Effects of Polymer Composition and Viscosity on Droplet Size of Recirculated Spray Solutions

Polymeric Drift Control Adjuvants for Agricultural Spraying

“…[65] For example, xanthan gums (semi-flexible) have poorer drift retarding performance (un-degraded) than the flexible long chain PAM polymers. [18] Currently DCAs are generally used in the concentration range of 100 to 1000 ppm, often corresponding to the dilute polymer regime. Dilute solutions are defined as having negligible interactions between neighbouring coils, which occurs below the critical overlap concentration (c*).…”

“…The number of droplets below 200 μm for a dilute non-ionic PEO solution increased by 355% after 11.4 cycles, with a VMD (after degradation) similar to that produced by pure water. [18] Increasing linear polymer molecular weight has been shown to increase the extent or probability of chain scission. [104] A molecular weight in the order of 1 x 10 7 gmol -1 is often needed for applications in dilute solution drag reduction and drift control, resulting in significant degradation for current additives.…”

“…This is believed to be due to the distribution of the stresses over multiple chains and the sacrificial breakage of physical bonds in the network over chemical bonds along the main chain. [18,105,118] Following on from this, a prominent design philosophy for mechanically stable polymers involves the use of lower molecular weight polymers (which are less susceptible to degradation) which can then assemble into higher molecular weight polymer chains through non-covalent interactions.…”

“…Zhu et al [18] tested various commercial drift retardants and found that the anionic polymer additives as a group experienced less mechanical degradation than their nonionic counterparts. The best performing polymer additive in terms of measured droplet sizes below 200 μm both before and after shearing was a 20 mol% anionic PAM.…”

“…[17] Within this classification there are long chain synthetic polymers which include polyacrylamide (PAM), hydrolysed polyacrylamide (HPAM), poly(ethylene oxide) (PEO) and polyvinyl polymers (Figure 1). [18,19] Also included in spray thickeners are polysaccharides such as xanthan gum and guar gum. Many of these polymers have also seen application in EOR and drag reduction.…”