Application of flame retardants in plastic products

Flame retardants are key additives for the safety protection of plastic products. By inhibiting the chain reaction of combustion, forming a barrier layer, or diluting flammable gases, they reduce the flammability of plastics, delay the spread of flames, and reduce the release of smoke and toxic gases. Plastics themselves are mostly flammable materials (such as PE and PP, with an oxygen index of only 17-19). Adding flame retardants can increase the oxygen index to 26 or above, and even reach non flammable levels. They are widely suitable for electronic, construction, automotive, household appliances and other scenarios. According to their mechanism of action, they can be divided into additive and reactive types. Currently, they are developing towards low smoke, low toxicity, halogen-free environmental protection, high efficiency and long-term effectiveness, which is the core support for ensuring the safe use of plastic products.

1、 The core mechanism of flame retardants: multidimensional blockade of combustion

1. Gas phase flame retardant: inhibits combustion chain reaction

Flame retardants decompose at high temperatures to produce free radical scavengers (such as hydrogen halides in halogenated flame retardants), which capture active free radicals during combustion, terminate chain reactions, and prevent flame propagation:

Representative products: Bromine flame retardants (decabromodiphenyl ethane, tetrabromobisphenol A);

Adaptation scenarios: ABS electronic casing, PP automotive components, high flame retardant efficiency, with an addition of 5% -15% to meet the standard.

2. Condensed phase flame retardant: forming a physical barrier layer

The carbonized layer, glassy substance or foam layer generated from the decomposition of flame retardant is covered on the plastic surface to isolate oxygen and heat and prevent combustion from continuing:

Representative products: Phosphorus based flame retardants (red phosphorus, phosphate ester), expansion flame retardants;

Adaptation scenarios: PVC building materials, PA electronic components, halogen-free and environmentally friendly, with low smoke generation.

3. Dilution flame retardant: reduce the concentration of combustible gases

The decomposition of flame retardants produces a large amount of non combustible gases (such as nitrogen and carbon dioxide), which dilute the concentration of combustible gases and oxygen during plastic decomposition, making it impossible to sustain combustion

Representative products: Nitrogen based flame retardants (melamine, guanidine salts);

Adaptation scenario: PE film, PP woven bag, combined with other flame retardants to enhance flame retardant effect.

2、 Mainstream flame retardant types and compatible plastics: characteristics and scene matching

1. Halogen based flame retardants: efficient and low-cost, suitable for multiple plastics

Core advantages: high flame retardant efficiency, good compatibility with plastics, low cost, and low addition amount (5% -15%);

Compatible plastics: PE, PP, ABS, PVC;

Typical applications: ABS TV casing, PP car interior parts, can achieve UL94 V-0 flame retardant level, but releases hydrogen halides during combustion, limited for high-end environmental protection scenarios.

2. Halogen free flame retardant: environmentally friendly and low smoke, suitable for high-end scenarios

Core advantages: halogen-free, low smoke, low toxicity, compliant with EU RoHS and REACH standards, divided into phosphorus series, nitrogen series, and expansion type;

Compatible plastics: PA, PC, PET, PP;

Typical applications: PA electronic connectors, PC laptop shells, PE wires and cables. Phosphorus based flame retardants (such as red phosphorus) can be added to PA by 10% -20% to achieve V-0 level. Expansion type flame retardants are suitable for PVC building materials.

3. Reactive flame retardant: long-lasting and stable, suitable for engineering plastics

Core advantage: Grafted onto plastic molecular chains through chemical bonds, without migration or precipitation, with long-lasting flame retardant effect;

Compatible plastics: PET, PC, epoxy resin;

Typical applications: PET flame retardant fiber, PC flame retardant board, electronic packaging epoxy resin, good temperature resistance, suitable for long-term use scenarios.

4. Inorganic flame retardants: environmentally friendly and inexpensive, suitable for mid to low end products

Core advantages: non-toxic, smoke-free, low cost, and smoke suppression function;

Representative products: aluminum hydroxide, magnesium hydroxide;

Compatible plastics: PE, PP, PVC;

Typical applications: PE water supply pipes, PVC flame-retardant cable sheaths, with an addition amount of 30% -60%, which will slightly reduce the mechanical properties of the plastic.

3、 Application Practice of Flame retardants in Key Plastic Products

1. Electronic and electrical plastics: high flame retardant+low smoke toxicity

PA electronic connector:

Formula: PA6 resin+15% red phosphorus flame retardant+5% synergist+0.3% antioxidant;

Effect: UL94 V-0 grade (1.6mm), oxygen index ≥ 32%, low smoke density, suitable for fire protection requirements of electronic devices.

ABS router casing:

Formula: ABS resin+12% decabromodiphenyl ethane+5% antimony trioxide+0.2% antioxidant;

Effect: UL94 V-0 grade, high flame retardant efficiency, controllable cost, meets home appliance safety standards.

2. Building materials plastics: weather resistant+long-lasting flame retardant

PVC flame-retardant cable conduit:

Formula: PVC resin+40% aluminum hydroxide+10% calcium carbonate+3% calcium zinc stabilizer;

Effect: Oxygen index ≥ 28%, non combustible level B1, strong weather resistance, suitable for pre embedded building scenarios.

PE flame retardant geomembrane:

Formula: PE resin+30% magnesium hydroxide+5% nitrogen based flame retardant+0.2% light stabilizer;

Effect: UL94 V-1 level, low smoke and non-toxic, suitable for fire prevention scenarios such as landfills and tunnels.

3. Automotive plastics: flame retardant+lightweight

PP car door panel:

Formula: PP resin+20% expansion flame retardant+10% talc powder+0.3% antioxidant;

Effect: UL94 V-0 grade, impact strength retention rate>80%, lightweight and low smoke, in line with automotive interior safety standards.

PC/ABS car bumper:

Formula: PC/ABS alloy+15% halogen-free phosphorus flame retardant+0.5% compatibilizer;

Effect: UL94 V-0 grade, good impact resistance, no toxic gas release during combustion, suitable for external fire prevention needs of automobiles.

4. Plastic for wires and cables: flame retardant+temperature resistant

PE flame retardant wire sheath:

Formula: PE resin+25% magnesium hydroxide+8% nitrogen phosphorus compound flame retardant+0.2% antioxidant;

Effect: The bundled combustion test meets the standard, with an oxygen index of ≥ 30% and a temperature resistance of 70 ℃, suitable for household and industrial wiring.

PVC flame-retardant cable material:

Formula: PVC resin+15% chlorinated paraffin+5% antimony trioxide+2% calcium zinc stabilizer;

Effect: Flame retardant grade B, high mechanical strength, low cost, widely used in low-voltage cables.

4、 Application Challenges and Development Trends

1. Existing challenges

High addition of halogen-free flame retardants can easily lead to a decrease in the mechanical properties of plastics;

Some flame retardants (such as halogenated compounds) have insufficient environmental friendliness and are limited in markets such as the European Union;

The balance between flame retardancy and processability is difficult, and some flame retardants affect the flowability of plastic melts.

2. Development Trends

Efficient halogen-free: Develop nanoscale, compound halogen-free flame retardants, reduce the addition amount (from 20% to below 10%), and balance performance and environmental protection;

Multi functional integration: Develop "flame retardant+antioxidant+weather resistant" composite additives, simplify formulas, such as flame retardant smoke suppression integrated additives;

Biobased flame retardants: made from plant extracts such as starch and lignin derivatives, non-toxic and biodegradable, suitable for environmentally friendly plastic products;

Reactive upgrade: Develop highly active reactive flame retardants to enhance their bonding stability with plastics and adapt to high-end engineering plastics.

5、 Summary: Flame retardants - the "firewall" for plastic safety

From the fire protection of electronic devices, to the flame retardant requirements of building materials, to the safety standards of automotive interiors, flame retardants block combustion from multiple dimensions, building a solid defense line for the safe use of plastic products. It is not only a "safety additive", but also directly determines the application boundary of plastic products (such as high-risk scenarios in electronics, automobiles, construction, etc.). In the future, with breakthroughs in halogen-free, high-efficiency, and green technologies, flame retardants will further promote the development of the plastic industry towards safety, environmental protection, and high-end, providing safety support for more plastic applications in various scenarios.