Polymer Degradation and Decomposition of Cable Insulation for Electric Vehicles

Electrical wires and cable insulation are the first components in highway vehicle fires to be ignited (28%) outranking even flammable or combustible liquid, gas filters, and piping (26%). These ignitions are a result of mechanical system failures or malfunctions and were the leading cause of vehicle fires in 2020. Mechanical failures increase with increased vehicle lifetime due to advanced aging of the mechanical components through various stresses such as (thermal, electrical, ambient, and mechanical). Changes in the past decade – (1) longer retention of vehicles – aged cable insulation, (2) increased electric vehicle production/consumption – new cable designs, and (3) replacement of metal and plastic vehicle components with novel bio-based composite materials – new materials – require further investigation into how cable insulation will perform in fire, degrade with age, and interact with electrical systems in electric vehicles. While investigations into the degradation of electrical wire and cable insulation have been conducted, studies typically focus on single-variable tests. However, electrical wires and cable insulation are rarely if ever exposed to a single variable stressor outside of the laboratory. Mechanism models that predict damage before catastrophic failure could reduce annual costs of mitigation, litigation, and project delays by millions of dollars annually. The work presented here examines the response of cable insulation to multiple single-variable stressors and their combined effect (multi-variable stressors). This process will provide insight into competing damage mechanisms in multivariate harsh electric vehicle environments and be transferable to real-world transient environments where past “single-variable” controlled laboratory experimental approaches have failed.