By 2014, this project will develop and implement measurement science to characterize, model, and predict surface damage and nanofiller release as a function of environmental and mechanical stresses for polymer nanocomposites used in infrastructure and manufacturing applications. The results will be embodied in ASTM and ISO standards, effectively transferring new knowledge to end-users and manufacturers for measuring surface damage and nanofiller release in polymer nanocomposites.
Objective: By 2014, this project will develop and implement measurement science to characterize, model, and predict surface damage and nanofiller release as a function of environmental and mechanical stresses for polymer nanocomposites used in infrastructure and manufacturing.
What is the new technical idea? It is well-documented that the surface properties of polymeric systems differ greatly from their bulk properties, and that the surface is the first point of attack in any degradation process initiated by ultraviolet (UV) radiation, mechanical stress, temperature, and/or moisture. Currently, polymer nanocomposites, which are either a polymer matrix containing nanofillers or are sophisticated nano-enabled fiber-reinforced polymer (NeFRP) composites (conventional fiber-reinforced polymer composites containing nanofillers), are increasingly used or being explored for use in manufacturing (e.g., automotive, aerospace, and electronics) and infrastructure. Surface damage caused by environmental and/or mechanical stresses can lead to the release of nanofillers incorporated within the polymer nanocomposites, changes in optical, morphological, and mechanical properties, pathways for ingress of moisture and corrosive agents, and/or cracks as stress concentrators. The surface damage not only affects the long-term performance of these complex materials but also potentially poses risks to environment, health, and safety (EHS). This project will develop advanced methods for characterization and modeling of surface damage to enable a comprehensive understanding of how nanofillers impact surface properties, and how surface properties influence the long-term performance (including EHS) of complex polymer nanocomposites., This project will develop scientifically-based performance protocols that will be incorporated into standard test methods for characterization and quantification of surface damage and ultimately serve as inputs into models to accurately predict the long-term performance of polymer nanocomposites. The results will be embodied in ASTM and ISO standards, effectively transferring new knowledge to end-users and manufacturers with a main goal to minimize surface damage and nanofiller release for all polymer nanocomposites.
What is the research plan? Measurement science research will address two critical problems that have hindered the innovation and commercialization of polymer nanocomposites:
The research plan consists of three major components:
Because the structure of NeFRP and related composites is very complex and has not been well investigated, initial research of this project will focus on two model matrix systems containing spherical nanoparticles: an acrylic polymer matrix containing nano-titanium dioxide (nanoTiO2) and an epoxy matrix containing nanosilica (nanoSiO2). These two model materials actually represent two of the most common polymer nanocomposites used in infrastructure and manufacturing, so this choice is practical as well as expedient for research. Data and knowledge gained from these nanocomposites will be directly applicable to nano-enabled fiber reinforced polymer composites and other types of nano-filled polymer composites. With inputs from industrial partners to improve/refine the measurement protocols, more complex nanocomposite systems will be identified and investigated.
Task 1: Characterization – Quantitative measurement of both the degree of dispersion of nanofillers in a polymer matrix and the release of nanofillers during the life cycle of nanocomposites is very challenging and so requires sensitive methods to be developed for these measurements. Scattering, microscopy, and chemical spectroscopy-based technologies will be developed/adopted for quantifying nanofiller dispersion, polymer/filler adhesion, and the resulting structure/morphology of the nanocomposites. Additionally, advanced techniques such as inductively-coupled plasma-optical emission spectroscopy (ICP-OES) will be investigated for quantitative measurement of nanofiller release. To characterize surface damage due to applied mechanical and environmental stresses, critical surface mechanical, morphological, and chemical properties will be measured using a number of sensitive surface analytical techniques (indentation, spectroscopy, and optical scattering). The data obtained from these measurements will be used for understanding the mechanism of surface damage resulting from environmental exposures in Task 2, and for validating the models developed in Task 3.
Task 2: Exposure – Polymer nanocomposite samples prepared with different levels of filler dispersion will be exposed to specified UV radiation/temperature/relative humidity conditions using the NIST SPHERE and special designed sample holders. Varying environmental and mechanical stresses will be applied to provide essential data for understanding the surface damage mechanism and for validating prediction models. Nanofiller release during environmental exposures will be captured using a novel sample holder and quantified using advanced techniques described in Task 1. To assess mechanically-induced surface damages, the NIST-developed scratch test method will be used under various force conditions.
Task 3: Modeling – Linkages between surface mechanical, morphological and chemical properties will be established. Mechanically-induced surface damage will be modeled using first principle polymer physics, and environmentally-induced nanofiller release will be modeled using the laws of chemical reaction kinetics. The models will be developed through collaborations with researchers from the Structural Systems Group and the Statistical Division at NIST and from academic institutes. Data obtained in Task 1 and Task 2 will be used as inputs and verification for the models that will be developed in Task 3.
This project involves collaborations with various partners. The Consumer Product Safety Commission (CPSC), Environmental Protection Agency (EPA), the National Institute for Occupational Safety and Health (NIOSH), and the National Institutes of Health are partners with a mission to understand and control the exposure of humans and the environment to nanomaterials. Boeing, BYK-USA, CSM International, and Eastman Chemical are all members of the NIST/Industry Polymer Surface and Interface (PSI) consortium. These companies, along with DuPont, Dow Chemical Inc., PPG, Eastman Chemical, Arkema, International Automotive Component (IAC) Group- North America, and CEA (France) are producers of nanofillers and polymers, formulators, or users of polymer nanocomposites who are engaged with NIST in characterizing and optimizing the properties of nanomaterial systems. The Federal Highway Administration (FHWA), Department of Defense (DoD) and Sandia National Laboratory are users of nano-filled and NeFRP composites who undertake joint research in the area.
 A Research Strategy for Environmental, Health, and Safety Aspects of Engineered Nanomaterials (2012),
Standards and Codes:
PIs working with ISO TC 229 Nanotechnologies, and are participating in ASTM E56.03 Nanotechnologies-Environment, Health and Safety on a measurement protocol for quantifying nanofiller release from polymer nanocomposites. Draft on standard practice and protocols for measuring nanosilica release from polymer nanocomposites exposed to UV radiation will be submitted to ASTM E56.03.
PIs working with ASTM D01 Paint and Related Coatings, Materials and Applications and subcommittees D01.23 Physical Properties of Applied Paint Films, D01.26 Optical Properties, and D01.24 Dispersion and Particle Size, to develop measurement protocols for quantifying nanofiller dispersion, related surface properties (mechanical and optical properties), and surface damage assessment for selected composites with the support of industrial users.
Start Date:October 1, 2011
Lead Organizational Unit:el
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