JEC COMPOSITES MAGAZINE - Issue #132 - January/February 2020 - 58

TECHNOLOGY curing agent
Focus
About Albemarle Corporation: Albemarle Corporation is a global
manufacturer and supplier of curing agents to the epoxy and polyurethane industry. The company supplies ETHACURE®100 (E100),
ETHACURE®270 (E270), ETHACURE®300 (E300), and ETHACURE®420
(E420) curing agents. Ethacure curatives are aromatic diamines that
are liquid at ambient temperature with low viscosity and good compatibility with epoxy resins. Diethyl toluene diamine (DETDA) (trade
name ETHACURE®100) is a proven effective curing agent for fibreglass
filament-wound epoxy pipes and carbon fibre-reinforced composites.

Fig. 4: Injection moulding process to make laminates with housed N2

gave a slightly higher dielectric strength, but a slightly lower
dielectric constant compared with the MDA-cured system.
The Tg of E100-cured epoxy systems was studied with respect
to cure temperature and time. The Tg increases with cure temperature and time, as shown in Figure 2. A cure temperature
of 175°C with a 3-hour curing time gives the best Tg development rate.
The Ethacure 270 curative blend was recently developed in
Albemarle's laboratory. E270, a liquid at room temperature
(see Figure 3), is an effective curing agent for liquid epoxy resins at ambient and elevated temperatures. It gives 55 min and
20 min gel times at 100°C and 130°C respectively, as shown
in Figure 3. The E270-cured epoxy system gives a Tg of 154°C
when cured at 175°C for 3 hours.
The ETHACURE® 300 (DMTDA) curing agent is a low-viscosity liquid aromatic diamine. It may be used as an epoxy
curing agent for advanced composites. It has utility in prepreg
applications because of its room temperature latency. The formulated resins containing E300 and diaminodiphenyl sulfone
(DDS) as described in Table 2 were used to produce prepregs.
Standard autoclaving procedures were used to prepare composite laminates in this study. The vacuum bag cure consisted
of a layup in a nylon bag comprised of the prepreg stack, separator, breather and bleeder layers. The laminates were prepared using the following cure procedure: (1) Hold at 270°F
with contact pressure for 45 minutes; (2) close mould to stop
and ramp up temperature from 270°F to 350°F at a rate of
25°F/min; (3) hold at 350°F for 2 hours; (4) cool to 150°F.
The laminate samples prepared above were cut into short
beam shear test coupons according to ASTM-2344.

The data obtained demonstrates that the E300-cured system
exhibits better moisture resistance and retention of mechanical properties. This reduced water content is most certainly
due to the reduced polarity of the amine moiety in these systems. There may also be a steric effect in the ortho substitution, which blocks the association of water at the amine functionality. The Tg indicates that the decrease of the value after
water boiling is less with the E300-cured system.
In this study, carbon fibre laminates were also produced using an injection moulding process with housed N2, as shown
in Figure 4. Before injecting the resin into the mould, the
vacuum was applied from the outlet first, and then the resin
(MY720-E300) was injected into the mould with pressure at
60 psi. The filled mould was placed into a pre-heated oven at
175°C for 2 hours, then cooled to ambient to demould. The
sample was cut for a bending test according to ASTM D7264.
The flexural strength and flexural modulus of the laminates
are 71 Mpsi and 4099 Mpsi, respectively.
Conclusions
In this study, a comparison between MDA and E100 was
conducted in Albemarle's curative laboratory. The obtained
data indicated that the E100-cured system delivers better
mechanical properties, higher deflection temperature, and
similar electrical properties compared with the MDA-cured
system. E100 is thus a viable alternative to MDA in advanced
composites. The new blend (ETHACURE®270) developed
in the lab also delivers adequate reactivity, suitable working
time and, when cured, it provides desirable Tg and mechanical properties. E300 also demonstrates potential utilization in
advanced composites. The amount of water absorbed by the
E300-cured system is considerably less than that of commonly used DDS, indicating improved resistance to the harmful
degradation effect of absorbed water.
The results discussed in this article provide a foundation for
customers to make FRP with Ethacure delivering desired
properties to meet and exceed their specifications.

jec composites magazine / N°132 January - February 2020

More information:
yong.tang@albemarle.com
www.albemarle.com

JEC COMPOSITES MAGAZINE - Issue #132 - January/February 2020

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