Showing papers by "Dean C. Webster published in 2023"

Biobased, Macro-, and Nanoscale Fungicide Delivery Approaches for Plant Fungi Control.

Abstract: In this report, two polymeric matrix systems at macro and nanoscales were prepared for efficacious fungicide delivery. The macroscale delivery systems used millimeter-scale, spherical beads composed of cellulose nanocrystals and poly(lactic acid). The nanoscale delivery system involved micelle-type nanoparticles, composed of methoxylated sucrose soyate polyols. Sclerotinia sclerotiorum (Lib.), a destructive fungus affecting high-value industrial crops, was used as a model pathogen against which the efficacy of these polymeric formulations was demonstrated. Commercial fungicides are applied on plants frequently to overcome the transmission of fungal infection. However, fungicides alone do not persist on the plants for a prolonged period due to environmental factors such as rain and airflow. There is a need to apply fungicides multiple times. As such, standard application practices generate a significant environmental footprint due to fungicide accumulation in soil and runoff in surface water. Thus, approaches are needed that can either increase the efficacy of commercially active fungicides or prolong their residence time on plants for sustained antifungal coverage. Using azoxystrobin (AZ) as a model fungicide and canola as a model crop host, we hypothesized that the AZ-loaded macroscale beads, when placed in contact with plants, will act as a depot to release the fungicide at a controlled rate to protect plants against fungal infection. The nanoparticle-based fungicide delivery approach, on the other hand, can be realized via spray or foliar applications. The release rate of AZ from macro- and nanoscale systems was evaluated and analyzed using different kinetic models to understand the mechanism of AZ delivery. We observed that, for macroscopic beads, porosity, tortuosity, and surface roughness governed the efficiency of AZ delivery, and for nanoparticles, contact angle and surface adhesion energy were directing the efficacy of the encapsulated fungicide. The technology reported here can also be translated to a wide variety of industrial crops for fungal protection. The strength of this study is the possibility of using completely plant-derived, biodegradable/compostable additive materials for controlled agrochemical delivery formulations, which will contribute to reducing the frequency of fungicide applications and the potential accumulation of formulation components in soil and water.

Differing unsaturation levels of soybean oils impact the properties of p eroxide‐vulcanized carbon b lack‐filled ethylene‐propylene‐diene monomer rubber

Abstract: Soybean oils having less unsaturation than conventional soybean oil (SBO) were studied as sustainable plasticizers for ethylene-propylene-diene monomer (EPDM) rubber compounds vulcanized with peroxide. In EPDM formulations, part of the petroleum-based paraffinic oil (PO) was replaced with soy-derived plasticizers such as high oleic soybean oil (HOSO), partially hydrogenated soybean oil (PHSO), and completely hydrogenated soybean oil (HSO). The mechanical and viscoelastic properties of EPDM rubbers formulated with soy-derived plasticizers were studied and compared with the properties of PO-based rubber. Torque rheometry was used to study the vulcanization process and the properties of the vulcanized rubber compounds were evaluated using tensile testing, compression testing, dynamic mechanical analysis, and solvent swelling experiments. The equilibrium swelling test and examination of gel fraction demonstrated the incorporation of soy-based process aids into the rubber network during vulcanization. It was found that soy-derived plasticizers could partially substitute for the petroleum-based plasticizer in EPDM compounds with minimal impact on properties. An additional benefit of the use of hydrogenated SBO is the increase of crosslink density in vulcanized rubber indicating enhanced peroxide efficiency.

Comprehensive Measurement of the Adhesion between Ice or Glass and Model PDMS Coatings

Abstract: Ice accretion is an unavoidable phenomenon that endangers the performance of outdoor infrastructure and vehicles at low temperatures. To combat ice accretion, the use of anti‐icing coatings has been one of the most appealing approaches because of their simplicity. Silicone elastomers have been increasingly employed due to their natural hydrophobicity, simple preparation, and low price. However, most of the characterization of silicone‐based polymers and other anti‐icing coatings has been done using unproven techniques that often do not directly relate to materials’ properties. In this work, the adhesion between glass and ice and four PDMS‐based elastomers has been studied by a combination of a macroscale shear test, a microscale technique (the Johnson–Kendall–Roberts (JKR) approach), and a commonly used push‐off test. Results are obtained at different temperatures and, importantly, different test velocities. The shear tests yield an energy release rate (the material's property related to adhesion) in the range of 1–10 J m−2, whereas the quasistatic JKR test yields values in the 0.1–0.5 J m−2 range for glass/PDMS interfaces. Ice/PDMS interfaces are found to have larger energy release rates in shear tests and lower values in quasistatic JKR tests. Both differences can be attributed to differences in interfacial crack dynamics.