General Information Cutaway Showing Slotted Mullion Improving the thermal performance of glazing systems has become increasingly important in recent years. Various designs that improve thermal performance are utilized by YKK AP as well as other manufacturers. Integral thermal barriers most commonly used are those produced by casting (pouring) a liquid mixture of isocyanate and a polyol in the pocket of an extrusion. The chemical reaction which occurs in the mixture cures as a polyurethane elastomer. Once the mixture properly cures, a section of aluminum is removed (debridged) to provide a thermal barrier. The thermal break material of typical poured and debridged systems are prone to shrinking and cracking due to the inherent differences in the expansion/contraction rate of polyurethane and aluminum. YKK AP employs a patented process, ThermaBond Plus® Mullion With PVC Isolator , to greatly improve the adhesion of the polyurethane to the aluminum extrusion. Combining science and technology, ThermaBond Plus resolves the problem of adhesion and the resulting dry shrinkage associated with typical poured and debridged systems. YKK AP also offers MegaTherm® , an integral thermal barrier system that Typical Mullion With Plastic Thermal Break Locking Clips In Place employs the use of 6/6 nylon polyamide glass fiber reinforced pressure extruded bars. This technology has several advantages over the more commonly used poured and debridged polyurethane barriers. It will not shrink or degrade over time. It will not crack if penetrated by screws or if weep holes are cut into it. Its lineal expansion is very close to that of aluminum, virtually eliminating creeping, thermal expansion and internal stresses. It also offers greater design versatility by allowing the use of different finish options from interior to exterior surfaces. YKK AP ThermaBond Plus® System Thermal Separator YKK AP Thermal Isolators MegaTherm® System Effective Date: February 7, 2022 | GI-1000-05 Page-15