A new nanoscale catalysis-based flame retardant system was developed and integrated into a polypropylene polymer matrix in a research paper published in the journal Materials Letters. This study offered a unique joint catalyzed carbonization technique that combines the advantages of nanoscale flame retardant technologies with catalyzed carbonization.
Study: An innovative binary nanocatalytic flame retardant system to improve the fire safety performance of polypropylene. Image credit: prapann / Shutterstock.com
Increased flame retardancy of polypropylene polymer
The polypropylene (PP) polymer burns completely without leaving any apparent carbonization. The carbon atoms of the polypropylene primary chains are burned to form gaseous chemicals such as carbon dioxide and carbon monoxide.
As a result, if the C atoms become catalytically trapped in the form of carbon, the combustion of the polypropylene slows down, resulting in a slower rate of heat discharge. As a result, catalyzed carbonization has emerged as a new method of flame retardancy.
The catalyzed carbonization impact of typical transition metals on polyolefin, on the other hand, is only marginally acceptable. Therefore, establishing a particularly effective nanoscale catalyzed carbonization and flame retardant technology is critical to improving flame retardancy in polymers.
Improve catalytic carbonization through the use of solid acids
Various solid acids have been used, such as organically modified clay or zeolite, along with carbonization catalysts. These combined catalysts have been successful in increasing the production of polymer coal.
The role of graphene
Graphene has received a lot of interest in the flame retardant industry due to its 2D shape. It has many binding points for immobilizing foreign nanoparticles (NPs).
Graphene is widely recognized for its sheet structure and highly dispersed graphene contributes to the physical barrier, causing slower heat loss. Reduced graphene oxide (RGO) nanofilms are coated with acid-stained phosphomolybdic acid (PMoA) NPs.
RGO-PMoA acts as a pyrolytic catalyst for PP. RGO-PMoA proton acid sites are involved in the main chains of PP, promoting the aromatization and dehydrogenation of PP degradation products.
Thus, once a small amount of RGO-PMoA is added, additional light hydrocarbons (HC) and additional aromatics are produced. RGO-Ni dehydrogenates and reassembles these tiny, aromatic molecules to generate additional carbonization layers. Organic decomposition chemicals with a smaller number of carbon and aromatic components are more likely to promote graphic carbon formation.
What was the research methodology?
In this study, a new system of catalyzed carbonization and flame retardant was devised from the decorated surface of reduced graphene oxide (RGO). The impact on the PP’s incendiary behavior was then investigated. The mechanics of catalytic carbonization and flame resistance were shown.
The polypropylene polymer compound containing 1% RGO-Ni and 1% RGO-PMoA was found to have the highest carbon residue and the most flame retardant characteristic. The optimal ratio of RGO-Ni and RGO-PMoA affects catalyzed carbonization and flame retardancy.
How does the carbonization process contribute to flame retardancy?
Transition metals with catalyzed carbonization properties include nickel, iron, and cobalt. However, the solitary element of transition metals is not conducive to coal production. Graphene nanofilms provide microscale reactors and carbonization templates with barrier effects.
Well-distributed graphene, which offers suitable configurations for catalyzed carbonization, slows the discharge of polypropylene gas degradation products. Instead of completely burning the gaseous components without leaving any residue, the flammable polypropylene chains are catalytically carbonized in the thermally stabilized, non-combustible carbon residue.
As a result of the barrier effects on heat and mass transfers, the generated layer of carbon that coats the surface inhibits the burning of the inner components. As a result, RGO-PMoA complements RGO-Ni to increase the flame retardancy of polypropylene.
Highlights of the study
The surface properties of the reduced graphene oxide nanofilms were altered by the addition of NPs of Ni and PMoA. The chemical composition, content and structure were thoroughly investigated. PMoA NPs were bonded to the RGO surface by electrostatic contact. These graphene-based nanoparticles were evenly distributed throughout the polypropylene matrix.
In polypropylene, the hybrid catalyst (RGO-PMoA: RGO-Ni = 1: 1) showed exceptional catalyzed carbonization and flame retardant properties. Due to its acidic nature of protons, RGO-PMoA catalytically decomposed polypropylene into more aromatic and finer molecules, which were susceptible to RGO-Ni-catalyzed carbonization.
The properties of this hybrid catalyst serve as a reference for the development of high-performance polymeric nanocomposites with exceptional flame retardancy and minimal doping of nanofarts.
Reference
Wang, S. and Zhang, Y. (2022). An innovative binary nanocatalytic flame retardant system to improve the fire safety performance of polypropylene. Materials Letters. Available at: https://doi.org/10.1016/j.matlet.2022.132663
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