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Advances in Rigid Thermal Insulation by Michael McAuley Photo courtesy BASF Plastic foams for thermal insulation have been available for more than 70 years. Extruded polystyrene (XPS) was introduced in 1943, followed by expanded polystyrene (EPS) in 1950, and polyisocyanurate (polyiso) in 1954. 1 Over the years, manufacturers have expanded these basic foams into a range of faced and un-faced products, with numerous options including fanfold bundles, composite panels, and specialty insulations with built-in drainage channels. Recently, a new class of rigid foam has become available: graphite polystyrene (GPS). To further boost the thermal performance of EPS insulation, GPS integrates high-purity graphite throughout the EPS polymer matrix (insulation bead). With graphite being the 40 the construction specifier | june 2016 CS_June_16.indd 40 most thermodynamically stable form of carbon, 2 GPS achieves impressive thermal properties when the bead is expanded with air (not a chemical reaction) into a solid rigid insulation. The addition of the graphite results in an insulation that can provide the same or greater R-values as EPS, but in a thinner product. This makes GPS insulation suitable for use in space-constrained areas and in colder climates. Another benefit is the graphite in GPS insulation enhances the material’s R-value as temperatures decrease. In the same way XPS products are recognized by a range of primary colors, GPS is readily distinguished by its gray/ platinum hue. GPS performance attributes While its chemistry starts with an EPS-based product, GPS insulation expands on EPS performance in two primary ways: R-value and water absorption. These factors, and other specification criteria for GPS, are discussed in the paragraphs that follow. 2016-05-16 8:59 AM