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Diffusion of polyphosphates into
(poly(allylamine)-montmorillonite) multilayer films:
flame retardant-intumescent films with improved
oxygen barrier
Laachachi A., Ball V., Apaydin K., Toniazzo V. and Ruch D.
AMS, Centre de Recherche Public Henri Tudor, Luxembourg
ECC Fire retardant coatings, 13-14 March 2012 Berlin
LBL Films - G. Decher et al., Thin Solid Films, 210, 831, 1992.
2
Reversal of the surface
potential after each deposition
step
The alternate deposition of polyanions and polycations on a solid substrate
leads to the formation of nanometer to micrometer films called
Polyelectrolyte Multilayers. Layer-by-layer (LbL) deposition process.
Nomenclature : (P - - P + ) n
n number of layer pairs
n layer
0 2 4 6 8 10 12 14 16
-F
3/3
/ H
z
0
200
400
600
800
1000
1200
Different growth regimes and different properties
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Linear growth Supralinear (exponential) growth
Some stratification remains
Elastic
Low permeability
«Intrinsic » charge compensation
Totally intermixed (?)
Liquid or gel like
Ion exchange membranes
« Extrinsic » charge compensation
!! For such coatings « LBL » is not the
appropriated word, one should call
them « films prepared by a step-by-step
adsorption method » !!
4
Intumescent Flame Retardant
Intumescent FR : systems are characterized by the
ability of the material to swell and to foam under
heat radiation. The foam serves to isolate heat and
oxygen from the fuel source and extinguishing the
fire.
The main ingredients of an intumescent coating
should be :
1. acid source such as PSP
3 +
2. swelling agent to facilitate the expansion of
the coating by releasing an inert gas (NH3) PAH
3. carbon source to a cross-linked char layer, PAH
4. inorganic fillers as MMT in order to reinforce the char strength
5
Substrat
Substrat
MMT PAH
PSP
Growth, structure and interaction with polyphosphates of (PAH-MMT)n films:
3 +
Silicium - PLA
6
Figure: AFM topographies and lines scans acquired in between the white lines for
a (PAH-MMT)15 film (a) and a (PAH-MMT)15+PSP film (b) treated with PSP
(1mg.mL-1 in 50 mM Tris buffer at pH 7.5 during 1h). The maximal height in the line
scans corresponds to 3.2 µm.
Figure: AFM topographies and lines scans acquired in between the white lines
for a (PAH-MMT)5 film (a) and a (PAH-MMT)5+PSP film (b) treated with PSP (1
mg.mL-1 in 50 mM Tris buffer at pH 7.5 during 1h). The maximal height in the line
scans corresponds to 400 nm.
Growth, structure and interaction with polyphosphates of (PAH-MMT)n films:
7
Figure: SEM images of detached (PAH-MMT)60+PSP film (a): upper part of the film and (b): lower part corresponding to the
film /substrate interface. EDX analysis of 150 µm2 of detached (PAH-MMT)n+PSP films showing the phosphorous content in the
upper part for n = 60 (c) and n = 30 layer pairs (e) and lower part for n = 60 (d) and n = 30 layer pairs (f).
Growth, structure and interaction with polyphosphates of (PAH-MMT)n films:
n=60 n=30
Upper part
Lower part
8
Figure: (a): Evolution of the thickness of (PAH-MMT)n films as a function of the number of deposited "layer pairs" as
obtained by cross-sectional SEM analysis ( : without PSP, : after incubation in a 1 mg.mL-1 containing PSP
solution during 1h) and by nanoscratch experiments (: without PSP, : with PSP). Each point corresponds to an
individually prepared film. All films were deposited on cleaned silicon wafers. (b) Cross-sectional SEM images of films
made from 5, 10, 30 and 60 layer pairs and doped with PSP (1 mg.mL-1 during 1h). (c): EDX spectrum of a (PAH-
MMT)60+PSP film put in contact with a PSP solution at 1 mg.mL-1 during 1h.
Growth, structure and interaction with polyphosphates of (PAH-MMT)n films:
9
Inte
nsi
ty (a
.u.)
2 Theta ( )
n=60
n=30
n=20
n=15
n=10
n=8
n=5
n=3
n=1
NaMMT
Figure: X-Ray diffraction patterns for neat NaMMT
and for films with an increasing number of "layer
pairs" (n) with (red) and without incorporated
(black) PSP.
Growth, structure and interaction with polyphosphates of (PAH-MMT)n films:
d=14.3 A
10
Figure: TGA curves of detached (PAH-MMT)60 films with and without PSP under air (heating rate:10 °C/min).
Growth, structure and interaction with polyphosphates of (PAH-MMT)n films:
the amount of inorganic residue at 600°C decrease from 80% to 70%
in the presence of PSP.
11
Figure: (a): Examples of nanoindentation curves before and after PSP incubation. (b): evolution of the elastic
modulus with the number of deposited layer pairs for films before and after PSP incubation. (c): evolution of the
hardness with the number of deposited layer pairs for films before and after PSP incubation. (d): detached (PAH-
MMT)60 as free standing membranes from the sample holder (Teflon, on the right part) used during the step-by-step
deposition experiments.
Mechanical properties of polyphosphate loaded (PAH-MMT)n films:
The sample holder (Teflon)
12
Figure: (a): evolution of the OTR values with the number of deposited layer pairs for films before and after PSP
incubation (1 mg.mL-1 during 1h). (b): evolution of oxygen permeability with the number of deposited layer pairs for films
before and after PSP incubation. (c): evolution of Oxygen Barrier improvement Factor with the number of deposited layer
pairs for films before and after PSP incubation.
Gas barrier properties of polyphosphate containing (PAH-MMT)n films:
very low oxygen
permeability
90% relative
humidity
PSP has a positive
impact on the
permeability
reducing
>30BL, OTR
lower than the
detection limit of
the instrument
13
Figure: evolution of heat release rate (HRR) as measured with a mass loss calorimeter (at an external heat flux of 35kW.m-2)
for uncoated PLA (black) and coated PLA with (PAH-MMT)30, (PAH-MMT)30+PSP , (PAH-MMT)60, (PAH-MMT)60+PSP .
Fire resistance properties of polyphosphate containing (PAH-MMT)n films:
0 50 100 150 200 250 300
0
200
400
600
800
1000
HR
R [
KW
/m2]
Time [s]
14
continuous char layer was observed
during the combustion
no char barrier layer was observed
for the uncoated PLA sample used
as reference
some defects and cracks are
presented on the surface to explain
why the decrease of pHRR is low at
30BL
Fire resistance properties of polyphosphate containing (PAH-MMT)n films:
30BL+PSP
uncoated PLA
30BL
15
60BL 60BL+PSP
Figure: EDX analysis of mass loss calorimeter residues for a PLA/(PAH-MMT)60 film (a) and for a PLA/(PAH-MMT)60+PSP film.
Fire resistance properties of polyphosphate containing (PAH-MMT)n films:
100 m
60BL+PSP
16
Figure: Pictures of mass loss calorimeter residue of PLA/(PAH-MMT)60+PSP (right) and of PLA substrate before combustion as a reference (left).
Uniform charring had occurred on the upper side of the sample during and after combustion.
Fire resistance properties of polyphosphate containing (PAH-MMT)n films:
the addition of PSP into the (PAH-MMT) coating also increases
the barrier effect due to the formation of an intumescent char
the thickness of the sample during combustion and at the end of
the combustion test is three times more important compared to
the initial thickness.
60BL+PSP
17
PLA-(PAH-MMT)60+PSP Uncoated PLA
Fire resistance properties of polyphosphate containing (PAH-MMT) films:
Videos
3/27/2012 ECC Fire retardant coatings, 13-14 March 2012 Berlin 18
Thank you for your attention !
