Halogen-free intumescent flame-retardant ethylene-vinyl acetate
copolymer system based on organic montmorillonite and graphene
Xuebao Wang ,
Chinese People’s Armed Police Forces Academy, Langfang 065000, People’s Republic of China
Beijing Research Center for Radiation Application, Beijing 100015, People’s Republic of China
Correspondence to: X. Wang (E -mail: email@example.com)
Halogen-containing flame retardants are not preferred for environmental reasons. Herein, a halogen-free intumescent
flame-retardant ethylene-vinyl acetate copolymer (EVA/IFR) system containing organic montmorillonite (OMMT) and graphene
nanosheets (GNSs) is fabricated with well dispersion structure, enhanced thermal-oxidative resistance at high temperature. Interest-
ingly, the amount of residual chars from thermogravimetric analysis is increased to 12.7 wt % at 700 8C, the EVA/IFR composite con-
taining both OMMT and GNSs exhibits the best flame retardancy with the lowest peak heat release rate value of 529.58 kW m
the highest limited oxygen index value of 24.8%. The excellent flame retardancy is attributed to the formation of complete and com-
pact protective char layer. Furthermore, the decreases of the mechanical properties caused by the addition of IFR are relieved and a
high volume resistivity is maintained when combining OMMT and GNSs in the EVA/IFR system together.
2018 Wiley Periodicals, Inc.
J. Appl. Polym. Sci. 2018, 135, 46361.
flame retardance; mechanical properties; thermogravimetric analysis
Received 30 July 2017; accepted 11 February 2018
Ethylene-vinyl acetate copolymer (EVA) is widely used in many
fields, such as toys, shoe industry, hot melt adhesives, and insulat-
ing materials due to its desirable physicochemical properties.
However, like most polymers, EVA is highly combustible, which
leads to fire risks in real application. Therefore, it is necessary to
enhance fire safety of EVA by incorporating flame retardants into
the EVA matrix.
Although halogen-containing flame retardants
show high flame-retardant efficiency in EVA composites, they
lead to environmental problems by releasing much toxic and cor-
rosive gas during combustion.
As a result, halogen-containing
compounds are not preferred for environmental reasons.
fore, many researchers have focused on exploiting environmental
friendly halogen-free flame retardants.
In recent years, intumescent flame retardant (IFR) is considered
as a promising halogen-free flame-retardant additive which gains
great attention due to the advantages such as low smoke, low tox-
icity, low corrosion, and excellent char forming ability during
Generally speaking, a typical IFR system mainly
consists of three components: an acid source, a carbonization
agent, and a blowing agent. These three components are beneficial
to the formation of intumescent char layers, which protect the
underlying polymer matrix well from heat flux and fire during
Unfortunately, there are many problems waiting to
be solved, for instance, the poor compatibility between IFR and
and the required high loadings due to the low
To overcome these problems, adding synergists has
been proved to be an effective strategy.
Nanofillers such as montmorillonite (MMT),
layered double hydroxides,
are extensively investigated as syner-
gists in IFR system during the past few years. Among those nano-
fillers, the two-dimensional nanofillers attract much attention
due to their barrier effect, which can inhibit the release of com-
bustible gases and improve the thermal stability of the compo-
sites. Graphene and organic montmorillonite (OMMT) are two
kinds of typical two-dimensional nanofillers. Previous studies
prove that graphene and its derivatives can change the pyrolysis,
improve the thermal stability and mechanical properties of poly-
mer, and reduce heat release rate (HRR) because of their strong
barrier effect, high thermal stability, and large specific surface
Graphene nanosheets (GNSs) are mul-
tiple thin sheets of graphene, which have similar excellent flame
2018 Wiley Periodicals, Inc.
J. APPL. POLYM. SCI. 2018, DOI: 10.1002/APP.46361
46361 (1 of 10)