It’s SOCO® polymer.
SOCO® polymer absorbing process
One-gram SOCO® polymer can absorb 300-1000 grams of pure water. In other words, it’s enough to contain 1 gram (or less) SOCO® polymer for each gel ice pack.
Recommended SOCO® polymer : SNN580H


The polymer is sensitive to the action of ultraviolet rays that, by breaking bonds, degrade the polymer into oligomers (molecules of much smaller size). It thus becomes much more sensitive to the aerobic and anaerobic processes of microbiological degradation. therefore it degrades naturally in soils in CO2, H20 and nitrogen
compounds.
Products demonstrate no systemic toxicity. Consult the safety data sheet for additional information.