Cytec, CSP cooperate on Chevy Spark composite battery enclosure

Resin specialist Cytec Industrial Materials develops a styrene-free vinyl ester for use by Continental Structural Plastics (CSP) in the manufacture of a compression-molded battery tray for the Chevrolet Spark electric car.

General Motors (GM) worked with Continental Structural Plastics (CSP, Auburn Hills, Mich., USA) and resins and fiber specialist Cytec Industrial Materials (Woodland Park, N.J., USA) on the development of a composite electrical vehicle battery enclosure that meets a number of rigorous performance requirements. These include 30° offset-barrier, side-impact, and rear-barrier crash; 50 G impulse shock (X, Y, Z); post-crash package integrity; fire-resistance testing; 3m drop testing (bottom/end); 1m water-submersion test; and vibration/shock testing.

To satisfy all criteria, new material, production process, post-mold finishing and non-destructive test methods were needed.

Cytec studied CSP requirements and developed MTM 23, a tailored, self-releasing rapid-cure vinyl ester resin system. Cytec and CSP also worked together on data generation, ply design and press production technology. That close collaboration enabled CSP to manufacture parts in less than 10 minutes at a 150°C/300°F cure, but MTM 23 has the capability to be rapid-cured in less than 3 minutes.

The result is the industry's first application of a volatile-organic compound (VOC)-free thermoset vinyl ester resin woven glass reinforced prepreg. The new material enabled CSP to form a complex-shaped enclosure that protects the EV's battery components in the event of a catastrophic event. The compression-molded structure is 40 percent lighter than metallic solutions, helping the vehicle achieve extended range and enhanced performance.

Since it is non-conductive, it also protects occupants and first responders to an accident scene. The specially formulated resin is free of styrene emissions, making it safer for workers and the environment. Selective pattern layups allow for localized reinforcement. The application also features a large structural joint of composite to steel.

This application earned GM an SPE Automotive Division award in the Electrical Systems category at the recent 43rd SPE Automotive Innovation Awards Gala.