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Environmental aging and degradation of multiwalled carbon nanotube reinforced polypropylene
Citation:
Han, C., E. Sahle-Demessie, A. Zhao, T. Richardson, AND J. Wang. Environmental aging and degradation of multiwalled carbon nanotube reinforced polypropylene. CARBON. Pergamon Press Ltd., New York, NY, 129:137-151, (2018).
Impact/Purpose:
Polypropylene is a broadly used purpose polymer that is low cost, mechanically robust, with high resistance to water and chemicals. We selected polypropylene for this study dues to this its broad range of applications such as automotive parts, food packaging, housing materials and electrical devices. Nanomaterials are incorporated into polymers to improve the physicochemical properties or provide multi-functions to pristine polymers. However, there are a limited number of studies on the aging of different nanocomposites, and the potential release of imbedded filler materials due to environmental aging. Environmental aging breaks down polymers composites as it is proved by different analytical methods. The potential pollution of drinking water supplies from the release of polymer imbedded nanomaterials is presented in this study. The data will be used to predict the possible degradation of other polymers due to aging.
Description:
The degradation of polypropylene (PP) and PP-multiwalled carbon nanotube (PP-MWCNT) panels during environmental weathering resulted in an increased degree of crystallinity, making them brittle, and creating surface cracks. The degradation led to a breakdown of the panels and increased the potential for nanorelease. Thermal analysis revealed that the thickness of the test panels and reinforcement with MWCNTs had a significant influence on the stability of PP-MWCNT composites. Differential scanning calorimetry indicated that the MWCNTs acted as nucleation points, increasing the crystallization temperatures of PP-MWCNT, which reduced the extent of aging. Weathering decreased both the melting and crystallization temperatures of PP by as much as 20 °C. The reduction in the temperatures was inversely proportional to the thickness of the panels. The activation energy (Ea) obtained using isoconversional kinetics of the TGA analysis showed that the effective thermo-oxidative degradations of PP changed during aging. The Ea for the initial stages of thermal degradation decreased from ∼330 kJ/mol to ∼100 kJ/mol for aged PP. During the late degradation stages, the Ea values increased to ∼300 kJ/mol. These results suggest that early degradation were altered because of the changes in the molecular structure of the aged PP and a shift in the degradation rate-limiting steps.
URLs/Downloads:
https://www.sciencedirect.com/science/article/pii/S0008622317310394?via%3Dihub
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