ASTM E3025-22

4.1?Natural and manufactured textiles fibers can be treated with chemicals to provide enhanced antimicrobial (fungi, bacteria, viruses) properties. In some cases, silver nanomaterials may be used to treat textile fibers (1).6 Silver nanomaterials are used to treat a wide array of consumer textile products, including, but not limited to, various clothing; primary garments (shirts, pants), outer wear (gloves, jackets), inner wear (socks and underwear), childrens clothing (sleepwear); childrens plush toys; bath towels and bedding (sheets, pillows); and medical devices (for example, wound dressings and face masks) 4.2?There are many different chemical and physical forms of silver that are used to treat textiles and an overview of this topic is provided in Appendix X1.

4.3?Several applicable techniques for detection and characterization of silver are listed and described in Appendix X2 so that users of this guide may understand the suitability of a particular technique for their specific textile and silver measurement need.

4.4?There are many different reasons to assay for silver nanomaterials in a textile at any point in a products life cycle. For example, a producer may want to verify that a textile meets their internal quality control specifications or a regulator may want to understand the properties of silver nanomaterials used to make a consumer textile product under their jurisdiction or what quantity of silver nanomaterial is potentially available for release from the treated textile during the washing process or during product use. Regardless of the specific reason, a structured approach to detect and characterize silver nanomaterials present in a textile will facilitate measurements and data comparison. Detection and characterterization of silver in textiles is one component of an overall risk assessment.

4.5?The approach presented in this guide (see Fig. 1) consists of three sequential tiers: obtain a textile sample (Section 7), detection of a silver nanomaterial (Section 8), and characterization of a silver nanomaterial (Section 9). If no forms of silver are detected in a textile sample using appropriate (fit for purpose) analytical techniques then testing can be terminated. If silver is detected, but present in a non-nanoscale form, the textile is a chemical or bulk silver-containing material. Silver ions may be released from silver-containing materials, and under reducing conditions these can transform into nanoscale silver-containing particles. If nanoscale silver is detected, one concludes that the textile contains a silver nanomaterial. Subsequent measurements can characterize the chemical and physical properties of the silver nanomaterial.

4.6?Numerous techniques are available to detect and characterize silver nanomaterials in textiles. The breadth of options can cause confusion for those interested in developing an analytical strategy and selecting appropriate techniques. Some techniques apply only to certain chemical forms of silver and all have limited ranges of applicability with respect to a measurand. No single technique is suitable to both detect and fully characterize silver nanomaterials in textiles. This guide describes and defines a tiered approach using commercially available measurement techniques so that manufacturers, producers, analysts, policymakers, regulators, and others may make informed and appropriate choices in assaying silver nanomaterials in textiles within a standardized framework. The user is cautioned that this guide does not purport to address all conceivable textile analysis scenarios and may not be appropriate for all situations. In all instances, professional judgment is necessary.

4.7?This guide provides a tiered approach to determine an efficacious and efficient procedure for detecting and characterizing silver in textiles and determine whether any silver nanomaterial is present. This tiered approach may also be used to determine whether a reported measurand for silver nanomaterials in a textile was obtained in an appropriate and meaningful way.

4.8?Material property measurement depends on the method. Caution is required when comparing data for the same measurand from techniques that operate on different physical or chemical principles or with different measurement ranges.

4.9?The amount of silver in a textile might decrease over time. Silver metal and silver compounds can react with oxygen and other oxidation-reduction (redox) active agents present in the environment to form soluble silver species. These soluble silver species can be released by contact with moisture (for example, from ambient humidity, washing, body sweat, rain, or other sources). As described in Appendix X1, release of soluble silver species may occur at varying rates. Release rates depend on many characteristics, including chemical nature, surface area, crystallinity, and shape, where the silver is applied to the textile (on the fiber surface, in the volume of the fiber, and so forth), and in what form the silver is applied to the textile (discrete particles, with carriers, and so forth). The condition and age of textile test samples must be considered when drawing temporal inferences from the results, as only a moment in time of the textile life cycle will be captured in the results.

4.10?Textile acquisition, storage, handling, and preparation can also affect silver content.

1.1?This guide covers the use of a tiered approach for detection and characterization of silver nanomaterials in consumer textile products, which can include some medical devices (for example, wound dressings or face masks), made of any combination of natural or manufactured fibers.

1.2?This guide covers, but is not limited to, fabrics and parts (for example, thread, batting) used during the manufacture of textiles and production of consumer textile products that may contain silver-based nanomaterials. It does not apply to analysis of silver nanomaterials in non-consumer textile product matrices nor does it cover thin film silver coatings with only one dimension in the nanoscale.

1.3?This guide is intended to serve as a resource for manufacturers, producers, analysts, policymakers, regulators, and others with an interest in textiles.

1.4?This guide is presented in the specific context of measurement of silver nanomaterials; however, the structured approach described herein is applicable to other nanomaterials in consumer textile products, including some medical devices.

1.5?UnitsThe values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6?This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.7?This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.