There are many halogen-free flame-retardant methods for PBT materials, including aluminum diethylphosphite,MPP systems and aluminum hypophosphite,MCA systems. Each halogen-free flame-retardant formulation has its own advantages and disadvantages. The former has better flame-retardant effects and is more mature in application, while the latter has price and cost advantages. The aluminum hypophosphite flame-retardant PBT formulation and its flame-retardant effect are roughly as follows:

1. Formulation:

Aluminum hypophosphite (grade: LXF-A24138): MCA = 3:1, coupling agent and other additives as needed, total amount of composite flame retardant added 20-25%

2. Flame-retardant effect:

The oxygen index (LOI) of PBT increases from 16.6% to 30%, and the flame-retardant rating reaches V-0.

3. Flame-retardant mechanism:

Aluminum hypophosphite decomposes into PH3 and aluminum phosphate upon heating. With further temperature increases, Al4(P2O7)3, water, carbon dioxide, etc., are generated. This decomposition process absorbs a large amount of heat from the material, producing non-combustible inert gases, and also generates a certain amount of phosphate ester carbon layer, contributing to the flame-retardant effect from multiple aspects.

In the flame-retardant PBT formulation of aluminum hypophosphite, silane coupling agents and titanate coupling agents have a significant impact on the dispersibility and compatibility of the flame-retardant system. Different particle sizes and stability result in significant differences in the flame retardancy of PBT composite materials. If yellowing, white spots, or flame retardant precipitation occur in the above formulation, appropriate PBT/PA flame-retardant synergists can be added to improve the situation.