synergists for hexaphenoxycyclotriphosphazene in

synergists for hexaphenoxycyclotriphosphazene in

Fraunhofer
ICT
SYNERGISTS FOR HEXAPHENOXYCYCLOTRIPHOSPHAZENE
IN CAST PA6
Carl-Christoph Höhnea,b, Bert Käbischa,b, Thorsten Andersa and Edwin Krokeb
a) Fraunhofer Institut für Chemische Technologie (ICT), Umwelt Engineering, D-76327, Pfinztal
b) Technische Universität Bergakademie Freiberg, Institut für Anorganische Chemie, D-09596, Freiberg
Introduction
Carbon fiber reinforced (CFR) anionic polyamide 6 (APA6) is a light
and at the same time very strong material. Therefore CFR APA6
components are of interest as lightweight construction materials e.g.
for aircraft manufacturing. Like many other organic polymers APA6 is
flammable and thus it is mandatory to protect the polymer matrix by
adding flame retardants (FRs). However, an suitable process for pro-
duction of CFR APA6 materials such as thermoplastic resin transfer
molding (T-RTM) process is highly sensitive to presence of polymer
additives such as FRs. E.g. commonly used FRs interrupt the anionic
ring opening reaction of ε-caprolactam to form PA6 or are filtered out
by the fiber fleece. With hexaphenoxycyclotriphosphazene (HPCTP)
we discovered an incorporable FR for CFR APA6.
Results
Preparation
FRs TESTED IN LAB SCALE
FR requirements for CFR APA6 produced via T-RTM:
• Solubility in molten ε-Caprolactam
• No interruption of the anionic polymerization process
Only the HPCTP-FR Rabitle FP110
(Nordmann, Russmann) is applicable
in T-RTM process for CFR APA6 with
higher loading (see tested FRs).
FR
Solubility
No interruption
Rabitle FP110 (HPCTP)
Yes (tested till 50 wt.%)
Yes
Methyl-DOPO
Yes (till 10 wt.%)
Yes (till 5 wt.%)
Aflammit PCO 960
Exolit AP 462
Apyral 40 CD
Apyral 40 VS1
Magnifin H5 IV
Red phosphorus
Melamine
Expandable graphit
Exolit OP 935
Exolit OP 1312
Yes (till 10 wt.%)
No
No
No
No
No
No
No
No
No
Yes (till 1 wt.%)
Yes
Yes
Yes
Yes
Yes
No
No
No
No
LOI
38.4 O2%
38
36
LOI [O2%]
34
V-0
34.2 O2%
n.b.
n.b.
n.b.
V-0
CFR APA6
32
30
FAR 25.853 F1
pass
fail
28
26
24
22
20
n.b.
n.b.
n.b.
0
24
LOI
24.4
23.1
APA6 + 8 wt.% HPCTP
22.6
APA6
23.1
Synergists:
n.b.
Aromatic carbon source
Dicumene (VELOX)
Triphenylmethane
21
25
Triazine based
Flamestab NOR116 (BASF)
2,4,6-Trimethoxy-1,3,5-triazine
CONE CALORIMETRY OF CFR APA6
Thermally thick charring material
0 % HPCTP
2
HRR [kW/m ]
10 % HPCTP
5 % HPCTP
120
15 % HPCTP
25 % HPCTP
80
40
20
Afterglow
0
0
50
100
150
30
10 % HPCTP
15 % HPCTP
25 % HPCTP
200
250
300
350
400
450
500
550
Surface
[mm2]
100x100
100x100
100x100
100x100
100x100
tig
[s]
47
44
40
47
54
Peak HRR
[kW/m2]
198
176
155
148
150
APA6 + 15 wt.% HPCTP
(syn. Air)
APA6 + 15 wt.% HPCTP
(Nitrogen)
60
HPCTP (syn. Air)
40
APA6 (syn. Air)
20
0
0
100
200
300
400
Temperature [°C]
500
600
700
2
3
4
Synergist [wt.%]
5
6
Conclusion
10
0
600
Time [s]
HPCTP
[wt.%]
0
5
10
15
25
1
40
2
160
80
3,3,9,9-Tetramethyl-2,4,8,10-tetraoxaspiro[5,5]-undecane
0
THR [MJ/m ]
5 % HPCTP
HPCTP (Nitrogen)
100
Oxygen source (ether)
Desmophen 2061BD (Bayer)
19
50
HRR
THR
0 % HPCTP
TGA
APA6 (Nitrogen)
20
200
Plate (650x480x2 mm3;
CFR: 64 wt.%, 53 vol.%)
TGA OF FIBER-FREE APA6
HPCTP promotes in oxygen rich
atmosphere (syn. air) the formation of thermally stable char. In
an innert atmosphere (Nitrogen)
no char formation is observed.
22.9
22
20
mold
23.3
23.3
23
10
15
HPCTP [wt.%]
APA6 + 8 wt. HPCTP + Synergist
APA6 + Synergist
23.7
n.b., V-0
fiber-free APA6
5
Polymerization
T: 150 °C
t: 360 s
p: normal
CFR: unidirectional
For future researches the influence
of six additional additives in lab scale experiments was studied. Five of the examined
compounds exhibited distinct synergistic effects with
HPCTP in APA6 matrix. Although Trimethoxytriazine
showed no synergy, it significantly improved flame
resistance of APA6 as a stand alone additive.
UL94
n.b.
Mixing (1:1)
T: 110 °C
4 wt.% Cat.
2 wt.% Act.
0-25 wt.% FR
Synergism
22.8 O2%
22.0 O2%
ε-Caprolactam
ε-Caprolactam
Catalyst
Activator
FR
Melting
T: 110 °C
Weight [wt.%]
FR-TESTS
CFR APA6 with 15 wt.% HPCTP pass FAR and
UL94 (V-0) test and shows highest LOI value.
T-RTM process
THE
TSR
[MJ/m2] [m2/m2]
35,6
94
29,3
404
25,3
528
23,4
526
19,4
654
The Heat Release
Rate (HRR) decreases
with increasing HPCTP load.
Without HPCTP, CFR APA6 shows afterglow.
Incorporation of HPCTP eliminates afterglow
and promotes char formation.
tb
MARHE
[s] [kW/m2s]
535
126,2
450
116,2
352
105,6
409
97,5
380
86,9
Peak CO
[ppm]
92
201
309
380
564
Peak CO2 Mass loss
[%]
[wt.%]
0,369
39,8
0,335
30,7
0,302
29,4
0,279
29,5
0,289
28,5
According to TGA and cone calorimetry, char formation is the essential
FR mechanism of HPCTP in CFR APA6.
Incorporation of only 15 wt.% HPCTP prevents afterglow (cone calorimetry) and allows
the material to pass FAR and UL94 (V-0) tests.
Following mechnaical properties were obtained
for CFR APA5 with 15 wt.% HPCTP (0° orientation).
Crystallinity: 40 %, Impact resistant: 96 kJ/m2
E-mod.: 118GPa (flex.) 103GPa (compr.) 134GPa (Young)
Strength: 1228MPa (flex.) 463MPa (compr.) 1471MPa (tens.)
Reference:
C.-C. Höhne, Master Thesis, TU Bergakademie Freiberg, 2014.
Acknowledment: We thank our colleague from Polymer Engineering (ICT) Rainer Wendel for performing of the T-RTM process.
Background: Photo of a CFR APA6 plate via T-RTM.
M.Sc. Carl-Christoph Höhne
Fraunhofer Institute for Chemical Technology ICT| Environmental Engineering | Polymers and Additives| Joseph-von-Fraunhofer-Strasse 7 | 76327 Pfinztal | Phone: +49 721 4640-310 | carl-christoph.hoehne@ict.fraunhofer.de |
FRPM 2015 | June 21th-25th 2015