Structure and properties of polypropylene-nanoclay composites

Enhancement of Thermal, Mechanical, and Oxidative Properties of Polypropylene Composites with Exfoliated Hexagonal Boron Nitride Nanosheets

This study investigates the enhancement of polypropylene (PP) composites through the incorporation of exfoliated hexagonal boron nitride (h-BN) nanosheets. The preparation process involved exfoliating h-BN in a liquid phase using a high-pressure homogenizer, followed by the coating of PP pellets with the exfoliated nanosheets using an acoustic mixer. Melt extrusion was then employed to fabricate h-BN-reinforced PP composite films. Characterization techniques, including scanning electron microscopy, confirmed the uniform dispersion of exfoliated h-BN within the PP matrix, which is crucial for improving thermal conductivity, mechanical strength, and oxidative stability. Tensile testing demonstrated that exfoliated h-BN significantly enhanced the strength and toughness of homopolymer PP, while the improvements in impact copolymer PP were more modest. Thermal analysis revealed no significant change in the decomposition temperatures of PP but indicated improved oxidative stability with the incorporation of h-BN nanosheets. Notably, the oxidation resistance of PP was enhanced, as evidenced by reduced carbonyl index values in thermally aged samples. Overall, exfoliated h-BN nanosheets significantly improve the performance of PP composites, demonstrating their potential for diverse industrial applications that require superior thermal and mechanical properties, as well as enhanced oxidation resistance.

Quaternized chitosan/polyvinyl alcohol anion exchange membrane enhanced by functionalized attapulgite clay with an ionic "chain-ball" surface structure

Biomass chitosan has garnered considerable interest for alkaline anion exchange membranes (AEMs) due to its eco-friendly and sustainable characteristics, low reactant permeability and easily modifiable nature, but it still faces the trade-off between high hydroxide conductivity and sufficient mechanical properties. Herein, a novel functionalized attapulgite clay (f-ATP) with a unique ionic "chain-ball" surface structure was prepared and incorporated with quaternized chitosan (QCS)/polyvinyl alcohol (PVA) matrix to fabricate high-performance composite AEMs. Due to the strengthened interfacial bonding between f-ATP nanofillers and the QCS/PVA matrix, composite membranes are synergistically reinforced and toughened, achieving peak tensile strength and elongation at break of 24.62 MPa and 33.8 %. Meanwhile, abundant ion pairs on f-ATP surface facilitate ion transport in the composite AEMs, with the maximum OH- conductivity of 46 mS cm-1 at 80 °C and the highest residual IEC of 83 % after alkaline treatment for 120 h. Moreover, the assembled alkaline direct methanol fuel cell exhibits a remarkable power density of 49.3 mW cm-2 at 80 °C. This work provides a new strategy for fabricating high-performance anion exchange membranes.

Matrix Degradation during High Speed Extrusion of Polypropylene/Clay Nanocomposites – Influence on Filler Dispersion

We prepared polypropylene/organoclay nanocomposites by melt blending in a twin-screw extruder, exploring the domain of high screw speeds (up to 1 100 min−1). The samples were characterized at both microscale (size of agglomerates) and nanoscale (level of exfoliation). We show that, despite a satisfactory exfoliation, the polymer matrix suffered important thermomechanical degradation by chain scission. We propose a way to correct this degradation on the viscosity curves and we confirm that high screw speeds are not necessarily favorable to clay exfoliation, essentially because of the too high melt temperatures encountered during the process.