SAMPE Journal - July/August 2022 - 59

Resin
35610
35700
35900
5292B-PPA
BisA-PPA 3957
BisM-PPA 2670
5292B-FA
BisA-FA
BisF-FA
Thio-FA
232
257
3462
3574
4306
305
302
287
233
273
326
324
294
Table 2. Homo-polymerization result of benzoxazines.
Toughened System for Furfuryl amine Based
Benzoxazine
The selected resin was melted in an oven and
transfer to a four-neck round bottom flask, and
toughener was added under vacuum until the
mixture become homogeneous, then catalyst was
added, the mixture was then degassed for 1 hour,
and transferred to a glass-pane plaque setting.
After initial cure, the plaque was removed and
further post cure. The cured sample was then
tested for tensile and flexural according to standard
procedure.
RESULTS
Homo-Polymerization
DSC scan shown the exothermic peak of those
benzoxazines has a very broad range. The DSC
scan of selected sample is shown in Figure. 1, and
the main peaks also listed in Table 1.
At 10°C/min, the range of exothermic peak
covers more than 200°C in most case, from around
100°C to above 300°C. All samples have the main
exotherm peak between 200°C and 240°C except
the FA-2, which has the highest peak around 250°C.
Propargyl amine benzoxazines generally have lower
onset and peak temperature compared to furfuryl
amine benzoxazine and aniline benzoxazines when
other keep the same, Commercial MT35610 has
a small peak at round 170°C and a bigger peak at
223°C, and MT35700 have a front shoulder peak at
193°C, and a big peak at 235°C. 35900 has a bigger
peak at 205°C and a small peak at about 300°C, it
may indicate the breakdown of cured network.
For propargylamine benzoxazine, there is only
one exothermic peak except the one derived from
bisphenol A, which DSC show a clear bimodal with
a second strong peak. The enthalpies are very high
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for propargylamine benzoxazine, that indicate the
transformation of carbon-carbon triple bond.
The directly raise the curing temperature close
to the onset temperature will made all the samples
outgassing. It is also similar to those commercial
benzoxazines. Thus, various staged cure schedule
has been tested. Eventually, most those benzoxazine
could be successfully homo-polymerized without
any catalyst, however, even with staged cure,
some sample could not yield a decent dish-casting
sample under similar condition.
When cured, those functionalized
benzoxazines have improved Tg significantly.
It was expected as the additional functional
group would take part in the cross-link network
to increase the cross-link density.
The storage
modulus Tg for the polymerized furfuryl amine
benzoxazines resin
could reach above 300°C,
for the propargylamine benzoxazine, the storage
modulus Tg would increase up to 260°C depend
on the primary structure. However, the thermal
stability of the polymerized propargylamine
benzoxazine resin was not as good, the 5% weight
loss temperature under nitrogen is similar to those
aniline benzoxazines, but the char yield is worse,
when additional allyl group present in the original
resin structure (5292B-PPA), the decrease even
more. On the other hand, when furfuryl amine
replaced aniline,
after polymerization the char
yield percentage improved by 8 - 12 points at 800°C
in nitrogen, but the 5% weight temperature has
different trend depend on the primary structure of
the bisphenol used.
241
302
340
342
301
Storage Modules
(MPa)
3544
2935
E' onset
Tg (o
C)
163
156
197[20]
Loss
Modulus
Peak (o
174
170
199[20]
C)
Tan δ Peak
(o
C)
189
187
213[20]
5% Weight
Loss
(o
C, in N2
366
377
301
370
327
398
365
402
358
342
)
Char Yield
at 800o
(%, in N2
41
46
51
29
34
39
39
54
58
62
C
)
JULY AUGUST 2022
|
SAMPE JOURNAL | 59
http://www.sampe.org
SAMPE Journal - July/August 2022

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