The search for more resistant plastics that release less smoke when exposed to fire is the focus of two research projects being conducted at Brazilian universities in partnership with Braskem, a huge Brazilian petrochemical company based in the city of Triunfo, State of Rio Grande do Sul. The objective of one of the research projects, developed at the Federal University of Rio Grande do Sul (UFRGS), was to transform polypropylene – used in cookie packaging, carpets, bottles and automobile parts – into a material with higher resistance to impact, yet maintaining the same structural qualities. “We added materials like rubber and clay to the thermoplastic resin, controlling the structure on a nanometric scale,” explains professor Ricardo Oliveira, from the Chemistry Institute of the UFRGS. “This control allowed us to distribute the clay on the interface between the rubber and the polypropylene, which resulted in significant gains in terms of impact resistance without jeopardizing the material’s toughness.” The decision to use clay was due to its chemical properties, which made it possible to separate the clay’s silicate layers, where the polymer chains are intertwined.
The research study, which began in 2007 as the topic of the doctorate thesis of student Patrícia da Silva, resulted in the filing of a patent and a scientific article which was published this year. “Our interest now is focused on the application of the same structure of polypropylene to other materials, such as polyester and polyethylene,” says Oliveira. He points out that the university’s partnership with Braskem involves approximately 10 projects. “These are two major lines of research involving nano technology and using resources from renewable sources.”
Another research project, conducted by Antônio Rodolfo Junior during his doctorate studies at the School of Chemical Engineering of the State University of Campinas (Unicamp), under the advice of professor Lucia Helena Innocentini Mei, evaluated the behavior of PVC (vinyl polychlorate) nano compounds mixed into clay and metal oxides to delay the release of heat and the emission of smoke in case of the material’s exposure to fire. The importance of this research project is due to the fact that this thermoplastic resin – the name derives from the fact that this resin softens when it is heated, which allows it to be merged and shaped countless times – can be used for many applications, ranging from medical-hospital materials and food packaging to products used in civil construction.
PVC is the only plastic material that doesn’t derive entirely from oil; ethane is the only oil by-product used in this plastic, which is composed of 43% ethane and 57% chlorine, which derives from sodium chloride. The existence of chlorine in the chemical structure makes the resulting product less flammable, but when it goes into combustion, this element is the main cause of the thick, dark smoke caused by the combustion. The research study has shown that adding oxides produces good results. “In the samples we analyzed, we observed that the smoke coming from the PVC compounds was controlled through the addition of metal oxides such as zinc, copper and molybdenum,” says Rodolfo, manager of PVC application engineering at Braskem.
DA SILVA, P.A.; JACOBI, M.M. et al. SBS nanocomposites as toughening agent for polypropylene. Polymer Bulletin. v. 64, v. 3, p. 245-57. Feb. 2010.
RODOLFO, A.; MEI, L.H.I. Poly(vinyl chloride) /metallic oxides/organically modified motmorillonite nanocomposites: fire and smoke behavior. Journal of Applied Polymer Science. v. 116, n. 2, p. 946-58. 15 Apr. 2010.