Processing and properties of carbon nanofibers reinforced epoxy powder composites |
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Authors: | C Palencia M A Mazo A Nistal F Rubio J Rubio J L Oteo |
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Institution: | 1.Departamento de Química Física de Superficies y Procesos,CSIC, Instituto de Cerámica y Vidrio,Madrid,Spain |
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Abstract: | Commercially available CNFs (diameter 30–300 nm) have been used to develop both bulk and coating epoxy nanocomposites by using
a solvent-free epoxy matrix powder. Processing of both types of materials has been carried out by a double-step process consisting
in an initial physical premix of all components followed by three consecutive extrusions. The extruded pellets were grinded
into powder and sieved. Carbon nanofibers powder coatings were obtained by electrostatic painting of the extruded powder followed
by a curing process based in a thermal treatment at 200 °C for 25 min. On the other hand, for obtaining bulk carbon nanofibers
epoxy composites, a thermal curing process involving several steps was needed. Gloss and mechanical properties of both nanocomposite
coatings and bulk nanocomposites were improved as a result of the processing process. FE-SEM fracture surface microphotographs
corroborate these results. It has been assessed the key role played by the dispersion of CNFs in the matrix, and the highly
important step that is the processing and curing of the nanocomposites. A processing stage consisted in three consecutive
extrusions has reached to nanocomposites free of entanglements neither agglomerates. This process leads to nanocomposite coatings
of enhanced properties, as it has been evidenced through gloss and mechanical properties. A dispersion limit of 1% has been
determined for the studied system in which a given dispersion has been achieved, as the bending mechanical properties have
been increased around 25% compared with the pristine epoxy resin. It has been also demonstrated the importance of the thickness
in the nanocomposite, as it involves the curing stage. The complex curing treatment carried out in the case of bulk nanocomposites
has reached to reagglomeration of CNFs. |
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