Organobentonites Modified with Poly(Acrylic Acid) and Its Sodium Salt for Foundry Applications

Abstract

The article aims to verify the possibility of obtaining an organic–inorganic material acting as both a binder and a lustrous carbon carrier in bentonite-bonded molding sands. Due to the wide industrial application, organoclays can be considered as innovative materials supporting the foundry technology in meeting environmental requirements. In this study, the organic modification of montmorillonite in calcium bentonite (SN) was performed by poly(acrylic acid) (PAA) and its sodium salt (PAA/Na). Additionally, for the purpose of comparison, the sodium-activated bentonite/poly(acrylic acid) (SN-Na/PAA) composites were also prepared. The collective analysis of the research results used in the assessment of the mineral/polymer interaction mechanism indicates surface adsorption combined with the intercalation of PAA monolayer into the mineral interlayer spaces. Materials were characterized by the combination of Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) methods. Based on the XRD analysis, the influence of PAA/Na on the aluminosilicate layered structure was found to be destructive, which may adversely affect the binding properties of SN/PAA/Na composites considered as a potential group of new foundry binders. The SN/PAA and SN-Na/PPA composites (with appropriate polymer content) can act as a binding agent in the synthetic molding sand technology, despite coating the bentonite particles with polymer molecules. The risk of losing the mineral′s binding capacity is reduced by the good binding properties of pol(acrylic acid) itself. The article is the first stage (preceding the thermal analysis and the strength tests of molding sands with the prepared organobentonites) in determining the possibility of obtaining a new full-value foundry binder in molding sands with bentonite.

Interactions between Nanoclay, CTAB and Linear/Star Shaped Polymers

“…In the low wavenumber range (below 1000 cm −1 ), the presence of bands with the maximum at 874 cm −1 and 800 cm −1 was associated with the occurrence of the γCH 2 and γ(O–H) wagging vibrations from the carboxyl groups, respectively. The presented data are in agreement with other works [ 54 , 55 , 56 , 57 , 58 ]. The assignments of the main bands of CTAB are placed in Table 1 .…”

“…This proves that the PAA polymer and the CTAB surfactant adsorbed on the external clay surface influence the primary distribution of the layered sheets but keep the same d-spacing. Recently the PAA adsorption mechanism on bentonite has been described in detail [ 55 ]. According to the proposed model, the interactions of montmorillonite with the polyacrylic acid chains are based on the surface and edge adsorption, combined with the intercalation of the galleries between the silicate sheets.…”

High-Loading Poly(ethylene glycol)-Blended Poly(acrylic acid) Membranes for CO2 Separation

“…In Figure b, the PEG shows the representative absorption bands at 1000–1200 cm –1 that are attributable to the C–O–C stretching vibration mode. Further, the PAA exhibited noticeable peaks at 1700 cm –1 due to the −COOH stretching vibration mode and a peak at 1246 cm –1 due to combined C–O and O–H in-plane bending vibrations. , As the PEG weight loading in the PAA/PEG blend membrane was increased, the intensity of PEG characteristic peaks at 1104 and 1032 cm –1 also increased (green-highlighted). However, the intensity of the PAA characteristic peaks at 1246 cm –1 (yellow-highlighted) and 1700 cm –1 (blue-highlighted) decreased.…”

Study on Preparation of Polymer-Modified Bentonite and Sand Mixtures Based on Osmotic Pressure Principle

“…Figure 5 shows the infrared spectroscopy of BT and APAM-modified bentonite. The main spectral bands of bentonite are: 3623 cm −1 attributed to the stretching vibration of montmorillonite structural hydroxyl -OH, 3440 cm −1, and 1640 cm −1 mainly due to the stretching vibration of an interlayer water molecule -OH and bending vibration of -OH, 1043 cm −1 and 797 cm −1 attributed to the stretching vibration and bending vibration of Si-O, and 915 cm −1 attributed to the bending vibration of montmorillonite structural hydroxyl -OH [ 8 , 34 ]. After APAM modification, the peak around 3440 cm −1 becomes broader, which may be caused by the asymmetric stretching vibration of -NH 2 .…”