Options for Halogen-free flame retardants
I. Consider the Substrate
When a customer requests flame retardancy, our first question is about the substrate on which flame retardancy will be achieved. There are many types of substrates, commonly including plastics, rubber, fibers, adhesive coatings, and fabrics. Each of these categories is further subdivided into many subcategories, such as polyethylene (PE), polypropylene (PP), nylon (PA), polyester (PBT or PET), polycarbonate (PC), ABS, and elastomers (TPU or TPE), etc. The flame retardant mechanisms involved are not entirely the same for each substrate, so the flame retardant systems used vary greatly! For example, polyolefins have a processing temperature of around 100-200℃, and can use halogen-free intumescent systems based on APP for flame retardancy. However, this is not suitable for nylon substrates, whose processing temperature is as high as 220-270℃, while the thermal decomposition temperature of APP is only around 260℃. Therefore, using APP flame retardant systems is inappropriate, and ultimately, flame retardants with higher temperature resistance, such as aluminum hypophosphite, must be chosen. The example above only considers decomposition temperature; in reality, the factors to consider are much more complex depending on the substrate.
II. Standards
There are many flame retardant standards, and different industries have different standards. However, some commonly used standards are applied in many industries. For example, the UL94 flame retardant standard is a relatively universal standard. Each flame retardant standard has different testing requirements, so the design of the flame retardant system must also differ. For example, in the cable and wire industry, bundled burning tests and VW-1 vertical burning tests are commonly used standards, sometimes with smoke density requirements. The base material is mainly polyolefin, and the flame retardant system primarily uses inorganic aluminum hydroxide or magnesium hydroxide, supplemented with small amounts of phosphorus-based or nitrogen-based flame retardants or charring agents. Why this choice? Because cable plastic sheaths are thin, and low smoke and halogen-free conditions are required, along with long burning test times and low costs. Therefore, low-cost, high-smoke, high-filling inorganic flame retardants become the best choice.
III. Consider the Process (Injection Molding? Extrusion? Spraying?)
The processing methods for each material are different. Even within plastics, polyolefins and nylon can be modified using twin-screw extruders, but the processing temperatures are completely different. Polypropylene’s processing temperature is 180-220℃, while nylon’s is around 250℃. Therefore, their requirements for the thermal decomposition temperature of flame retardants differ. Injection molding and extrusion are both major plastic processing methods, but their requirements for the morphology of flame retardants differ.
The processing technology for flame retardants in the coating industry is even more complex. First, we need to consider whether the chosen emulsion is water-based or oil-based. In water-based emulsions, the water solubility and acidity/alkalinity of the flame retardant have a crucial impact on its mixed performance and storage stability. Second, the particle size and distribution of the flame retardant also have a significant impact. Too coarse a particle size will result in a rough coating surface, and the emulsion will settle during storage. Too fine a particle size may sometimes affect matrix dispersion and emulsion viscosity. Third, the addition of different flame retardants will alter the rheological properties of the emulsion. All of these factors make the selection of flame retardants for emulsions a more professional and cautious process.
IV. Consider Performance Requirements
When designing flame-retardant materials, in addition to flame retardancy as the primary indicator, other properties need to be considered, such as color, transparency, toughness, weather resistance, and mechanical strength. In typical flame-retardant formulations, halogen-free flame retardants are added in larger quantities than halogenated flame retardants, resulting in lower mechanical strength. Furthermore, because each type of halogen-free flame retardant has a different molecular structure and thermal decomposition temperature, their impact on color also differs; flame retardants containing amine groups will cause the product to gradually yellow during use. Sometimes, customers also specify requirements for product toughness, which necessitates the addition of toughening agents to the formulation. However, this increases the amount of flame retardant used.
V. Consider Total Cost(not just Unit Price)
For halogen-free flame retardant products, from a cost-effectiveness perspective, we should choose the lowest-priced flame retardant solution while meeting product requirements, and appropriately discard some unnecessary material properties. For example, in halogen-free PP flame retardants, there are two flame retardant systems: APP and PPAP. The APP system requires a large amount and will leach out, but it is cheaper. The PPAP system requires a small amount and will not leach out, but it is more expensive. Therefore, when developing flame retardant materials, if the product does not require passing the IEC-60068-2-78 test, choose the APP system because it is cheaper and offers the best cost-effectiveness.
How to reduce the amount of halogen-free flame retardant added? How to make the material performance the same as halogenated flame retardant materials? How to reduce the price of high-end halogen-free flame retardants? These are the eternal goals and missions of us halogen-free flame retardant developers. Taifeng Flame Retardant is a professional company specializing in the development and sales of APP flame retardants. We welcome inquiries and discussions on flame retardant issues, and we provide the most professional and suitable flame retardant solutions.
Post time: Jul-10-2026
