A THIRTY-YEAR controversy over the behaviour of molten plastics may be at an end. Researchers in Delaware claim liquid polymers slither like snakes when two chunks of polystyrene are fused.
Plastics such as polystyrene consist of thousands of carbon-rich units linked together in a chain. But how these chains intermingle when two pieces are welded to make a bottle, for example, has been hard to understand. Some people have suggested that the "head" and "tail" of each chain snake across into the adjacent piece of plastic, followed by the middle bit. But attempts over the past 30 years to prove this "reptation" theory have met with little success.
Now Richard Wool, a chemical engineer at the University of Delaware in Newark, thinks he has cracked it at last. His team made two types of polystyrene by adding deuterium, a heavy isotope of hydrogen, to the ends of the chains in ...
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