Flame-retardant formulations for PC are relatively limited. Sulfonates are commonly used, while flame-retardant silicone resin formulations are less common, but they have certain research value. As temperature increases, the compatibility between silicone resin and PC deteriorates. Due to its low surface energy, silicone resin spontaneously migrates to the surface of the PC material, forming an enriched layer. At high temperatures, silicone resin catalyzes the Fries rearrangement reaction in PC. The phenolic hydroxyl groups produced in this reaction crosslink with segments in the silicone resin, rapidly forming a dense, hard protective char layer on the material surface composed of Si-O-Si bonds and aromatic compounds. Below, we will briefly introduce the flame-retardant PC formulation with silicone resin.

I. Raw Materials and Formulation/Parts by Weight

PC: 100

Silicone Resin: 6.0

Other Additives: Appropriate Amount

Antioxidant 1010: 0.5~1.0

II. Preparation Method

Before use, PC must be thoroughly dried in a forced-air oven at (120±2)℃. The material layer thickness should be less than 30mm, and the drying time should be at least 12 hours, ensuring the PC moisture content is below 0.015%.

Add PC, flame retardant silicone resin, antioxidant 1010, and other additives in different proportions to a high-speed mixer and knead thoroughly. Then, add the mixture to a two-roll plasticizer at a roller temperature of 160~170℃ for melt mixing, ensuring the PC, flame retardant, and additives are evenly mixed. Next, use a flat vulcanizing machine to press and shape the mixture at an upper and lower mold temperature of 220℃. After preheating for 5 minutes, apply pressure for 3 minutes, then cold press for 5 minutes, and demold to obtain flame-retardant PC sheets with thicknesses of 3mm and 4mm respectively.

III. Flame Retardant Effect

1. Adding phenylmethyl silicone resin to PC effectively improves its flame retardancy. When the silicone resin mass fraction is 6%, the oxygen index of the material increases from 28% to 40.6%, and the flame retardant rating improves from UL94V-2 to V-0, ensuring the PC material can be used in environments with high flame retardant performance requirements.

2. Due to the excellent compatibility between phenylmethyl silicone resin and PC, the blending of the two not only does not impair the mechanical strength of PC but also effectively improves its notched impact strength, tensile yield strength, and tensile breaking strength.

3. The addition of phenylmethyl silicone resin can increase the heat distortion temperature of flame-retardant PC, but has little impact on its electrical properties.

4. Using phenylmethyl silicone resin as a flame retardant modifier for PC fully meets environmental protection requirements, causes no harm to the environment, and its flame retardant performance is superior to traditional halogen-based and phosphorus-based flame retardants.