Why are the casings of PD chargers made of PC flame-retardant materials?

Anyone who is engaged in the power supply industry knows that the charger shells produced by major mobile phone manufacturers are all made of PC flame-retardant materials. Why don't they use ABS and PC+ABS plastics? Now let's analyze the advantages and disadvantages of these three materials.
1. ABS plastic is actually a kind of acrylic resin-butadiene-styrene copolymer, which is cheap and easy to process. It is mainly used for electroplating. However, relatively speaking, this material has low strength and is not resistant to high temperatures. The temperature exceeds 60 ℃, there may be deformation
2. PC plastic is actually a kind of polycarbonate. The shell of the famous Nokia mobile phone was made of this material. This material has high strength, is durable, and is not easy to deform under high temperature conditions. harmless to human body
3. PC+ABS plastic is actually made of PC plastic + ABS plastic, with high gloss and good toughness, but its heat resistance is not as good as that of pure PC plastic.
We all know that the PD charger is actually a transformer, which converts the household 220V AC power into a suitable low-voltage DC power. During the conversion process, about 30% of the electric energy will be consumed and radiated out through the air in the form of heat energy. . Therefore, when the mobile phone is charging, the charger will generate a lot of heat energy. In order to protect the user's charging safety, we have chosen a pure PC flame-retardant material that is more resistant to high temperatures.