JEC COMPOSITES MAGAZINE - Issue #83 - August/September 2013 - 78

epoxy

Degradable epoxy resin for
sustainable carbon fibre composites
Adesso’s Cleavamine® curing agents offer a new approach
to the problem of composite material recycling, and are
available for both liquid and prepreg resin systems.
Further optimization of the Cleavamine® systems is in
progress to meet specific formulation and performance
requirements.

By
Bo Liang
Chairman & CEO
Adesso Advanced Materials

Recycling processes

n all forms of transportation, the drive for
improved efficiency has led to efforts to
reduce the weight of structures through
the use of materials such as advanced
composites. The introduction of the largely
carbon fibre/epoxy Boeing 787 constituted
a step change in the commercial aerospace
industry, where from now on the structural
weight of commercial aircraft will comprise
between 35% and 50% advanced composite
materials. In the automotive industry, the
use of these materials is transitioning from
niche, luxury or high-performance vehicles
to production vehicles. In the marine industry, where composite materials have long
been used, more advanced materials such
as epoxy resins and carbon fibres are being
increasingly used.
One of the benefits of composite materials – their durability – is also one of their
disadvantages when it comes to recycling.
Recycling is important for a number of
reasons, including the relatively high cost
of raw materials compared to traditional
materials, and the fact that most composite materials are based on non-renewable
resources. These factors make the reuse
of materials at the end of their lives highly
desirable.

A number of recycling processes have been
proposed and demonstrated [1]. However,
most of these end-of-life materials are still
destined for landfill or incineration. For
example, the fluidized bed recycling process
– the only industrialized process for recycling carbon fibre reinforced composites –
involves pre-fragmentation and pyrolysis at
high temperature (around 550°C) [2]. The
recycled materials are typically shortened
fibre with significantly deteriorated mechanical properties. Alternative supercritical
solvation processes [3], where it is claimed
that the recycled carbon fibres retain a high
proportion of their original strength and
stiffness (up to 99% in some cases), need
to operate under high pressure (up to 22
MPa) and at high temperature (200-450°C)
to ensure solvents go supercritical. Therefore, finding a feasible solution to recycle
these end-of-life composite wastes under
mild conditions with minimal secondary
pollution is still a challenge in the composite
industry. This paper describes Adesso’s novel
approach of designing degradable curing
agents for the manufacturing of next-generation recyclable composites [4].

Degradable epoxy
Comparing the current research efforts
in recycling the existing fibre reinforced
composite materials, Adesso Advanced Ma-

78 jec composites magazine / No83 August - September 2013

terials has developed a completely different
approach by designing degradable epoxies
from the starting materials. Based on novel
Clevamine® degradable curing agent chemistry [5], the company has developed recyclable epoxies suitable for liquid and prepreg
processes. Cured epoxy resins and composites made with such degradable amine
curing agents can be broken down under a
specific, relatively benign and environmentfriendly process. This process is expected to
yield environmental and economic benefits,
compared with current recycling techniques,
and to increase the proportion and value of
the materials recovered. Whilst the current
focus is on carbon fibre composites, the
technology is equally applicable to glass fibre
composites.

Mobile phone case
The diagram below (Figure 1) is a real example illustrating the recycle and re-use of an
‘end-of-life’ mobile phone case made from
a carbon fibre fabric and one of Adesso’s
proprietary Recycloset® epoxy products.
After the epoxies are degraded in a specific
solution, the three pieces of carbon fibre
fabric are recovered and can then be re-used.
The degraded epoxy polymer is also recovered as white solids after removing solvent
and reagents, and can be used as a thermoplastic additive in adhesives and moulding
compounds.

JEC COMPOSITES MAGAZINE - Issue #83 - August/September 2013

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #83 - August/September 2013