Evaluation of Rewetting Agents

AATCC 27-2004 pdf download.Wetting Agents: Evaluation of Rewetting Agents.
3.1 rewetting agent,n.—in textilepreparation,dyeing and finishing, a sur-factant which, after application and dry-ing onto textiles， promotes rapid wettingon subsequent exposure to an aqueoussolution.
3.2 wetting agent,n.—achemicalcompound which when added to waterlowers both the surface tension of the liq-uid and its interfacial tension against thesolid material.
4.Safety Precautions
NOTE: These safety precautions arefor information purposes only.The precautions are ancillary to the testing procedures and are not intended to be all inclusive. It is the user’s responsibility to usesafe and proper techniques in handlingmaterials in this test method. Manufacturers MUST be consulted for specificdetails such as material safety data sheetsand other manufacturer’s recommendations. Al1 OSHA standards and rulesmust also be consulted and followed.
4.1 Good laboratory practices shouldbe followed. Wear safety glasses in alllaboratory areas.
4.2 Observe padder safety. Normalsafeguards on pad should not be moved.Ensure adequate guard at the nip point.Afootoperated kickoff is recommended.5.Apparatus and Materials
5.1 Rewetting agents.
5.2 Cloth,fairly heavy cotton,in thegreige; cloth must not have been boiled,bleached or desized. Cotton sateen (see9.1) is suggested for use in this test.
5.3 Small padder. A household wringerwith improvised pad box is satisfactory inlieu of a small padder.
5.4 Embroidery hoop, 15.2 cm (6 in.).5.5 Burette delivering 15-25 drops permL.
5.6 Stopwatch.
5.7 Conditioned room in which stan-dard temperature 21 ±1°C (70±2°F) andhumidity (65 ±2%RH) are maintained.Although satisfactory comparisons canbe made in the ordinary laboratory,theresults should be more reproducible un-der standard conditions.
6.Procedure
6.1 Application of rewetting agent-asolution of the rewetting agent is preparedby pouring 100 mL of hot water over therequired amount of the product in a smallbeaker or casserole. This solution isheated above 97°C (200°F) for a momentand then is diluted with hot water to a fi-nal volume of 1 L.The temperature of thesolution in the padder box for application should be 70 3C (158 ±5°F).
6.2 The padder is adjusted to a uniformly firm squeeze from side to side. Ona household wringer it has been foundthat a dozen half turns of the wing nutsfrom the place where they just begin totake hold is satisfactory.
6.3 A strip of the selected cotton goodsis padded three times through the solutionof the rewetting agent.Three timesthrough ensures thorough and uniformpenetration of the cloth.The pickupshould be from 60-90%.
6.4 The padded cloth is dried in air atapproximately 82C (180°F) for 30 min.
6.5 Four strips of padded cotton areprepared for each rewetting agent representing, respectively, four concentrationsfor each product to be tested.Concentrations generally suitable are 2.50,5.0,10.0and 20.0 g of rewetting agent per liter.
6.6 Rewetting a square of the padded,dried and conditioned cloth ismounted in the embroidery hoop. The burette containing either distilled water ortap water，whichever is desired for thetest，is adjusted so that it delivers onedrop of water at 21 ±1C (70±2°F) approximately every 5 s.The surface of thetaut cloth is held about 1 cm (0.375 in.)below the tip of the burette and the stop-watch is started just as the drop falls on the cloth.The watch is stopped when theliquid on the surface of the cloth loses itsspecular reflective power. This point isdetermined by placing the hoop betweenthe observer and a source of light-suchas a window—at such an angle that thespecular reflection of light from the sur-face of the flattened drop can plainly beseen. As the drop is gradually absorbedthe area of this tiny mirror diminishes andfinally vanishes entirely leaving only adull wet spot behind. It is at this momentthat the watch is stopped.
7.Evaluation
7.1 Readings of rewetting time aremade so easily and quickly that ten aretaken for each concentration.The average times of disappearance of a drop for2.50，5.0，10.0 and 20.0 g of rewettingagent per liter of pad liquor are then plotted on loglog coordinate paper with concentration as the abscissa (X-axis). Astraight line is drawn to approximate thefour points as nearly as possible.
7.2 From this line relating disappearance time to concentration, one can findthe concentration which would give a disappearance time of 10 s.This is called therewetting concentration for the product.A corresponding value is then determinedfor the second rewetting agent.By usinga simple proportion with these figures itcan be calculated how many parts of thesecond product are equivalent to 100parts of the first product (or Standard) forrewetting.
8. Precision and Bias
8.1 Precision. Precision for this testmethod has not been established. Until aprecision statement is generated for thistest method, use standard statistical techniques in making any comparisons of testresults for either within-laboratory orbetween-laboratory averages.
8.2 Bias. Rewetting agents can be defined only in terms of a test method.There is no independent method for determining the true value. As a means ofestimating this property, the method hasno known bias.AATCC 27 pdf download.Evaluation of Rewetting Agents