Expanded Perlite Particles Research Articles

Low-density expanded perlite–aluminium syntactic foam

This paper addresses an innovative syntactic foam (SF) formed by counter-gravity infiltration of a packed bed of low-cost expanded perlite (EP) particles with molten A356 aluminium. The uniform distribution of EP particles in foams causes an even density throughout the height. Due to the low density (~0.18g/cm3) of EP, the average density of these foams is only 1.05g/cm3 which is considerably lower than most studied SFs. Owing to the high porosity of the filler material (~94%), the total porosity of the new foam reaches 61%. Microstructural observations reveal no sign of damage or unintended EP particle infiltration. EP shows a good wettability whilst essentially no reaction occurs at the EP–metal interface. Under compression, EP/A356 syntactic foam shows stress–strain curves consisting of elastic, plateau and densification regions. On account of its consistent plateau stress (average value 30.8MPa), large densification strain (almost 60%), and high energy absorption efficiency (88%) EP/A356 syntactic foam is an effective energy absorber.

Study on Paraffin/Expanded Perlite Composite Phase Change Energy-Storage Materials

Paraffin/expanded perlite composite phase change energy-storage material (PPCM) was prepared by vacuum adsorption method with expanded perlite as adsorption material and paraffin as phase change energy-storage material. The diffused-exudative circle method was used to determine that the best adsorption quantity of expanded perlite was 65%. The phase transition process and microstructure of PPCM with the best adsorption quantity were characterized by DSC and SEM. The results shown that the internal micropores of expanded perlite particles were almost completely filled with paraffin and the expanded perlite particles became close-grained particles. The phase change temperature of PPCM was basically similar with that of paraffin and its phase change latent heat was corresponded with that of paraffin in the PPCM.

Sorption and Thermal Properties of Insulating Mortars with Expanded and Vitrified Small Ball

Abstract Expanded vitrified small hollow ball (EVSB), made from a special type of perlite mineral is one of the recently developed materials in China. It is widely used as a cementitious thermal insulating mortar for building envelope construction in hot-humid areas of southern China. However, EVSB is a porous material sensitive to environmental moisture. The thermal insulating property of the EVSB mortar is dependent on its moisture transport and storage characteristics. In this study, hygroscopic sorption properties of EVSB mortars have been investigated in comparison with those of normal expanded perlite particle (NEPP) mortars. The Brunauer, Emmett and Teller specific surface area and the Barrett, Joyner and Halenda pore size distribution, as well as the scanning electron microscope micromorphologies of the mortars were assessed. It was observed that EVSB mortars had lower moisture sorption capacity than NEPP mortars when the relative humidity (RH) was higher than 70 % because of its lower total pore volume. The addition of water-repellent admixtures in the mortar decreased the moisture sorption capacity of EVSB mortars but still maintains the same physisorption isothermal characteristics. It is also evident that the thermal conductivity values of both NEPP and EVSB mortars increased rapidly when RH is above 90 %. However, the increased rate of thermal conductivity of NEPP mortars was apparently higher than that of EVSB mortars. It is hoped that finding from this study will help to develop a better understanding of the in situ thermal performance of the EVSB mortar used for the building envelope construction in hot and humid areas of southern China.

Experimental Study on a New Dual-Layer Granular Bed Filter for Removing Particulates

A new dual-layer granular bed filter for hot gas cleanup was invented and studied experimentally. Fine sand, 0.5-1 mm grain size and about 1350kg/m^3 bulk density, was used as the lower layer of the filter. Expanded perlite particles, 2-5 mm grain size and about 70kg/m^3 bulk density, was used for the upper layer of the filter in this study. It was confirmed that the sizes and densities of these two media matched well; the binary media remained in complete segregation during regeneration by fluidization. Test results show that the filtration of the expanded perlite particle layer was characterized as ”deep bed filtration.” Filtration of the fine sand layer was ”surface cake filtration.” The expanded perlite particle layer contributed about 90% to the bed dust capacity, but only about 20% to the total bed pressure drop, which increased the bed dust capacity ten fold compared to a single-layer bed of the same sand and the same total bed pressure drop. The dust cake on the surface of the fine sand layer raised the collection efficiencies to over 99.99%.

The effect of moisture content on sound absorption of expanded perlite plates

Expanded perlite is a porous, lightweight, fire resistant and moisture retaining material with sound and thermal insulation properties. In this research, acoustical behaviour of plates made of expanded perlite was studied experimentally. Since these plates are used for sound absorption, the acoustical parameter selected for this study is “sound absorption coefficient”. Preliminary experiments indicated that moisture reduced the sound absorption coefficient on plates and there is not much significant difference between the dry and 50% humid conditions. However, there is a significant difference in acoustical properties for the 50–95% humid conditions. Thus, this interval was studied in detail. A number of expanded perlite plates having different mixtures were prepared and tested. It was observed that, coating the expanded perlite particles with sodium silicate increased the moisture resistance, and the addition of mineral fibres into the mixtures increased the strength and sound absorption coefficient of the plates.

Sound absorption coefficient changes of acoustical plates made of expanded perlite in moist environment

Expanded perlite is a porous, lightweight, fire resistant and moisture retaining material with sound and thermal insulation properties. In this research, acoustical behaviour of plates made of expanded perlite was studied experimentally. Since these plates are used for sound absorption the acoustical parameter selected for this study is sound absorption coefficient. Preliminary experiments indicated that moisture reduced the sound absorption coefficient on plates and there is not much significant difference between the dry and 50% humid conditions. However, there is a significant difference in acoustical properties for the 50% -95% humid conditions. Thus, this interval was studied in detail. A number of expanded perlite plates having different mixtures were prepared and tested. It was observed that coating of expanded perlite particles with sodium silicate increased moisture resistance, and that the addition of mineral fibre into the mixtures increased the strength and sound absorption coefficient of the plates.