Kaolin, powder

Catalog NumberACM1332587-19

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
Density	2.6 g/cm³ at 20 °C
Storage	no temp limit
Bulk Density	470 kg/m3
Content	impurities, max. 0.001% Pb (Lead), max.2.0% Substances soluble in hydrochloric acid
pH	6-7 (20 °C, 50 g/L in H2O, slurry)

Case Study

Kaolin Enhances Flame Retardancy in Intumescent Fire-Retardant Coating Formulations

Ullah, Sami, et al. Polymer Degradation and Stability, 2014, 110, 91-103.

This research presented the outcomes of various formulations created to examine how kaolin clay influences the expansion of coatings and thermal protection during fire testing.
Preparation of Fire-Retardant Coatings
The intumescent components were combined according to their specified weight percentages, as detailed in Table 1, which lists six intumescent coating formulations (ICFs) - one control formulation without kaolin clay and five containing kaolin clay. A shear mixer was employed to blend the ingredients with epoxy and hardener at 40 rpm for 30 minutes. A structural steel plate measuring 100 cm2 served as the substrate. The coating was applied with a brush, achieving an average thickness of 1.5 mm, which was measured using a digital vernier caliper. The coated substrate was then cured in an oven at 60 °C for one hour.
Key Findings
· The intumescent coating formulations (ICFs) were subjected to testing at 950 °C for one hour. The results indicated that the coatings remained stable and adhered well to the substrate.
· XRD and FTIR analysis revealed the presence of carbon (graphite), boron phosphate, boron oxide, sassolite, and kaolinite in the residual char.
· TGA demonstrated that the kaolin clay-reinforced formulation, IF5-KC, exhibited a 49% increase in residual weight compared to the IF-Control formulation.
· XPS analysis indicated that the char residue of IF5-KC contained 41.80% carbon.
· An accelerated weathering test, ASTM D 6695-03, showed that the IF5-KC coating maintained its integrity for up to 90 days in an accelerated weathering chamber.

Kaolin Improves Flame Retardancy and Smoke Suppression of Polypropylene Composites

Zhang, Sheng, et al. Polymers for advanced technologies, 2014, 25(9), 912-919.

An intumescent flame-retardant system containing kaolin clay, ammonium polyphosphate as an acid source and pentaerythritol as a carbonization agent was used to improve thermal stability and fire resistance in polypropylene (PP) composites.
Sample Preparation
The ratio of the PP matrix to the additive was set at 100:40, with the additive comprising IFR (APP:PER ratio of 3:1) and kaolin. The formula for the PP/IFR/kaolin composites is detailed in Table 1. The composites were melt compounded using a corotating twin-screw extruder, with temperature settings ranging from the hopper to the die at 180/190/195/200/200/190°C, and the screw speed maintained at 50 rpm. The resulting pelletized granules were dried for 12 hours at 80°C before being injected to achieve the appropriate thickness and size. The injection molder operated under temperature settings of 180/190/195/200°C from the hopper to the spray nozzle while maintaining an injection pressure within 25 to 50 MPa. The injection process lasted for 15 seconds before entering a subsequent 20-second cooling phase.
Key Findings
The limiting oxygen index (LOI) value increased from 30 to 33 with the addition of 2 phr kaolin. The peak heat release rate reduced from 1002 kW/m2 for neat PP to 318 kW/m2 for PP containing 40 phr IFR, and further decreased to 222 kW/m2 with 38 phr IFR and 2 phr kaolin. The introduction of kaolin significantly extended the time of the peak heat release rate. Scanning electron microscopy analysis of the char morphology after combustion revealed a denser char structure formed in the presence of kaolin.

If the product of interest is not available in our catalog, please contact us to see if there is any relevant stock or other purchase channels.