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Measuring Silver in Antimicrobial Fabric with HDXRF


INTRODUCTION

No one wants to make a stink. That’s why manufacturers are introducing premium innerwear and activewear using antimicrobial fabrics treated with a solution of silver ions to kill odor-causing bacteria. Fabrics treated with products such as Silvadur™ are effective as long as a minimum concentration of the silver remains after washing. The longevity of the treatment is partially based on the initial concentration applied to the fabric, so an important quality control test is to quantify the amount of silver found in the fabric. To comply with manufacturer standards of quality, a minimum concentration of silver is required based on the application, and HDXRF provides a reliable, low-cost, and non-destructive test for quality assurance programs.


CHALLENGE

Overall customer satisfaction with anti-odor activewear requires a minimum concentration of silver after dozens of washes. Manufacturers will perform tests through an International Antimicrobial Council (IAC) certified test lab to demonstrate that even after dozens of washes, fabric with the anti-microbial treatment is still effective in killing 99% of bacteria. However, this testing process can take weeks for overseas manufacturing sites, and is not conducive to on-demand, on-site quality control measures. Delays in testing results may cause substantial inventory holding, and correspondingly large batches of rework if a problem is found. So, timely alternative methods that strongly correlate with IAC lab results are needed for cost-effective anti-microbial testing.

In addition to satisfying customers, other stakeholders require quality control assurance that the appropriate concentration of antimicrobial treatment is present. Manufacturers of the antimicrobial treatment technology require a minimum concentration to be applied to products bearing their trademark, to insure their brand is associated with apparel that demonstrates long-term anti-odor performance.

Effective testing alternatives for quality control need to be quantitative, non-destructive, repeatable and correlated with results produced by IAC labs. While Colorimetric tests can provide a visual indicator for the presence of silver, it is a qualitative and subjective measure that is sometimes challenging to get consistent results. Testing using wet chemistry is quantitative, but is also destructive and requires highly trained experts to provide reliable results.

 

SOLUTION

While XRF has been used in the past for inspection of precious metals in mining and jewelry, only HDXRF provides the level of sensitivity required to measure these low concentrations of silver in a low-density fabric matrix. HD Mobile® is able to quantify the amount of antimicrobial treatment present in a wide range of textiles, from cotton to polyester, and thin layers to the warmest fleece. Table 1 below has examples of fabrics measured using HD Mobile and corresponding ICP measurements. Samples were selected to represent the full range of fabrics used by athleticwear products, and were measured at different spots to get an average value and standard deviation.

In less than 4 minutes, HDXRF is able to indicate if specific fabric blends or treatments meet their specifications or if they require higher concentration solutions to reach the target levels for the finished product, without rework or expensive delays.

 

* Silvadur™ is a trademark of the Dow Chemical Co.

 

Table 1

Fabric Color ICP Result* HDXRF
2628P – 90/10 Cotton/Poly blend Heather Grey 14 ppm 17 ppm +/- 4
5228 – 100% Cotton Grey 19 ppm 14 ppm +/- 4
R60501 – Fleece Black 14 ppm 14 ppm +/- 4
R60501 – Fleece Navy 13 ppm 15 ppm +/- 5

* ICP results reported without an estimate of the uncertainty in the measurement




HD Mobile analyzer

HD Mobile® Powered by HDXRF®

Trace multi-elemental analysis has never been so convenient. HD Mobile is designed for various work environments - the manufacturing floor, shipping dock, warehouse, or retail shelf. It offers a portable handheld analyzer for users to easily switch from stationary to handheld analysis. HD Mobile precisely measures precious metals like silver.




Under ideal conditions,

a bacteria population can

double in size

in 20 – 30 minutes.




Silver-based technologies

represented

25 percent

of all antimicrobial textile

treatments in 2011.