The type of foam used and the bond between the foam and the surface skins are the most important characteristics of SIPs. SIPs use one of three types of foam cores. The most common is expanded polystyrene (EPS). The second most frequently used foam type is urethane, which is divided into two sub-types: polyisocyanurate, and polyurethane. The third is extruded polystyrene. There are major differences between the types of foam cores. Murus uses a true polyurethane foam for its panel cores.
Plastics are generally categorized as either thermoplastic or thermoset plastic. In a thermoset plastic, a chemical change occurs during manufacture called Polymerization, which will not allow the thermoset plastic to be reformulated into another shape or form. Polyurethane is a thermoset plastic. Once polyurethane has been formed, it cannot be melted back down to form another shape.
The Murus manufacturing method is called the "Uniform Dispersion Method," or UDM, and is unique in the industry. UDM is a combination of the best techniques and methods from the lamination process and the injection molding process. UDM utilizes a dispersion technique very similar to the lamination process. The liquid foam is injected (dispersed) uniformly on the bottom skin (from side to side and end to end) as the mold moves past the injection point. After injection and before the foam starts to expand, the mold is placed into a press where it is contained until the foam is cured. The reaction of the foam (expansion and polymerization) takes only about two minutes to complete. The rapid expansion creates 12 to 14 psi of pressure in the mold, which produces the tongue and groove profile edge on the panel, and enables the incorporation of the cam-lock connectors.
The combination of uniform foam dispersion and pressure molding produces a spherical cell in the foam rather than an elongated cell. A spherical cell is preferred because it provides uniform strength in all directions without concern for cell orientation. A spherical cell ensures that the foam is consistent throughout the entire panel.
The Murus SIP is the only SIP made by the UDM method. It is a process unique to Murus, and we believe it is a superior manufacturing method to all the others.
The Murus EPS panel is manufactured using a pressure laminating method. A controlled amount of one-part urethane structural adhesive is applied between the foam core and each skin, then the panel is placed under pressure in a press while the adhesive reacts and cures. While the panel is under pressure, the adhesive reaches about 80% of its total strength before the panel is removed from the press. This insures the adhesion line is not compromised from post-press handling, storage or temperature variations. The result is a permanent bond between the foam core and the skins which is stronger than the materials it bonds together. After manufacture, the panels are stored in a controlled environment for a 24 hour period and are then ready for shipment to the building site.
The Murus Company, Inc.
PO Box 220 • 3234 Route 549 • Mansfield, PA • 16933
Phone: 570-549-2100 Fax: 570-549-2101
Email:
