Synthesis of ammonium polyphosphate with crystalline form V (APP-V) from melamine polyphosphate (MPP)

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Abstract

Ammonium polyphosphate (APP) is a well known component of halogen-free flame retardants. Ammonium polyphosphate with crystalline form V (APP-V) was prepared by diammonium phosphate and melamine polyphosphate (MPP). The prepared APP-V was characterized by FTIR and XRD, its water solubility and thermal stability were tested and compared with those of APP-I, APP-II and MPP, its flame retardancy was measured by limiting oxygen index (LOI) and compared with APP-II. Finally, the synthesis mechanism of APP-V from MPP was discussed.

Introduction

Ammonium polyphosphate (APP) is a halogen-free flame retardant [1], [2], [3], [4], it has six crystal forms [5], [6]. The common and commercial available forms are form I (APP-I) and form II (APP-II), they differ from each other in their polymerization and water solubility. It is commonly accepted that APP-II has larger polymerization degree and lower water solubility than APP-I.

APP-V was prepared by phosphoric acid process [7] and by ammonium dihydrogen phosphate process [8]. Melamine polyphosphate (MPP) is a reaction product of melamine and phosphoric acid, it is commonly used alone or in combination with pentaerythritol in many fields, such as fire proof coatings and flame retardant plastics, its structure is shown in Fig. 1.

In this paper, APP-V was prepared by using MPP and diammonium phosphate as raw materials, and was characterized by XRD and FTIR, its retardancy properties were tested by LOI.

Section snippets

Materials

Diammonium hydrogen phosphate (DAP) was supplied by Sinopharm Chemical Reagent Co. Ltd., China, Melamine polyphosphate was supplied by Zhen Jiang Xing Xing halogen-free flame retardant Co. Ltd., Industrial samples (APP-I and APP-II) were supplied by Shanghai Xusen Non-halogen Smoke Suppressing Fire Retardants Co. Ltd., with a measured polymerization degree of APP-I equal to 34 and APP-II equal to 994. The polymerization degree of APP-I and APP-II was measured by the Chinese chemical industrial

XRD analysis

The XRD patterns of synthesized product are shown in [Fig. 2], the XRD patterns of APP-V in literature are also shown in Fig. 2.

Fig. 2 shows that the synthesized APP-V has the same peak positions and peak intensities as APP-V in literature.

The X-ray diffraction data of synthesized APP-V are listed in Table 1, the characteristic peaks belonging to APP-V in literature [5], [6] are also listed in Table 1.

Table 1 shows that, in comparison with literature [5], [6], the synthesized APP-V in this

Conclusion

APP-V was successfully synthesized by DAP and MPP as raw materials, its XRD patterns was exactly the same as APP-V in literature, its water solubility was similar to APP-II. However, its thermal stability was inferior to APP-I and APP-II, with residual weight 4.8% at temperature 700 °C for APP-V, the residual weight was 39.9% for APP-I, 31.0% for APP-II, respectively. Its flame retardancy results showed it has a similar flame retardancy compared with APP-II when acting in the IFR system.

References (14)

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