Molybdenum(VI) oxide

Catalog	ACM1313275
CAS	1313-27-5
Structure
Synonyms	Molybdenum trioxide
Molecular Weight	143.94
Molecular Formula	MoO3
Canonical SMILES	O=[Mo](=O)=O
InChI	1S/Mo.3O
InChI Key	JKQOBWVOAYFWKG-UHFFFAOYSA-N
Boiling Point	1155 °C
Melting Point	795 °C(lit.)
Purity	0.9997
Density	4.692 g/cm³
Solubility	H2O solubility, 0.68 g/mL
Appearance	Molybdenum trioxide is an odorless, white crystalline powder that turns yellow when heated.
Application	Molybdenum trioxide is a condensed-phase flame retardant.Molybdenum is also a smoke suppressant for poly(vinyl chloride).
Storage	Store at +5°C to +30°C.
Packaging	5, 25 g
Particle Size	25 µm
Specific Gravity	4.69

Case Study

Molybdenum Trioxide-Loaded Graphene Synergy for High-Efficiency Polyurethane Fire Protection

Xu, Wenzong, et al. Industrial & Engineering Chemistry Research 55.17 (2016): 4930-4941.

Challenge: Achieve simultaneous flame retardancy, smoke suppression, and thermal stability in polyurethane elastomers (PUE) without compromising material flexibility.
Solution: Engineered molybdenum trioxide-graphene nanosheet hybrids (MoO3-GNS) via hydrothermal synthesis. Integrated at only 2.0 wt% into PUE matrix.
Key Results:
· The integration of 2.0 wt% MoO3-GNS hybrids delivered transformative fire safety improvements in polyurethane elastomer (PUE):
· Peak Heat Release Rate (PHRR): Achieved 61.9% reduction vs. neat PUE (measured via cone calorimetry at 50 kW/m2).
· Total Smoke Density: Demonstrated 29.5% lower optical density.
· Char Residue Yield: Catalytically enhanced char formation with >35% increase in residual mass (TGA-verified).
· Total Heat Release (THR): Complementary 10.2% reduction.
· Mechanistic Advantages: Synergistic effect of physical barrier effect of graphene sheets and catalytic coking effect of MoO3.
Conclusion: The MoO3-GNS hybrid delivers leading heat/smoke suppression (>60% PHRR reduction), self-reinforcing char networks via gas-to-solid catalysis, and effective performance at ultralow loading (2 wt%).

Molybdenum Trioxide and Intumescent Flame Retardants for Styrene-Butadiene-Styrene Composites

Zang, Baichao, et al. Thermochimica Acta (2025): 180013.

Challenge: Synergistically improve the flame retardant properties of styrene-butadiene-styrene (SBS) composites with intumescent flame retardants (IFRs), while enabling the observation of char layer formation and evolution in real time.
Solution: Add 1 wt% MoO3 to the SBS/IFR formulation and monitor char evolution via in situ electrical resistance alongside TGA, XPS, FTIR, and microscopic examination.
Key Results:
· UL-94 Rating: Upgraded from unclassified to V-1 with 1 wt% MoO3.
· Thermal Behavior: Decomposition onset shifts from ~240 °C to ~231 °C, but char yield increases.
· Char Chemistry/Morphology: Ammonium polyphosphate of the IFR decomposed faster and to form phosphate esters with help from MoO3, leading to a more viscous and crack-resistant char.
· Resistance Monitoring: Char forms earlier and shows fewer resistance fluctuations, indicating faster, more stable barrier development.
· Mechanism: MoO3 acts as a catalyst (not a crosslinker), accelerating IFR decomposition to build a denser char that better inhibits heat/mass transfer.
Conclusion: MoO3 at only 1 wt% increased SBS/IFR flame retardancy through catalyzing the char-forming reactions and creating a stronger, more robust barrier. Real-time resistance tracking confirms earlier and steadier char formation, validating MoO3's role as an effective synergist in polymer IFR systems.

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