100W lower and bearing loads and belt torque 0.5Nm lower. This enables CO₂ emission reductions of around 1g CO₂/km, compared to PA66 stretch belts.

Trusted by leading OEMs

Manufacturers of numerous automotive accessory drives and small engine components have relied on Stanyl PA46 for more than 20 years. Hutchinson and Gates, both top global belt drive system suppliers based in Europe and America, developed the elastic Stretchy and StretchFit Belt, made with Stanyl PA46-based cords. In 2019, General Motors (GM) selected Hutchinson to supply elastic belts for the accessory belt drive systems used in its new “light trucks” fleet. The Stretchy Belt was installed in V-6 and V-8 powertrains used in prominent GM vehicles, including the 2019 Chevrolet Silverado and GMC Sierra. The switch enabled GM to meet goals to lighten engines, lower production costs, and reduce fuel emissions.

Envalior takes a collaborative approach to aligning our material solutions to our customers’ changing needs. Since launching Stanyl over 30 years ago, we’ve partnered with leading automakers to ensure our product portfolio enables manufacturers to produce lighter, greener and more cost-effective vehicles. As part of our organization-wide commitment to sustainability, we’re also on track to launch bio-based or recycled-based versions of all our materials solutions by 2030. As your dedicated manufacturing partner, we help you capitalize on advanced materials innovation that strengthens your business. 

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