Selecting the right Flame-Retardant Polycarbonate
2026-06-30
Foreword
Unlike polypropylene (PP) and polyethylene (PE), conventional polycarbonate (PC) materials have an aromatic molecular structure and a high charring capacity, which gives them inherent flame-retardant properties. Under normal circumstances, PC resin can achieve a UL 94 HB flame-retardant rating.
However, in electronic and electrical components, automotive applications, and battery applications, conventional polycarbonate materials cannot meet the high flame-retardancy requirements. Therefore, manufacturers add specialized flame retardants to achieve polycarbonate with a higher flame-retardancy rating, such as UL 94 V-0.
This article will provide a detailed overview of the differences in the methods used to produce flame-retardant polycarbonate (FR PC), as well as the advantages, disadvantages, and application scenarios of each flame-retardant system.
Major Flame-Retardant Systems for PC resin
Currently, the most common flame-retardant systems for flame-retardant PC resin on the market include:
- Halogen Flame-Retardant PC
- Phosphorus-based Halogen-Free Flame-Retardant PC
- Sulfate-Based Flame-Retardant PC
- Siloxane PC
- Inorganic Mineral-Based Flame Retardant Systems
1. Halogen flame-retardant polycarbonate
1.1 Principles of Flame Retardancy
Polycarbonates containing halogen-based flame retardant systems (primarily bromine flame retardant PC) are currently one of the most common types of flame-retardant polycarbonates. The mechanism by which they achieve flame retardancy is as follows:
·Bromine-based flame retardants decompose upon heating to release Br radicals
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·These radicals capture the H and OH radicals generated during combustion
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·Thereby interrupting the chain reaction of combustion.
1.2 Halogen flame retardant PC advantage and disadvantage
| Advantages | Disadvantages |
|---|---|
| Low addition rate (5%–10%) | Combustion produces corrosive hydrogen halide gases |
| Highly effective flame retardancy | A lot of smoke. |
| Minimal effect on the flowability of the resin | Poor environmental performance; subject to regulatory restrictions in Europe and the United States |
| Low cost | Not applicable to electronic and electrical products |
| The technology is very mature |
1.3 Main application scenarios:
Since halogen-based flame-retardant PC resin emits irritating fumes during manufacturing and combustion, which seriously affect human health and cause severe corrosion to the metal components of electronic products, it is rarely used; however, due to its low cost, it is still used in some low-cost applications where flame-retardant performance is not a high priority.
Sabic Lexan 940A FR PC is a brominated flame retardant polycarbonate that achieves UL 94 V0 flame-retardant performance at a test thickness of 3 mm.
Since Sabic FR 940A offers excellent flame retardancy even at relatively thin wall thicknesses, and has a melt volume rate (300°C, 1.2 kg) of 9.5 cm³/10 min—which represents a moderate flow rate—it is suitable for thin-walled flame-retardant products.
2. Phosphorus halogen-free flame-retardant polycarbonate
2.1 Principles of Flame Retardancy
Phosphorus-based flame retardant systems are rarely used in pure PC resin because they compromise the high transparency of PC; they are more commonly found in PC/ABS alloys. The mechanism by which they achieve flame retardancy is as follows:
·Phosphorus-based components accelerate the carbonization of PC, forming a dense carbon layer
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·The carbon layer blocks heat transfer and blocks oxygen
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·Known release of flammable gas.
Common flame retardant components in phosphorus-based halogen-free flame-retardant PC resins include: phosphate esters, phosphite esters, phosphonates, and polymeric phosphorus-based flame retardants.
2.2 Phosphorus flame retardant PC advantage and disadvantage
| Advantages | Disadvantages |
|---|---|
| Does not contain chlorine or bromine | More expensive than halogen-free flame-retardant PC resin. |
| Low levels of corrosive gases | Some phosphorus-based flame retardants have only moderate heat resistance. |
| Excellent environmental performance | Reduced transparency of PC resin |
| Transparent, flame-retardant PC resin |
2.3 Main application scenarios:
Because phosphorus based flame-retardant polycarbonate offers low transparency and releases fewer corrosive substances, it is commonly used in high-end electronic products, such as cell phones, laptops, tablets, routers, batteries, medical electronic devices, and home appliance housings.
Since phosphorus-based flame retardants have a significant impact on the transparency of transparent polycarbonate, they are generally used in materials such as PC/ABS, where transparency requirements are less stringent.
Bayblend FR3010 flame-retardant PC/ABS alloy uses triphenylphosphate as a flame retardant (a type of phosphorus-based flame retardant). Because this flame retardant significantly affects the transparency of PC, the material is available only in opaque colors such as white and black; transparent versions are not available.
Bayblend FR3010 PC/ABS achieves UL 94 V0 flame retardancy even at a test thickness of 1.5 mm, making it particularly suitable for the production of thin-walled and complex products that require high-performance flame retardancy.
3. Sulfate flame-retardant polycarbonate
3.1 Principles of Flame Retardancy
Polycarbonates with sulfonic acid-based flame retardant systems—which are also a type of halogen free flame retardant PC—account for a significant share of the current FR PC market. The mechanism by which they achieve flame retardancy is as follows:
·Alkali metal ions in sulfonate flame retardants catalyze the restructuring, cross-linking, and ester exchange of PC resin molecules
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·Accelerate the formation of a dense carbon layer
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·The charcoal layer acts as a barrier, causing the fire to go out
3.2 Sulfate flame retardant PC advantage and disadvantage
| Advantages | Disadvantages |
|---|---|
| Halogen-free flame retardant | Not suitable for large-area, thick-walled products |
| Highly effective flame retardancy with low dosage | Yellowing is likely to occur during processing. |
| High Transparency | The amount of smoke produced cannot be reduced |
| Minimal impact on mechanical properties |
3.3 Main application scenarios:
Because Sulfate-based flame retardants have minimal impact on the performance and transparency of polycarbonate, they are suitable for applications such as automotive lamp covers, explosion-proof devices, optical lenses, and instrument panels.
Sabic Lexan 945A halogen-free flame-retardant PC resin uses perfluorobutane sulfonate as a flame retardant. Since this flame retardant achieves highly effective flame retardancy at an addition level of less than 1%, the PC resin retains its high transparency.
In addition, Sabic Lexan 945A contains a blend of siloxane and phosphate ester synergists, which effectively enhance its resistance to dripping and its ability to form a char layer at high temperatures. It achieves UL 94 V-0 flame retardancy at a test thickness of 3 mm and still demonstrates good flame retardancy in thin-walled products.
4. Siloxane Polycarbonate
4.1 Principles of Flame Retardancy
Siloxane flame-retardant PC is also a common halogen free flame-retardant PC resin. Because it contains siloxane components, it is less likely to yellow during high-temperature processing compared to other transparent flame-retardant PC resins; however, its flame-retardant properties are relatively poor, so it generally needs to be used in combination with other flame retardants. The mechanism by which they achieve flame retardancy is as follows:
·When heated, siloxanes improve the thermal stability of PC and promote the formation of a high-temperature carbon layer.
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·The carbon layer combines with silicon to form a silicon-rich protective layer
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·Reduce the risk of PC resin sagging and slow the spread of flames
4.2 Siloxane PC advantage and disadvantage
| Advantages | Disadvantages |
|---|---|
| Excellent environmental performance | High cost, generally used only in high-end electronic products. |
| Can improve the flexibility of PC resin | When used alone, its flame-retardant efficiency is low, so it is often used in combination with other flame retardants. |
| Low smoke emission | |
| Improve Weather Resistance |
Since the flame-retardant effect of siloxane PC resin is achieved solely through physical shielding—which reduces the risk of flame droplet formation—its flame-retardant efficiency is relatively limited. It is generally not used on its own but is often combined with phosphorus-based flame retardants to balance the flame-retardant, mechanical, and processing properties of the PC resin.
4.3 Main application scenarios:
Because phosphorus-based flame-retardant polycarbonate offers high transparency and releases fewer corrosive substances, it is commonly used in high-end electronic products, such as cell phones, laptops, tablets, routers, batteries, medical electronic devices, and home appliance housings.
Comparison of the Properties of FR PC resin
|
Flame-retardant system
|
Flame-retardant efficiency
|
Environmental Friendliness
|
Maintaining the Mechanical Properties of PC |
Cost
|
Transparency
|
Market Applications
|
|---|---|---|---|---|---|---|
| Halogenated PC resin | ★★★★★ | ★ | ★★ | ★★★★★ | Mederate | Moderate; environmental issues account for a smaller share |
| Phosphorus-based, halogen-free PC resin | ★★★★ | ★★★ | ★★★ | ★★★ | Low | Commonly used in PC/ABS alloys |
| Sulfate PC resin | ★★★★★ | ★★★★★ | ★★★★★ | ★★ | High | Flagship Products |
| Siloxane PC resin | ★★ | ★★★★★ | ★★★★★ | ★★ | High | High-End Products |
Since different flame retardants perform differently when applied to PC, and in order to preserve PC’s inherent properties of high transparency and impact resistance, flame retardancy in FR PC resin is generally achieved through the synergistic use of multiple flame retardants rather than a single flame retardant component. For example, the commonly used Sabic 945A FR PC employs a combination of sulfonates, silicone, and stabilizers.
References and Notes
- Sabic,"Sabic Lexan flame retardan (FR) PC resin ",Saudi basic industries company, 02/07/2026
- 环球聚氨酯网,"如何实现聚碳酸酯（PC）阻燃又透明？",中国复合材料学会, 02/07/2026
- Teijin resin,"Brominated Flame Retardant FG Series",TEIJIN LIMITED, 02/07/2026
- Idemitsu,"Siloxane copolymer grade (TARFLON NEO™)", Idemitsu Kosan Co.,Ltd, 02/07/2026
- Covestro,"透明阻燃聚碳酸酯解决方案", Covestro AG, 02/07/2026
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