Fiberglass reinforced plastic (FRP), a new composite material, has been widely used in construction, shipbuilding, transportation, chemical engineering, and other fields due to its excellent mechanical properties, corrosion resistance, and insulation properties. In practical use, the flame retardancy of FRP has become a key safety consideration. With increasing fire safety requirements, the flame retardancy of FRP and related industry standards have received increasing attention.

I. Flame Retardancy of FRP Sheets

1. Composition and Flame Retardancy Mechanism of FRP

FRP (glass fiber reinforced plastic) consists of glass fiber and resin (such as unsaturated polyester or epoxy resin). While glass fiber itself has strong high-temperature resistance, the resin is the key factor affecting its flame retardancy. The flame retardancy of the resin depends primarily on its chemical composition and the addition of flame retardants. Typically, flame retardants are added to resins to enhance their fire resistance. These flame retardants decompose under the influence of a fire source, releasing cooling gases that effectively slow the spread of flames.

2. Specific manifestations of flame retardant properties

The flame retardant properties of FRP sheets are manifested in their ability to delay the combustion process in high-temperature environments and reduce the speed of flame spread. Depending on different application requirements, the flame retardant grades of FRP vary. Generally speaking, FRP sheets with better flame retardant properties can provide longer time for evacuation and self-rescue when a fire occurs, which is crucial for the safety of public buildings, ships and vehicles.

3. Common flame retardant treatment methods

In order to improve the flame retardant properties of FRP sheets, common treatment methods include:

(1) Adding flame retardants: By adding inorganic or organic flame retardants, such as ammonium chloride, phosphate, etc., the flame retardancy of the resin is improved.

(2) Surface coating of flame retardant paint: Applying a layer of flame retardant paint on the surface of the FRP sheet can effectively prevent the spread of flames.

(3) Modified resin: Using a special resin formula to improve the flame retardant properties of FRP. For example, using resins containing elements such as halogens and phosphorus.

II. Industry Standards for FRP Sheets

Flame retardant performance standards for FRP sheets are primarily established by national and industry organizations to ensure their safety in various applications. The following are several key standards related to the flame retardancy of FRP sheets:

(I) Chinese Flame Retardant Standards

GB 8624-2012, "Classification of Combustion Behavior of Building Materials and Products": categorizes the combustion performance of materials into A (non-combustible), B1 (difficult to burn), B2 (combustible), and B3 (combustible).

GB/T 2408-2021, "Determination of Combustion Behavior of Plastics"

GB/T 4189-2022, "Plastics - Combustion Behavior - Medium-Sized Fire Tests on Fiber-Reinforced Polymer Composites"

GB/T 5169, based on IEC standards, is used for fire hazard testing of electrical and electronic products.

GB 8410-2006 "Combustion Characteristics of Automotive Interior Materials"

(II) European Flame Retardant Standards

EN 13501-1 "Classification of Burning Behavior of Building Products": Adopts the Euroclass classification (A1-F), taking into account heat of combustion, smoke, and dripping.

EN 45545-2013

(III) US Flame Retardant Standards

ASTM E84 "Surface Burning Characteristics Test": Determines the Flame Spread Index (FSI) and Smoke Index (SDI).

NFPA 701 "Test Methods for Flame Retardancy of Textiles and Films": Applicable to curtains, drapes, etc.

UL 94 "Test Methods for Flammability of Plastic Materials": Classifies them into HB, V-0/V-1/V-2 grades, evaluating vertical/horizontal burning performance.

UL 746: Evaluates the long-term flame resistance of plastics.

According to GB 8624-2012, the current mainstream flame-retardant products in the domestic FRP sheet market are B1 and B2 grades. The specific classification criteria are as follows:

Runsing's flame-retardant FRP products meet the ASTM E84 Class A standard, significantly exceeding Class B1 flame retardancy. Product testing meets both ASTM E84 and the national standard GB/T 4189-2022, "Plastics—Fire Behavior—Medium-Sized Fire Resistance Tests for Fiber-Reinforced Polymer Composites" (Runsing participated in the development of this national standard).​

III. The Importance of Flame Retardancy in Practical Applications of FRP Sheets​

The flame retardancy of FRP sheets is crucial in many fields, particularly in the following applications:​

Construction: Since FRP sheets are widely used in exterior walls, interiors, and ceilings, ensuring their flame retardancy meets relevant standards is fundamental to building safety.​

Marine: FRP materials used in ship interiors must provide sufficient flame retardancy in the event of a fire to ensure the safe evacuation of crew members.​

Transportation: In transportation, including aviation, railways, and subways, the flame retardancy of FRP sheets can effectively prevent the spread of fire and ensure passenger safety.​