The additive method is to mix the flame retardant directly with wood fibre material and the resin material, and then make the fire retardant WPC composite by the certain forming method. This is the most common flame-retardant treatment method for WPC, which is generally adopted by APP, Al(OH) 3 and others. Coating method refers to the flame retardant, such as paste coated on the surface of WPC to achieve the purpose of heat insulation and oxygen isolation. The method is simple to operate and has little effect on the properties of materials. In view of the possibility that the coating method may lead to the failure of flame retardant performance, at present, most flame retardants are added.

Synergistic flame retardant synergistic flame retardant refers to two or many kinds of flame retardants will be according to certain proportion mixture compound flame retardants, add it to WPC, can overcome the single flame retardants drip-proof, smoke abatement effect is not good, the shortcoming of the flame retardant performance is not high. The expanded flame retardant used at present is a combination of acid source, gas source and carbon source. Other types of flame retardants are widely used in wood and plastic flame retardant but seldom used in wood flame retardant. Therefore, we can get the effective reference from the research of material and plastic flame retardant.

1) most of the flame retardants are additive powders, which are generally of strong polarity and have water-loving bases. They are not compatible with the oil-loving polymer matrix. When the amount is large, it is easy to create a gap with the substrate interface and reduce the physical and mechanical properties of WPC.

2) flame retardant WPC is not only related to wood fire retardant, flame retardant polymer materials, also related to the interaction of the two, flame retardant is very complex, has led to some suitable for application in the wood or plastic flame retardant cannot be directly applied to the WPC fire retardant, studies have shown that the APP for WPC composite flame retardant is different from plastic, added in the plastic PER can obviously improve the flame retardant properties of APP, in WPC, not PER flame retardant synergistic effect was observed, this is because the WPC wood fiber material as the carbon source. The research on fire retardant mechanism of WPC has just started.

3) a single flame retardant efficiency is low, affect the physical and mechanical properties of polymer material, a variety of flame retardant association effect is a hot spot, but there are various kinds of flame retardants in the process of the compound with possible interaction or other new problems, coordination mechanism to explore and flame retardant modification is very critical.