Flammability and fire retardancy of leather
Fire protection and leather
Leather exhibits a certain degree of resistance to moderate heat. This is because leather has relatively low thermal conductivity, meaning it does not conduct heat quickly. As a result, it can provide a protective barrier by somewhat insulating against heat for a short period.
Leather is a relatively dense material, making it difficult to ignite. Its dense structure hinders the spread of fire. Additionally, leather typically retains some moisture content, which contributes to its reduced flammability. When exposed to heat, the moisture in leather evaporates, making it harder for the fire to propagate or sustain.
If you hold a lighter to a piece of leather, it may shrink and char but will often not continue to burn. Therefore, it is easier compared to other materials to provide leather with additional flame-retardant properties. Leatherette is much more flammable than genuine leather.
Aircraft leather, leather on ships, trains and buses must meet minimum standards for fire protection. Special demands on flammability also apply in public buildings (hotels, waiting areas, administrative buildings, retirement homes, etc.).
Leather furniture in public areas.
Whether as aircraft seats or in the waiting area, the standards are strict.
A tanner needs to know at the start of the production process if a leather has to meet fire protection standards. The flammability and the formation of smoke also needs to be considered. Various steps in the tannery must be adapted accordingly. The selection and quantity of the retanning agents, the right choice and amount of refatting components and the addition of flame retardants are also important. It has been said in various articles that the chrome content in the leather should be less than 3.5% and that fish oil-based refatting agents are poorer than other refatting agents. Synthetic oils are also referred to as problematic. Leather fibres must not be too loose.
There are a lot of legal regulations and standards, and many countries have their own regulations.
Leather can be tested according to different standards.
Devices for testing the fire protection properties.
The standards for fire protection in leather
The following standards are associated with leather: FAR 25.853 a) and b): For the equipment of airplanes, private jet or sports machines. .
DIN 4102: Classification into classes of flammability.
DIN 4102 part 1 (B2): Materials for use in construction.
DIN 4102 part 15/16 (B1): Reaction of combustible and non-combustible products on fire.
EMPA: Swiss Federal Institute for Materials Testing and Research.
BS 5852 1990 (Great Britain): Definition of a test method in which a specially designed model simulates an armchair.
DIN 54 342 part 1 (= EN 1021-1, cigarette test): Furniture. Evaluation of the flammability of upholstered furniture. Part 1: Ignition source smouldering cigarette (ISO 8 191), EN 1021-1.
EN 1021 - 1/2: 1994: This standard applies throughout the EU and examines the reaction of a substance to a burning cigarette and a butane flame (a simulated match). It replaces a variety of national tests, including DIN 54342 - 1/2 in Germany and BS 5852: 1990 in Great Britain.
EN 1021 - part 1: In part 1 of the test, a burning cigarette is placed in the angle of the test model and is glowed in its entire length. After 60 minutes the fabric should not glow or burn.
EN 1021 - part 2: A 35 mm high butane flame represents a burning match and is also placed in the angle between the backrest and seat of the test model for 15 seconds. After the flame has been removed, the fabric should not start to burn within 2 minutes.
EN 13501 - part 1: Similar to DIN 4102-1. The fire behaviour of building materials for use in construction is tested.
Can leather be made flame retardant after being processed?
Normally such questions or requirements may not arise after a particular leather has been produced. However, this happens when leather has been offered for bidding at auctions without having a certificate or because the leather has already been bought.
First, the tannery (or the leather dealer) should be asked which standards are already met for this type of leather. If no standard has been tested, chances are bad. The lower the requirements for the leather, the quicker a test can reveal if it conforms to basic requirements or not. To test if a leather meets the standard, the leather must be destroyed by heat. According to the present state of the art, there is no treatment method which subsequently changes a non-standard leather according to the standard.
Furthermore, subsequent treatment methods, such as chemical or wet cleaning, washing, painting, printing etc., may adversely affect the fire behaviour. This should be considered or should be excluded for use.
Video about leather and high temperatures