Properties and Thermal Decomposition of SBS Flame Retarded with Phosphorus- and Nitrogen- Containing Flame Retardants

Abstract

Flame retardant and mechanical properties of ammonium polyphosphate (APP), melamine phosphate (MP) and their combination with dipentaerythritol (DPER) in styrene-butadiene-styrene rubber (SBS) were studied. The results indicate that MP is more effective in raising limiting oxygen index (LOI) in SBS than APP. When DPER is incorporated into the SBS/APP and SBS/MP composites, a great improvement in flame retardancy of the composites is observed. Moreover, thermal decomposition and mechanical properties of the SBS composites were investigated. Introduction Styrene-butadiene-styrene rubber (SBS) is an important rubber, which is widely used as wires and cables, conveying belts, and tires, and so on. However, SBS is very flammable, and flame retardation is needed in some applications. Nowadays, it is usually flame retarded with halogen-containing compounds or their combination with antimony oxide. Nevertheless, these halogen-containing compounds on heating or in fires can produce a lot of smoke and toxic gases. Therefore, halogen-free flame retardation of SBS products has aroused a great attention. Halogen-free flame retardants used in rubbers include metal hydroxides [1,2], phosphorus and nitrogen compounds [3,4], etc. Nowadays, phosphorusand nitrogen-containing compounds such as ammonium polyphosphate (APP) and melamine phosphate (MP) are promising flame retardants. However, incorporation of the above compounds alone is usually difficult to meet strict flame retardancy requirement of the rubber products (e.g. conveying belts). In recent years, intumescent flame retardants (IFR) have been the focus of flame retardancy of polymers. The IFR system is composed of three components, i.e. an acid source (e.g. APP, MP), a carbon source, such as pentaerythritol (PER) and starch, and a blowing agent, e.g. melamine (MEL) [5,6]. There are also some publications on the application of IFRs in rubbers. For example, the effect of metallic oxides on flame retardancy and thermal stability of styrene butadiene rubber (SBR) composites based on ammonium polyphosphate (APP) and pentaerythritol (PER) were studied [7]. Wang, et al. investigated flame retardation of natural rubber using APP, microencapsulated APP and some synergists (i.e. 4A zeolite) [8,9]. The aim of this paper was to study flammability, mechanical properties and thermal decomposition of intumescent flame retarded SBS.