Effect of Cellulose Nanocrystals (CNC) Particle Morphology on Dispersion and Rheological and Mechanical Properties of Polypropylene/CNC Nanocomposites

Abstract

Polypropylene (PP) nanocomposites containing spray-dried cellulose nanocrystals (CNC), freeze-dried CNC, and spray-freeze-dried CNC (CNCSFD) were prepared via melt mixing in an internal batch mixer. Polarized light, scanning electron, and atomic force microscopy showed significantly better dispersion of CNCSFD in PP/CNC nanocomposites compared with the spray-dried and freeze-dried CNCs. Rheological measurements, including linear and nonlinear viscoelastic tests, were performed on PP/CNC samples. The microscopy results were supported by small-amplitude oscillatory shear tests, which showed substantial rises in the magnitudes of key rheological parameters of PP samples containing CNCSFD. Steady-shear results revealed a strong shear thinning behavior of PP samples containing CNCSFD. Moreover, PP melts containing CNCSFD exhibited a yield stress. The magnitude of the yield stress and the degree of shear thinning behavior increased with CNCSFD concentration. It was found that CNCSFD agglomerates with a weblike structure were more effective in modifying the rheological properties. This effect was attributed to better dispersion of the agglomerates with the weblike structure. Dynamic mechanical analysis showed considerable improvement in the modulus of samples containing CNCSFD agglomerates. The percolation mechanical model with modified volume percolation threshold and filler network strength values and the Halpin-Kardos model were used to fit the experimental results.

Properties of polypropylene and polypropylene/poly(ethylene-co-vinyl alcohol) blend/CNC nanocomposites

“…60% when a good state of dispersion is achieved using the compatibilizer. Similar results were obtained by Khoshkava and Kamal [34]. Fig.…”

Effect of cellulose nanocrystal polymorphs on mechanical, barrier and thermal properties of poly(lactic acid) based bionanocomposites

“…Due to presence of such interfibrillar entanglement, the PLA/CNC II nanocomposites are able to withstand higher strength compared to other CNC polymorphs. Similar phenomenon of increase in aspect ratio due to aggregations was observed by Khoshkhava et al 27 , for freeze dried CNCs in the polypropylene matrix. Presence of such interactions between the PLA/CNC II is due to the enhanced hydrogen bonding as discussed before which led to decrease in Figure 5(c)).…”

“…Several studies related to the dispersion of CNCs either in wet or dry state in the polymer matrix have been compared 27 . For example, incorporation of CNCs in spray and freeze dried condition into the polymeric system improves its dispersion compared to wet state when dispersed in organic or inorganic solvents 27 .…”

Cellulose nanocrystals prepared via formic acid hydrolysis followed by TEMPO-mediated oxidation

“…Rheological behaviour of CNC suspensions (a: viscosity vs shear rate; b: shear stress vs shear rate; F-CNC (sample 7 in Table 1): prepared by FA; T-CNC: modified F-CNC by TEMPO-mediated oxidation).It is known that the rheological behaviour test is of vital importance for the prediction of composites performance in the potential end applications(Urena-Benavides, Ao, Davis, & Kitchens, 2011;Yang, Tang, Wang, Kong, & Zhang, 2014) and the rheological behaviour of CNC suspensions is highly related to the shear stress, solid concentration, ionic strength and the nature of CNC (e.g. size, surface charge density) products(Khoshkava & Kamal, 2014). In this work, the rheological behaviour of CNC suspensions at the concentration of 0.3% was measured.…”