August 1, 2005 Ropes and fishing lines made of a new plastic that changes color when damaged or heated can let climbers and fishermen know when it's time to get a replacement. Made of a polymer mixed with a dye, the new material changes color when its molecules are spread apart.
CLEVELAND--Researchers are constantly looking for new ways to make the materials we use better. Now, they may have found one -- a plastic that changes color when it's about to be damaged.
It's a fishermen's worst nightmare: A fish bites, the line snaps! They haven't invited an unbreakable fishing line, but research chemist Chris Weder and his team at Case Western Reserve University in Cleveland have created the next best thing, a line that changes color when too much stress is applied.
"It might mean potentially fewer fish will get away because the line breaks, because you're aware of the fact that your line has been worn out," Weder tells DBIS.
But fishing isn't the only use for this new polymer. Part of a family of new materials, it changes color when stressed or heated and could one day help climbers know their rope needs to be replaced or reveal drug tampering. Tiny holes would light up and alert consumers that something's wrong. The same goes for spoiled food. If meat temperature is too warm, the packaging would change color.
They would see it because of the sensor molecules that are mixed with plastic. When the molecules are together, everything looks normal. When the molecules are damaged or spread apart, that's when it changes color.
Weder says, "My hope is that this will be seen on the market in products before long and will help to make this a better world."
Researchers are also working on using this new technology to develop material to use in the construction of bridges and airplanes. They say items made with it could hit the market with the next two years.
BACKGROUND: Researchers at Case Western Reserve University are developing a fishing line that changes color when it becomes overstressed and ready to break.
THE PROBLEM: Nylon fishing line is designed to have some natural stretch to it. But if you pull on it too hard -- which happens when fighting to reel in a particularly large fish -- it can stretch so much that its structure is badly weakened.
HOW IT WORKS: The new fishing line contains a type of polymer that fluoresces -- emits light -- when viewed under ultraviolet light. The color of light emitted depends on how much stress the polymer molecule has experienced. When the line is not under stress, the molecules are close together and emit reddish-brown light under a UV lamp. When it stretches, the molecules pull apart and emit green light. A fisherman can check his line under UV light and discard it if it glows green.
A small amount of the polymer is mixed in with a standard plastic blend to make a fishing line. The prototype is not strong enough for bass-fishing, for example, but the same technique should be easily applied to standard nylon fishing line. The same polymer blend used in the fishing line could be used to make tamper-resistant packaging. A barely visible puncture mark from a hypodermic needle would be clearly visible as a green dot under UV light, because the puncture stressed the material at that point. The scientists are also looking at how temperature may affect the polymer's ability to change color.
WHAT ARE POLYMERS: "Polymer" comes from the Greek word polumeres, which means "having many parts." Polymers are large molecules made of repeated chemicals joined together in a long strand, like beads on a string. Most of the plastics we use every day are made of polymers.
The Optical Society of America contributed to the information contained in the TV portion of this report.