## 3 Results and Discussion
### Water Repellency Tests  
Evaluation of fabric hydrophobicity is difficult to assess by any one method. The drop test enables a quick and easy determination, while multiple methods of testing help us to know performance and quality of the material more precisely. To ascertain the water-repellency characteristics of the fabric, the resistance of the fabric to surface penetration by a spray and resistance to surface wetting should be measured. Tests have to be carried out in combination with each other in order to obtain a complete understanding of performance. Samples were assessed for performance using drop test, spray test and contact angle measurement.  
Interlock cotton knit modified with polyacrylates PA1 and PA2 displayed drop test results greater than 30 min. In fact, superhydrophobic character was found with contact angles of 150\({}^{\circ}\) for PA1 and 160\({}^{\circ}\) for PA2. Figure 5 shows static contact angle results for the various fabric samples, all of which displayed strong hydrophobic character. With a contact angle near 160\({}^{\circ}\), PA2 had the highest value observed. The remaining fabric samples have contact angles around 150\({}^{\circ}\) or less. Contact angles in this range result from a combination of chemical composition and surface microstructure. The microstructure includes fibers within the cotton yarns and possibly texture on the surface of the fibers due to the  
Figure 4: Stress-strain plot of untreated fabric and treated fabric with formulations PA1 and PA2.  
presence of the fluoropolymer. The SEM and EDS data suggest that the higher fluorocarbon content explains why PA2 exhibits a higher contact angle than PA1.  
Samples were repeatedly home laundered with washing and drying steps to gauge durability characteristics. Results for the drop test with number of laundering cycles appear in Figure 6. Treated fabric with PA1 passes with as many as 20 washes while PA2 can hold its treatment up to 30 home launderings. As shown above, PA2 has greater fluorine content and, as such, would be expected to have lower solubility which might explain its ability to endure more home launderings. Findings for fabrics modified by admicellar polymerization were compared to commercial materials. The off-the-shelf knit sample (Ref. 1) fared poorly as it failed the drop test after only 5 washes. The interlock knit material PA1 with the lower fluorochemical content compared well to the woven commercial sample (Ref. 2) with both passing the drop test for 20 washes. The interlock knit PA2 surpassed them all with 30 washes.  
Figure 5: Comparison of contact angles for treated and commercial reference samples.  
Figure 6: Comparison of durability of treated fabrics with commercial reference samples by the drop test.  
In the spray test (AATCC 22), repellency of fabric is assessed in a dynamic system by comparison to wetting patterns on a standard chart. Measurements of spray test rating were made after a series of home laundering which were discontinued once the fabric failed the drop test. From Figure 7, the interlock commercial sample (Ref. 1) is seen to exhibit a decrease in performance with each home laundering down to a rating of 60 when the drop test result was less than 30 min. The woven material (Ref. 2) performed well with a rating of 100 up to 15 home launderings where it decreased to a rating of 90. Performance of PA1 was comparable to the woven fabric. Notably, PA2 showed substantially greater durability. Trends observed among the different fabric samples by the spray test were consistent with those of the drop test.