Preparation and application of expanded and exfoliated vermiculite: A critical review

Li, Mingliang; Zhao, Yunliang; Ai, Zhong; Bai, Haoyu; Zhang, Tingting; Song, Shaoxian

doi:10.1016/j.chemphys.2021.111313

Cited by 26 publications

(18 citation statements)

References 126 publications

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“…Experimental research findings of EVAM samples are summarized in Table 3. C or higher, it transforms into clinoenstatite, which can include deformation of the material and deterioration of its thermal insulation properties [20,21]. Therefore, the maximum heating temperature should not exceed 1000-1100 o C. The experimental study determined that the furnace temperature is a direct factor in the exfoliation time and exfoliation rate of the vermiculite aggregate, and the heating time varies between 6 and 550 s. In addition, it has been observed that the exfoliation characteristics of the vermiculite material show variable values in terms of both time and temperature values, depending on whether Na + is modified or not.…”

Section: Resultsmentioning

confidence: 99%

Effects of exfoliation temperature for vermiculate aggregates modified by sodium ions on thermal and comfort properties of a new generation cementitious mortar

Gündüz

KALKAN

2022

Journal of Sustainable Construction Materials and Technologies

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Vermiculite exfoliation is based on the principle when water between the layers evaporate, and the crystal layers spread out pressured by the steam. As a result, elongated, curved particles are formed. The thermal properties of the final product formed are directly related to this exfoliation amount. In this experimental work, exfoliation characteristic of natural vermiculate is studied. A series of experimental analyzes were carried out to examine the expandability of natural vermiculite at different heating temperatures by the Na+ modification method. In addition, the expansion ratios of Na+-modified and unmodified vermiculite samples were analyzed comparatively. Each of the raw and Na+ modified vermiculite material groups prepared for the thermal expansion process was experimentally performed by recording the exfoliation states and times at six different heating temperature values of 350 oC, 450 oC, 530 oC, 620 oC, 710 oC and 840 oC, respectively, in a laboratory environment. In the second phase of the study, thermal properties of new generation composite mortars produced with exfoliated vermiculite aggregate were experimentally analyzed. Parameters such as thermal conductivity, heat storage capacity, specific heat and heat dissipation coefficient of mortar test samples prepared with exfoliated vermiculite aggregates are analyzed and discussed here. Test results showed that Na+-modified vermiculite samples expanded better than unmodified vermiculite samples for all expansion temperatures. When Na+-modified expanded vermiculite is evaluated in composite mortars, it also reduces the unit weight of the mortar as it expands more and the unit weight of itself decreases. Accordingly, the compressive strength of the mortar decreases relatively. However, it has been determined that the thermal comfort properties of mortars using Na-modified exfoliated vermiculite are better than the thermal comfort properties of composite mortars produced using unmodified exfoliated vermiculite.

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Section: Resultsmentioning

confidence: 99%

Effects of exfoliation temperature for vermiculate aggregates modified by sodium ions on thermal and comfort properties of a new generation cementitious mortar

Gündüz

KALKAN

2022

Journal of Sustainable Construction Materials and Technologies

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“…There are a large number of water molecules between the VMT layers in three states: constitutive water, bound water formed by the combination of water molecules and interlayer cations, and free water in the free state. 16 Figure 1 and Table 1 are the thermogravimetric curves and data of VMT and OVMT. From the diagram, we can see that the weight loss of VMT is mainly within 200 C, while before 100 C is mainly due to the evaporation of free water in the free state in VMT.…”

Section: Thermal Analysis Of Vmt and Ovmtmentioning

confidence: 99%

Preparation and properties of silane coupling agent modified vermiculite and its composite films

Pei

Shang

et al. 2023

Polymer Composites

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Vermiculite (VMT) was used as a filler and it was modified with silane coupling agent KH570 to produce OVMT. VMT/PBAT and OVMT/PBAT composite films were prepared using the solution method using polybutylene terephthalate (PBAT) as a matrix. The structure, thermal properties, crystalline properties, rheological properties, cross‐sectional microstructure, and tensile properties and antibacterial properties of the pure PBAT film, VMT/PBAT, and OVMT/PBAT composite films were tested, including comparative analysis. The results showed that VMT was successfully modified with silane coupling agent to produce OVMT. Furthermore, the thermal stability of VMT/PBAT and OVMT/PBAT composite films decreased compared with pure PBAT film. As the content of VMT and OVMT increases, the energy storage modulus and loss modulus of VMT/PBAT and OVMT/PBAT composite films increase, while the loss factor, complex viscosity and crystallinity gradually decrease. Additionally, the tensile strength and elongation at break of VMT/PBAT and OVMT/PBAT composite films decrease. All three films had no effect on Staphylococcus aureus or Escherichia coli. The modification of VMT with the silane coupling agent KH570 improved the compatibility of OVMT with PBAT, resulting in improved mechanical properties of the OVMT/PBAT composite film compared with the VMT/PBAT composite film. The mechanical properties of the OVMT/PBAT‐20% composite film increased by 35.9% in tensile strength and 10.8% in elongation at break compared with the VMT/PBAT‐20% composite film.Highlights VMT successfully modified with silane coupling agent to produce OVMT. The modification promotes the compatibility of the filler with PBAT. VMT modification helps to improve the mechanical properties of composite materials. Vermiculite modification helps to improve the toughness of composite materials.

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“…Vermiculite (Vrm) has excellent properties such as light weight, low thermal conductivity, thermal insulation, sound insulation, and adsorption, so it is widely used in construction, agriculture, thermal insulation, and environmental protection [ 1 , 2 , 3 ]. Vrm layers are mainly connected by hydrogen bonds and van der Waals forces [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

The Expanded Vermiculite Was Quickly Prepared by the Catalytic Action of Manganese Dioxide on Hydrogen Peroxide and Its Adsorption Properties to Cd

et al. 2023

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The structure and activity of vermiculite can be maintained by expanding vermiculite (Vrm) with hydrogen peroxide. However, it is time-consuming. In past studies, little attention has been paid to the catalytic properties of manganese dioxide on hydrogen peroxide to improve the swelling efficiency of vermiculite. In this experiment, this catalytic effect was utilized to swell Vrm in a short time. The samples were then used to adsorb Cd from the solution. Through a series of characterization tests. The results showed that the exothermic rate was 1960.42–2089.164 J/min and the total exothermic heat was 39,208.4–41,783.28 J when expanding 10 gVrm, which could have a good expansion effect. The expansion was completed in about 40 min. Compared with Vrm, the adsorption of Cd is enhanced by about 30%. It is consistent with the proposed secondary kinetic adsorption model. This study provides a new perspective and theoretical guidance for improving the efficiency of Vrm stripping by hydrogen peroxide. A kind of expanded Vrm with better Cd adsorption efficiency was also prepared.

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Preparation and application of expanded and exfoliated vermiculite: A critical review

Cited by 26 publications

References 126 publications

Effects of exfoliation temperature for vermiculate aggregates modified by sodium ions on thermal and comfort properties of a new generation cementitious mortar

Effects of exfoliation temperature for vermiculate aggregates modified by sodium ions on thermal and comfort properties of a new generation cementitious mortar

Preparation and properties of silane coupling agent modified vermiculite and its composite films

The Expanded Vermiculite Was Quickly Prepared by the Catalytic Action of Manganese Dioxide on Hydrogen Peroxide and Its Adsorption Properties to Cd

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