Biodegradable polyurethane foams (PUFs) as coating materials for the controlled release of fertilizer were prepared from a four-component system consisting of diisocyanate, polyester, Acacia mearnsi bark, and corn starch. Ammonium sulfate [(NH 4 ) 2 SO 4 ] was used as a fertilizer to evaluate the effects of the preparation conditions on the release ratio. The release ratio of (NH 4 ) 2 SO 4 decreased with an increasing amount of biomass in PUFs and increasing sizes of sample particles; the ratio increased with increasing doses of water, which was used as a foaming agent in the preparation of polyurethane, regardless of the amount of coating material. The remaining fertilizer in the polyurethane seemed to be released completely because the PUFs were degradable, to some extent, by soil microorganisms.

ABSTRACT:A new kind of polyurethane (PU) foam was synthesized from wattle tannin (WT), which has good prospects of application for its biodegradation and bacteriostasis. The effects of WT content, diisocyanate dosage, and chemical modification of WT on properties of PU were investigated. It was found that WT could contribute not only to bacteriostatic activity, but also to biodegradability during soil micro-organism treatment for the polyurethane foams. Furthermore, the bacteriostasis of PU is improved by modifying the chemical structure of WT.