Synthesis and Evaluation of Antimicrobial Biobased Waxes as Coating Materials.

The objective of this study was to synthesize and evaluate the efficacy of antimicrobial waxes to be used as both physical and biological protection to perishable fruits and vegetables. The existing wax materials used in postharvest coating applications do not provide this antimicrobial functionality. One class of such waxes was obtained by covalently linking quaternary ammonium compounds (QACs) featuring alkyl, benzyl, and stearyl ester hydrophobic side groups to the terminal position of a bromo stearyl ester. A second class was obtained by linking these QACs to the pendant hydroxyl group of an aliphatic diamide made of 12-hydroxystearic acid, stearic acid, and ethylene diamine. In total, six distinct structures having three different QAC groups were synthesized. Compounds containing QACs with C8 alkyl groups exhibited potent inhibition toward the growth of both bacteria and fungi. Notably, the complete inhibition of Penicillium italicum and Geotrichum candidum, two fungi detrimental to the postharvest quality of fruits, as well as the complete destruction of viable cells for Gram-positive and Gram-negative bacteria was observed when these organisms were incubated in contact with QAC waxes or dispersed in an aqueous system at a concentration of 1.0 mM. Comparatively, benzalkonium chloride with an alkyl chain length of 10 carbon can completely inhibit Staphylococcus aureus at a concentration of 1.44 mM. The properties of the attached hydrophobic groups appeared to exert a strong influence on antimicrobial activity presumably due to differences in molecular orientation, size, and differences among microbial cellular structures.

Soybean Oil-Based Biopolymers Induced by Nonthermal Plasma to Enhance the Dyeing of Para-Aramids with a Cationic Dye.

To overcome the recalcitrance of para-aramid textiles against dyeing, this study demonstrated that increasing the functionalities of soybean oil applied to the surface of para-aramids followed by a nonthermal plasma (NTP) treatment improved the dyeing color strength compared with the use of soybean oil alone, and that dyeing occurred through covalent bonding. Particularly, compared with the pretreatment using soybean oil that obtained the highest color strength of 3.89 (as K/S value determined from spectral analysis of the sample reflectance in the visible range), the present pretreatments with either acrylated epoxidized soybean oil (AESO) or a mixture of acrylic acid and soybean oil (AA/Soy) achieved K/S values higher than nine (>9.00). The NTP treatment, after the AESO or AA/Soy pretreatment, was essential in inducing the formation of a polymerized network on the surface of para-aramids that bonded the dye molecules and generating covalent bonds that anchored the polymerized network to the para-aramids, which is difficult to achieve given the high crystallinity and chemical inertness of para-aramids. As an important economic consideration, the sequential experimentation method demonstrated that a simple mixture of AA/Soy could replace the expensive AESO reagent and render a comparable performance in dyeing para-aramids. Among the auxiliary additives tested with the AESO and AA/Soy pretreatments followed by NPT treatment in this study, Polysorbate 80 as a surfactant negatively affected the dyeing, benzyl alcohol as a swelling agent had minimal effect, and NaCl as an electrolyte showed a positive effect. The dyeing method developed in this study did not compromise the strength of para-aramids.