Poly(propylene) Nanocomposites Containing Various Carbon Nanostructures

Abstract

PP nanocomposites containing different carbon nanofi llers (CNTs, CNFs, GnPs, CB) are fabricated and further processed by hot compression molding. A high level of nanofi ller dispersion is found. The NCs exhibit improved thermal stability and higher crystallinity. Both electrical conductivity and real permittivity increase with increasing nanofi ller loading. A strongly aspect ratio dependent electrical conductivity percolation is observed at loadings of 15.0, 12.0, 5.0, and 3.0 wt% for CB, GnPs, CNFs, and CNTs, respectively. The rheological behavior of the NC melts is also investigated. A small concentration of the nanofi llers is found to affect the modulus and viscosity of the PP melts signifi cantly.

Effect of Carbon-Based Particles on the Mechanical Behavior of Isotactic Poly(propylene)s

“…[ 30 ] Moreover, rheology can detect the presence of complex morphologies, such as a percolated structure associated to the formation of a 3D network of nanoparticles along the nanocomposite, [ 42,43 ] This network changes the behavior of the melt matrix at low shear rates and low frequencies from a liquid-like Newtonian fl uid to a solid-like Hooke fl uid. The dependence of viscoelastic parameters on the concentration of carbon-based fi ller has been widely studied in the literature for polymer composites with CNTs, [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] but little has been addressed in composites with other fi llers such as graphite, [59][60][61] and/or TrGO. [ 36,45,60,62,63 ] Isotactic poly(propylene) nanocomposites with CNTs have a rheological percolation at concentrations between 0.3 and ≈ 3 wt%, [ 45,49,51,[56][57][58] while iPP/TrGO composites require concentration above 5 wt% to achieve rheological percolation, [ 45 ] showing that the size and aspect ratio of the carbon-based fi ller affect the melt rheology of the composite.…”

“…Melting temperature, T m , was determined in the second scan and the degree of crystallinity was calculated from enthalpy of fusion data obtained from the DSC curves (209 J g was used for 100% crystalline material). [ 40,45,64 ] Rheological measurements were run on an ARES-G2, TA-Instruments rheometer with 25 mm parallel plate geometry conducting an isothermal frequency sweep at 190 °C with ω = 0.01-100 rad s −1 . All measurements were conducted in the linear (mechanical response) regime, with deformation amplitude γ 0 = 3%, and under nitrogen atmosphere to avoid oxidative degradation.…”

“…For instance, a variation of less than 5% in both X c and T m , was found between iPP ( T m ≈ 161.3 °C and X c ≈ 53%) and iPP + 10 wt% of TrGO ( T m ≈ 163.1 °C and X c ≈ 53%), similarly as reported by Guo and coworkers. [ 44,45 ] Therefore, changes in Young's modulus are just explained by the presence of the carbon-based particles rather than by changes in crystallinity. Figure 2 b shows the decrease in elongation at break of the different composites as the concentration of carbonbased fi llers is increased, especially when CNTs, TrGO, or both together (hybrid composites) were used.…”

Dielectric and Electromagnetic Behavior of Conductive Nanocomposites Polymers: PP/MWCNT Investigations for EMI Applications

“…The dielectric behavior [9] can be analyzed based on Debye-equation (2). The Cole-Cole plot or Argand plot displays dielectric spectra as ε''(ω) versus ε''(ω) and can be helpful for representing the relaxations in polymers.…”

“…In order to remove this circumstance is to use absorbing materials with dielectric EMC performances for projecting and designing shielding systems and structures. Nanocomposite dielectric materials containing conductive inclusions assigned randomly, including carbon nanotubes, at lower or higher concentrations can be used for shielding electromagnetic waves at RF and microwave frequencies [2]. Nonetheless, the request to reduce the weight and the cost of these "safety" structures requires the replacement of metal by novel materials like conducting polymers and composites.…”