For a long time, halogen flame retardants have been widely researched and applied because of their small dosage, obvious effect, and moderate price. However, they will produce toxic smoke and corrosive gas when burned, which will cause harm to the environment and people. It is replaced by other halogen-free flame retardants (nitrogen-phosphorus, silicon, intumescent and aluminium-magnesium flame retardants). The current patents and technologies are difficult to meet the needs of high-end wood-plastic furniture materials for aesthetics, strength, flame retardancy and cost. Therefore, it is particularly important to develop a low-cost, high-strength, flame-retardant WPC materials, which has good market prospects and social benefits and increases the added value of the application of plastic-wood composite materials.

Application of halogen-free flame retardant in wood plastic composite decking

Nitrogen-phosphorus flame retardant: The mechanism of plastic-wood composites decking is that phosphorus and nitrogen compounds need to absorb a lot of heat when they are heated. The phosphoric acid produced can promote the dehydration and carbonization of the polymer to form a graphite-like coke layer, which acts as a thermal insulation and oxygen barrier and delay The role of material burning. APP (ammonium polyphosphate) and inorganic red phosphorus are the current hot spots in the flame retardant research of wood plastic composites decking.

Silicon-based flame retardants: The flame-retardant mechanism of silicon-based flame retardants is that when the organosilicon compound burns, the molecular Si—C bonds are converted into Si—O bonds, forming a composite layer of white residue and carbides to prevent the escape of volatiles. Insulate oxygen from contact with the substrate to prevent the melt from dripping, thereby playing a flame retardant effect. Inorganic SiO2 itself can act as a covering layer of the material, and it can also strengthen the mechanical properties of the plastic-wood composite material.

Intumescent flame retardant: With nitrogen, phosphorus, and carbon as the main elements, the system itself has a synergistic effect. Its flame-retardant mechanism is that a carbon foam layer is formed when the material burns, which acts as oxygen barrier, heat insulation, drip prevention, and smoke suppression effect.

Application Prospects of Flame-retardant WPC Materials

Aluminum-magnesium flame retardant: Because of its obvious environmental protection advantages and low price, this type of flame retardant has increasingly become a hot spot for scholars at home and abroad. Its flame-retardant WPC materials mechanism is that the decomposition of the compound can absorb a large amount of energy, and the water vapour produced by the decomposition dilutes the surrounding area. O2 in the air, compound residues cover the surface of the material matrix, further blocking the material from contacting the air.

Problems in flame-retardant plastic-wood composites

The flame retardant research of plastic-wood composites is still in its infancy. During the processing, there are still many problems to be solved.

1) Most flame retardants are additive powder materials, which are generally very polar, have a hydrophilic base, and are incompatible with the lipophilic polymer matrix. When the amount of addition is small, the flame retardant effect cannot be achieved; large amount At this time, it is easy to produce voids at the interface with the matrix, which reduces the physical and mechanical properties of plastic-wood composites.

2) The flame retardant of plastic-wood composite materials not only involves wood flame retardant and polymer material flame retardant, but also related to the interaction of the two. The flame retardant situation is very complicated, which makes some flame retardants suitable for wood or plastics unable to It is directly applied to the flame retardant of plastic wood composite material.

3) The efficiency of a single flame retardant is low, and it has a great impact on the physical and mechanical properties of polymer materials. The synergy of multiple flame retardants is a hot spot, but there may be interaction or other new effects during the compounding process of various flame retardants. The question, the discussion of the synergy mechanism and the modification of flame retardants appear to be very critical.

Development prospects of flame-retardant plastic-wood composite materials

The main development directions of the research on the flame retardant properties of wood plastic composites decking can be summarized as follows:

1) Continue to study new coupling agents to improve the combination rate of flame retardants and wood plastic composite products.

2) Study a multi-effect flame retardant for wood-plastic composite materials, which can improve the flame-retardant properties of wood-plastic composite materials while giving them anti-corrosion, weather resistance, insect resistance, and ageing resistance.

3) There must be a breakthrough in the method of adding flame retardants, so that the addition of flame-retardant WPC materials can be realized in the existing wood-plastic composite production equipment (or slightly improved).

4) Research and develop new flame retardants to achieve the flame retardant effect without reducing the mechanical properties of wood-plastic composites.


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