Structure–Property Relationships of Nanocomposites Based on Polypropylene and Layered Double Hydroxides

Abstract

Nanocomposites based on polypropylene (PP) and organically modified ZnAl layered double hydroxides (ZnAl-LDH) were prepared by melt blending and investigated by a combination of differential scanning calorimetry (DSC), small- and wide-angle X-ray scattering (SAXS and WAXS), and dielectric relaxation spectroscopy (DRS). An average number of stack size of LDH layers is calculated by analyzing the SAXS data which is close to that of pure organically modified ZnAl-LDH. Scanning microfocus SAXS investigations show that the ZnAl-LDH is homogeneously distributed in the PP matrix as stacks of 4–5 layers with an intercalated morphology. DSC and WAXS results show that the degree of crystallinity decreases linearly with the increasing content of LDH. The extrapolation of this dependence to zero estimates a limiting concentration of ca. 40% LDH where the crystallization of PP is completely suppressed by the nanofiller. The dielectric spectra of the nanocomposites show several relaxation processes which are discussed in detail. The intensity of the dynamic glass transition (β-relaxation) increases with the concentration of LDH. This is attributed to the increasing concentration of the exchanged anion dodecylbenzenesulfonate (SDBS) which is adsorbed at the LDH layers. Therefore, a detailed analysis of the β-relaxation provides information about the structure and the molecular dynamics in the interfacial region between the LDH layers and the polypropylene matrix which is otherwise dielectrically invisible (low dipole moment). As a main result, it is found that the glass transition temperature in this interfacial region is by 30 K lower than that of pure polypropylene. This is accompanied by a drastic change of the fragility parameter deduced from the relaxation map.

Adsolubilization of 2,4,6-trichlorophenol from aqueous solution by surfactant intercalated ZnAl layered double hydroxides

“…Surfactant modified ZnAl-LDHs were prepared by a co-precipitation method [47,50]. Solution A: 0.02 mol of Zn(NO 3 ) 2 Á6H 2 O and 0.01 mol of Al(NO 3 ) 3 Á9H 2 O was dissolved in 100 mL of deionized water (Zn 2+ :Al 3+ molar ratio = 2:1).…”

“…the dissolution of hydrophobic organics in the three-dimensional (3D) hydrophobic organic phase, rather than the uptake on the LDH external surface [44,45]. The concept of adsolubilization has been extensively used in a range of organic-anion intercalated LDHs adsorption investigations [46][47][48][49][50].…”

Morphology‐ and Phase‐Controlled Iron Oxide Nanoparticles Stabilized with Maleic Anhydride Grafted Polypropylene

“…Maleic anhydride grafted polypropylene (PP-g-MA) is commonly used as a compatibilizer between a polymer matrix and fillers like organoclay, [7] double-layered hydroxides, [8] and carbon nanotubes [9] in the fabrication of polymer nanocomposites. The advantages of PP-g-MA are that its PP backbone structure is miscible with polyolefins and its MA functional groups are capable of bonding with many organic and inorganic compounds.…”

Dehydration-rehydration induced structural changes in pristine and composite layered double hydroxides

“…The more intense is called β-relaxation and it corresponds to the dynamic glass transition related to segmental fluctuations. The third one is the γ-relaxation, corresponding to localised fluctuations within the amorphous regions [132][133][134].…”

“…The dielectric behaviour of polymers with a high degree of crystallinity like sodium polyacrylate, in general, follows a sequence of relaxation processes different from that of the amorphous ones [102,133]. Figure 52 displays the dielectric behaviour of sodium polyacrylate vs. frequency and temperature in a 3D representation.…”