Materials Science

Toughened by Worms

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Science  28 Nov 2003:
Vol. 302, Issue 5650, pp. 1480-1481
DOI: 10.1126/science.302.5650.1480e

Epoxy resins, particularly those that are flame retardant, are of special importance to the microelectronic and aircraft industries, where their use is mandated. Unfortunately, many epoxies are intrinsically brittle, and this tendency to fracture is worsened by the brominated monomers that are added to improve resistance to fire. Attempts to make these materials tougher often lead to a loss of modulus and temperature stability.

Previous work has shown that block copolymers can form micelles or vesicles within the epoxy and increase its toughness without affecting other key properties. Dean et al. find that when the block copolymers form wormlike micelles, the toughness is enhanced even more, and, surprisingly, the glass transition temperature of the composite, and hence its useful operating range, is increased. Control over which morphology forms is governed by the ratio of the two polymers that form the diblock component. The most dramatic increase was seen in a blend that contained 50% brominated monomer: With the addition of just 5% wormlike micelle-forming polymer, the virtually useless fragile glassy material was transformed into a tough resistant plastic. — MSL

Macromolecules 10.1021/ma034807y (2003).

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