Effect of viscosity modifiers on soil wicking and physico-mechanical properties of a polyurethane based sprayable biodegradable polymer membrane

Abstract

Most sprayable polymers are known to undergo wicking into soil due to their low viscosity and have poor efficacy as barriers to reduce soil water evaporation. To minimize wicking, we investigated four different viscosity modifiers (VMs); gelatine (GL), sodium alginate (ALG), xanthan gum (XAN) and polyacrylamide (PAM) in our waterborne polymer formulation (PF). The viscosity modifiers were assessed based on their water solubility, miscibility with the PF and their effect on sprayability.The PF without a viscosity modifier (VM) exhibited a very low viscosity, 7–8 mPa.s, at ambient temperature. Addition of VMs in the range of 2–8 wt% concentration in the PF significantly increased the viscosity. All viscosity modified PF showed varying degrees of a shear thinning characteristic. Viscosity modified PFs showed reduce soil wicking by between 10–90% and, in general, retained mechanical properties similar to the unmodified PF without compromising their sprayability. Among the viscosity modifiers tested, the PF containing 5–9% weight of 2 wt% concentration of XAN provided the best combination of properties for wicking, sprayability, hydrophobicity, membrane formation and tensile strength. It also reduced soil evaporation by more than 60% at a low PF application of 0.58 kg/m2. PF with PAM showed similar results but sprayability was not good. PF with ALG however, required a higher concentration of 8 wt% or increased weight fractions of 2 wt% concentration to show similar effects.