Flame retardant coatings by atmospheric plasma and layer-by-layer processes

Context

Organic polymers are intrinsically flammable and therefore any commercial polymer needs to be modified to prevent or delay the outbreak of fire. This is usually done by adding of flame retardant (FR) fillers into the polymer.

Polymers are generally treated in bulk by incorporating significant amounts of various types of these fillers, such as halogen, phosphorus, inorganic and nitrogen compounds. Even if the effects are beneficial for fire retardancy, the consequences include higher cost, lower processability and degradation of the mechanical properties.

Overview

LIST offers an alternative and innovative way to provide flame retardant properties to polymers by applying a flame retardant coating, leaving the bulk material free of flame retardant fillers. Two surface treatments have been developed:

• Layer-by-layer: this coating technique allows good control of the structure and chemistry of the coating, making it possible to incorporate nanoparticles such as nanoclays in the coating or adding flame retardant macromolecules such as polyphosphates as a building block of the coating.
• Coating deposition by plasma: This technique uses atmospheric pressure plasma, which has become a promising technology, due to its ability to be operated in-line.

Benefits

The two methods provide a number of advantages over traditional flame retardant fillers:

• the bulk of the material remains unmodified
• efficient surface treatment
• good control of structure and chemistry of coatings
• lower cost

Potential Applications

These new flame retardant composite materials are applicable in many industrial fields where an improvement of the thermal stability and fire resistance is needed. As an example, the flame retardant coatings may be used in the fields of transportation (cars, trains, planes, etc.), building materials, electrical engineering as well as many other products used in daily life.