Ammonium phosphate ranks high among common flame retardant additives and is particularly effective for cellulose. Alfa Chemistry offers high quality ammonium phosphate flame retardants to meet fire safety challenges.
The flame retardant effect of ammonium phosphate on cellulose mainly works in the condensed phase through a char formation mechanism. Phosphate is attached to the cellulose chain through an ester group, which is easily eliminated to form a conjugated double bond, which eventually cyclizes to form carbon.
Similarly, ammonium phosphates impart flame retardancy to polymers such as polystyrene by charring. This occurs through a series of processes including initial peroxide formation, decomposition into alcohols and aldehydes, alkyl phosphate formation, dehydration and subsequent char formation. 
Microencapsulated Ammonium Phosphate
I. Vroman developed three types of diammonium hydrogen phosphate (DAHP) microcapsules with different polymer shells as intumescent flame retardants for polypropylene (PP) fabrics. The results showed that DAHP microcapsules with PU shells provided better results than DAHP in terms of HRR and THE reduction, while results were comparable to microcapsules with melamine-formaldehyde and PHMA shells, which were low in phosphate. 
HRR and THE curves of filled PP fabrics 
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