J. Lefebvre

Flexible polyurethane foams: Flammability

Polyurethane flexible foam is a very versatile, high quality cushioning material. By its chemical nature, polyurethane foam is a combustible material. Test methods have been progressively introduced to classify the fire behaviour of foam and legislation based on these tests has been introduced in various countries to ensure that the foam complies with these fire standards. A notable example of this is British Standard 5852 on which the United Kingdom bedding and furniture legislation is based. The influence of formulation variables such as the type and particle size of the filler, the foam density, the air flow (openness) are some of the well documented parameters. Another important variable is the liquid flame retardant (halogenated phosphate type) which is the objective of the present study. This paper provides a basic understanding of foam combustibility based on the British Standard 5852 test method. Dynamic weight loss made with two types of liquid flame retardants with and without melamine is used to provide this understanding. Thermogravimetric analysis and cone calorimeter have been used to support the discussion. In melamine free foams, our study has shown that the decomposition temperature of the liquid flame retardant is a key parameter, which governs the foam combustion. In melamine containing foams, the overall combustion behavior is dependant on the type of liquid flame retardant used. However, intrinsic differences do exist and synergy is seen between melamine and liquid flame retardant under specific conditions. Applying this basic understanding and the actual combustion standards, foam producers can attain flexibility in designing cost effective foam formulations.

Vinyl acetate/butyl acrylate copolymers—part 1: mechanism of degradation

This work deals with the mechanism of degradation of vinyl acetate/butyl acrylate (VA/BA) copolymers varying the VA/BA ratio. It is shown that for higher VA contents, the degradation starts at comparatively lower temperature but a more thermally stable material is formed. The mechanism of degradation of VA/BA copolymers is then compared with PVA and PBA homopolymers. It appears that the fractions of degradation (gases, high boiling products and residue) for VA/BA copolymer is a combination of those of polyvinyl acetate (PVA) and polybutyl acrylate (PBA). However, a slight stabilisation occurs when VA/BA are co-polymerised together compared with a VA and BA combination. Moreover, the comparison of the thermo-oxidative degradation with the pyrolysis demonstrates that the mechanisms are similar at least up to 450 °C.

Effect of Bonding Resins on the Flammability Properties and Thermal Behaviour of Cotton and Cotton/PESFR Woven Fabrics

This study deals with the influence of two binder resins (acrylic and styrene-butadiene resins) on the fire properties and the thermal behaviour of cotton and cotton/flame retardant polyester (PESFR) textiles. Lab-scale fire testings (limiting oxygen index and vertical fire test) have shown that the impregnation of the cotton/polyester fabrics leads to a dramatic loss of fire performance. Therefore, a thermogravimetric study (under oxidative and inert atmospheres) of cotton/polyester blends, impregnated or not impregnated, were carried out to understand the interactions between the fabrics and resins. Data of these thermogravimetric analyses (TGA) were then modelled using Invariant Kinetic Parameters methods to determine the kinetics parameters and the modes of degradation of the impregnated fabrics.