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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.


Schematic illustration of the synthesis route for PGO and digital photos of GO, and PGO (500 mg) dispersions in H2O, EtOH, DMK and THF (4 ml) after standing for 2 h.
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Figure 1: Schematic illustration of the synthesis route for PGO and digital photos of GO, and PGO (500 mg) dispersions in H2O, EtOH, DMK and THF (4 ml) after standing for 2 h.

Mentions: Polypropylene (PP) is easily ignited and burned, and improving its fire safety properties is highly desirable due to the huge applications of PP [25]. Intumescent flame retardants (IFRs) comprise three basic elements which are called dehydrating agent [26], char-forming agent and foaming agent. And the IFRs are preferred due to their environmental friendly property [27]. A caged structure organic compound, namely 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) [28], is a high-performance environment friendly char-forming agent for fire-retardant PP. It can be spontaneous or catalytic materials to form a molten char layer (equation (1)) at the surface of polymer materials [29, 30] under combustion. The molten char layer acts as a protective coat. However, there is a hydroxyl group in its structure, which makes it hydrophilic. The hydrophilic properties of PEPA make the flame retardant PP composites moisture sensitive, which will decrease flame retardancy because of the exudation of the additive [31]. To reduce the hydrophilicity and raise flame retardancy of GO and PEPA, we present a scheme for the covalent attachment of PEPA to GO nanosheets by the intermediary agent, toluene diisocynate (TDI) (figure 1), which is a perfect medium for the char-forming agent [32, 33]. It is expected that PEPA and TDI could form a molten char layer on the surface of PGO under the fire, which prevents graphene from burning out, and then the graphene may act as a physical barrier to protect the underlying polymers.


Novel PEPA-functionalized graphene oxide for fire safety enhancement of polypropylene
Schematic illustration of the synthesis route for PGO and digital photos of GO, and PGO (500 mg) dispersions in H2O, EtOH, DMK and THF (4 ml) after standing for 2 h.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Schematic illustration of the synthesis route for PGO and digital photos of GO, and PGO (500 mg) dispersions in H2O, EtOH, DMK and THF (4 ml) after standing for 2 h.
Mentions: Polypropylene (PP) is easily ignited and burned, and improving its fire safety properties is highly desirable due to the huge applications of PP [25]. Intumescent flame retardants (IFRs) comprise three basic elements which are called dehydrating agent [26], char-forming agent and foaming agent. And the IFRs are preferred due to their environmental friendly property [27]. A caged structure organic compound, namely 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) [28], is a high-performance environment friendly char-forming agent for fire-retardant PP. It can be spontaneous or catalytic materials to form a molten char layer (equation (1)) at the surface of polymer materials [29, 30] under combustion. The molten char layer acts as a protective coat. However, there is a hydroxyl group in its structure, which makes it hydrophilic. The hydrophilic properties of PEPA make the flame retardant PP composites moisture sensitive, which will decrease flame retardancy because of the exudation of the additive [31]. To reduce the hydrophilicity and raise flame retardancy of GO and PEPA, we present a scheme for the covalent attachment of PEPA to GO nanosheets by the intermediary agent, toluene diisocynate (TDI) (figure 1), which is a perfect medium for the char-forming agent [32, 33]. It is expected that PEPA and TDI could form a molten char layer on the surface of PGO under the fire, which prevents graphene from burning out, and then the graphene may act as a physical barrier to protect the underlying polymers.

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.