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IRG-II Nugget

Baroplastics: Plastics that mold without heating

In IRG-II, Mayes has developed a novel class of polymeric materials termed "baroplastics." Unlike thermoplastics, baroplastics do not require elevated processing temperatures to mold. Instead, flow is achieved through pressure-induced mixing of nanophase domains of high Tg (100 ºC) and low Tg (-50 ºC) components. Baroplastic block copolymers and core-shell nanoparticles have been synthesized and subsequently processed at room temperature into transparent objects by compression molding. Characterization of these materials before and after molding indicates that they transform to a semi-solid state under pressure, allowing them to be formed into the desired shape (see images below).

The unique pressure-based processing of these materials suggests their potential as "evergreen" plastics that are highly recyclable. Currently, some 80 billion pounds of thermoplastics are produced each year in the U.S. alone, only 3 billion of which are recovered for recycling. As a consequence, plastics are the second largest non-organic component of U.S. garbage, accounting for some 10% of generated municipal waste. Unlike inorganic glasses and metals, recycling of plastics results in substantially lower grade materials compared with the virgin resin, greatly limiting their reuse. A primary reason is the poor thermal stability that polymers exhibit at the elevated temperatures necessary for processing, which causes substantial discoloration and a loss of mechanical performance. By circumventing such elevated temperatures, baroplastics can potentially be remolded many times with negligible degradation of their chemical structure, allowing for multiple reuses. Preliminary studies simulating the reprocessing of baroplastics are promisingóbaroplastics shredded and remolded 10 times at room temperature without rinsing exhibit mechanical and optical properties (discounting incorporated dust particulates) comparable to the original molded specimen.

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