fl ame retardants | Additives In general, hindered amine light stabilisers (HALS)
Figure 1: Phoenix project schematic shows the effect of each type of FR particle and the mechanism to protect plastics from fi re
extrusion and injection equipment, will assure high nanoparticles dispersion in the polymer nanocompos- ites and in the fi nal pieces, thus achieving optimal properties,” according to Phoneix project partners. Begoña Galindo, Technical Coordinator of the Phoenix project at Spanish plastics technology institute Aimplas, says that nanotechnology “allows the replace- ment of hazardous chemicals to produce sustainable fl ame retardants additives based on nano-layered structures produced using innovative green chemical routes. Nano-layered nanoparticles such as metallic nanohydroxides and graphene nanoplatelets are being synthesised and functionalised. The synergic effect of combining different nano-layered nanoparticles is studied by preparing fl ame retardant systems by means of a self-assembly process (Figure 1). “Hollow nanoparticles are produced to allow the encapsulation of organic fl ame retardant aiming to increase their heat resistance during production. The last development of new FR additives is based on modifi ed lignins from renewable sources.” Lignins are modifi ed in order to contain phosphorous functional groups. Nanoparticles are dispersed in thermoplastic polymers by melt compounding.
Fire tests have shown promising results to date, says Galindo. UL94 V-0 classifi cation has been achieved with an additive content of 15% in polyolefi ns. Fire behaviour has been improved in ABS with phosphorylated lignins by decreasing the heat release rate in 58% and reducing the time to ignition in 50%. Further trials are being carried out with ABS and other high temperature polymers.
Polyolefi n solutions The range of applications for polyolefi ns continues to multiply, thanks in part to the abundance of low cost raw materials, according to Adeka. However, since polyolefi ns are combustible materials, the addition of a fl ame retardant is necessary for those applications where fl ame retardance is required. On the other hand, polyolefi ns have poor weatherability and it is necessary to add light stabilisers to inhibit photo-degradation of polyolefi ns for outdoor applications, which the company says can impact on fi re performance.
18 COMPOUNDING WORLD | December 2015
are used to improve the weatherability of polyolefi ns. However, it has been diffi cult to provide polyolefi ns that are fl ame retarded using halogenated systems with good weatherability because HALS is deactivated by hydrogen halide generated during processing by the fl ame retardant. For this reason Adeka has been developing a new halogen-free intumescent fl ame retardant system, the ADK STAB FP-2000 series, for polyolefi ns. It says the new system can depress smoke density and generation of carbon monoxide gas during combustion. “Moreover,” it says, “ADK STAB FP-2000 series offers excellent weatherability by the combina- tion with HALS because of low acidity. This may help expand the scope of the fl ame retarded polyolefi ns.” See Figure 2 for more data. Huber Engineered Materials is also working on functional halogen-free fi re retardant additives (along with ground calcium carbonate fi llers for a variety of applications) and has been building up its fl ame retardant business in recent years. Its 2010 acquisition of Sherwin-Williams’ Kemgard fl ame retardant and smoke suppressant business was followed three years later by that of the specialty hydrate fl ame retardant business from Almatis. This June, Huber acquired Safi re nitrogen and phosphorus halogen-free fi re retardant technology from Floridienne Group and Catena Additives. Safi re products are specialised char-forming additives that Huber says impart high levels of fi re retardance and smoke suppression in engineering plastics and also coatings. The company intends to integrate the technol- ogy within its existing halogen-free portfolio, and rapidly develop a line of commercial products. Producers of cable compounds can gain a perfor- mance advantage from Huber’s expertise in surface
Figure 2: Weatherability of PP-B with FP-2200S in the presence of HALS Source: Adeka
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