Polypropylene-clay composite prepared from Indian bentonite

In the present work, a set of experimental polypropylene (PP) clay composites containing pristine bentonite clay of Indian origin has been prepared and then characterized. The polymer clay composites are processed by solution mixing of polypropylene with bentonite clay using a solvent xylene and high speed electric stirrer at a temperature around 130 degrees C and then by compression molding at 170 degrees C. The mechanical properties of PP-clay composites like tensile strength, hardness and impact resistance have been investigated. Microstructural studies were carried out using scanning electron microscope and transmission electron microscope and the thermal properties were studied using differential scanning calorimeter. Mechanical properties of the prepared composites showed highest reinforcing and toughening effects of the clay filler at a loading of only 5 mass % in PP matrix. Tensile strength was observed to be highest in case of 5 mass % of clay loading and it was more than 14% of that of the neat PP, while toughness increased by more than 80%. Bentonite clay-PP composite (5 mass %) also showed 60% increase in impact energy value. However, no significant change was observed in case of hardness and tensile modulus. Higher percentages of bentonite clay did not further improve the properties with respect to pristine polypropylene. The study of the microstructure of the prepared polymer layered silicate clay composites showed a mixed morphology with multiple stacks of clay layers and tactoids of different thicknesses

Thermal decomposition of layered double hydroxides: Kinetic modeling and validation

Solid state kinetic process during the multistage thermal decomposition of Layered Double Hydroxide (LDH) reaction has been modeled utilizing model-free and model-based multivariate non-liner regression analysis. The physically most meaningful kinetic triplet for each of the stages reaction model f (alpha), activation energy (E-a) and pre-exponential factor (A)] is reported for multiple layer charges. The first two stages involved removal of water from interlayer and brucite layer respectively, of the material and follows an n-dimensional Avrami-like model. The removal of NOx from interlayer nitrate anion (third stage) follows a 3-dimensional diffusion model of Dander type. The proposed kinetic model is validated by the comparison of the reaction extent (for each of the stages) both theoretically (chemical formula) and experimentally (from fitting curve) for LDH of multiple layer charges. The isothermal prediction based on the assigned kinetic model predicted the degree of decomposition of LDH with reasonable accuracy. (C) 2016 Elsevier B.V. All rights reserved

Intercalation of LDH NO3 with short-chain intercalants

Intercalation behaviour of layered-double hydroxide (LDH) with short-chain intercalants (-(CH2)n-,nnH2O,] by an ion-exchange intercalation technique in a slightly acidic medium (pH=5.4). The adverse effect of a carbonate anion was avoided by performing the ion-exchange intercalation in slightly acidic medium (pH=5.4). It was found that basal spacing (d003) and experimental organic loading of intercalated LDH (O-LDH) increase monotonically with increasing anion-exchange capacity of LDH and intercalant chain length. The evolution of intercalated LDH (O-LDH) structures with increasing intercalant chain length and layered charge has been deciphered by correlating basal spacing of O-LDHs (by X-ray powder diffraction), organic loading data (by thermogravimetric analysis) and molecular conformation of O-LDHs (by Fourier-transform infrared spectroscopy) within the LDH gallery. Successful intercalation of LDH with these short-chain intercalants in slightly acidic medium has not been reported previously

Partial replacement of metakaolin with red ceramic waste in geopolymer

Metakaolin was incrementally replaced (33.3%, 50% and 66.6%) by red ceramic waste in geopolymer formulation to study the effect on geopolymerisation and its resultant properties. The geopolymer binders composed of two calcined aluminosilicates (viz. Metakaolin and Red ceramic waste), NaOH and sodium silicate. In the experimental compositions, metakaolin was replaced gradually up to 66.6% in the clay fraction, the Si/Al increased from 3.36 to 5.16 and Na/Al increased from 0.93 to 1.38. The FTIR spectroscopic studies of geopolymer pastes along with XRD analysis indicated that the red ceramic waste partly reacts with alkali and takes part in geopolymer formation. Replacement of 33.3% metakaolin by the red ceramic waste in geopolymer binder did not reduce the compressive strength with respect to the pure metakaolin geopolymer here. Additional replacement resulted in a drastic decrease in the compressive strength of the geopolymer binder. However, the compressive strength of geopolymer mortars revealed interesting synergy between the amount of binder and particle packing in the mortar. Despite having a lower amount of binder phase, mortars with 33% and 50% red ceramic waste exhibited maximum compressive strength values. This has been attributed to improved particle packing through incorporation of red ceramic waste particles

Intercalation of montmorillonite with dialkylammonium cationic surfactants

Three montmorillonite (Mt) clays with different cation exchange capacity (CEC) were intercalated by a series of dialkyl ammonium cations with carbon numbers (Nc= ) 8, 10, 12 and 18 in each alkyl chain. The intercalated clays were characterized by X-ray Diffraction, Thermogravimetric Analysis, Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy. The basal spacing of intercalated Mts in-creased gradually with increasing chain length. Interlayer arrangement of dialkyl surfactant cations in the intercalated clay gallery changed from flat bilayer to paraffinic and reached as high as 3.57 nm for the highest CEC clay intercalated with cations having Nc= 18 in each alkyl chain. For dialkylammonium inter-calants, the increase in basal spacing was predominantly guided by the intercalant's structure and organic loading values lacked such direct correlation. Mt with low CEC showed large expansion in the clay inter-layer with increasing alkyl chain length even with marginal increment in the organic loading. The highest basal spacing was observed always with the highest CEC clay for every intercalant irrespective of alkyl chain length. The wide expansion of clay gallery for the longest dialkyl intercalant in this series for all clays might be attributed to presence of intercalated surfactant molecules along with physically adsorbed surfactant cations in the clay interlayer. The change in conformations of intercalated dialkyl ammonium intercalants with increasing alkyl chain length was analyzed from FTIR study. With increasing alkyl chain length, methylene symmetric and asymmetric stretching frequency shifted to lower wavenumber for all Mt clays-which indicated greater ordered conformations obtained with increasing alkyl chain length.(C) 2022 Elsevier B.V. All rights reserved

Efficient removal of Evans blue dye by Zn-Al-NO3 layered double hydroxide

Evans blue (EB) dye has been successfully removed from aqueous solution through chemisorption process with synthetic layered double hydroxides (LDH) Zn1-x Al (x) (OH)(2)NO3 center dot nH(2)O, x = 0.2-0.33]. Detailed evaluation of dye adsorption characteristics in aqueous medium has been studied for different layer charged hydroxides. The objective of the study was efficient removal of a dye by LDH and understanding the structure-property relationship of the LDH on its adsorption behaviour. Highest Langmuir monolayer adsorption capacity (Qt) of 113.64 mg g(-1) was observed for highest layer charge x = 0.33, and it is higher than previously reported values for the LDH-EB dye system. Under optimized condition, 99% of EB dye is removed from aqueous solution within 60 min at 313 K. The monotonous increase in Qt value with increasing layer charge is correlated with layer charge density (LCD) and lower particle size of the synthetic LDH. The variation in Qt among different layer charged materials is marginal (3.46-4.17%) with respect to the respective anion exchange capacity (AEC) of LDH NO3. The limited contribution of AEC surmises the occurrence of surface-only adsorption and absence of intercalation as validated by the XRD analysis. The spontaneity of the EB dye removal increases with increasing temperature and LCD. The chemisorption nature of the adsorption reaction is well supported by the thermodynamics values

Dependence of bonding interactions in Layered Double Hydroxides on metal cation chemistry

The evolution of various Infrared bands of Layered Double Hydroxides (LDH) with variable Zn:Al ratio was analyzed to correlate it with the changes in octahedral metal cation chemistry, interlayer carbonate anion and hydroxyl content of LDH. The synthesized phase-pure LDHs were crystallized as hexagonal 2H polytype with a Manasseite structure. The broad and asymmetric hydroxyl stretching region (2400-4000 cm(-1)) can be deconvoluted into four different bands. With increase in Zn2+:Al3+ metal ratio, the peak position of stretching frequencies of Al3+-OH and carbonate-bridged hydroxyl (water) decrease almost linearly. Individual band's peak position and area under the curve have been successfully correlated with the carbonate and hydroxyl content of LDH. Due to lowering of symmetry of the carbonate anion, the IR-inactive peak nu(c-o), (symm) at 1064 cm(-1) becomes IR active. The peak position of metal-oxygen bands and carbonate bending modes are practically unaffected by the Zn2+:Al3+ ratio but the area under the individual M-O bands shows a direct correlation. (C) 2016 Elsevier B.V. All rights reserved

Differences in densification behaviour of K- and Na-feldspar-containing porcelain bodies

Porcelain bodies fabricated from triaxial mixtures of clay, quartz and feldspar with different amounts of Na2O and K2O were investigated to study their densification behaviour on thermal treatment at which the bodies achieve full vitrification. The high temperature dilatometric study has shown a distinct behaviour in their densification rate. The degree of vitrification of the densified samples and samples separately heated at different temperatures was determined by measuring the shrinkage, bulk density (BD), percent water absorption (%WA) and flexural strength. It was found that Na-rich feldspar containing body composition achieve full vitrification at lower temperature compared to K-rich feldspar containing composition with improved flexural strength. Differential thermal analysis-thermogravimetric analysis (DTA-TGA) confirms similar reaction steps for both the compositions up to 1000 degreesC, beyond which feldspar forms eutectic melt and starts reacting. As the purity of raw materials has a strong influence on the colour of the fired bodies, the bodies were also subjected to colour measurement and their differences in whiteness also compared, and is discussed in this paper. The scientific and technological importance of such vitrified porcelain products has also been touched upon, highlighting their industrial application. (C) 2003 Elsevier Science B.V. All rights reserved

Formulation of some frit compositions for rapid once-fixed wall tile glaze

Three frit compositions were formulated and studied by varying the major constituents - alkalis (K2O + Na2O) and alkaline earth oxide (CaO) with minor changes in ZnO, Si02, AI2O3 and 8203 content. The frits produced were characterized with respect to fusion, flow and thermal expansion properties and compared with a frit of imported origin. It is observed that fusion and flow characteristics of the frits are strongly influenced by the combined fluxing effect of CaO and calcium borate. The thermal expansion value increases with the increase in alkali content. The performance of the frits in rapid once-fired wall tile glaze was also studied by preparing a slip made of 90 wt% frit and 10 wt% white burning clay applied on green wall tile sample and fired at 1100°C. The performance of one formulation produced in the present study was almost on a par with imported frit