Effect of alkylammonium salt on the dispersion and properties of Poly(p-phenylene sulfide)/clay nanocomposites via melt intercalation

Recyclable and Mendable Cellulose-Reinforced Composites Crosslinked with Diels⁻Alder Adducts

Owing to their natural abundance and exceptional mechanical properties, cellulose fibers (CFs) have been used for reinforcing polymers. Despite these merits, dispersing hydrophilic CFs in a hydrophobic polymer matrix is challenging. To address this, an amphiphilic ammonium salt was employed as the dispersant for CFs in this study. The hydrophobic CFs were mixed with a healable polymer to produce CF-reinforced composites. As the thermosetting polymer was crosslinked with Diels–Alder (DA) adducts, it was mended and recycled via a retro DA reaction at 120 °C. Interestingly, the CF-reinforced polymer composites were mended and recycled as well. When 5 wt % of the hydrophobic CFs was added to the polymer, maximum tensile strength, elongation at break, Young’s modulus, and toughness increased by 70%, 183%, 75%, and 420%, respectively. After recycling, the CF-reinforced composites still featured better mechanical properties than recycled polymer.

Enhanced Oxidation Resistance of Polyphenylene Sulfide Composites Based on Montmorillonite Modified by Benzimidazolium Salt

Organic montmorillonite (MMT) modified by 1,3-dihexadecyl-3H-benzimidazolium bromide (Bz) was used to prepare polyphenylene sulfide (PPS)/MMT composites by melting intercalation. The PPS/MMT composites showed mixed morphology, being comprised of exfoliated and intercalated structures with slight agglomerates. The tensile property of PPS/MMT composites was significantly improved due to the good dispersion of the MMT nanolayers. The test results showed that the tensile strength retention of PPS/MMT composites was higher than that of pure PPS after the oxidation treatment. Moreover, FTIR and XPS analyses were also used to evaluate the oxidation resistance of PPS composites. The FTIR analysis confirmed that adding MMT could better limit the damage of the C⁻S group and retard the generation of sulfuryl groups (⁻SO₂⁻) during the oxidation treatment compared to pure PPS. The XPS analysis also suggested that the addition of MMT could reduce the chemical combination of the elements sulfur (S) and oxygen (O) during oxidation treatment. Furthermore, the MMT nanolayers could also promote the transfer of S from a C⁻S bond into an ⁻SO₂⁻ group.

SiC-fixed organophilic montmorillonite hybrids for poly(phenylene sulfide) composites with enhanced oxidation resistance

SiC-fixed organophilic montmorillonite hybrids exhibited improved dispersion and excellent antioxidant ability in a poly(phenylene sulfide) matrix.

Nonisothermal crystallization kinetics of polyphenylene sulfide composites based on organic clay modified by benzimidazolium salt

Polyphenylene sulfide (PPS)/organic clay nanocomposites were prepared by simple melt blending. A synthesized benzimidazolium salt was used to modify the sodium montmorillonite in order to improve the compatibility with the PPS. The nonisothermal crystallization kinetics of PPS/organic clay composites were investigated by differerntial scanning calorimetry(DSC). It was observed that the crystallization peak temperature of PPS/organic clay composites was higher than pure PPS at various cooling rates. Several models such as the Ozawa and Mo equation were used to characterize the nonisothermal cooling crystallization kinetics of the PPS/organic clay composites. The results indicated that the Ozawa equation was not successful, while the Mo equation was successful to describe the nanoisothermal ctystallization kinetics of PPS/organic clay nanocomposites. The results also indicated that organic clay not only served as heterogeneous nucleating agents for PPS crystallization at lower content but also restricted the mobility and diffusion of PPS chains at higher content. These results were further supported by the crystallization activation energy of the samples determined by the Kissinger method.

Preparation and characterization of poly (phenylene sulfide) nanocomposites with both silica and clay fillers

Poly (phenylene sulfide) (PPS)/silica (SiO2)/organophilic montmorillonite OMMT(clay) nanocomposites are prepared and two kinds of nanofillers of different dimensions, the plate-like OMMT(clay) and globe-like SiO2, are dispersed through their “filler–filler” interaction in melt processing. In PPS/SiO2/clay system, strong filler–filler interaction is established by different responses to shear flow of inorganic clay and SiO2, thus the well dispersion of nanofillers is achieved successfully. However, the OMMT platelets are prone to be entangled by PPS molecular chains in PPS/SiO2/OMMT composites due to the extremely low interfacial tension between PPS and OMMT, which blocks the interaction between OMMT and SiO2. The result reveals two key points in realizing well dispersion of nanofillers in polymer by establishing filler–filler interaction in processing, namely, the distinct responses to shear flow of nanofillers provide an important condition for filler–filler interaction, while the direct collision between each other is another key point to successfully realize this interaction.

Modification of montmorillonite by different surfactants and its use for the preparation of polyphenylene sulfide nanocomposites

Polyphenylene sulfide (PPS)/clay composites were prepared by simple melt blending. Three different kinds of surfactants such as cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl benzene sulfonate (SDBS), and synthetic 1,3-dihexadecyl-3H-benzimidazolium bromide (Bz) were used as organic modifiers for the organic modification process. The benzimidazolium-modified montmorillonite (Bz-MMT) and CTAB-modified MMT (CTAB-MMT) exhibited larger interlayer spacing than SDBS-modified MMT (SDBS-MMT), while SDBS-MMT and Bz-MMT exhibited higher thermal stability compared with the CTAB-MMT. The morphology of the PPS/organic MMT nanocomposites was evaluated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The nanocomposites based on SDBS-MMT and Bz-MMT exhibited good overall dispersion of organic MMT with a mixed dispersion of intercalated and exfoliated structures. Differential scanning calorimetry and thermogravimetric analysis (TGA) were used to evaluate the thermal properties of PPS/organic MMT nanocomposites. The crystallization process of PPS in all nanocomposites was accelerated, and the crystallinity also increased, when compared with the pure PPS from the DSC analysis. The TGA analysis indicated that nanocomposites based on SDBS-MMT and Bz-MMT exhibited higher thermal stability than composites based on CTAB-MMT due to the well-dispersed nanoplatelets.

Enhanced thermal properties of poly(ethylene tetrasulfide) via expanded graphite incorporation by in situ polymerization method

In this study, a novel poly(ethylene tetrasulfide) (PETS)/expanded graphite (EG) nanocomposite with 40°C improvement in melting point is prepared via in situ polymerization technique. The morphology, chemical characteristics and the structural behavior of nanocomposites are characterized using scanning electron microscopy, Fourier transform infrared spectroscopy and x-ray diffraction (XRD) techniques, respectively. XRD observations show about 0.1 nm increase in d-spacing of PETS crystals in the presence of 2 wt% EG in nanocomposite. This behavior could be related to the intercalation of polysulfide macromolecules in the interlayer structure of EG sheets. Furthermore, the thermal properties of nanocomposites are investigated using differential scanning calorimetry and thermogravimetric analysis techniques. The thermal degradation temperature of nanocomposite containing 2 wt% graphite shows an improvement of about 10°C compared to unfilled polysulfide. Moreover, the chemical resistance of nanocomposites in different common solvents increases in the presence of EG, which could be accounted as a clear proof of interconnections for EG and macromolecular structure of the polymer.