Water and Oil Repellent and Durable Press Finishes for Cotton

Water and Oil Repellent and Durable Press Finishes for Cotton

Water and Oil Repellent and Durable Press Finishes for Cotton Based on a Perfluoroalkyl-Containing Multi-Epoxy Compound and Citric Acid
Textile Research Journal,  Oct 2004  by Shao, Hui,  Sun, Jian-Ying,  Meng, Wei-Dong,  Qing, Feng-Ling
A novel perfluoroalkyl-containing multi-epoxy compound (PFME), designed and synthesized in our laboratory, is applied to cotton fabrics by the pad-dry-cure process to give durable water and oil repellency by developing permanent covalent bonds to the textile substrate. The specimens pretreated by citric acid are further treated with PFME. The dual finished cotton shows both durable water and oil repellent appearances and durable press properties. The optimum treatment conditions for the dual finishing are discussed.

The requirements placed on apparel, home and technical textiles grow constantly. Serviceability properties, in particular, repellency to water, oil, and soil, are increasingly becoming the focus of interest [7]. To achieve the goal of repellent properties, different methods have been used in the past [5]. Among them, fluorinated coatings are the most important class of water and oil repellent finishes for textiles due to their ability to provide optimum performance in terms of both hydro- and oleophobicity without impairing the textile's permeability to air and vapor or modifying the fabric's hand [4]. However, conventional finishing by such fluorinated coatings does not always show sufficient stability during use, since the finishing agents mostly constitute only surface layers and do not develop permanent chemical bonds to the textile substrate. New strategies for textile repellent finishing are therefore required [6]. In order to improve the durability of fluorinated coating finishes, we have designed and synthesized a novel perfluoroalkyl-containing multi-epoxy compound (PFME, Figure 1) that contains both a perfluoroalkyl chain and multicrosslinking groups. Cotton fabrics treated with PFME by the pad-dry-cure method should possess durable water and oil repellency.

In addition, since the late 1980s, the marketplace has shown increased demand for easy care, wrinkle-resistant 100% cotton apparel. Among the formaldehyde-free durable press finishing agents for cotton textiles, 1,2,3,4-butaneteracarboxylic acid (BTCA) and citric acid (CA) are representatives of polycarboxylic acids that crosslink with cotton through an esterification reaction. BTCA combined with sodium hypophosphite monohydrate (SHP) is the most effective of these polycarboxylic acids; however, because BTCA is expensive, intensive studies have focused on using CA, even though it is less effective than BTCA and causes fabric yellowing [10]. To improve the whiteness index (WI) various additives have been included in the finishing formulations, and substantial improvements to the WI have been achieved with triethanol amine (TEA) [2].

In this study, we apply PFME and CA to cotton by the pad-dry-cure method to develop dual function fabrics. The objectives of our study are to evaluate the durable press appearance and water and oil repellency of dual finished cotton and to investigate the effect of CA and PFME treatments on fabric properties.

Experimental

The fabric used in this study was a 100% cotton plain weave that had been desized and scoured (weight 118 g/m^sup 2^). Samples were washed thoroughly with running tap water before finishing. Citric acid (CA), sodium hypophosphite monohydrate (SHP), and triethanol amine (TEA) were purchased from the Shanghai Chemical Reagent Company, China National Medicine Group, with 98-99% purities.

We applied the perfluoroalkyl-containing multi-epoxy compound (PFME) synthesized in our laboratory [9] as a fluorinated coating-finishing agent to the fabrics by the pad-dry-cure method. We then investigated the water and oil repellency of the fabric treated with PFME under various conditions.

For durable press finishing, the fabrics were padded twice with a solution containing 8% CA, 6% SHP, 4% TEA, and an 0.1 (owb) % nonionic surfactant at approximately 85% wet pick-up on a laboratory padder, dried for 3 minutes at 80¡ãC, then cured for 2 minutes at 160, 170, and 180¡ãC.

For the dual finishing, the specimens pretreated by CA were further treated with ethanol solutions containing 3% (owb) PFME and 1.5% potassium thiocyanate (KSCN) as a catalyst to a wet pick-up of about 70%. Once impregnated, the fabric samples were dried at 80¡ãC and cured at 160¡ãC for 3 minutes before rinsing.

Two technological tests based on industrial standard methods were used to evaluate the water and oil repellent properties of the finished fabrics, respectively: the water/isopropyl alcohol test (3M water repellency test II, water/alcohol drop test) [1], and the hydrocarbon resistance test method (AATCC test method 118-1984). The standard liquids are listed in Table I with their corresponding repellency ratings [3].

The dry wrinkle recovery angle (WRA) and tensile and tear strengths of the treated cotton fabrics were evaluated according to the following standard methods: AATCC test method 66-1990, ASTM method D5035-95, and ASTM method D1424-82, respectively. Whiteness of the fabrics by the CIE whiteness index was measured on the Spectraflash data color SF600. All measurements were performed at least in triplicate, and the arithmetical average of every experimental result is given.
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