Abstract:Environmental concerns related to perfluoroctanoic acid (PFOA) led to a re-examination of the methods for imparting stain resistance and stain repellency to textiles. Non-PFOA fluoropolymer finishes have been formed on cotton knits by admicellar polymerization, a surface analogue of emulsion polymerization. Fabric samples were characterized by a drop test, contact angle measurements, SEM, elemental analysis and durability studies. Stain resistance and stain release properties were assessed by reflectance and AATCC tests with results comparing favorably with swatches from commercially available garments. Admicellar polymerization enabled the formation of durable finishes that exhibited high performance in stain resistance and stain repellency.

The adsorption of surfactants and adsolubilization of organic compounds on knit cotton fabric are fundamentally important in admicellar polymerization to impart characteristics like water repellency, stain resistance, and flame retardancy. The main objective of this research is to study adsorption and adsolubilization of fluororsurfactants and fluoromonomers used to obtain water repellency characteristics. Adsorption of nonionic (fluoroaliphatic amine oxide) and cationic (fluoroaliphatic quaternary ammonium surfactant) fluororsurfactants at the interface of cotton is investigated with and without fluoroacrylate monomers. A two-site adsolubilization model was used to predict the aggregation number of fluorosurfactant.

Admicellar polymerization (AP), a surface analogue of emulsion polymerization was used to obtain a thin layer of hydrophilic polymer coating on multi-walled carbon nanotubes (MWCNTs). The hydrophilic nature can facilitate integration of carbon nanotubes into a variety of composite materials. To develop hydrophilic polymer by AP, acrylate monomers were copolymerized using sodium dodecyl sulfate as a surfactant. Development of a system for AP involves measurement of surfactant adsorption and adsolubilization or partitioning of monomer into adsorbed structures (reverse hemimicelles). A modified two-site adsolubilization model was used to calculate the size of surfactant aggregates over the surface of MWCNTs and a binary adsolubilization model was employed to predict number of monomers adsolubilized from single component experiments.Adsolubilized monomers were polymerized to form a polymer nanocomposite, which was then hydrolyzed to obtain a hydrophilic nanocomposite. SEM, Energy Dispersive Spectroscopy (EDS), Thermo Gravimetric Analysis (TGA) and FT-IR confirmed the formation of polymer on multi-walled carbon nanotubes (MWCNTs). Modified MWCNTs readily dispersed in aqueous media and were stable after 3 days.

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Mass transfer in a laboratory dyeing machine, consisting of cylindrical canisters mounted on a carousel with a horizontal axis, has been examined to adapt the unit for modification of cotton by admicellar polymerization. Canisters located at the periphery of the carousel are canted relative to the axis of rotation so that fluid in the canister moves front-to-back and back-to-front over the course of one revolution in a fashion similar to a rocking reactor. Dissolution of benzoic acid in water at 30 °C has been used to determine mass transfer coefficients β in the dyeing system as a function of rotational rate and fill volume. Mixing in the dyeing system improved with canister fill fraction to an optimum of 0.9, while rotation rate had little effect over the available range. Findings for β as well as predictions for β obtained from estimates of specific mixing power are compared to values from the literature for a rocking reactor. The process of admicellar polymerization on cotton was subsequently examined in the laboratory dyeing machine. Cotton with a water repellent coating prepared in the unit was evaluated using various techniques. Conditions favorable to mass transfer in the model experiments were consistent with those providing optimal performance of the water-repellent coating applied by admicellar polymerization.

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