Fire-proof plastic for travel safety Specialised fireproof polypropylene (PP) fittings must be developed with unique properties for the car and aircraft sector. A European project has developed flame-retardant PP that can take the necessary stresses and strains. Industrial Technologies © Thinkstock The PP fittings in cars and aircrafts must be flame retardant to improve survivability. Moreover, smoke and toxic gas emissions must be suppressed which automatically excludes some of the most efficient flame retardants such as brominated compounds. The most promising flame retardant for PP is magnesium hydroxide (MH). Consequently, the EU-funded Flaretpol project aimed to develop the best MH/PP composites with optimal processability and mechanical properties. Use of MH in required concentrations for flame-retarding behaviour adversely affects crucial properties of the PP such as ability to tolerate stress, strain and impact. To overcome this, Flaretpol researchers drew up target properties of the MH/PP composites as a first step and tested resulting materials on cables and car parts. Flaretpol devised various possible chemical routes to achieve their target including direct coupling of MH to tailor-made reactive peroxide oligomers (made up of up to three monomer units). The peroxide element of the oligomer enables potential grafting to modify viscosity properties. Another option was to create a nano-sized polymer layer around the MH while a third course combined the first two only with the use of a treated nanoclay. Overall, compounding oligomers with modified MH microparticles and nanoclay was the favoured route which the team used to produce prototypes. Testing of small kilogramme-sized batches of monomers and reactive oligomers was followed by industrial-level production of cables and car details. The Flaretpol scientists tested the prototypes for processability, mechanical performance and, of course, fire resistance. Recyclability of all materials was also assessed. Potential benefits include novel flame retardants in view of the European ban on halogenated compounds for the vehicle and aircraft industry in particular. Flaretpol success also promises to guarantee an elevated position in the sector for manufacturers of MH/PP composites.