Kaolin, heavy, powder

Catalog NumberACM1332587-18

CAS Number1332-58-7

CategoryNano Flame Retardant

Description	Kaolin is hydrated aluminum silicate.
Synonyms	Bolus, Aluminum silicate hydroxide, Hydrated aluminum silicate, Kaolin
Molecular Formula	~Al2Si2O5(OH)4
Appearance	powder
Content	impurities, max. 0.01% heavy metals (as Pb), max.1% soluble in acid (as SO4)
Packaging	5kg

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Case Study

Kaolin Powder as a Synergistic Carrier in NaHCO3/Kaolin Composite Explosion Suppressant for Aluminum Powder

Yan, Ke, et al. Combustion Science and Technology 194.4 (2022): 815-831.

Kaolin powder acts as an effective carrier and synergistic agent for NaHCO3 in a composite explosion suppressant, significantly enhancing the inhibition of aluminum powder deflagration through combined physical and chemical mechanisms.
Fabrication Process: Kaolin powder was mixed with NaHCO3 via an anti-solvent dissolution method. NaHCO3 was dissolved in deionized water and added to a kaolin suspension in absolute ethanol under stirring, followed by ultrasonication, aging, filtration, and vacuum drying at 30 °C. Composites with 10-50 wt% NaHCO3 loadings were prepared; 40 wt% loading gave optimal performance.
Performance Evaluation: SEM showed NaHCO3 crystals uniformly coated on kaolin surfaces, forming a fluffy scaly structure. TG-DTG indicated two-stage decomposition (NaHCO3 decomposition at 70-150 °C and kaolin loss above 500 °C). In Hartmann tube tests, 50 wt% composite powder completely suppressed flame propagation of aluminum dust, reducing peak flame velocity by 78.2% and average velocity by 59.1% vs. pure aluminum. In 20 L spherical explosion tests, 75 wt% composite achieved complete explosion suppression (Pmax < 0.07 MPa), outperforming pure NaHCO3 or kaolin alone. XPS analysis confirmed the formation of stable Al2O3, Na2CO3 and NaOH residues. The suppression mechanism involves physical heat absorption, oxygen dilution, and kaolin's barrier effect, alongside chemical decomposition of NaHCO3.
Application Significance: Kaolin-based composite suppressants offer a cost-effective, environmentally friendly solution for mitigating aluminum dust explosion hazards in industrial settings.

Kaolin as a Nanofiller in PLA/Kaolin Nanocomposite for Flame-Retardant Flexible Polyurethane Foam

Kambel, Rifkatu D., et al. International Journal of Materials and Chemistry 7.1 (2017): 14-19.

Kaolin, when incorporated into a polylactic acid (PLA) matrix, forms a nanocomposite that acts as an effective flame retardant for flexible polyurethane foam, enhancing ignition resistance and reducing flame propagation.
Fabrication Process: Raw kaolin was activated with HCl, organically modified with sodium aminolauric acid, and then dispersed in a PLA/chloroform solution by solution casting to obtain PLA/kaolin nanocomposite powder. This powder was added at 1-5 g levels during polyurethane foam synthesis, followed by curing at room temperature.
Performance Evaluation: FTIR of treated foam showed new peaks at 1099 cm⁻¹ (Si-O) and 1267 cm^-1 (Si-C), confirming chemical interaction between kaolin and the foam matrix. SEM revealed well-dispersed nanoparticles (613 nm to 5 μm) forming an intercalated structure. With increasing nanocomposite loading (up to 5 g), flame propagation rate decreased from 0.39 to 0.16 cm/s, flame duration from 43 to 11 s, and after-glow time from 31 to 11 s, while ignition time increased from 7 to 35 s and char formation rose from 13% to 42%. The kaolin-rich char layer acts as a physical barrier, insulating the foam from heat and oxygen.
Application Significance: Kaolin-based nanocomposites offer a low-cost, eco-friendly flame retardant alternative for flexible polyurethane foams used in furniture and packaging.

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