JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 42

curing agent
peroxide AAP), Accelerator NL-49P
(Cobalt-1% solution) and several Nouryact cobalt-free accelerators as curing
system (data in Table 1). The test data
100 100 100 were generated at 20°C according to the
ASTM D7029 method. The gel time
400 400 400 is defined as the time required for the
curing mixture temperature to increase
by 5.6°C. The time to peak is the time
2
2
2
elapsed from the beginning of the test
to the moment the peak exotherm is reached. The cobalt-based reference system
2
has a 5-min gel time, a 20-min time to
2
peak and a peak exotherm of approximately 60°C. The tests show that the dosage
2
level is important; the best results are
achieved with 2 phr (parts per hundred
5
4
5
parts of resin) Butanox M-50 and 2 phr
17
20
19
Nouryact accelerator. The data also show
that all three Nouryact cobalt-free acce68
56
57
lerators perform well. It should be noted
that similar to cobalt the dosage level of the peroxide
should preferably be higher or equal to the accelerator
dosage level to avoid poisoning of the curing system.

Tab. 1: General reactivity data for Nouryact cobalt-free accelerators in filled system

Highly reactive
orthophthalic resin (parts)

100

Quartz fillers (parts)

400

Trigonox 44B (phr)

1
1

Butanox M-50 (phr)
Accelerator NL-49P (phr)

Nouryact CF13 (phr)

Nouryact CF31 (phr)

1
1

Nouryact CF32 (phr)

1
1

Gel time at 20°C (min)

Time to peak (min)

Peak exotherm (°C)

6 Nouryact cobalt-free accelerators which all have their
specific characteristics.
Although legislation is still on the way, several companies
have already switched to Nouryact cobalt-free accelerators. One of them is Holonite in Tholen, the Netherlands,
who has a strong sustainable approach to raw materials
and curing systems. Holonite is a leading manufacturer
of polymer concrete for the building industry and manufactures, among many other end products, door sills and
façade panels.

Cobalt-free polymer concrete casting process
The polymer concrete casting process typically uses highly filled resin systems cured at ambient temperature with
relatively low peak exotherms. The process requires easy
fine tuning during production in order to adjust for the
summer and winter periods. The equipment for polymer
concrete is usually set up in a production carrousel. To
avoid problems in the carrousel, it is important that the
gel time, time to peak and demoulding time remain the
same when changing raw materials such as, in this case,
the curing system. If one of the steps in the process progresses too fast or too slowly, the efficiency of the whole
production chain in the carrousel decreases; ideally, the
cobalt-free accelerator should react exactly the same way
as a cobalt-based one.

Reactivity data
General reactivity data were generated by AkzoNobel for
a high reactive orthophthalic resin using standard quartz
filler, Butanox® M50 (medium reactive methyl ethyl
ketone peroxide - MEKP), Trigonox 44B (acetyl acetone

42 jec composites magazine / No84 October 2013

Nouryact CF13 selected by Holonite
After considering the above general test results, Holonite
verified these in their test facility. An issue of attention was that the curing process is normally carried out
with Trigonox 44B, an acetyl acetone peroxide which
is commonly preferred for its fast curing and high peak
exotherm. However, it is not the optimal peroxide when
used in combination with Nouryact CF13. In order to use
Nouryact CF13 to its full potential, a standard methyl
ethyl ketone peroxide (MEKP) such as Butanox M-50 is
required. As a consequence, Holonite had to change both
the accelerator and the peroxide when switching to a cobalt-free curing system. Holonite carried out a reactivity
test using their own raw materials and plotted time-temTime temperature curves:
1: Trigonox 44B (1 phr) +
cobalt 1% solution (1 phr)
2: Butanox M-50 (2 phr) +
Nouryact CF13 (2 phr)

temperature (°C)

Amounts in parts per 100 resin (phr)

2
3

1
4

3: Butanox M-50 (2 phr) +
Nouryact CF13 (1 phr)
4: Butanox M-50 (1 phr) +
Nouryact CF13 (2 phr)
5: Butanox M-50 (1 phr) +
Nouryact CF13 (1 phr)

time (relative scale)

Fig. 3: Defects in the material due to manufacturing resulting in voids and nonuniform mesostructure in some parts of the UD composite specimens lead to low
transverse tensile strength"

JEC COMPOSITES MAGAZINE - Issue #84 - October 2013

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