Calcium sulfate dihydrate

Catalog	ACM10101414-2
CAS	10101-41-4 / 13397-24-5
Synonyms	Calcium sulfate dihydrate;Alabaster; Calcium (II) sulfate dihydrate (112); CI 77231; CI pigment white 25; Gypsum Gypsum stone; Land plaster; Light spar; Magnesia white; Mineral white Native calcium sulfate; Pigment white 25; Precipitated calcium sulfate; Terra alba
Molecular Formula	CaSO4 2H2O
Application	Supplement, Flame Retardant, Acid, Stabilizer
Notes	Calcium sulfate dihydrate uses and applications include: manufacturing of Portland cement, plaster of Paris, artificial marble, sulfuric acid, calcium carbide, and ammonium sulfate; white pigment, filler, extender, glaze in paints, pharmaceuticals, paper, insecticide dusts, yeast, polishing powders; soil conditioner; water treatment; flame retardant for plastics; foods (nutrient, calcium source, dietary supplement, yeast food, dough conditioner, firming agent, sequestrant, stabilizer, thickener, pH control agent, carrier for bleaching agents); brewing and fermentation processes; pharmaceuticals (excipient, filler, desiccant, tabletcapsule diluent; in plaster casts); food-contact applications Suggested storage of Calcium sulfate dihydrate: Hygroscopic; store in cool, dry location; keep containers well closed when not in use

Case Study

Calcium Sulfate Dihydrate Whiskers for Fire-Resistant Architectural Coatings

Yang, Hsi-Chi, et al. Chemical Papers, 2017, 71, 1343-1350.

Highly crystalline calcium sulfate dihydrate (CaSO4·2H2O) whiskers were prepared from wastewater using an efficient microwave-assisted method. The CaSO4·2H2O whiskers have a one-dimensional structure with an aspect ratio of up to 40. Adding them to architectural coatings can effectively enhance the fire resistance of architectural coatings.
Performance evaluation of CaSO4-coatings
· Thermal resistance properties of CaSO4-coatings were examined through thermo-gravimetric analysis and differential scanning calorimetry as well as direct flaming evaluations at temperatures of 150, 570, and 1100 °C.
· Through TGA and DSC analyses it was shown that CaSO4·2H2O whiskers improved construction painting by enhancing anti-flammability characteristics and lowering ignition temperature.
· The area fraction of pyrogenation and carbonization declined as the content of CaSO4·2H2O whiskers increased which demonstrates that CaSO4·2H2O whiskers provide outstanding thermal insulation to prevent heat transfer and flame spread.
These findings show that CaSO4·2H2O whiskers act as a valuable fire retardant additive to enhance fire resistance.

PLA-Calcium Sulfate Nanocomposites with Flame Retardant Properties

Murariu, Marius, et al. Polymer Degradation and Stability, 2010, 95(3), 374-381.

Composites were produced by melt blending polylactic acid (PLA) and this filler, which was previously subjected to a specific dehydration treatment (dehydration at 500°C for 1 h) to obtain anhydrite II (AII), using gypsum (β-calcium sulfate hemihydrate) as raw material. Further introduction of organically modified layered silicates (OMLS) resulted in PLA-AII composites with flame retardant properties for specific end uses.
· Preparation of PLA-AII Composites
Prior to melt blending, PLA was vacuum-dried at 80 °C for 4 hours. Due to its sensitivity to moisture, OMLS were dried under vacuum at 130-150 °C for 1 hour and then used directly in the melt-compounding process. The OMLS were mixed with PLA pellets and AII at 190 °C with moderate mixing using cam blades in a bench-scale kneader, following a specific procedure: 3 minutes of premixing at 30 rpm to prevent excessive torque during PLA melting, followed by 3 minutes of mixing at 60 rpm. The representative formulations discussed contain highly filled (nano)composites with 40% AII filler and 3% OMLS.
· Flame Retardant Properties of PLA-AII Composites
When AII and OMLS are added together to PLA (nano)composites they demonstrate outstanding (nano)filler dispersion along with enhanced thermal stability and adequate mechanical strength. Cone calorimetry tests showed pure PLA has a shorter ignition time than the composite and the maximum heat release rate of composite decreased by roughly 40%. The UL94 HB test results confirmed non-dripping properties and substantial char formation in the samples.

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