Normally, a single halogenated FR is enough to achieve UL94 V0 due to its high FR efficiency. But by contrast, for formulation of a halogen-free flame retardant PC, a combination of different types of halogen-free flame retardants is mostly entailed to achieve UL94 V0, especially for a thickness of 1.6 mm or below. This is because a single halogen-free FR might not be so efficient as to meet the specific requirement for flame retardancy and a good synergy between different halogen-free FRs becomes a must. Designing a certain combination of different types of halogen-free FRs needs to take into account factors such as flame-retarding efficiency, cost, mechanical strength, HDT, appearance, resin quality & MI, processing conditions and so on. Lab work might be needed to evaluate and determine a recommended FR combination.