PAPP, short for piperazine pyrophosphate, is a charring agent suitable for PP to achieve V-0 flame retardancy. MPP's flame retardant effect on PP is a well-established and mature formulation in the flame retardant industry, having been used for many years. For example, the halogen-free flame retardant LXF-C5800A is a compound formulated with MPP and PAPP as the main raw materials. It easily achieves V-0 flame retardancy on PP, featuring halogen-free properties and a high oxygen index. The effectiveness of this MPP and PAPP flame retardant system is manifested in the following aspects:

1. LOI reaches 32%. Due to the large amount of P-N elements, the flame retardant system effectively utilizes the synergistic flame retardant effect of the gas phase and condensed phase.

2. The product exhibits excellent charring properties after combustion tests. PAPP can produce a large amount of dense char layer in PP materials, playing a crucial role in preventing oxygen and heat transfer from the PP material. The compounded flame retardant can also be used for flame retardancy of EP, demonstrating high flame retardant efficiency. After adding the compound flame retardant, the content of phosphorus and nitrogen, the flame-retardant elements in the EP char layer, increased compared to before the addition of the flame retardant.

3. Both MPP and PAPP flame retardants are halogen-free, environmentally friendly, and have low hygroscopicity, exhibiting good compatibility with PP. This formula demonstrates superior resistance to exudation compared to flame retardants compounded with ammonium polyphosphate and triazine macromolecular charring agents; flame-retardant PP products do not exhibit surface whitening or blooming. The decomposition temperature is also better.

The flame-retardant effect of PAPP and MPP on PP is mainly achieved through the interaction of acid, gas, and carbon sources, forming a continuous expanded char layer on the material surface, isolating oxygen and heat to exert its flame-retardant effect. The intumescent compound system improves the flame-retardant performance of PP.