Special polyether composite material for solar water heaters
Overview
As an insulation material, polyurethane rigid foam has an irreplaceable position in many aspects due to its extremely low thermal conductivity and convenient molding process. However, as a reaction-molded polymer, its molding shrinkage (the foam volume after completing the molding reaction is smaller than the maximum volume during the molding process) inevitably becomes one of its main flaws. The existence of molding shrinkage often causes the final volume of the foam to be smaller than the volume of the filled cavity, causing peeling of the foam and the shell, seriously affecting the appearance, insulation effect and even service life of the product. Therefore, in most applications, polyurethane insulation layers often use increased filling foam density and molding to solve this problem.
Due to its special structure (thin outer shell and liner, complex nozzle shape), solar water heaters are inconvenient to be molded, and high-density filling will inevitably increase costs. Currently, most use relatively high-density ones. Free foam filling, which brings defects to the solar water heater: the foam layer is separated from the shell, the shell is squeezed during foam molding, and the inner tank is deformed. Especially when the above defects occur at the mouth of the heat collecting tube, it is particularly serious, resulting in a large number of process failures. Taste.
Based on extensive research and analysis, our company's technical staff realized that reducing the shrinkage rate during foam molding without increasing the foam filling density is the key to the materials used for solar water heaters. To this end, we have worked on formulas, material selection and other aspects to develop composite materials suitable for solar water heaters. Trials on some solar water heater production lines have achieved satisfactory results: the degree of peeling of the foam body from the outer shell is light, and the probability of deformation of the inner tank and outer shell is greatly increased. reduce.
Chemical composition and properties
Polyether composite materials used in solar water heaters are composed of polyether, foaming agent, catalyst, foaming agent and other components. According to different foaming agents, they can be divided into high There are several types such as fluorine type, fluorine-free b-type, fluorine-free all-water type, etc.
Usually the polyether composition is in the form of a light yellow or brownish red viscous transparent liquid with no coagulation, thick matter or unevenness, and no mechanical impurities.
Reference process performance parameters
< r::/r/~/_.
< r::/r/~/_.
Manual mixing foaming machine injection Molding
Milk time
~
Gel time~~
< r::/r/~/_. Curing time
Note: The above parameters are required according to different manufacturers. Adjustable.
Basic physical properties of box foam:
Filling density: ~/3 Compression strength ():
Thermal conductivity:
Dimensional stability (℃,):
Packaging Storage and transportation
Packed in dry and clean special galvanized iron drums, sealed and stored in a dry, cool and ventilated place, waterproof, sun-proof and heat-proof. The optimal storage environment temperature is:
~℃
.
Special polyether composite material for solar water heaters