Flame Retardant Polypropylenes: A Review

Abstract

Polypropylene (PP) is a commodity plastic known for high rigidity and crystallinity, which is suitable for a wide range of applications. However, high flammability of PP has always been noticed by users as a constraint; therefore, a variety of additives has been examined to make PP flame-retardant. In this work, research papers on the flame retardancy of PP have been comprehensively reviewed, classified in terms of flame retardancy, and evaluated based on the universal dimensionless criterion of Flame Retardancy Index (FRI). The classification of additives of well-known families, i.e., phosphorus-based, nitrogen-based, mineral, carbon-based, bio-based, and hybrid flame retardants composed of two or more additives, was reflected in FRI mirror calculated from cone calorimetry data, whatever heat flux and sample thickness in a given series of samples. PP composites were categorized in terms of flame retardancy performance as Poor, Good, or Excellent cases. It also attempted to correlate other criteria like UL-94 and limiting oxygen index (LOI) with FRI values, giving a broad view of flame retardancy performance of PP composites. The collected data and the conclusions presented in this survey should help researchers working in the field to select the best additives among possibilities for making the PP sufficiently flame-retardant for advanced applications.

Towards Selection Charts for Epoxy Resin, Unsaturated Polyester Resin and Their Fibre-Fabric Composites with Flame Retardants

“…From Figure 8 a and Figure 9 a, it can be depicted that, whatever the FR/polymer system, there is a direct correlation between FRI and LOI values. This finding is in agreement with previous reviews [ 39 , 40 , 41 ]. However, in the case of UL-94 results, there is no specific correlation between FRI and UL-94 results, as it can be seen in Figure 8 b and Figure 9 b.…”

“…These charts will provide a quick selection tool for the production sector to select the needed FR/polymer materials that can meet the end needs of the final product. Combining data from future studies together with the data collected in this review and other reviews [ 39 , 40 , 41 ] will provide a large database and open the avenue to develop numerical models that can evaluate different aspects of flame-retarded polymers. From the environmental perspective, research should concentrate on using biobased FRs to overcome the negative impacts of FRs on human health and the environment.…”

“…This index helps the investigators to evaluate the performance of flame-retardant system. Vahabi et al and Movahedifar et al [ 39 , 40 , 41 ] have applied this index on a comprehensive set of data collected from literature to evaluate the fire performance of Polypropylene (PP), Poly (methyl methacrylate) (PMMA), Ethylene vinyl acetate (EVA), Poly (lactic acid) (PLA) and epoxy resin filled with different types of flame retardants. Moreover, literature lacks a simple selection tool that can be used to correlate between the effect of adding flame retardants on the flammability behaviour of polymeric materials and their effect on the mechanical, thermal and physical properties.…”

Cross-Linking Modification of Ammonium Polyphosphate via Ionic Exchange and Self-Assembly for Enhancing the Fire Safety Properties of Polypropylene

“…Therefore, it is particularly significant to improve both its flame retardancy and smoke suppression performance simultaneously. Recently, phosphorus-based (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, APP), nitrogen-based (melamine phosphate, melamine salt of pentaerythritol phosphate kaolinite), mineral-based (aluminum trihydroxide), and carbon-based (graphene) flame retardants have gradually replaced the halogen-containing flame retardants due to their high efficiency, low smoke, and low toxicity [ 6 , 7 ]. Among them, the intumescent flame retardant (IFR), which is made of an acid source (APP, organic phosphoric acid and phosphate ester), blowing agent (urea, melamine, dicyandiamide and their derivatives) and a carbonizing agent (pentaerythritol and piperazine derivatives) is popular.…”

Enhancement of the Surface Properties on Polypropylene Film Using Side-Chain Crystalline Block Copolymers

“…Among them, polypropylene (PP) has been widely used in consumer products such as packaging materials [ 2 ], pipes [ 3 ], rope [ 4 ], and automobiles [ 5 , 6 ]. This is because, compared to other plastics, PP has exhibited superior properties including high chemical and heat resistances, easy molding, and high mechanical tensile and compression strengths [ 7 ]. Therefore, PP had been used in various fields spanning from the industrial scale to daily life and accounts for 17% of the total plastic production [ 1 ].…”