Novel Polymers Containing Short Fluoroalkyl Chains: Synthesis And Applications On Cotton Fabrics

Fluorocarbons especially those with long perfluoroalkyl chains (C_nF_2n+1,n=6-10) are widely used as the most important class of water and oil repellent finishing agents for textiles due to their optimum performance in lowering the surface free energy and improving both hydrophobicity and oleophobicity. In recent years, the fluorocarbons containing long perfluoroalkyl chains are facing the problems such as the persistence, bioaccumulation, and/or toxicity in the environment. The use of perfluorooctyl contained surfactants such as PFOS and PFOA have been restricted in the international community. Sooner or later, fluorocarbons with long perfluoroalkyl chains will face the same problems. So it is important to find the alternatives to replace the present long perfluoroalkyl-contained fluorocarbons. As reported that compounds with short perfluoroalkyl group can be decomposed in the environment with low toxicity. In this paper, we have designed and synthesized two types functional polymers containing short perfluorocarbon chains and studied their applications on cotton fabrics.Firstly, starting from tribromoneopentylglycol, the readily available cheap material, the bromomethylated oxetane was obtained under basic condition, which was converted to fluoroalkyl-contained oxetane 2 by treatment with trifluoroethanol or pentafluoropropanol in the presence of base and phase transfer catalyst respectively. In the presence of BF₃·Et₂O and neopentylglycol or methanol, the monomers 2 were polymerized to give two novel fluorinated polyether diol 4 or polyether semiol 3 respectively. The hydroxyl values were measured as 39.14 and 20-25 mgKOH/g. Polyether diol 4 was then condensed with isophorone diisocyanate (IPDI) to form prepolymer 9, which was extended by compounds diethylentriamine (DETA) and 2,2-dihydroxymethylpropanoic acid (DMPA) to form polyurethanes 5 and 8 respectively. Polyurethanes 5 and 8 were then grafted by perfluoropolyether acyl fluoride 6 and fluorinated polyether semiol 3 to form fluorinated polyether grafted polyurethanes CFPU and AFPU.Secondly, tris(3-prefluorohexylpropyl) pentaerythritol (TFPE) was synthesized from triallyl pentaerythritol (APE) and perfluorohexyliodide via radical addition initiated by sodium hyposulfite followed by reduction with lithium aluminium hydride. It was used to synthesize the emulsions of fluorinated polyacrylate (FPA) and fluorinated polyurethane (SiFPU).Finally, these emulsions of CFPU, AFPU, FPA and SiFPU were diluted with water, and applied on cotton fabrics by pad-dry-cure process. The fabrics treated with SiFPU and AFPU possessed good water repellent properties, and their contact angles were 153°and 148°respectively. The fabrics treated with CFPU and FPA possessed moderate water repellent properties, and their contact angles were 125°和135°. But only the fabrics treated with SiFPU showed a little oil repellent property at grade 2 level. On the other hand, the tear strength, durable washing property, static hydraulic pressure and white index of treated cotton fabrics were also examined, and the effects of cross-linking agent, baking temperature and densities of finishing agents on water repellent property were also discussed. The surface properties of treated cotton fabrics were examined by XPS and SEM. Accordingly, it was found that SiFPU showed the best performance on the cotton fabrics, AFPU possessed good water repellent property and CFPU and FPA only had general effect on cotton fabrics.