JEC COMPOSITES MAGAZINE - Issue #96 - April 2015 - 65

resin

Polyaryl ether amide resins - a prospective
alternative to phenolic and epoxy resins
A few years ago, polyaryl ether amides were assessed as a new
promising matrix resin material for composites due to an exceptional resin-fibre adhesion that results in high mechanical
properties. Cured polyaryl ether amides also have good intrinsic
flame-smoke-toxicity (FST) properties. These properties made
the material an attractive alternative for long-established solutions. However, previous curing conditions using temperatures
over 200°C and long curing times hampered its full breakthrough.

he efficient processing of high-performance fibre-reinforced plastics
(FRP) is one of the key challenges
of the composites industry. Evonik
Industries AG has accepted the challenge of providing sustainable potential
for lightweight design with high quantities and low cost. Within the House
Composites Project, the company is currently developing, among others, novel
polymer systems which are intended to
solve this challenge.
Finding an alternative to phenolic resins
is becoming more important from the
perspective of component manufacturers
and OEMs. Composites with low surface
quality and poor mechanical properties
require high efforts and costs for postprocessing and result in lower weight
advantages of the fibre composites. A
new one-component matrix resin system
based on polyaryl ether amide, named
Calidur®, combines high mechanical
performance and surface quality while
fulfilling flame-smoke-toxicity (FST)
requirements for aviation interior applications. The new resin combines a high

degree of crosslinking with an intrinsic
flexibility of the chemical network.
Introduced some years ago, it is suitable,
for example, for prepreg processing. Due
to new developments, it is now possible
to cure the resin system at a lower range
of temperatures. By varying the curing
temperature from 140°C to 220°C at curing times of 5 to 45 minutes, a Tg range
from 135°C up to 195°C is feasible.

Advantages of the
new prepreg resin
A new benchmarking programme for
glass fibre composites showed the advantages of Calidur® compared to state-ofthe-art prepreg resins for aviation interior
applications. The prepregs were produced using E-glass fabric (type 07781)
with a resin content of 40wt%. The epoxy
and phenolic reference resin systems
were commercially-available standard
aerospace prepregs for interior applications (epoxy resin fulfils the FAR 25.853
requirements; phenolic resin fulfils the
DAN 407-08 requirements). The glass
fibre laminates produced for mechanical
testing were observed to be void-free.
In contrast to fibre-reinforced phenolics, the surface quality of the Calidur®

Dr. Silke Witzel
Senior Project Manager
Project House Composites
Kirsten Alting
Product Manager Custom Manufacturing
Performance Materials
Evonik Industries AG

panels was excellent. The mechanical
testing methods were primarily chosen
in regards to fibre matrix resin adhesion
and impact behaviour. The Calidur® data
showed superior mechanical properties
compared to the phenolic resin. In the
case of in-plane shear strength, there was
even a difference by the factor of two.
The epoxy resin showed only slightly
superior mechanical properties with
regards to residual strength after 30-J
impacts.
The flammability properties of composites were checked in a comparable
benchmark programme using the same
epoxy and phenolic prepregs. Major aircraft testing methods like vertical Bunsen
burner, heat release and smoke density
were chosen for this programme, which
was carried out at the Airbus test laboratory in Bremen, Germany. In all test
methods, Calidur® fulfilled the Airbus
and FAA fireworthiness requirements
and proved competitive with phenolic
and superior to epoxy resins.
Another beneficial property of cured
prepregs based on polyaryl ether
amide resin is their adhesion to sandwich core materials. Foams based on

No96 April 2015 / jec

composites magazine 65

JEC COMPOSITES MAGAZINE - Issue #96 - April 2015

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #96 - April 2015