S. Zhong, M. Rutkevicius, C. Stoner
ABB US Corporate Research Center,
Keywords: intumescent, polymer composite, injection molding, thermal resistant, graphite
Summary:Intumescent plastic composites have found wider applications in recent years thanks to their excellent thermal-resistant performance, low cost and high compatibility in mass production. These intumescent composites act as a passive thermal-resistant material that expands under heat, forming a highly porous carbonized insulation layer, which stops fire spread and reduces heat transfer. Unlike well-studied intumescent coatings, there is a lack of knowledge in the field of intumescent polymer composites. A series of polymer composites containing commercially available intumescent masterbatches were prepared. Moldflow simulation has been adopted to establish injection molding processing parameters and indicated that intumescent polymer composites could be processed at a lower melting temperature compared to virgin polymer. The molded composites were analyzed before and after exposure to heat, suggesting that expansion of the samples increased with higher intumescent loading, but higher intumescent content decreased composite mechanical properties. Highly porous network structures were observed in the Scanning Electron Microscopy images of the expanded composites, confirming a porous structure. This porous structure created highly thermally insulating layer, whose performance was evaluated via a thermal test. Surprisingly, glass fiber-reinforcement did not change thermal expansion behavior but improved mechanical properties of the composites. Mechanically strong yet easily moldable intumescent composites enable to engineer products with desired thermal-resistant performance.