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The powder is called carbon black. Until very recently, engineers did not have a proper scientific explanation for why adding more of it makes rubber stronger.<\/p>\n
The main ingredient<\/p>\n
Pure rubber<\/a> on its own is soft, stretchy, and springy, but it is not very durable and becomes unreliable under heavy loads.<\/p>\n The standard fix for this is carbon black, a fine soot produced by burning oil or natural gas in low oxygen.<\/p>\n Manufacturers blend microscopic particles of it into rubber, which is why nearly every tire<\/a> is black.<\/p>\n The formula has changed little since the 1920s. When soot is added, rubber gets tougher. <\/p>\n Tire companies buy dozens of carbon black grades and figure out which ones work by testing them on real tires.<\/p>\n A century of guessing<\/p>\n There are three theories as to why. One argues that the particles are linked into chains running through the rubber, carrying the load. <\/p>\n Another argued that polymer chains cling to each particle and stiffen like glue.<\/p>\n A third claim focused on space, arguing that the particles took up room, and the rubber around them was forced to deform more sharply than ordinary rubber would.<\/p>\n None of the three options fully proved what reinforced rubber actually does under real strain. Each model explained part of the behavior but missed the full picture.<\/p>\n Professor David Simmons at the University of South Florida (USF<\/a>) wanted a clear answer. The problem, however, was nobody could watch the mechanism in action.<\/p>\n This is because the process is too small to see directly, and too fast to film. The rubber itself is a tangle of long chain molecules wrapping around each particle.<\/p>\n Inside the simulation<\/p>\n Simmons and his team rebuilt the inside of a tire on a computer to draw a conclusion. <\/p>\n Alongside Dr. Pierre Kawak and doctoral student Harshad Bhapkar, he ran 1,500 separate molecular dynamics simulations.<\/p>\n Each one tracked hundreds of thousands of atoms moving the way they do inside a real piece of reinforced rubber. <\/p>\n An earlier paper<\/a> by the same group had hinted at where the answer might be found. This time, however, the team gathered enough data to support the theory.<\/p>\n Rubber fights itself<\/p>\n The key turned out to involve a property called Poisson\u2019s ratio<\/a>. This is a measure of how material changes shape in one direction when you pull it in another.<\/p>\n When you stretch an ordinary rubber band, it gets thinner in the middle while keeping roughly the same overall volume. <\/p>\n When carbon black is added, the rules change. The hard particles don\u2019t compress sideways the way the rubber would, which prevents the usual thinning.<\/p>\n Only one option remains: the whole composite has to expand in total volume as it stretches.<\/p>\n In doing so, the rubber resists strongly. Simmons describes it as the material fighting against itself.<\/p>\n \u201cHow is it that we\u2019ve been using this for 80, 90, 100 years and haven\u2019t really known how it works?\u201d Simmons said.<\/p>\n Three theories merge<\/p>\n The new explanation does not throw out the old ones. Particle networks and sticky polymer layers around each particle still contribute to the effect.<\/p>\n The simple geometry of taking up space all contribute to the same effect. The rubber maintains a growing resistance to changing its overall volume.<\/p>\n An earlier study<\/a> from the same group had laid groundwork for combining the theories. Until this test, no one had shown all three pointing in the same direction.<\/p>\n The Magic Triangle<\/p>\n Tire engineers have long talked about something they like to call the \u201cMagic Triangle.\u201d <\/p>\n This is where fuel efficiency<\/a>, traction, and durability all pull against one another. Selecting one usually costs you another.<\/p>\n When you try to improve a tire\u2019s grip on a wet road, you tend to lose mileage benefits. When tires are made to last longer, they loosen their grip on the road.<\/p>\n With a model of what carbon black is actually doing at the atomic level, engineers can start picking particle sizes and rubber chemistry on purpose.<\/p>\n Going beyond the tire<\/p>\n The same physics show up wherever a rubber part is needed. This includes power plant seals, aircraft hydraulics, medical devices, and more.<\/p>\n The 1986 Space Shuttle Challenger broke apart after a cold-stiffened rubber<\/a> O-ring failed at launch. <\/p>\n If the new theory holds, manufacturers in those fields can design parts with greater confidence.<\/p>\n It is important to note that the data comes from computer models, not physical experiments.<\/p>\n The simulations are built to match real rubber, but any mechanism the model identifies still needs experimental confirmation.<\/p>\n The future of rubber<\/p>\n The study may have solved the mystery. Carbon black<\/a> makes reinforced rubber stronger because it forces the material into a state where stretching demands volume expansion.<\/p>\n Rubber resists volume expansion strongly, an answer that has been needed since the 1920s.<\/p>\n What changes from here is design. Tire companies no longer have to treat carbon black grades as a black box. <\/p>\n \u201cWith these findings, we\u2019re laying a new foundation for rationally designing tires,\u201d said Simmons.<\/p>\n The same approach can be aimed at other composite materials with stubborn, unsolved mysteries.<\/p>\n The study is published in Proceedings of the National Academy of Sciences<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"Every airplane tire has to absorb the impact of a fully loaded jet, then do it again, hundreds…\n","protected":false},"author":2,"featured_media":457506,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[61,60,82],"class_list":["post-457505","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-ie","tag-ireland","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/457505","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=457505"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/457505\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/457506"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=457505"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=457505"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=457505"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}