CARBON NANOTUBES WITHIN POLYMER MATRICES
NanoRelease Steering Committee (SC) members deliberated over a 9-month period to identify potential nanomaterials and release methods for further study. More than 20 materials were identified and grouped into 3 tiers
. After conducting an extensive evaluation
as well as ranking and voting on the materials, the committee narrowed the list of nanomaterials to either nano-silver (n-Ag) or (MWCNTs). Forty-five experts from academia, industry, and US and Canadian government agencies attended a May 10–11, 2011 workshop
in order to:
Refine the project objectives,
Select the material that will be used to develop methods to measure release, and
Select and charge experts to develop white papers that will inform the development of a state-of-the-science document and workplan for “Phase 3” methods testing, development, and proof of utility for articles in commerce.
MATERIAL SELECTION AND APPLICATIONS
After considerable discussion, the SC selected MWCNTs embedded within polymer matrices to carry forward to the next phases of the project.
With funding from the US EPA, Environment Canada, and the American Chemistry Council, over the next 9 months the project will convene expert groups to develop a state-of-the-science evaluation of material properties and measurement methods relevant to understanding the release of MWCNTs from polymers used in products in commerce.
We are selecting the specific polymer to use in methods development, in consideration of applications such as:
Fabrics such as flame-retardant toys and blankets;
Tennis racquets, bicycle frames, baseball bats, and sports safety equipment;
Boat hulls; and
- Coaxial cable.
TASK GROUP 2 POLYMER DECISION PROCESS
Recently, Task Group 2 (Materials) went through a decision process in which experts from a variety of stakeholder groups voted to choose a set of five polymers as the most relevant to MWCNT/polymer systems at this time. Details of the process and final outcome are explained in the Task Group 2 (Materials) Polymer Decision Process.
TIER 1 AND TIER 2 TESTING
For purposes of discussion here, an “article” is something that is made and sold in commerce. In common parlance this is often referred to a “finished product”.
The legal definition an “article” in the U.S. Toxic Substances Control Act is:
“a manufactured item (1) which is formed to a specific shape or design during manufacture, (2) which has end-use function(s) depending in whole or in part upon its shape or design during end use, and (3) which has either no change of chemical composition during its end use or only those changes of composition that have no commercial purpose separate from that of an article, and that results from a chemical reaction that occurs upon end use of other chemical substances, mixtures, or articles.”
In terms of the value chain, U.S. regulators refer to the precursor materials that are made into articles as either “chemical substances” or “products”. For example, carbon nanotubes can be sold in a free form (the powder in the above diagram) for research purposes and this would be referred to as a product. Similarly, carbon nanotubes can be mixed with plastic (the pellets in the above diagram) and sold as a “master batch” to subsequent manufacturers and this master batch would also be called a product in U.S. regulatory terms. The subsequent manufacturers would use the master batch to mix with other materials to make an “intermediate” product or “pre-preg” which can then be sold again or made into a finished product, these would be called articles.
Image source: Left and middle images courtesy of Nanocyl with permission.
The project is currently recruiting experts to develop white papers on three general topic areas, including:
Methods that may be used to detect and measure release of MWCNTs from polymers;
Material characteristics of polymers and MWCNTs that influence release from products and articles in fabrication, commerce, and disposal; and
Release scenarios along the life cycle of the product and articles made from it for the most common uses that are of the greatest importance to the potential for exposure pathways (human health).
After the white papers are completed, a workshop will be convened to facilitate feedback on the documents. A set of independent authors will then create the state-of-the-science document and Phase 3 workplan.
In subsequent phases, the project will conduct testing and methods development using an interlaboratory testing approach, in which US and Canadian government, industry, and academic laboratories are convened using a “cooperative research and development agreement” approach often used by US government agencies to enable technology transfer between public and private sectors.
FOR MORE INFORMATION
For additional information on the NanoRelease project, please contact us