Is it true that if PP flame retardant masterbatch is added to PP flame retardant sheets, they won't burn at all?

Will the plate not burn at all if PP flame retardant masterbatch is added? That's not the case. A flame retardant is also known as a fire-retardant agent. After adding a flame retardant, it will only increase the difficulty of the plate's combustion. When the plate catches fire accidentally, it can extinguish itself to prevent greater harm and more losses. 

We can see this from the flame retardant testing standards. In the UL94 flame retardant testing standard, 

V2 level: After two 10-second combustion tests on the sample, the flame extinguishes within 60 seconds. There can be burning substances falling off.

 V1 level: After two 10-second combustion tests on the sample, the flame extinguishes within 60 seconds. There should be no burning substances falling off. 

V0 level: After two 10-second combustion tests on the sample, the flame extinguishes within 30 seconds. There should be no burning substances falling off. 

It can be seen that none of them mention the situation where the plastic cannot be ignited. At the very least, the flame extinguishes within 30 seconds after combustion. Therefore, adding PP flame retardant masterbatch to PP flame retardant plates does not mean that they will not burn at all.