New PP Compounds Target Complex EV Battery Pack Applications

Two new polypropylene (PP) compounds from Sabic designed for sheet extrusion and thermoforming offer an alternative to traditional sheet metal forming and compression or injection molding of large, complex structural parts. Sabic PP compound H1090 and Stamax 30YH611 resins are 30% glass-fiber-reinforced, intumescent, flame-retardant (FR) materials that can be used for electric vehicle (EV) battery pack components such as top covers, enclosures, and module separators.

Putting a damper on thermal runaway

Both grades offer thermal barrier properties to help delay or contain thermal runaway propagation. Furthermore, extruding or thermoforming the materials delivers advantages in design, system cost, inherent thermal and electrical insulation, and weight compared with stamped sheet metal. In addition, extrusion and thermoforming can be more cost-effective and efficient than injection molding thermoplastics or compression molding thermosets, both of which require expensive tooling and equipment.

Bluehero to the validation rescue

Sabic’s development and validation of these new materials is made possible by Bluehero, an initiative that supports the automotive industry’s mission to create reliable, safe, and efficient EVs, with an emphasis on helping optimize structural battery components. Bluehero leverages, among other things, Sabic’s knowledge of and expertise in large part molding, compression molding, thermoforming, and advanced injection molding.

According to Abdullah Al-Otaibi, general manager of ETP & Market Solutions at Sabic: “By providing new alternatives to traditional materials and processes, Sabic can enable customers to design and manufacture the next generation of battery components while driving down costs and gaining a competitive advantage. Our experts have helped pioneer the successful adaptation of glass-fiber-reinforced materials for the extrusion and thermoforming of large, complex, structural parts. The development and validation of these novel resins showcase Sabic’s leadership in polymer technologies for vehicle electrification.”

Sabic has validated the mechanical and fire safety performance and manufacturability of its PP compound H1090 resin and Stamax 30YH611 resin in EV battery applications with complex geometries, both in its labs and with customers. These materials not only provide new options for the replacement of sheet metal or thermosets in final applications, they can also be used to create prototypes to determine the feasibility of investing in injection molding tools.

The long and short of glass-fiber-reinforced resins

Both short glass-fiber-reinforced Sabic PP compound H1090 resin and long glass-fiber-reinforced Stamax 30YH611 resin feature a distinct combination of intumescence for fire safety and balanced stiffness and ductility. Exposing these materials to vertical and horizontal flames at 1200°C for 10 minutes demonstrates excellent flame-retardant behavior. Efficient charring and intumescence keep the temperature of the reverse side of parts below 210°C and help prevent burn-through. Intumescence is enhanced by non-brominated/non-chlorinated FR that meets the UL94 V0 standard at 1.5 mm. (The video demonstrates a thermal runaway test for a Stamax resin.)

In addition to stiffness, strength, and impact resistance over a wide temperature range, key properties of Sabic PP compound H1090 and Stamax 30YH611 include dimensional stability, low coefficient of thermal expansion (CTE), and creep resistance. As the polymer matrix for both products, PP offers good electrical insulating properties, low density, global availability, and processability.

Sabic also offers injection and compression moldable flame-retardant long- and short-glass PP materials for various internal components and complete enclosures of EV battery packs.