Synergistic effect between aluminum hypophosphite and a new
intumescent flame retardant system in poly(lactic acid)
Gousheng Liu ,
College of Chemistry, Nanchang University, Jiangxi 330031, China
State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
Correspondence to: G. Liu (E -mail: email@example.com)
A hyperbranched charring agent (CT) was synthesized by triglycidyl isocyanurate and diethylenetriamine in water, and a
new intumescent flame retardant (IFR) system was formed by ammonium polyphosphate (APP) and CT. The different formula and
synergistic system between IFR and aluminum hypophosphite (AHP) have been studied through limit oxygen index (LOI), UL-94,
cone calorimetry test and TGA. It was found that the LOI for poly(lactic acid) (PLA) with 30 APP/CT (4:1) and 20 wt % IFR/AHP
(3:1) were 41.2% and 43.5%, respectively, and the both could achieve UL-94V-0 rating with no melt dripping. The heat release rate
(HRR), maximum HRR value and average mass loss rate of PLA could be dramatically decreased by combination of IFR and AHP
while the thermal stability was greatly enhanced. The study of morphology and structure of char illustrated that more intumescent
and compact char layer with good intensity was formed during the degradation of IFR/AHP, which resulting to better flame retard-
ancy and anti-dripping than IFR or AHP alone.
2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46359.
degradation; flame retardance; thermogravimetric analysis
Received 23 October 2017; accepted 8 February 2018
Poly(lactic acid) (PLA), an environmental-friendly material
using renewable crops as raw material, has some advantages
such as non-toxic, nonirritant, high intensity, good biocompati-
bility, and biodegradation, and is widely used in medical appa-
ratus and instruments, packaging, electronic products,
automobile industry, and building field.
However, as a kind
of aliphatic polyester, PLA is flammable, so it is necessary to
enhance its flame-retardant property especially when it is used
in electronic products, automobile industry and building field.
Due to the environmental-friendly property of PLA, it is appro-
priate to employ intumescent flame retardant (IFR) to improve
its flame retardancy, which has the advantages of safety, non-
halogen, low toxicity, and little smoke. But the conventional
IFR system, usually composed of acid source, charring agent
(CT), and blowing agent, exhibits high loading, poor dispersion,
and low flame retardant efficiency.
So adopting new method
and exploring better IFR are significant for the application and
development in PLA.
The CT of IFR is usually polyhydric compound, such as polyhy-
which can form the frame-
work of intumescent char and determine the flame retardancy.
To overcome the migration, moisture absorption and bad
compatibility of some micromolecule CT such as pentaerythritol
(PER), some kind of macromolecular CT such as triazine-based
and novel polymers
are developed. However, the
synthetic process of most macromolecular CT use cyanuric chlo-
ride as raw material, which is poisonous and high reactive, and
the reaction usually is carried out in organic solvent.
In addition, through the synergistic effect, the flame-retardant
efficiency of IFR can be greatly improved, and then the negative
influence of IFR on the appearance, mechanical property and
process ability of material can be decreased.
hypophosphite (AHP), as a kind of phosphorus-containing
flame retardant, is widely used in some halogen-free flame-
retardant field. Tang et al.
have shown that the addition of
AHP can resolve the serious dripping of PLA while have little
effect on the limit oxygen index (LOI). Zhou Xuan et al.
studied the synergy between AHP and the traditional IFR sys-
tem [ammonium polyphosphate (APP)/PER], and found that
satisfactory flame retardancy can be obtained through the syner-
gist effect between IFR and AHP.
The above mentioned IFR systems usually contain some micro-
molecule components such as PER, which may have some
application problems such as migration and moisture absorp-
tion. In present work, using water as solvent, a hyperbranched
CT was synthesized based on triglycidyl isocyanurate (TGIC)
2018 Wiley Periodicals, Inc.
J. APPL. POLYM. SCI. 2018, DOI: 10.1002/APP.46359
46359 (1 of 9)