Silane-Coated Ammonium Polyphosphate in Polymer Materials
1. Synergistic Flame Retardant Mechanism of the Composite System
Silane-coated ammonium polyphosphate (APP) acts as a solid intumescent flame retardant, which mainly exerts a flame retardant effect in the condensed phase by forming a dense carbon layer to block heat and oxygen. Liquid flame retardants (mostly phosphorus-based and organosilicon liquid reagents) play a flame retardant role in the gas phase by capturing free radicals during combustion. The silane coating layer on the APP surface improves the interfacial compatibility between solid and liquid flame retardants, forming a complete “gas-phase quenching + condensed-phase charring” synergistic system, achieving a better flame retardant effect with a lower total addition amount.
2. Optimization of Typical Compound Ratio and System Stability
In practical applications, the ratio of silane-coated APP to liquid flame retardants directly affects the overall performance of the material. The conventional optimal compound ratio is controlled within the range of 3:1 to 5:1, which can balance flame retardant efficiency and material mechanical properties. Meanwhile, the silane coating structure effectively inhibits the moisture absorption of APP and the migration of liquid flame retardants, enhancing the storage stability and long-term service stability of the composite flame retardant system in high-temperature and humid environments.
3. Development Prospects and Existing Challenges
At present, the compound application of silane-coated APP and liquid flame retardants still faces challenges such as high cost of high-efficiency liquid reagents and unclear long-term aging mechanism. With the upgrading of halogen-free flame retardant standards and the development of new materials, the future research direction will focus on the development of reactive liquid flame retardants and the structural design of multi-component composite coatings, further improving the synergistic efficiency and environmental adaptability of the system.
