Going a step beyond the bullet-resistant security glazing familiar in banks and taxicabs, a new type of “structural envelope” based on a special polycarbonate sheet laminate from Bayer MaterialScience LLC, Pittsburgh, is said to establish a new level of bomb-blast resistance for building structures. Patent-pending Hygard BL80 Shock-Wave Sentinel is a structural solution incorporating clear PC laminate, generally less than 2 in. thick, which is said to replace several feet of concrete while providing an open, attractive appearance. Hygard BL80 reportedly exceeds the toughest explosion-resistance standards by about 30%. In blast tests, Hygard BL80 sheet flexed over 1 ft while it absorbed peak blast pressures above 80 psi. Reinforced concrete structures fail at around 20 to 30 psi and glass at 2 to 3 psi, according to Roger Rumer, marketing leader for Public Sector Business. For comparison, he notes that a Category 5 hurricane exerts 5 to 10 psi peak wind pressure. He adds that the new structure will be useful in storm protection, too.
Hygard BL80 is based on the same high-molecular-weight PC resin used in bullet-resistant sheet, but the laminate structure is different and it is used in a brand-new structural design that includes a footer, support framework, and tie-ins to the building structure. The flexible, structural envelope or “shell” of Hygard BL80 utilizes a wall of the PC laminate, supported by a structural steel frame that is tied into the building structure and separated by 7 ft of buffer space from the outside wall of the building it protects.