Terminology

We have tried to make the web site an “easy reading guide to flame retardancy” and in so doing, tried to avoid the use of technical terms.

However, there are instances where their use is required. There follows a brief explanation of some terms that are likely to be encountered within the site.

TEST METHODS: These describe the equipment to be used and the procedure to be followed. They also describe sample preparation (dimensions), conditioning and any cleansing procedures needed prior to testing.

SPECIFICATIONS: A specification will indicate a method of test to be used and will describe the performance requirements which should be attained by a test sample having followed the procedures described in the test method.

IGNITION SOURCES: These are the means by which an attempt is made to instigate combustion in a test sample. Ignition sources vary according to the test method and include flames (such as gas flames and burning wooden structures (cribs)) and smouldering sources such as cigarettes.

CALORIFIC OUTPUT: Within the context of this account of textile flammability, this is the amount of heat given out by a burning material.

COMPOSITES: A composite refers to a group of test components which constitute the “test specimen” for a test procedure. Many of the tests pertinent to upholstered items of furniture are composite tests, i.e. filling material plus cover fabric. The test results will relate only to that particular combination of components and the certification issued by the test authority will reflect this.

NON-COMPOSITES: This is where a fabric or material is tested in isolation, i.e. the test assesses the ignitability of the fabric alone without any influence from other items which may be included in a finished furnishing item. Curtain testing would be an example of non-composite procedure.

STATUTORY INSTRUMENT: This is a legislative document. It contains regulations which carry the force of law. Within the context of textiles used in furnishings discussed throughout this site, the term will refer to “Consumer Protection, The Furniture and Furnishings (Fire) (Safety) Regulations 1988” and the amendments which followed in 1989 and 1993. A section covering UK domestic furniture fire safety legislation can be found here.

STANDARD FOAM: This is a type of non-flame retardant polyurethane foam specified in the statutory instrument. It is not available as a legal filling material for upholstered furniture and is supplied for testing purposes only. The statutory instrument defines the foam as “a non-fire retardant polyurethane foam corresponding to the specification set out in BS3379 Type B Hardness grade 130 and of a density of 20 – 22 kg per cubic metre”.

CMHR FOAM: This is a melamine based combustion modified high resilience foam. This represents the major class of foam filling material used in upholstered furniture within the United Kingdom.

SCHEDULE 3 INTERLINER: This is a fabric which complies with the specification given in schedule 3 of the statutory instrument. If the fabric is flame retarded it must be subjected to a thirty minute water soak described in BS5651 prior to testing. The schedule 3 specification requires the fabric is tested between “standard foam” and a specified polyester cover fabric (details in the statutory instrument). The test method specified in the statutory instrument is BS5852:Part 2:1982:ignition source 5. The pass/fail criteria are specified in clause 4 of BS5852:Part 2:1982.

 

SMOULDERING: The combustion of a material with or without the emission of light. Smoke is usually produced and an increase in temperature occurs but a flame is not evident.

PROGRESSIVE SMOULDERING: Smouldering that is self-propagating, i.e. independent of the ignition source.

FLAMMABILITY: The ability of a material or product to burn with a flame under specified conditions.

IGNITABILITY: A measure of the ease with which a material, product or component can be ignited so as to flame or progressively smoulder.

FLAMING: Undergoing combustion in the gaseous phase with the emission of light and heat.

NATURAL FIBRES: These are fibres derived from the use of materials which occur within nature, i.e. have not been modified or synthesised by man. Examples would be cotton (derived from plant cellulose) or wool (a protein fibre derived from the fleece of sheep).

MAN MADE FIBRES: These are fibres which do not occur in nature. They may be derived from materials which occur in nature but during the manufacturing process they are chemically transformed into a new material. For example viscose, although derived from cellulose, is chemically modified during the production and spinning of the fibre and is therefore a man-made material and is not considered a natural fibre.

POLYMER: A high molecular weight organic compound, natural or synthetic, whose structure can be represented by a repeated small unit, the monomer. Synthetic polymers are formed by addition or condensation polymerization of monomers. If two or more different monomers are involved, a copolymer is obtained. Some polymers are elastomers, some plastics.

MONOMER: A molecule that can join with other molecules to form a large molecule called a polymer. A monomer is the smallest repeating unit in a polymer chain.

ATOM: The basic component of all matter. The atom is the smallest particle of an element that has all of the chemical properties of that element. Atoms consist of a nucleus of protons and neutrons surrounded by electrons.

MOLECULE: The smallest particle of a compound that has all the chemical properties of that compound. Molecules are made up of two or more atoms, either of the same element or of two or more different elements

PYROLYSIS: From pyro- meaning heat and -lysis meaning break down. It is the process whereby a material is decomposed by the action of heat.

COPOLYMER: A polymer molecule incorporating two or more different types of monomer.

HYDROGEN BOND: All chemical bonds are essentially the interaction of the electrons of constituent atoms within a molecule. It is possible for the atom at one end of a bond to have a net positive or net negative charge compared with the atom at the other end (due to unequal sharing of negatively charged electrons which compose the bond). Molecules containing hydrogen frequently have a net positive charge associated with the hydrogen. Many atoms in molecules frequently have negative charges associated with them e.g. oxygen. A hydrogen bond is a weak bond which develops between the positive charge on the hydrogen of one molecule and the negative charge on an atom of another molecule. This weak bond can attract and bind two individual molecules together.

HydrogenBondImage

Example of hydrogen bonding between polymer chains in a protein fibre such as wool.