Rub-fastness

The rub-fastness test examines resistance of the pigment coat to abrasion and the transfer of color to other surfaces (crocking). The test is carried out on the VESLIC rub-fastness tester (Fig. 11-11). This testis governed by the standards DIN 53339 and I.U.F. 450. 

On a Stretched leather a felt is rubbed back and forth. The felt is 10 mm x 10 mm in size and weighted with 1 kg. The leather is stretched 10 %. The test is customarily carried out in three variations  

The damage or change in the finish coat and the transfer of color to the rubbing element are assessed after fixed mbbing intervals. This method provides data on the sensitivity of the finished leather surface to mbbing through, abrasion or transfer of color from the pigment coat under both dry and moist conditions. 

Rub-fastnesses are also tested using the SATRA rub-fastness tester. In this test a rotating pad of felt acts on the leather surface under a certain pressure and at a defined speed of rotation. The leather is evaluated after fixed numbers of cycles. This test is likewise carried out with both a dry and a wet felt pad. 

As a further variation, the test can be carried out under exposure to various, defined test liquids perspiration rub-fastness, chemical rub-fastness, etc. 

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During dyeing and rinsing, the dyeing is less sensitive to oxidation (bronzing, rubbing-fastness). 

Oxidation of Dyes [73], Sulfur dyes, like vat dyes, are fixed on the substrate by oxidation. First, the remaining reducing agent, salts, and alkali, as well as the unfixed dye, must be removed by rinsing or washing to attain optimal rubbing fastness. The following methods of oxidation are common. 

After development, the textile is rinsed and subjected to careful afterwash in which excess dye lake is removed from the fiber surface. Otherwise, it severely impairs the rubbing-fastness of the dyeing. In addition, through the change in pigment crystal structure occurring during aftertreatment, a stable final shade is achieved with enhanced fastness. ... 

Properties provided by these finishes are mostly improved wet fastness, for example washing, water, perspiration and ironing fastness, then better light fastness and only to a small extent improved crocking and rubbing fastness. For other kinds of colour fastness, for example dry ironing, chlorine, peroxide and carbonisation, there are no known possibilities for improvement by an after treatment. The market importance of these finishes is based on customer preferences and economic production demands. For abetter understanding, each of these three quite different fastness improvements will be dealt with separately. 

Improved rubbing fastness can be achieved with partially hydrolysed poly vinylacetate (PVAc/PVA) or polyvinylether and the application of pigment binders, mostly based on acrylic copolymers similar to those nsed as hand builders (Chapter 4). Application methods mostly nse pad-dry techniqnes. 

Possible problems with finishes nsed to improve rubbing fastness include the following. 

References concerning finishes that improve crocking and rubbing fastness... 

When applied to goods that have been dyed with disperse dyes, however, CONDENSOL I New may impair the rub fastness. For this reason it is better to use CONDENSOL II in such cases. 

CONDENSOL II protects coloured goods from any loss of rub fastness caused by water-repellent finishing. CONDENSOL II is affected by metal salt. If fairly large quantities of cross-linking agent and catalyst are to be used, preliminary trials should always be carried out to test whether the bath stability is adequate. 

In some cases it may be preferable to use the combination of PERSISTOL SIN and CONDENSOL I New. The possibility of the rub fastness of coloured goods being impaired by this combinations must, however, be taken into consideration. 

PERAPRET HVN is used as additive in resin finishing. It cuts down the loss of tear strength and abrasion resistance and improves the crease-recovery, so that the amount of N-methylol compound in the recipe can be reduced somewhat without Impairing the crease-recovery. The rub fastness of naphtol and Indanthren dyeings is improved. 

Before the availability of sodium dithionite (1871), the reduction of indigo was brought about by bacteria with reducing properties (fermentation vat). The vat of indigo has a brown-yellow colour. The cloth is dipped in the vat and then exposed to air to allow reoxidation to indigo which is precipitated and finely distributed onto the fibre. A consequence of this process is the low rubbing fastness of the dyes. It causes the faded appearance of indigo-dyed jeans and makes possible the manufacture of faded jeans . 

Figure 2.24 Surface of the thennochromic textile printed with red microcapsuies after rub-fastness testing (5000x original magnification).

Laser marking is an ink-free process which produces a permanent rub-fast, solvent resistant, scratch proof mark with no waste, and is free of flammable or volatile solvents and then-subsequent disposal. These permanent markings cannot be removed without damaging the product, which is ideal for safety concerns. The laser marking process does not require any form of surface treatment, in fact, a film of water on the product will have no effect on the marking process. Since the mark is etched into the plastic product, there is no problem of adhesion, even on polyethylene and polypropylene. 

Zhang and Fang (2009) investigated dry and wet rubbing fastness of inkjet-printed polyester fabrics. The results show that there is almost no difference between rubbing fastness of untreated and air/Ar plasma-treated samples. This result indicates that plasma treatment has no effect on colorfastness of inkjet-printed polyester fabrics. 

About 10 % of the silicone production is used for apparel and technical textiles. In this field silicones are mainly used to functionalize textiles. The characteristic hydrophobicity of silicones was firstly utilised in the mid-1950s. The products used in this period were based on combinations of hydrogen siloxanes and OH-terminated dimethylsiloxane fluids. Catalyzed with metal compounds like tin laurate, these products lead to a crosslinked silicone film on the fiber surface. Compared to the previously used impregnating agents like paraffin waxes or stearylchromium compounds, the silicones provide a much better hydrophobicity and even rubbing fastness and wash resistance are improved dramatically. 

The addition of triester compounds improves the waterfastness of printed images and dry and wet rub fastness to have good colorfastness on the paper (36). An example is shown in Figure 3.19. 

It was confirmed that the images formed with the aqueous ink composition on a plastic medium have superior characteristics against bleeding (15). In contrast, when glycerol is added, the resulting image is inferior in rub fastness. 

An inkjet recording ink composition, which is particularly suitable in textile use, has been described. The composition exhibits a high rub fastness and a dry cleaning resistance, as well as a high ejection stability. This can be achieved by adding a poly(urethane) resin to the ink composition. A key factor is that the poly(urethane) resin should contain 50% or more of a tetrahydrofuran-insoluble portion. Then, the resulting inkjet composition could be superior in rub fastness, dry cleaning resistance and ejection stability. 

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