Silicone rubber (abbreviated as silicone) is a type of polymer elastic material with a silicone-oxygen bond as the main chain. Depending on the vulcanization method and application scenario, it is mainly divided into three categories: high-temperature vulcanized silicone rubber (HTV), liquid silicone rubber (LSR), and room-temperature vulcanized silicone rubber (RTV). HTV uses peroxide or platinum catalysis and requires heat curing, making it suitable for high-temperature scenarios such as seals and wire\/cable jackets; LSR is a two-component addition-curing type with good fluidity and can be injection molded, and is commonly used in fields with high purity requirements such as medical catheters and infant products; RTV can cure at room temperature and is mainly used in building sealants, electronic potting compounds, and the like.<\/p>\n
The common feature of the three types of silicone is that they themselves do not have flame-retardant properties; their limiting oxygen index (LOI) is only about 21%. After ignition, they are difficult to self-extinguish, so flame retardants must be added to meet safety requirements. In practical applications, the same silicone substrate in different application scenarios has greatly different requirements for flame-retardant grades\u2014high-risk scenarios such as electronic jackets usually require UL94 V-0 grade, while general industrial products may only need HB grade. When selecting a flame retardant, the influence of product thickness on the difficulty of flame retardancy must also be considered\u2014the thinner the material, the harder it is to pass flame-retardant tests.<\/p>\n
Different silicone types have significantly different requirements for flame retardants. HTV silicone has high processing temperatures (usually above 150-200\u00b0C), so flame retardants with excellent thermal stability should be selected. Inorganic flame retardants, represented by aluminum hydroxide (ATH) and magnesium hydroxide (MH), absorb heat and lower the temperature by decomposing upon heating and releasing water of crystallization, dilute flammable gases, and simultaneously generate oxides to form a thermal insulation layer. This type of flame retardant is environmentally friendly and low-cost, but usually requires a high loading of 50%-60% to achieve ideal results, which may affect the flexibility and transparency of silicone. For medical and food-grade silicone, inorganic flame retardants such as ATH or MH are preferred because they are non-toxic and meet biocompatibility requirements. For liquid silicone rubber (LSR), special attention must be paid to the compatibility between the flame retardant and the matrix to avoid sedimentation in the liquid state; addition-curing LSR generally achieves high flame retardancy more easily and without by-products.<\/p>\n
Phosphorus-nitrogen flame retardants are currently widely used halogen-free environmentally friendly solutions\u2014ammonium polyphosphate (APP) compounded with melamine derivatives can form an intumescent flame-retardant system, which blocks oxygen and heat by forming a dense char layer; melamine cyanurate (MCA) and melamine pyrophosphate (MPP) are also commonly used in the flame-retardant modification of silicone rubber. Platinum-based flame retardants have both catalytic crosslinking and flame-retardant functions, making them suitable for high-temperature scenarios above 300\u00b0C.<\/p>\n
In summary, the following principles should be followed when selecting flame retardants for silicone: clarify the flame-retardant grade (UL94 V-0, V-1, etc.) and application scenario (electronics, medical, construction, etc.), and match the corresponding type of flame retardant accordingly; evaluate compatibility with the processing technology\u2014HTV requires high-temperature resistance, while LSR requires anti-settling; ensure compliance with environmental requirements (RoHS, REACH, etc.); and give priority to verifying the compatibility of the flame retardant with the matrix through small-scale tests.<\/p>\n
Dongguan Hongtaiji Flame Retardant Materials Co., Ltd. has been deeply engaged in the field of environmentally friendly flame retardants for more than 20 years, customizing a high-performance halogen-free flame-retardant series for elastomers such as silicone rubber, with excellent compatibility and anti-migration properties. Its silicone flame retardant FR-3035 is a nitrogen-containing halogen-free environmentally friendly product in the form of a white fine powder, offering advantages such as economical use, high efficiency, excellent electrical and mechanical properties, no discoloration, low smoke, and low corrosiveness. The ultra-thin silicone flame retardant FR-562A is specially designed for thin-walled silicone products and achieves V-0 flame retardancy at a thickness of 0.8 mm. In addition, Hongtaiji can also provide phosphorus-nitrogen flame-retardant solutions centered on MCA, MPP, etc., helping customers find the best balance between flame-retardant efficiency, processing performance, and cost.<\/p>","protected":false},"excerpt":{"rendered":"
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