Development and characterization of sandwich panels for thermal insulation in a cold storage chamber

Sandwich composites are materials that have superior properties including low weight, high impact energy absorption and high thermal insulation features, compared to conventional materials. In this study, four different sandwich samples were explored for use in cold storage chambers. The composites were created using an injection molding process with polyurethane foam as the core and different materials (glass fiber reinforced polyester, galvanized steel, aluminum sheets and crimped aluminum) as face materials. Morphological, physical and mechanical properties were evaluated. An inexpensive and nondestructive method was used to determine the thermal behavior of the sandwich panels, and the surface temperature evolution was thermally monitored during the tests. In general, results showed that polyurethane had a homogeneous distribution of size and shape with closed cells, which can improve the retention of the insulating gas. Additionally, the compressive strength of polyurethane within the composites exhibited typical values to be used in specific applications. Thus, the sandwich with galvanized steel exhibited lower flexural strength, which provides more freedom in panel design. The overall heat transfer coefficient of the panels in the form of cubes presented values below the maximum limit requested by ABNT NBR-15457. Finally, the composite galvanized steel/polyurethane/galvanized steel achieved the best performance for use as a thermal insulation material in a cold storage chamber.