How to choose Halogen-Free Flame Retardants?
I. Substance
The customer raised a flame retardant requirement, and the first thing we need to ask is on which substrate the flame retardancy should be achieved. There are many types of substrates, with major categories including plastics, rubber, fibers, adhesive coatings, fabrics, etc. Each major category further subdivides into numerous subcategories, such as polyethylene (PE), polypropylene (PP), nylon (PA), polyester (PBT or PET), polycarbonate (PC), ABS, elastomers (TPU or TPE), and so on under plastics. For each type of substrate, the flame retardation mechanisms involved are not entirely the same, so the flame retardant systems used also vary significantly! For example, polyolefins have a processing temperature of around 100-200°C, making them suitable for halogen-free intumescent systems primarily based on APP. However, nylon substrates are not suitable for this approach, as their processing temperature reaches 220-270°C, while APP's thermal decomposition temperature is only around 260°C. Using an APP-based flame retardant system would be inappropriate, necessitating the selection of higher-temperature-resistant flame retardants like aluminum hypophosphite. The example given above is based solely on decomposition temperature, but in reality, the factors considered for different substrates are far more complex.
II. Standards
There are many flame retardant standards, and different industries have different flame retardant standards. But there are also some commonly used standards that are used in many industries, such as UL94 flame retardant standard, which is a relatively universal standard. The testing requirements corresponding to each flame retardant standard are also different, so there must be differences in the design of flame retardant systems. For example, in the cable and wire industry, bundle burning test and VW-1 vertical burning test are commonly used standards, sometimes with requirements for smoke density. Its substrate is mainly polyolefin, and its flame retardant system mainly selects inorganic aluminum hydroxide or magnesium hydroxide, supplemented by a small amount of phosphorus based, nitrogen based flame retardants or carbonization agents. Why did you choose this way? Due to the thin plastic coating of cable wires, as well as the requirements for low smoke and halogen-free, long combustion testing time, and low cost, low-cost, smoke reducing, and high filling inorganic flame retardants have become the best choice.
III. Process (injection molding, extrusion, spraying?)
The process of each material is different. For plastics, polyolefins, and nylon, twin-screw modification can be used, but the processing temperature is completely different. The processing temperature of polypropylene is 180-220 ℃, while that of nylon is 250 ℃. Therefore, their requirements for the thermal decomposition temperature of flame retardants are different. Injection molding and extrusion are both the main processing methods for plastics, but they have different requirements for the form of flame retardants.
The processing technology of flame retardants in the coating industry is even more complex. First, we need to see whether the selected lotion is water-based or oil-based? In water-based lotion, the water solubility and acid-base property of flame retardant have a key impact on its mixed performance and storage stability. Secondly, the particle size and distribution of flame retardant also have a very important impact. If the particle size is too large, the subsequent coating surface will have a rough feeling, and lotion will settle during storage. If the particle size is too small, the matrix dispersion and lotion viscosity will be affected. Thirdly, the addition of different flame retardants will change the rheological properties of lotion. For all these reasons, it is more professional and prudent to choose flame retardant in lotion.
IV. Performance requirements
When designing flame retardant materials, in addition to the main indicator of flame retardancy, we also need to consider other properties such as color, transparency, toughness, weather resistance, and mechanical strength. In typical flame retardant formula design, the amount of halogen-free flame retardants added is larger than that of halogenated flame retardants, so the mechanical strength is relatively low. At the same time, due to the different molecular structures and thermal decomposition temperatures of each halogen-free flame retardant, their effects on color are also different. Flame retardants containing amine based structures will gradually yellow the product during use. Sometimes, customers also have requirements for the toughness of the product, which requires developers to add toughening agents to the formula. But it will increase the use of flame retardants.
V. Total cost(not just the unit price)
For halogen-free flame retardant products, we choose from the perspective of cost-effectiveness. We should adapt to lower priced flame retardant solutions while meeting product requirements, and appropriately discard some unnecessary material properties. For example, in halogen-free PP flame retardant, there are two flame retardant systems: APP and PPAP. The APP system has a large amount of addition and will precipitate, but it is cheap, while the PPAP system has a small amount of addition and will not precipitate, but it is expensive. So when making flame retardant materials, if the product does not require IEC-60068-2-78 testing, choose the APP system because it is cheap and the best cost-effective solution.
How to reduce the amount of halogen-free flame retardants added? How to make the performance of the material the same as that of halogenated flame retardant materials? How to reduce the price of high-end halogen-free flame retardants? This is the eternal goal and mission of our halogen-free flame retardant developers. Taifeng Flame Retardant is a professional company engaged in the development and sales of APP flame retardants. Welcome to consult and discuss flame retardant issues. We provide the most professional and suitable flame retardant solutions.