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| Water absorption principle of water retaining agen |
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The water absorption principle of water retaining agents is that the polymer electrolyte molecular chains interact with each other due to the repulsion of amide or carboxyl groups in water, resulting in the expansion force of the molecular chains and the limited expansion force of the molecular chains caused by crosslinking points. A large number of amide and carboxyl hydrophilic groups, utilizing the osmotic pressure generated by the concentration difference between their internal ions and groups and the relevant components of the aqueous solution, as well as the affinity between the polymer electrolyte and water, can absorb a large amount of water until the concentration difference disappears. The rubber elasticity is what controls the water retention agent to achieve satisfactory water absorption. The higher the cross-linking degree of the molecular structure, the stronger the rubber elasticity, and the balance point between rubber elasticity and water absorption is its apparent water absorption capacity.
In general, the lower the crosslinking degree of the polymer with the same composition, the higher the water absorption ratio, the lower its water retention, stability and gel strength, and vice versa. Therefore, internationally, water retaining agents with longer usage cycles naturally require higher crosslinking degrees and do not pursue high water absorption rates and speeds. Because of the long production cycle of forestry, the water retaining agent used should have high water retention, stability and gel strength. Because water retaining agents are generally added to 5-20cm underground, 80% to 95% of the water absorbed can be utilized by plants.
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