Research on manufacturing green polyurethane composite film from rubber seed oil-based polyol and PEG-modified bentonite for slow-released fertilizer application

Abstract

The Hildebrand solubility parameter, Hansen parameter, and evaporation rate were instrumental in developing three solvent systems for GPUC film fabrication. Among these, the SS3 solvent system was selected for its superior tensile properties and the resulting more durable film. Both the PEG-Ben content and NCO/OH molar ratio significantly affected the tensile properties of the GPUC films. Specifically, the GPUC film prepared with 7 wt% PEG-Ben content and an NCO/OH ratio of 1.1/1 exhibited a tensile strength of 24.51 MPa and an elongation at break of 28.02%. By adjusting the PEG-Ben content and the NCO/OH ratio, the hydrophilic/hydrophobic properties, water absorption, moisture absorption, water vapor transmission, and water vapor permeability of the GPUC films can be precisely controlled. This, in turn, directly influences the nitrogen permeability characteristics of the GPUC films. Consequently, the nutrient release rate of fertilizer pellets can be regulated when the granules are coated with these GPUC films. Experimental results further demonstrated that the GPUC film prepared with 7 wt% PEG-Ben content and an NCO/OH ratio of 1.1/1 achieved the greatest hydrophobicity, along with the lowest water absorption, moisture absorption, water vapor transmission, water vapor permeability, and nitrogen permeation. These combined properties make it highly suitable for coating slow-release fertilizers.