Polyplastics’ New PPS Resin Withstands Thermal Runaway in EVs

Durafide grade 6150T73 holds insulation properties after 30-minute exposure at 1,000°C

Resin suppliers are formulating grades to boost the thermal and electric insulation properties of plastics for electric vehicles. The goal is to protect occupants from the heat generation and potential fire hazards caused by the lithium-ion (Li-ion) batteries that power EVs, as well as thermal runaway events created by accidents or other damage that can set vehicles on fire.  

One of the latest entrants in this category is Polyplastics Co. Ltd., of Tokyo (U.S. office is in Farmington Hills, Mich.), which has added Durafide polyphenylene sulfide (PPS) 6150T73 to its line of engineering resins. The high-purity, linear grade reportedly delivers outstanding heat resistance and high thermal and electric insulation properties without the use of inorganic insulative sheet structures in EVs powered by Li-ion batteries. Polyplastics says the material maintains the insulation properties of busbars and module covers even after being left in environments of 1,000°C (1,832°F) for 30 minutes. 

Heat Threat From Thermal Runaway

During a thermal runaway event, a Li-ion battery cell can reach 800 to 1,000°C (1,472 to 1,832°F), and the gas it ejects can reach 700 to 800°C (1,292 to 1,472°F). If a thermal runaway occurs in one cell, energy transfer to neighboring cells must be reduced. As a safety measure, structural insulative sheets and plates have been used to reduce energy transfer between cells. Such components, however, increase weight and take up vehicle space. 

In addition to heat resistance, grade 6150T73 has optimal properties for components such as module covers and busbars, Polyplastics says. The PPS resin also provides high toughness and impact strength and exhibits low ionic impurities (extracted components). The resin is close to white in color and can be tinted.  

Auto OEMs Ramp Up EV Sales

Global EV sales remain strong, according to one consultant, EV-Volumes.com, of Trollhätten, Sweden. A total of 10.5 million new battery powered EVs and plug-in hybrid EVs were delivered in 2022, an increase of 55 percent compared with 2021, the company says.  

“The regional growth pattern is shifting, however. Following two years of steep sales increases in Europe, EVs gained only 15 percent over 2021 there,” writes Roland Irle, R&D and data developer. “Weak overall vehicle markets and persistent component shortages are among the reasons,” along with the war in Ukraine.  

“EV sales in the U.S. and Canada increased 48 percent year-on-year, despite a weak overall light vehicle market which plunged 8 percent during 2022 from 2021,” Irle finds. “The second half of 2022 saw a mild recovery of auto markets. Global light vehicle sales for 2022, 81 million units, were 0.5 percent lower than in 2021 and 15 percent below pre-2020 levels,” he reports.  

In the U.S., analysts say the Environmental Protection Agency and the Biden Administration are promoting strict federal pollution rules that are intended to increase EV sales by 2032. The government wants 67 percent of new light-duty passenger vehicle sales and 46 percent of medium-duty trucks (e.g., delivery vans) to be all-electric then. In 2022, only 5 to 8 percent of all new cars sold in the U.S. were EVs, sources note, and less than 2 percent were heavy-duty trucks.