Polypropylene/graphite nanocomposites by thermo‐kinetic mixing

Abstract

Polypropylene (PP)/graphite nanocomposites have been prepared by melt-mixing PP with different levels of graphite (G) and graphite oxide (GO) using maleated PP(PPg-MA) and graphite oxide (GO) as interface modifiers. Melt-mixing was achieved using a Gelimat, a high-speed thermo-kinetic mixer. The Gelimat system is specifically designed to handle difficult compounding and dispersion applications by completely mixing, heating and compounding products within a few minutes. Therefore, the thermal history of the compounded polymer is very short, which limits degradation.Interfacial modification by addition of maleated PP and graphite oxide is essential for producing PP/G nanocomposite. The graphite oxide then interacts with the maleic anhydride group of the PP-g-MA. The structure and properties of PP/PP-g-MA/GO/G nanocomposites were compared by different techniques. Evidence of the nanoscale dispersion of graphite sheets within the PP were provided by wide-angle X-ray diffraction (WAXD) and supported by scanning electron microscopy (SEM). The high mechanical shear stresses generated by the Gelimat greatly reduced the ordering initially measured by WAXD between graphite sheets and sheet aggregates, indicating a dispersion of the graphite in the polymer to the extent that graphite particles could hardly be observed by SEM. It was found that the addition of PP-g-MA and GO leads to excellent dispersion of G within the PP matrix. The flow behavior of the material was also studied by means of a parallel-plate rheometer. The addition of graphite to PP caused a drastic change in the flow behavior of PP. The thermal degradation behavior, studied using thermogravimetric analysis (TGA), showed higher thermal stability of the nanocomposite than that of pure polypropylene. The dispersion of the graphite in the resin promoted the nucleation of ␤ crystallites in PP. The ␤ crystallites, normally less abundant than ␣ crystallites in pure PP, were found to constitute the dominant phase in the nanocomposite.

Nanocompósitos de polietileno/argila bentonítica com propriedades antichama

“…Diferentes tipos de cargas em dimensões nanométricas têm sido utilizada para preparar nanocompósitos sendo: grafite, argila, sílica, nanotubos de carbono entre outras [3,4] .…”

Caracterização De Nanolâminas De Grafeno (Ng) Produzidas Pelo Método Da Esfoliação Química

“…Quimicamente similar aos nanotubos de carbono e estruturalmente análogo às camadas de silicatos, o grafite tem o potencial para ser uma excelente nanocarga, sob a forma de camadas individuais de grafeno ou agregados de nanolâminas. O grafite natural como ocorre na natureza não pode ser utilizado como nanocarga devido à ligação química existente em suas camadas, bem como ao espaçamento entre elas, por esta razão precisa ser modificado quimicamente (GOPAKUMAR, 2004).…”

“…Quimicamente similar aos nanotubos de carbono e estruturalmente análogo às camadas de silicatos, o grafite tem o potencial para ser uma excelente nanocarga, sob a forma de camadas individuais de grafeno ou agregados de nanolâminas. O grafite natural como ocorre na natureza não pode ser utilizado como nanocarga devido à ligação química existente em suas camadas, bem como ao espaçamento entre elas, por esta razão precisa ser modificado quimicamente (GOPAKUMAR, 2004).As nanolâminas de grafeno são compostas de carbonos constituídos por camadas com espessura atômica extraídas do grafite. Elas são consideradas um dos materiais mais finos no que diz respeito a sua estrutura, e apresentam flexibilidade, transparência, impermeabilidade e condutividade elétrica.…”

Exfoliated graphite nanoplatelet-filled impact modified polypropylene nanocomposites: influence of particle diameter, filler loading, and coupling agent on the mechanical properties

“…Therefore, producing graphitereinforced PP nanocomposites is very difficult because of the lack of affinity between the two constituents. This issue can be overcome by adding a coupling agent such as polypropylene-graft-maleic anhydride (PP-g-MA) (Gopakumar and Page 2004;Spoljaric et al 2009). According to a study by Page et al (2006), XRD and SEM results indicate that the functionalization of PP by addition of PPg-MA leads to an excellent dispersion of graphite, and improvement in flexural properties of the material.…”