Life Cycle Aspects of Nanoproducts, Nanostructured Materials, and Nanomanufacturing: Problem Definitions, Data Gaps, and Research Needs
Chicago, Illinois: November 5-6, 2009
Life Cycle Aspects of Polymer Nanocomposites-
Materials, Manufacturing and Applications
L. James Lee
Department of Chemical and Biomolecular Engineering
The Ohio State University
Polymer nanocomposites (PNCs) are multicomponent systems in which the main matrix is a polymer resin and at least one dimension of one of the reinforcements is in the “nano” scale, i.e. below 100 nm. They are a new breed of composites which promise many novel functionalities to the otherwise uni-functional composites. The three most widely used nanoparticles in PNCs are nanoclays, carbon nanofibers (CNFs) and carbon nanotubes (CNTs). Recent market surveys have estimated polymer nanocomposites consumption at tens of millions of pounds (~ $250 million), with a potential annual growth rate of 24%. This trend estimates a $500-$800 million market for PNCs in 2011[1]. Main application areas are large commercial opportunities like automobile parts, functional coatings, packaging etc where high performance materials are needed to improve durability and design flexibility while lowering unit price and life cycle cost.
The widespread adoption of PNCs has recently been challenged by increasing concerns of unknown risks associated with the use of nanomaterials. Moreover, evaluation of economic and environmental trade-offs of nanoproducts vs. conventional alternatives is important. The detailed toxicity studies of carbon based nanoparticles and nanoclays are still in their infancy. A few in-vitro studies showed disagreement. Magrez et al[2]. studied the toxicity of carbon based nanomaterials and observed severe cell death and inhibition in cell proliferation. They also concluded that this toxicity depends on particle size and shape, and surface chemistry. They noted that surface functionalization of the nanoparticles increased their cytotoxicity. On the other hand, Sayes et al[3]. at Rice university showed that surface modification of carbon nanoparticles rendered them a benign nature with respect to cytotoxicity. Reaching a consensus on this issue is extremely important before widespread manufacture of nanoproducts begins.
Besides the health effects, a holistic understanding of the economical and environmental effects of nanoproducts is equally important. A systems analysis approach is essential for directing the sustainable development of nanomaterial based products. However, there are some unique challenges presented by nanomaterials and nanoproducts which make analysis difficult. These include the lack of inventory data about nano-manufacturing methods, weak knowledge of health and environmental effects of nanomaterials, and the rapidly evolving nature of manufacturing processes and chemistries in this field.
Some recent work in this area has been done regarding CNFs, CNF/polymer PNCs and their use in products for automobile body panels[4]. Their results indicated a significantly higher life cycle energy intensity and higher environmental impact of these materials when compared to traditional materials like aluminum and steel on a per kilogram basis. This was attributed mainly to the high energy, low yield vapor deposition processes that are used to manufacture CNFs. Depending on the quantity of nanomaterials used, and energy savings in the product-use phase of these products, they can still be greener alternatives to current materials (even though their manufacture is more energy intensive).
In this presentation, I will discuss current and future applications of PNCs, their manufacturing methods, and related health, energy and environmental issues that require in-depth life cycle analysis.
References
- Winey, K.I. and R.A. Vaia, “Polymer nanocomposites”, MRS Bulletin, 2007. 32(4): p. 314-319.
- Magrez, et al., “Cellular toxicity of carbon based nanomaterials”, Nanoletters, 2006, 6(6), 1121-1125.
- Sayes, et al., “Functionalization density dependence of single-walled carbon nanotubes cytotoxicity in vitro”, Toxicology Letters, 2006, 161(2), 135-142.
- Khanna, V., B. Bhakshi and L.J. Lee, “Carbon nanofiber production: life cycle energy consumption and environmental impact”, Journal of industrial ecology, 2008, 12(3), 394-410.