Effects of Modified Layered Double Hydroxides on the Thermal Degradation and Combustion Behaviors of Intumescent Flame Retardant Polyethylene Nanocomposites

Unveiling a robust and high-temperature-stable two-dimensional ZnAl layered double hydroxide nanosheet based flexible triboelectric nanogenerator

Triboelectric nanogenerators have the ability to harvest low- and mid-frequency vibrational energy from the environment; however, achieving stable performance of the nanogenerator device in high-temperature conditions remains challenging. In this work, a flexible and temperature-stable polyvinyl alcohol (PVA)/layered double hydroxides (LDH) nanocomposite-based triboelectric nanogenerator was developed to harvest unexploited vibrational energy for the first time. Crystalline ZnAl LDH nanosheets grown by a hydrothermal route are used to fabricate the high-performance flexible nanogenerator. The ZnAl LDH exhibits fire-retardancy and high-temperature stability (∼500 °C). A triboelectric nanogenerator based on the ZnAl LDH-PVA nanocomposite generated a very high output voltage of 60 V even under a low vertical pressure of 1 kgf. Surprisingly, the developed device shows ultra-stable output performance even up to a temperature of 200 °C. In addition, a ZnAl LDH-nanosheet-reinforced PVA nanocomposite film shows very high dielectric constant of about 5 × 105 at the low-frequency side. The tremendous increase in the output voltage and stable performance are discussed in terms of the high dielectric constant and synergistic effect of the LDH nanosheets and PVA. Furthermore, the device was also used to monitor human body movements such as finger and wrist bending to develop self-powered sensors.

Polypropylene Color Masterbatches Containing Layered Double Hydroxide Modified with Quinacridone and Phthalocyanine Pigments-Rheological, Thermal and Application Properties

Polypropylene color masterbatches containing modified layered double hydroxides, LDHs, were created. The simple, industry-acceptable method of LDH surface modification with quinacridone and phthalocyanine pigments using the pulverization method in ball mills was applied. It was reported that the modification parameters such as time and rotational speed affected the tendency to create the aggregates for modified fillers. TGA analysis of the modified LDH showed that modification with phthalocyanine pigment shifted the temperature at which 5%, T5%, and 10% of mass loss, T10%, occurred compared with that for unmodified LDH. The viscoelastic properties of prepared masterbatches were investigated. The incorporation of the modified fillers instead of neat pigments led to an increase in the loss shear modulus, G″, indicating a stronger influence on the dissipation of energy by the melted masterbatch. The similar values of tan, δ, were determined for melted masterbatches containing phthalocyanine pigment and green modified LDH filler. The incorporation of both LDHs modified by phthalocyanine and quinacridone pigment fillers slightly increased the zero-shear viscosity, η0, compared with that of the masterbatches based on the neat pigments. The Cole-Cole plots and the analysis of the Maxwell and continuous relaxation models showed that modified colored LDH fillers facilitated the relaxation of the melted masterbatch, and shorter relaxation times were observed. The phthalocyanine-modified LDH filler improved the thermal stability of the masterbatches. Additionally, the impact of pigments and modified, colored LDH on the crystallization of polypropylene was investigated.