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Novel PEPA-functionalized graphene oxide for fire safety enhancement of polypropylene

View Article: PubMed Central - PubMed

ABSTRACT

Polypropylene (PP) is a general-purpose plastic, but some applications are constrained by its high flammability. Thus, flame retardant PP is urgently demanded. In this article, intumescent flame retardant PP (IFRPP) composites with enhanced fire safety were prepared using 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) functionalized graphene oxide (PGO) as synergist. The PGO was prepared through a mild chemical reaction by the covalent attachment of a caged-structure organic compound, PEPA, onto GO nanosheets using toluene diisocynate (TDI) as the intermediary agent. The novel PEPA-functionalized graphene oxide not only improves the heat resistance of GO but also converts GO and PEPA from hydrophobic to hydrophilic materials, which leads to even distribution in PP. In our case, 7 wt% addition of PGO as one of the fillers for IFRPP composites significantly reduces its inflammability and fire hazards when compared with PEPA, by the improvement of first release rate peak (PHRR), total heat release, first smoke release rate peak (PSRR) and total smoke release, suggesting its great potential as the IFR synergist in industry. The reason is mainly attributed to the barrier effect of the unburned graphene sheets, which protects by the decomposition products of PEPA and TDI, promotes the formation of graphitized carbon and inhibits the heat and gas release.

No MeSH data available.


TGA (a) and DTG (b) of IFRPP composites.
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Figure 8: TGA (a) and DTG (b) of IFRPP composites.

Mentions: TGA and DTG curves of flame retardant composites are shown in figure 8 and their data are listed in table 1. The thermal degradation processes of the samples are similar, but there are still some differences. There is a small decomposition peak at about 280 °C based on the DTG profile (figure 8(b)) of sample 7, which might be due to the decomposition of carboxyl and hydroxyl that creates water. The Tmax of the IFRPP with 7 wt% PEPA or PGO are 438 and 434 °C, respectively, which are lower than that without one, since PEPA and PGO is thermally unstable compared to IFRPP composite and its major mass loss occurs below 350 °C due to the decomposition of the oxygen-contained functional moiety. It is worth to mention that the Rmax of sample 7 decreases as well, owing to the multifunctional groups of PEPA and TDI, which could form a crosslinking char layer during heating or burning and covers on the surface of graphene sheets, protecting the graphene from burning out. However, the Rmax value of sample 5 is the highest, even higher than that of sample 1, which is due to the high thermal conductivity of GO [42] as well as the high barrier layer material [43, 44]. If GO is insufficient in IFRPP composite, its thermal conductivity effect would prevail instead of the barrier effect, which results in the rapid decomposition of the IFRPP material. When GO is sufficient in IFRPP composite it would present an excellent flame retardant effect, as the curve for sample 7 in figure 8(a) and table 1, which exhibits a lowest Rmax value and a maximum char yield. The results indicate that the PGO is much better than that of PEPA in terms of delaying the thermal degradation of flame retardant PP and enhancing the char formation.


Novel PEPA-functionalized graphene oxide for fire safety enhancement of polypropylene
TGA (a) and DTG (b) of IFRPP composites.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036477&req=5

Figure 8: TGA (a) and DTG (b) of IFRPP composites.
Mentions: TGA and DTG curves of flame retardant composites are shown in figure 8 and their data are listed in table 1. The thermal degradation processes of the samples are similar, but there are still some differences. There is a small decomposition peak at about 280 °C based on the DTG profile (figure 8(b)) of sample 7, which might be due to the decomposition of carboxyl and hydroxyl that creates water. The Tmax of the IFRPP with 7 wt% PEPA or PGO are 438 and 434 °C, respectively, which are lower than that without one, since PEPA and PGO is thermally unstable compared to IFRPP composite and its major mass loss occurs below 350 °C due to the decomposition of the oxygen-contained functional moiety. It is worth to mention that the Rmax of sample 7 decreases as well, owing to the multifunctional groups of PEPA and TDI, which could form a crosslinking char layer during heating or burning and covers on the surface of graphene sheets, protecting the graphene from burning out. However, the Rmax value of sample 5 is the highest, even higher than that of sample 1, which is due to the high thermal conductivity of GO [42] as well as the high barrier layer material [43, 44]. If GO is insufficient in IFRPP composite, its thermal conductivity effect would prevail instead of the barrier effect, which results in the rapid decomposition of the IFRPP material. When GO is sufficient in IFRPP composite it would present an excellent flame retardant effect, as the curve for sample 7 in figure 8(a) and table 1, which exhibits a lowest Rmax value and a maximum char yield. The results indicate that the PGO is much better than that of PEPA in terms of delaying the thermal degradation of flame retardant PP and enhancing the char formation.

View Article: PubMed Central - PubMed

ABSTRACT

Polypropylene (PP) is a general-purpose plastic, but some applications are constrained by its high flammability. Thus, flame retardant PP is urgently demanded. In this article, intumescent flame retardant PP (IFRPP) composites with enhanced fire safety were prepared using 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) functionalized graphene oxide (PGO) as synergist. The PGO was prepared through a mild chemical reaction by the covalent attachment of a caged-structure organic compound, PEPA, onto GO nanosheets using toluene diisocynate (TDI) as the intermediary agent. The novel PEPA-functionalized graphene oxide not only improves the heat resistance of GO but also converts GO and PEPA from hydrophobic to hydrophilic materials, which leads to even distribution in PP. In our case, 7 wt% addition of PGO as one of the fillers for IFRPP composites significantly reduces its inflammability and fire hazards when compared with PEPA, by the improvement of first release rate peak (PHRR), total heat release, first smoke release rate peak (PSRR) and total smoke release, suggesting its great potential as the IFR synergist in industry. The reason is mainly attributed to the barrier effect of the unburned graphene sheets, which protects by the decomposition products of PEPA and TDI, promotes the formation of graphitized carbon and inhibits the heat and gas release.

No MeSH data available.