Nanocomposites of foamed LCB-PP with MWCNT

Nanocomposites of foamed long chain branching polypropylene (LCB-PP) with multi-walled carbon nanotubes (MWCNT) were prepared by melt mixing and compression molding. The LCB-PP was kindly donated by Braskem, Brazil and the MWCNT was Nanocyl NC7000, from Belgium. LCB-PP was foamed with azodicarbonamide (AZDC), donated by Proquitec, Brazil. The AZDC decomposition temperatures and the crystallization kinetics of the LCB-PP with and without AZDC at different cooling rates were studied by thermal gravimetric analyses (TGA) and differential scanning calorimetry (DSC), respectively; the foaming process was followed by polarized light optical microscopy (PLOM) at different cooling rates. It was found that the AZDC incorporation did not change the crystallization kinetics of the PP; the Avrami index (n) was the same. To produce the foamed nanocomposites, the LCB-PP was mixed with 2.5 wt% of AZDC and 1.5, 2, 3 and 5 wt% of MWCNT in a melt rheometer (Haake, 120rpm, T=175°C) and subsequently allowed to foam in a hot press. The electrical conductivity of the nanocomposites were measured using a Solartron impedance analyzer; the foamed nanocomposites, had a higher conductivity than the non-foamed. (author)