JEC COMPOSITES MAGAZINE - Issue #79 - March 2013 - 100

matrix

Defining the matrix standard for thermal
resistance improvement of epoxy-prepregs

By

Prepreg : a fibre reinforcement material, usually in fabric,
roving or unidirectional form, pre-impregnated with a resin
matrix in controlled quantity, providing ultimate composite
performances.

Philippe Christou
Head of European Technical Support
Huntsman Advanced Materials (Switzerland)

P

repregs which were once prevalent in the aerospace and performance sectors such as Formula 1,
have now become increasingly common
across many sectors of the composites
industry for the ultimate mechanical
performances they provide, their consistent properties, their ease of use, the
high quality surface finish they achieve
and the wide choice of types that are
now available.
Inside the prepreg world of applications, and more perhaps than in the
composite world in general, an unfailing and growing trend lies in thermal
resistance needs. But of course without
sacrificing other performances and/or
processing capabilities and as always
the best balance and compromise must
be found by the formulating scientists.
Increasing or maintaining thermal
resistance while providing additional
benefits has always been one of the
main focuses of Huntsman associates,
from scientists designing new molecules to production specialists bringing concepts to real and commercial
molecules.
To illustrate this commitment, the fol-

lowing products – either well-proven,
recently introduced or under developmental status - can be highlighted.

Highest glass transition temperatures in epoxy chemistry
Tactix® 742 resin is best described
chemically as a triglycidylether of
tris-(hydroxyl phenyl) methane. Its
chemical structure (figure 1) shows a
very symmetrical and rigid skeleton
with strong aromatic character. A
consequence of this unique profile is
that with a given hardener, the resin
provides the highest glass transition
temperatures achievable among current
commercial epoxy resins (figure 2).
This is a solid resin but which is very

Fig. 1: Chemical structure of the Tactix® 742 resin

100 jec composites magazine / No79 March 2013

compatible with other epoxy resins. It
also shows quite low viscosity when
heated at medium temperatures (η:
600-700 mPa.s @ 80°C) so it is easily
processed into prepreg formulations
designed for high temperature applications.

Reducing water sensitivity of
epoxy matrices and maintaining
their thermal resistance
When formulators try to improve thermal performance of thermoset systems
based on standard diglycidylether
of bis-phenol A (such as Araldite®
GY250), then often look at epoxydized
phenol novolacs (known as EPNs).
Tactix® 556 is a special EPN whose
chemical structure can be described as
the introduction of dicyclopentadiene
entities between each phenolic entity of
the prepolymer structure. This chemical
modification creates a very hydrophobic skeleton so that this unique epoxy
resin absorbs significantly less water
than standard multifunctional epoxies
commonly used in advanced prepreg
composites (figure 3), without sacrificing the thermal resistance of the cured
network (glass transition temperatures
in dry condition equivalent to standard
EPNs).
This makes Tactix® 556 ideal for new
JEC COMPOSITES MAGAZINE - Issue #79 - March 2013

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #79 - March 2013
