Effect of a dodecylsulfate‐modified magnesium–aluminum layered double hydroxide on the morphology and fracture of polystyrene and poly(styrene‐co‐acrylonitrile) composites

Abstract

Composites of polystyrene (PS) and poly (styrene-co-acrylonitrile) (SAN) containing a fraction of a dodecylsulfate-modified Mg-Al layered double hydroxide (LDH) were prepared by means of a melt-extrusion process. The structure and morphology were analyzed with wide-angle X-ray scattering and transmission electron microscopy, respectively. The X-ray spectra of the PS matrix composite displayed the diffraction peak characteristic of the hybrid LDH basal plane at 2y ¼ 3.1 deg. The SAN matrix composite did not exhibit such a diffraction peak. Both PS and SAN composites displayed an intercalated type of morphology with respect to the LDH platelets, as assessed by transmission electron microscopy. A plasticizing effect due to the hybrid LDH particles was observed for all composites and was supported by a decrease in the glass-transition temperature values and by Fourier transform infrared spectra. Besides tensile properties, the fracture toughness of the composites was compared with that of the pure polymers through the linear elastic fracture mechanics parameters. They were determined from fracture tests under a three-point-bending configuration. The results indicated that the effect of adding a small fraction of modified LDH particles to SAN caused an improvement in fracture toughness of 50% with respect to that of the pure polymer. Moreover, the relative increase in the fracture energy was about 200%. For PS matrix composites, both tensile properties and linear elastic fracture mechanics fracture parameters remained unaffected. These results were explained on the basis of the different plasticities developed by both polymers around the particles.

Morphological, mechanical, and thermal features of PMMA nanocomposites containing two‐dimensional Co–Al layered double hydroxide

“…However, in case of PMMA nanocomposites, all these small peaks are present which indicate the presence of LDH layers in the PMMA matrix . Other than MO vibration bands, absorption band corresponding to OH stretching vibration of LDH (around 3450 cm −1 ) is also present in PMMA/Co–Al LDH nanocomposites which further verifies the presence of LDH layer in the PMMA matrix . From the FTIR spectra, it is clearly seen that all nanocomposites possess similar bands when compared with those of pristine PMMA, in addition to that there are some extra peaks originating from LDH.…”

“…For PMMA nanocomposites, the metal–oxygen bond (MO, OMO) corresponding to LDH layers (400–700 cm −1 ) is absent in neat PMMA. However, in case of PMMA nanocomposites, all these small peaks are present which indicate the presence of LDH layers in the PMMA matrix . Other than MO vibration bands, absorption band corresponding to OH stretching vibration of LDH (around 3450 cm −1 ) is also present in PMMA/Co–Al LDH nanocomposites which further verifies the presence of LDH layer in the PMMA matrix .…”

“…Several researchers have used LDHs to prepare different polymer nanocomposites . Ding and Qu reported that the completely exfoliated morphology of PS nanocomposites was obtained even at 20 and 10 wt % loading of Zn–Al LDH, that was synthesized by emulsion and suspension polymerization, respectively.…”

In situ synthesis, morphology, and thermal properties of polystyrene—MgAl layered double hydroxide nanocomposites

“…In the region of 2000–1680 cm −1 , bands of weak aromatic overtone and combination were also observed. Other bands found in the spectrum of pure PS are in the region of 1598 and 1491 cm −1 , due to the stretching vibration of C=C in the phenyl ring group; in 1459 and 1361 cm −1 , characterizing the bending vibration of CH 2 group; in 747 and 693 cm −1 , characterizing the C–H out of plane bending of the phenyl ring; and in 533 cm −1 , characterizing the C–H out of plane deformation of the phenyl ring [22, 23].…”

Effects of a phosphorus compound on the morphology, thermal properties, and flammability of polystyrene/MgAl‐layered double hydroxide nanocomposites

“…1a, a broad band around 3,500 cm −1 is explained by the superposition of stretching vibration bands of MgOH, AlOH, and OH, the last one corresponding to the water molecular within the layers. It also displays the characteristic CH aliphatic chain stretching vibration bands at 2,957, 2,921, and 2,852 cm −1 as well as SO at 1,213 cm −1 because of the presence of modifier SDS [17]. From Fig.…”