Application of insulation material in solar water heater

At present, as a heat-insulating material, the polyurethane hard foam has an irreplaceable position in many aspects with its extremely low thermal conductivity and convenient molding process. However, as a reaction-molded polymer, the mold shrinkage (foam volume after completion of the molding reaction is less than the maximum volume during the molding process) is inevitably one of its major defects.

The existence of molding shrinkage often causes the final volume of the foam to be smaller than the volume of the filled cavity, and the phenomenon of foam and shell peeling occurs, which seriously affects the appearance, heat preservation effect, and even service life of the product. Therefore, in most applications, the polyurethane insulation layer is often used to increase the density of the filled foam, take the molding method to solve this problem.

Thin shells and liners, complicated nozzle shapes are not easy to mold, and high-density filling will inevitably increase the cost. At present, the relatively high density of free foam is used to fill the solar water heaters. There are: the foam layer and the shell out of the foam forming shell extrusion, liner deformation caused, in particular, the above defects occur when the collector nozzle is particularly serious, resulting in a large number of process defects.

Based on extensive research and analysis, it is recognized that reducing the shrinkage rate of foam molding without increasing the foam packing density is the key to solar water heater materials. To this end, from formula, material selection and other aspects, research and development of the water heater for the combination of materials, in a part of the solar water heater production line has achieved satisfactory results: the peeling of foam and shell is light, the probability of deformation of the inner shell is greatly reduced ,safer.