- Rubber toughening
thermoplasticssuch as polystyreneand PMMAare brittle when stressed, a property which limits applications. A good way of strengthening such polymers is to copolymerise elastomeric chains during manufacture. The elastomerchains form separate phases in the solid, typically 10-20 microns in diameter, so that when the material is strained, crazes form at their surfaces, increasing the energy needed to break the material. In other words, the material is toughened. The technique is known as rubber toughening, and has been applied to a wide range of polymers.
While incorporation of 10-25% rubber into rigid
thermoplastics increases the toughness, the much lower tensile modulusof the rubber component lowers the stiffnessof the product. The copolymerwill be sensitive to all the chemicals which may attack the rigid chains as well as the elastomeric chains, so care is needed when specifying such rubber-toughened grades in place of a rigid polymer.
One of the best known examples is
Acrylonitrile butadiene styreneor ABS plastic, where polybutadieneis grafted onto the styrene-acrylonitrilechains, so converting a brittle polymer into a much tougher material. The method has also been used with PMMA, high-impact polystyrene or HIPS, epoxy resinand nylon.
* [http://openlearn.open.ac.uk/mod/resource/view.php?id=196629 Polymer Structure]
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