I. Are Rubber and Plastic Materials Inherently Flame-Retardant?

Rubber and plastic insulation materials (usually referring to rubber and plastic foam insulation materials) are organic polymer materials. From a material property perspective:

❌ Not a naturally non-combustible material

⚠️ Untreated rubber and plastic materials are flammable

✅ Flame-retardant or fire-resistant properties can be achieved through formulation modification

Therefore, the flame-retardant properties of rubber and plastic materials are not inherent properties, but are achieved through flame-retardant formulation design.

II. The Principle of Achieving Flame-Retardant Properties in Rubber and Plastic Materials

Rubber and plastic insulation materials typically improve their flame retardancy through the following methods:

1. Adding Flame Retardants

Adding the following to the rubber and plastic foam system:

Halogen-free flame retardants

Phosphorus-based or nitrogen-based flame retardant systems

This causes the material to form a char layer when exposed to fire, inhibiting flame spread.

2. Closed-Cell Structure Inhibits Combustion

Rubber and plastic have a highly closed-cell structure:

Oxygen does not easily enter the interior

Flame propagation speed is limited

This helps reduce the risk of combustion spread. 3. Flame-retardant Surface Coating (Some Products)

Some rubber and plastic sheets have an added flame-retardant surface layer or a fireproof layer to improve overall fire resistance.

III. Common Fire Ratings of Rubber and Plastic Materials

In engineering and bidding processes, determining whether rubber and plastic materials are flame-retardant requires looking at the fire rating, not just the words "flame-retardant."

Common Domestic Standards (GB 8624)

| Fire Rating | Flame Retardant | Description |

| ---- | ----- | --------- |

| B1 Grade | ✅ Yes | Flame-retardant material, self-extinguishing upon removal of flame |

| B2 Grade | ⚠️ Limited | Combustible material |

| B3 Grade | ❌ No | Flammable material |

Most commonly used rubber and plastic insulation materials in engineering projects are B1 grade flame-retardant rubber and plastic.

Common International Standards

EN 13501-1 (European Standard)

ASTM E84 (American Standard, focusing on flame spread index)

IV. Performance of Flame Retardant Rubber and Plastics in Fire

Qualified flame-retardant rubber and plastic materials typically possess the following characteristics:

* Do not support combustion when exposed to open flame

* Self-extinguishing after the flame source is removed

* Relatively controllable smoke density (depending on the formulation)

❌ Not a non-combustible material and cannot replace rock wool or glass wool

This is why inorganic non-combustible insulation materials are often preferred in smoke control systems or areas with high fire protection requirements.

V. Engineering Applicability of Flame Retardant Properties of Rubber and Plastic Insulation Materials

Suitable Application Scenarios

Central Air Conditioning Duct Insulation

Chiller Water Pipes, Condensate Pipes

HVAC Systems in Residential and Commercial Buildings

Areas requiring a B1 fire rating

Scenarios Not Recommended for Solo Use

Fire Barriers

Smoke Exhaust Duct Systems

Parts requiring a Class A non-combustible rating

VI. Rubber and Plastic vs. Inorganic Insulation Materials (Fire Resistance Comparison)

| Material | Flame Retardant | Maximum Fire Rating |

| ------ | ------ | ------- |

| Rubber and Plastic Insulation Materials | ✅ Flame Retardant | Class B1 |

| Glass Wool | ✅ Naturally Non-combustible | Class A |

| Rock Wool | ✅ Naturally Non-combustible | Class A |

| Aerogel Felt | ✅ Mostly Non-combustible | Class A (depending on substrate) |

Rubber and plastic insulation materials can acquire flame retardant properties through formula modification, commonly as... Class B1 flame-retardant materials. Their flame-retardant properties stem from the flame-retardant system design and closed-cell structure; however, the material itself is still an organic combustible material and cannot be equated with inorganic non-combustible insulation materials. In practical engineering applications, the appropriate type should be selected based on the fire resistance rating requirements.