JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 63

Tab. 1: Hexion's portfolio of epoxy systems for fast RTM/LCM processing of automotive parts

Epikote™ Trac resin systems

Suitability

Curing time

Curing
temperatures

Glass transition temperature °C (DSC midpoint)

Epikote™ Trac 06170
Epikure™ Trac 06170
Heloxy™ additive Trac 06805

RTM/LCM

45 sec-3 min

110-145°C

115-140°C

Epikote™ Trac 06150
Epikure™ Trac 06165
Heloxy™ additive Trac 06805

RTM/LCM

90 sec-3 min

115-130°C

110-125°C

Epikote™ Trac 06150
Epikure™ Trac 06150
Heloxy™ additive Trac 06805

RTM, large parts

5-10 min

110-120°C

110-125°C

fibres. After this latency period, a 3D
cross-linked network develops. Once sufficiently cured, the part is de-moulded.
Proper execution of all of these steps is
essential to part quality and must occur
in just a few minutes.

Epoxy products
optimized for HP-RTM
In the 1990s, CFRP cure time took
hours, not minutes. Recent automotive
opportunities have prompted advances
in epoxy resins for significant curing and
total cycle time reduction, and fast-curing epoxy systems were introduced in the
past 5 years. These systems have rapidly
reduced cycle times from several minutes
to below 90 seconds, and current, stateof-the-art systems operate close to the
60-second industry target.
The Epikote™ epoxy resin systems
introduced by Hexion 2 to 3 years ago
offered long latency periods, during
which viscosity stayed below 200
mPa*s. This allowed manufacturers
to inject a lot of resin slowly (60 g/s)
to achieve high-quality laminates.
However, with the new HP-RTM
equipment on the market today, a long
latency may not always be required.
Newer Epikote™ epoxy resin systems aim
to reduce total cycle times by optimizing
both injection and curing times. These
systems typically exhibit a low initial
viscosity, but offer a shorter injection
window. Field application experience

shows that with modern HP-RTM
equipment, around 80% of automotive
parts can be produced with these newer
resin systems injected at higher rates (>
100 g/s).
Careful selection of the resin system
to suit both part and equipment is
important as well (see Figure 1). A full
portfolio of fast-curing RTM/LCM
epoxy systems suited to various part sizes
and complexities is available (Table 1).
The benefits of the new Epikote™ resin
Trac 06170, Epikure™ curing agent Trac
06170 and Heloxy™ additive Trac
06805 designed for RTM and LCM
processing include very low viscosity
during infusion, and fast glass transition
temperature (Tg) development to above
the moulding temperature. This system
offers very easy de-moulding and very
short cycle times, with excellent wetting

and adhesion on carbon, glass or aramid
fibres. Typical uses include mass production of structural automotive parts such
as frame, chassis, monocoque structure,
floor pan and firewall. The new system
exhibits very low and almost constant
viscosities (15-20 mPa*s) at the recommended processing temperatures. Once
thermally activated, it will react rapidly.
Curing times from around 200 seconds
at 100°C down to 45 seconds at 140°C
have been recorded. The result is a cycle
time of under 60 seconds above 130°C
(see Figure 2).

Fast part production
with liquid compression moulding
Complementing HP-RTM's facilitation
of rapid, high-quality complex part production, LCM can facilitate even faster
production of lower complexity parts.
In LCM processing, the resin is not

Fig. 2: Cycle time (s) of Epikote™ resin Trac 06170, Epikure™ curing agent Trac 06170 and Heloxy™
additive Trac 06805 as a function of moulding temperature (°C)

No99 September 2015 / jec

composites magazine 63

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #99 - September 2015