http://www.nytimes.com/2014/11/20/business/takatas-switch-to-cheaper-airbag-propellant-is-at-center-of-crisis.html 2014-11-20 03:59:29 Takata’s Switch to Cheaper Airbag Propellant Is at Center of Crisis Takata switched to ammonium nitrate, which is cheaper but is highly sensitive to temperature changes and breaks down over time. === The new airbag propellant was supposed to be the next big thing for Takata in 1998. An engineer for the company, Paresh Khandhadia, declared it “the new technological edge” in an interview with a trade magazine then. But despite the fanfare, by 2001 Takata had switched to an alternative, ammonium nitrate, and started sending the airbags to automakers including Honda. That compound, according to experts, is highly sensitive to temperature changes and moisture, and it breaks down over time. And when it breaks down, it can combust violently, experts say. “It shouldn’t be used in airbags,” said Paul Worsey, an expert in explosives engineering at the Missouri University of Science and Technology. The compound, he said, is more suitable for large demolitions in mining and construction. “But it’s cheap, unbelievably cheap,” he added. Takata would not immediately comment on why it made the switch. More than a decade later, that compound is at the center of a safety crisis involving Takata and its airbags. More than 14 million vehicles with the Takata-made airbags have been recalled over concern than they can explode violently when they deploy, sending metal debris flying into the cabin. At least five deaths have been linked to the defective airbags. On Thursday, Takata’s decision to change the propellant is expected to be among the lines of questioning before the Senate Commerce Committee, which is investigating Takata’s defective airbags. Takata will be represented at the hearing by Hiroshi Shimizu, the company’s senior vice president for global quality assurance. He will be joined by representatives for Chrysler and Honda, as well as a victim, Stephanie Erdman. David Friedman, the deputy administrator of the National Highway Traffic Safety Administration, will also appear. Committee investigators were contacted by a former Takata engineer, who said he had warned the company about switching to such a risky compound, according to a person briefed on the committee’s preparations for the hearing. The former engineer told the committee’s staff that ammonium nitrate was a cheaper alternative to tetrazole, that person said. Takata’s struggle with propellant stretches back to 1991, when the Tokyo-based supplier first started to manufacture airbag inflaters in the United States. Like other airbag manufacturers at the time, Takata based its airbag propellant on a toxic compound called sodium azide. But sodium azide is volatile and could release toxic fumes into the car, causing chemical burns or breathing problems when the airbags deployed. And azides could explode unpredictably during manufacture when exposed to the air or light or when jostled. Takata then turned to a compound called tetrazole to make a new propellant, which it promoted to automakers at the time as environmentally friendly. Marketed as “Envirosure,” Takata began introducing the propellant to automakers in the mid-1990s for inclusion on 1998-model vehicles. “I said, ‘Wow! This is the break!’ ” Mr. Khandhadia, Takata’s lead propellant engineer, told the industry publication, Automotive News, at the time, describing the moment tests showed that the new propellant worked. “There are some of the moments you never forget, and this was the moment,” he says. “I should say the auto industry is always looking for the new technological edge.” But tetrazole, which is produced in limited quantities and can be expensive, started to squeeze margins at Takata, especially as airbags became increasingly commodified, the former Takata engineer told congressional investigators. By 1999, Takata executives were pressing its engineers in the United States for a cheaper alternative. Under pressure, Takata researchers in Michigan proposed and developed a propellant made with the ammonium nitrate. But the engineering team at Takata’s propellant factory at Moses Lake, Wash., raised objections to basing a propellant on such an explosive compound. To bolster its case, the team pointed to explosives manuals warning that the compound “tended to disintegrate on storage under widely varying temperature conditions” with “irregular ballistic” consequences, the former Takata engineer told committee members. Ammonium nitrate cycles through five solid states, experts say. As the vehicle goes from receiving the heat of sunshine to the cold overnight, the temperature swing is large enough for the ammonium nitrate to change from one phase to another and back again every time the temperature swings. Ammonium nitrate also absorbs moisture from the atmosphere readily. Those two things together make ammonium nitrate tablets prone to damage, experts say. A focus on the mushrooming recalls has been that the airbags are more susceptible to malfunction in humid regions. “Speaking generally, ammonium nitrate can be unstable. Its crystal structure can change according to temperature,” said Katsumi Kato, an assistant professor in safety engineering at Japan’s Fukuoka University. “It changes the burn rate. It leads to various malfunctions.” Other airbag makers have said they stayed away from the explosive compound. “We’ve made another choice for the propellant we produce,” Thomas Jonsson, vice president at the Swedish-American automotive safety products manufacturer, said in an email. Key Safety Systems, another airbag maker, said it used guanidine nitrate and amino-tetrazole — which experts said was more stable and durable than ammonium nitrate — in its inflaters. TRW also uses a propellant based on guanidine nitrate, experts said, though the airbag maker did not respond to requests for confirmation. Still, at Takata, the answer at the time was to try to stabilize the ammonium nitrate to try to mitigate those cycling effects, but there are limits to just how far ammonium nitrate can be stabilized, experts said. The doubts over Takata’s propellant raise questions of whether the recalls should be limited to humid regions. The National Highway Traffic Safety Administration, however, said Tuesday that it would urge automakers to expand recalls of certain drivers’ side airbags that had previously been limited to regions with high humidity, including Florida, Hawaii, the Virgin Islands and Puerto Rico.