Rheological characteristics of aqueous wax emulsions used for the controlled release of pheromones as an alternative to the use of pesticides for insect pest management
- WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
- Stephen Daniel Ballew (Creator)
- Institution
- Western Carolina University (WCU )
- Web Site: http://library.wcu.edu/
- Advisor
- Cynthia Atterholt
Abstract: Most pesticides produce some risk of harm to the environment because pesticides
are designed to kill or adversely affect living organisms (US EPA, 2010). It is desirable
that alternate, safer forms of pest control be developed. One alternative is the controlled
release of pest insect sex pheromones to produce a mating disruption effect (Ahmed et al.,
1993; Atterholt, 1996). Aqueous paraffin wax emulsions have shown much promise as
formulations for this controlled release when applied to tree bark or foliage (Atterholt et
al., 1996; Rice et al., 1997; Atterholt et al., 1998; Atterholt et al., 1999; Meissner et al.,
2000; de Lame, 2003). Soy wax has recently become of interest in pheromone
formulations because it is renewable, biodegradable, commercially available, and
acceptable for organic farming (Behle, 2008).
Emulsions exhibit complex flow behavior which can be studied using rheometry
(Macosko, 1994; Mezger, 2006). Rheometry refers to experimental techniques to
determine the fundamental relationships between force and deformation in materials
(Macosko, 1994). The rheological properties of emulsions are very important for
production, storage, and application of these formulations (Mezger, 2006). In this project the flow and viscoelastic properties of aqueous 30% paraffin wax and soy wax emulsions
were investigated using three different emulsifiers: sorbitan monostearate (Span 60®),
triethanolamine (TEA) stearate, and a 50%-50% mixture of both. Span 60® has already
been used to make effective emulsions for the controlled release of pheromones, and it is
food safe (Atterholt et al., 1996; Rice et al., 1997; Atterholt et al., 1998; Atterholt et al.,
1999; Meissner et al., 2000; de Lame, 2003). TEA stearate is widely used to make nontoxic
wax emulsions in the cosmetics industry (Wilkinson, 1940).
The investigations were carried out in both the rotational and oscillatory modes of
a parallel-plate rheometer. The flow curves at three different temperatures (15 °C, 25 °C
and 35 °C) of each emulsion were fitted with the Herschel-Bulkley model with the yield
points determined using the one tangent method. The resulting equations can predict
flow behavior at different conditions (Mezger, 2006). The emulsions were also tested
using a temperature sweep at low shear from 15 °C to 50 °C to investigate temperature
dependent changes. The viscoelastic properties were investigated using oscillatory shear
tests and expressed in terms of elastic modulus and loss modulus. This gives information
about time-dependant behavior like storage and the elastic character of the formulations
which were found to be weak gels (Mezger, 2006). The Span 60® emulsions displayed
faux shear-thickening behavior due to droplet subdivision while the other emulsions
generally displayed shear-thinning behavior. Each emulsion approaches an infinite shear viscosity. The yield points and other flow parameters for the emulsions varied with
temperature, depending on the formulation in question. All soy wax emulsions showed
an increase in viscosity between 45 °C and 50 °C while the paraffin wax emulsions did
not. Every emulsion showed long-term and short-term stability (Mezger, 2006).
Rheological characteristics of aqueous wax emulsions used for the controlled release of pheromones as an alternative to the use of pesticides for insect pest management
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Created on 7/1/2011
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Additional Information
- Publication
- Thesis
- Language: English
- Date: 2011
- Keywords
- emulsion, paraffin wax, pesticide, rheology, rheometry, soy wax
- Subjects
- Pheromones
- Emulsions
- Rheology