Why does ABS need flame retardants?
ABS resin is a copolymer of three monomers, acrylonitrile (A), butadiene (B) and styrene (S), and is a thermoplastic polymer between general-purpose plastics and engineering plastics. ABS resin has the properties of impact resistance, heat resistance, low temperature resistance, chemical resistance, easy processing and molding, and good surface gloss. It is currently widely used in the fields of automobiles, electronics, electrical appliances, textiles, appliances, and building materials. Therefore, the flame retardancy requirements of ABS are also getting higher and higher.
Like most polymer materials, ABS is a flammable material (its oxygen index is only 22%), and it burns fast when it catches fire, and produces a lot of smoke. In practical applications, flame retardants should be added to improve its flame retardant effect.
Flame Retardants for ABS
There are three common types of flame retardant additives used to improve the flammability of ABS, including highly flame retardant resins (such as PVC, CPE, etc.), inorganic flame retardants (such as Al(OH)3, Mg(OH)2, MoO3, etc.) and organic flame retardants (such as halogen compounds, phosphorus flame retardants, etc.). Different types of flame retardants have their own advantages and disadvantages, the following are just a few examples:
- Chlorinated polyethylene (CPE) flame retardants
As an elastomer polymer, CPE has good compatibility with various high polymers, and can be used as a modifier for ABS, PVC, PP, PE, PS, etc. At the same time, because CPE contains halogen, it has flame retardancy and can be used as a second flame retardant. Moreover, the price of CPE is lower than that of ABS, so CPE is an ideal choice for flame-retardant ABS modification.
- Synergistic flame retardancy of CPE and Sb2O3
There is a synergistic effect between CPE and Sb2O3. When CPE is added to the material of ABS and composite flame retardant DBDPE/Sb2O3, the oxygen index of the composite material will increase, and the heat release rate, effective heat of combustion, and mass loss rate will decrease. In addition, after adding CPE/Sb2O3, the smoke generation rate of the composite material can be significantly reduced, indicating that CPE/Sb2O3 also has a good smoke suppression effect on ABS.
- Phosphorus-based flame retardants
Phosphorous-based flame retardants like red phosphorus, triphenyl phosphate (TPP), aluminum hypophosphite (AHP), and resorcinol bis(diphenyl phosphate) (RDP) are often used in ABS formulations. These additives inhibit flame propagation by producing a protective char layer upon heating.
- Inorganic flame retardants
Aluminum hydroxide and magnesium hydroxide are two common inorganic filler-type flame retardants. Its characteristics are halogen-free, non-toxic, smoke-suppressing, and cheap.
- Nitrogen-based flame retardants
Nitrogen-containing flame retardants mainly form incombustible gases such as nitrogen during the decomposition process, dilute and dilute flammable gases or cover the surface of materials to prevent flames. The common ones are melamine, melamine cyanurate (MCA), melamine pyrophosphate and so on.
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