Vermiculite: Structural Properties and Examples of the Use

Valášková, Marta; Martynková, Gražyna Simha

doi:10.5772/51237

Cited by 24 publications

(20 citation statements)

References 138 publications

(139 reference statements)

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“…VMT is a mica‐type silicate with 2 : 1 layered phyllosilicate; it has a large internal surface, high cation exchange capacity (CEC), and high negative charge on its silicate layers. VMT has a tetrahedral–octahedral–tetrahedral layer (or sheet) and an interlayer (or gallery), and the thickness of the structural unit (2 : 1 layer and interlayer space; basal spacing) is up to 1.4 nm, depending on the interlamellar water layer and the interlayer cation . When instantaneously heated, VMT sheets will be quickly dehydrated, and expand to form the expanded vermiculite (EVMT) with large interlayer spacing, macromolecules is more likely to be inserted into EVMT than MMT, and consequently EVMT serves as polymer modifier in this article.…”

Section: Introductionmentioning

confidence: 99%

Applying vermiculite‐modified polypropylene film to flexible packaging material

et al. 2014

J of Applied Polymer Sci

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This article presents a process for preparing organovermiculite by ball-milling expanded vermiculite (EVMT) in waterbased ethylene vinyl acetate (EVA) latex. In this process, the vermiculite (VMT) is exfoliated to prepare a kind of EVMT/EVA modifying agent, in which EVA serves as both intercalating polymer into VMT and compatibilizer between VMT and polypropylene (PP). During melt blending between EVMT/EVA and PP, shear force exfoliates VMT sheets, dispersing them relatively well in the PP matrix. Compared with raw PP, EVMT-modified cast polypropylene (CPP) are better when EVMT loading ranged from 0.5 to 1.0%, with improvement in both the strength and toughness of the EVMT/EVA-modified CPP film. Specifically, tensile strength was increased by 44-54%, yield stress increased by 26%, stress at break increased by 37-43%, energy at break (toughness) increased by 29-34%, oxygen transmission rate decreased by 6.2-12.9%, the water vapor transmission rate was not significantly affected, the peel bond strength of laminated CPP film increased by 18-27%, and the processability and melt flow index (MFI) of EVMT/EVA/PP composites were improved as well. Increasing MFI attributes facilitated the processing and formation of EVMT/EVA/PP. V C 2014 Wiley Periodicals, Inc. J.Appl. Polym. Sci. 2014, 131, 40954.

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Section: Introductionmentioning

confidence: 99%

Applying vermiculite‐modified polypropylene film to flexible packaging material

et al. 2014

J of Applied Polymer Sci

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“…The exfoliation relies on an impulsive build-up of the steam produced by evaporating interlayer water within the mosaic-like multiphase lamellar structures (Hillier et al, 2013). Expanded vermiculite has remarkable properties: it is lightweight and has low thermal conductivity, it is chemically inert, has a high melting point and good sorption ability due to its capillary pore structure and active silicate surface (Valášková & Martynková, 2012;Rashad, 2016). These properties are required in order for ideal sorption of liquid hazards to work effectively under harsh conditions.…”

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Thermally expanded vermiculite as a risk-free and general-purpose sorbent for hazardous chemical spillages

2019

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Expanded vermiculite with excellent thermal and chemical stability was investigated as a reliable sorbent for hazardous liquid spillages, including those leading to fire and explosion risks. Many expanded samples were prepared by rapid heating using both different temperatures and dissimilar vermiculite dimensions. Their capabilities for hazard clean-up were correlated with the structural characteristics of expanded vermiculite with slit-shaped porosity. When using optimized vermiculite, the moderate sorption capacities of 1.5–3.0 g g−1 were obtained for various hazardous chemicals, including hydrophilic/hydrophobic organic chemicals and strongly acidic/basic solutions. The sorption capacities depended more strongly on physical properties, such as the pore volume of the sorbent and the density of the absorbed liquid, rather than the vermiculite's chemical composition. The void space interconnected by interparticle/intraparticle pores worked as imbibing pathways due to their capillarity, resulting in the rapid, spontaneous sorption of hazardous chemicals. The hazardous chemicals may be removed from a testing vessel via sorption with an efficiency of >94 wt.% for 10 min. These results demonstrate that the expanded vermiculite may be a potential candidate as a reliable general-purpose sorbent for hazardous materials clean-up under harsh conditions.

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“…Vermiculite is typical clay which belongs to the montmorillonite-vermiculite group. The general structure of vermiculite can be described as a silicate sheet consisted of two flat layers of silica and alumina tetrahedral layers joined in an octahedral layer from oxygen, magnesium, iron atoms and hydroxyl molecules [7]. A variety of analytical instruments are used for the structural, physical, and chemical characterization of natural minerals.…”

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confidence: 99%

A comparative study on phyllosilicate and tectosilicate mineral structural properties

Stylianou

Inglezakis

Agapiou

et al. 2018

Desalination and Water Treatment

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The present study examines various methods used for the characterization of three common natural silicate minerals, one zeolite (clinoptilolite) and two clays (montmorillonite and vermiculite). Characterization of natural minerals were performed through a series of analytical measurements so as gather all the information needed regarding their properties, in order to distinguish them from "similar" minerals such in the case of clinoptilolite vs heulandite and vermiculite vs hydrobiotite; this will enable their further use in environmental applications. The methods used in the present study are XRD, XRF, FTIR spectroscopy, TG/DTG/DTA and N2-porosimetry (BET). Data revealed from XRD, FTIR, TG/DTG/DTA showed that all three minerals have characteristic bands that can characterized and distinguish each other. The key difference between Heulandite and Clinoptilolite is their behavior upon heating. Clinoptilolite is stable at temperatures exceeding 450 o C, where heulandites undergo structural collapse below 450 o C. XRF analysis showed that Vermiculite sample is rich in MgO (Mg-vermiculite) and the low concentration of K2O revealed the presence of Vermiculite instead of Hydrobiotite. Thermogravimetric analysis showed that the main regions of Clinoptilolite weight loss are the release of looselybound water (50-200°C), release of "zeolitic" water (200-700°C) and finally the collapse of crystal structure (700-900°C). In the range 25-400 o C, the endothermal (DTA diagram) process of dehydration occurred in one step. This reveals the presence of clinoptilolite, because for heulandites dehydration occurs in two steps. As far as porosity is concerned, all three minerals are generally dominated by micro/mesopores. BET surface area for clinoptilolite is between 17-100 m2/g, for bentonite 22-42 m 2 /g and for vermiculite 7-18 m 2 /g. The acquired analytical results enabled the full characterization of the examined minerals, despite their common properties.

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Vermiculite: Structural Properties and Examples of the Use

Cited by 24 publications

References 138 publications

Applying vermiculite‐modified polypropylene film to flexible packaging material

Applying vermiculite‐modified polypropylene film to flexible packaging material

Thermally expanded vermiculite as a risk-free and general-purpose sorbent for hazardous chemical spillages

A comparative study on phyllosilicate and tectosilicate mineral structural properties

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