Polymeric Drift Control Adjuvants for Agricultural Spraying

Abstract

---------The movement of a pesticide or herbicide to an off-target site during agricultural spraying can cause injury to wildlife, plants and contamination of surface water. This phenomenon is known as spray drift and can be controlled by spraying during favorable environmental conditions, and by using low drift nozzles and drift control adjuvants (DCAs). Polymeric DCAs are the most common type of DCA and function by increasing the droplet size produced during spraying. There are, however, two main drawbacks of polymeric DCAs; they are prone to mechanical degradation during spraying which reduces their performance and they can produce oversized drops which reduces the efficacy of the spray. In this review, existing DCA technology is reviewed including the mechanism through which they function.This then provides a platform for the discussion of novel polymeric architectures which have currently not been applied in DCA formulations.-2 -

Ultra-high molecular weight linear coordination polymers with terpyridine ligands

“…This array of molecular weight characterisation was conducted in part to determine the suitability of SF measurements (commonly performed as part of polymeric DCA testing) to UHMW LCP analysis. This technique exploits the phenomenon that polymer solutions with increased extensional viscosity (generally due to the presence of UHMW linear polymers) will resist the extensional flow created in the screen pack, causing an increased elution time 4,46…”

“…Ultra-high molecular weight (UHMW, M n > 1000 kDa) linear polymers are able to increase solution extensional viscosity at concentrations as low as 100 ppm, with application in mist control,1 drag reduction2,3 and reducing agrichemical spray drift 4,5. Extensional stresses along the elongated chain can also cause mechanical degradation of the polymer (covalent bond scission), with longer chains being more susceptible due to a greater accumulation of stress 6.…”

Water‐soluble polymers in agriculture: xanthan gum as eco‐friendly alternative to synthetics

“…These aim to reduce the fraction of droplets with a diameter < 100–200 µm, generally referred to as driftable fines (Hilz and Vermeer, 2013). Frequently, WSPs of high molecular weight ranging around 10 6 g mol ‐1 are used, such as polyacrylamide (PAM), polyethyleneoxide (PEO), polyvinylppyrrolidon (PVP) and polysaccharides (Spanoghe et al ., 2007; Lewis et al ., 2016). Even highly diluted, typically to 100–1000 ppm (Lewis et al ., 2016), these polymers are effective in delaying the break‐up of the spray sheet and reducing the formation of satellite droplets (Harrison et al ., 1999).…”

“…Frequently, WSPs of high molecular weight ranging around 10 6 g mol ‐1 are used, such as polyacrylamide (PAM), polyethyleneoxide (PEO), polyvinylppyrrolidon (PVP) and polysaccharides (Spanoghe et al ., 2007; Lewis et al ., 2016). Even highly diluted, typically to 100–1000 ppm (Lewis et al ., 2016), these polymers are effective in delaying the break‐up of the spray sheet and reducing the formation of satellite droplets (Harrison et al ., 1999). Polymer rigidity strongly influences extensional viscosity in response to the strain the liquid experiences when ejected through a nozzle.…”

Synthesis and Assembly of Designer Styrenic Diblock Polyelectrolytes

“…was used. We note that since NaN3 is known to cleave RAFT thiol-end groups,39 samples were dissolved and immediately run. dn/dc values in each respective mixture are in Table S-2.…”