Upload
others
View
0
Download
0
Embed Size (px)
Citation preview
©Si
rris
1
Thanks to their lower weights, composites typically lead to lower
CO2 emissions. Despite advances in industries such as aerospace
and automotive, another sustainability aspect is putting the material
to the test: two materials joined together form an inherently strong
and tough entity that is almost impossible to separate again. This
results in substantial consequences for the material complexity
of waste fl ows on product disposal. Because of this complexity, a
closed recycling loop can only be achieved by deploying energy-
intensive separation processes.
The following processing routes for recycling composites are
normally suggested: mechanical milling, thermal processing (e.g.
pyrolysis and processing in the cement industry) and solvolysis
(the chemical route). Although these technologies can be applied
to both carbon and glass composites, a shift has taken place in
practice. Glass fi bre composites are mostly processed using
mechanical shredding and end up in the cement industry, while for
carbon fi bre composites either pyrolysis or solvolysis is often used.
This white paper discusses recycling both types of materials
individually:
1. Recycling composites: hopeful developments for the
Belgian circular economy (introduction)
2. Recycling carbon fi bre composites: high quality recyclate
in response to ambitious legislation
3. Recycling glass fi bre composites: what is the cheapest
way of disposing of this enormous waste mountain?
RECYCLING COMPOSITES
WHITE PAPER
The use of lightweight components
stands or falls on the choice
of materials. Product value,
product costs, production costs,
development costs and risks are
however diffi cult to estimate when
talking about less known materials
such as composites. Moreover,
the wide range of materials and
processes makes selection even
more diffi cult.
This is why the SLC-Lab, the
Sustainability Department at
Sirris and their partners in the
CompositeBoost project, want
to pass on essential tools and
methodologies to help designers
and OEMs make the right choices.
In providing support, we want
to give more clarity with the
publication of various white papers
dealing with current issues. The
fi rst white paper introduced the
issue of sustainability, the second
white paper goes deeper into
‘recycling composites’.
SirrisLeuven-GentCompositesApplication Lab
©Sirris
2
1. RECYCLING COMPOSITES: PROMISING DEVELOPMENTS FOR THE BELGIAN CIRCULAR ECONOMY
The quality of separated materials is very important in the recycling
process. The properties should be as near to the original quality
as possible so that both materials can be directly integrated into a
new production cycle. However in practice, the materials cycle of
composites is not closed. After milling the waste material, normally
just the fibres can be recovered for recycling. This means relatively
short fibres (up to 150 mm) that can only be used in low-performing
applications such as injection moulding applications or SMC/BMC.
Currently, the industry is giving a lot of attention to the development
of higher quality applications in answer to the rapidly growing
composites waste mountain, and it is also searching for cheaper
raw materials. Using recycled carbon fibres could offer significant
cost reductions.
About 6,000 tons of composite waste material is created each year
in Belgium. On top of that, there is another 4,000 tons of production
waste, mainly from glass fibre composites. The waste from carbon
fibre composites is a fraction of this. The greatest part of the
waste is currently sent to landfill, although from the large, pure,
homogeneous flows of glass fibre composite, a substantial part of
this is currently processed by way of co-processing in the cement
sector. The glass fibre acts as a replacement raw material and the
polymer provides energy thanks to its calorific value. Although all
the composite components are usefully processed this way, the
reinforcing properties of the fibres are not put to use. This has
resulted in increasing global interest in finding alternative, high
quality methods of recycling composites. As there are substantial
©Sirris
3 ©Si
rris
3
differences in these new developments between the carbon fibre
and glass fibre sectors, the latest recycling technologies and the
individual applications are dealt with separately in this paper.
It can be estimated that around twenty companies are involved
in composite recycling around the world. This number includes
companies who carry out their own recycling, as well as companies
who take in this waste for recycling. These companies are currently
overcoming obstacles such as collecting consistent flows and
upscaling and optimising technologies. A lot of attention is also
being paid to outlets for these new materials, which is done by
gaining the trust of their customers for example. This requires very
detailed technical supporting information about the properties of
the materials created from recyclate.
Glass fibre reinforced composite waste being shredded to be used in the cement industry [1]
©Sirris
4
The arrival of composite recycling companies goes hand in hand
with increasing interest from the academic world. Still at different
levels of maturity, various technologies have already been developed
for separating the fibre and plastic materials from each other while
retaining the original properties. Some have already upscaled to
industrial levels and are commercially active, others are still at the
development stages.
Recycling therefore puts a halt to landfilling composites, which
complies with a landfill ban that operates in some countries, or is
mandatory according to product legislation, but that’s not all. It also
lowers the environmental impact of new products by limiting
energy-intensive fibre production. It has been estimated for example
that if 50 percent of the current glass fibre production was replaced
by recycled fibres, the annual level of CO2 emissions would be at
least two million tons less. Recycling significantly lowers the cost
of reinforcement fibres. [3] Recycled carbon fibre with a decrease
in mechanical properties would be 20 to 40 percent cheaper than
the primary material. Thanks to these advantageous economic
conditions, the recycling option is actually cheaper than landfilling,
certainly where carbon is concerned.
An example of production waste incurred by cutting fibre mats to size at BMW [2]
©Sirris
5
2. RECYCLING CARBON FIBRE COMPOSITES: HIGH QUALITY RECYCLATE IN RESPONSE TO AMBITIOUS LEGISLATION
In most European countries landfilling is the most common practice
for end of life-cycle plastics. There is currently a landfill ban post-
consumer plastics in nine European countries. So in Flanders for
example, this means that composites collected separately may no
longer be landfilled. [4] The automotive industry has also set its
limits: it has said that it must be possible to reuse or recycle 85
percent, and to reuse, recycle or recover 95 percent of the weight
of a vehicle. (“Recover” includes burning for energy recovery in
compliance with the End-of-life Vehicles Directive, ELV.)
The need to comply with such legislation is reinforced by the sharply
growing volume of carbon fibre composites. The automotive
industry together with the aerospace industry represents more than
50 percent of the global demand for carbon fibre composites. It is
anticipated that this demand will triple by 2020 when compared
with 2010. [5] Moreover, by that year the global demand will exceed
supply. Therefore economically feasible answers must be found in
the short-term for the end-of-life stage of this growing volume of
carbon composites. This will involve recycling technologies, but
also new logistical chains for the waste flows, as well as new end-
use applications.
Two typical processes for dealing with carbon composites are
pyrolysis and solvolysis.
©Sirris
6
Pyrolysis
The most advanced is the thermal process: pyrolysis with or without
oxygen. Waste in the form of prepregs, dry fibres or hardened
laminates are processed in temperatures between 450 and 700 °C.
The waste is converted into fibres, oils and gases. For example
pyrolysis applied to SMC glass fibres results in 75 percent solid fibre,
14 percent oil and the remainder gas by weight. [4] The oil contains
monomers that in principle can be reused in new resin. However,
extraction of monomers is not carried out in practice because of the
economic reasons. After milling the recyclate, it typically consists of
fibres (up to 150 mm) that can be used in the compounding industry
as milled powder, or as non-wovens. The figure below shows some
commercially available semi-finished products.
The pyrolysis process is the most commercially used process. The
process is currently at an optimisation phase in which the parameters
are gradually being altered and fine-tuned. For example, leading UK
company ELG, managed to lower processing energy consumption in
2015 by 35 percent. There are also thermal processes (e.g. fluidised
bed technology and microwave technology) that are currently being
developed, yet with limited applications.
Prepreg
Compounds [7]
Short fibres [9]
Non-wovens, with or without TP binder [8]
Milled carbon [9]
Dry fibres/fabrics
Laminates
POSSIBLE TYPES OF WASTE [7] COMMERCIAL SEMI-FINISHED PRODUCTS
©Sirris
7
A kayak made from fibres recovered from the aerospace industry [10]
Solvolysis
Solvolysis is a recycling technology in which a solvent dissolves
composite resin at lower temperatures. The process gives
good results at laboratory level, whether or not in combination
with pyrolysis. Commercial applications currently remain limited.
Although it appears to be a very promising route making it possible
to retain the fibre structure, as well as the plastic monomers. The
process also avoids the formation of carbonized materials, which
following pyrolysis contaminates the fibre surface and as such
prevents good fibre matrix adhesion. The kayak below for example
is a demonstrator made from fibres recovered from the aerospace
industry.
©Sirris
8
Search for high quality recyclate
Recycled fibres are usually milled shorter than the primary ones so
that a uniform level of quality can be achieved. The properties of
the shorter fibres are the same as those of the primary fibres.
Companies state that after recycling by pyrolysis, recycling the
modulus remains virtually unchanged and the tensile strength can
be about 10 to 20 percent lower. There is also a potential cost
reduction of 20 to 30 percent in comparison with primary carbon
fibre. [6] The recycled fibres recovered from the pyrolysis process
are best used in the manufacture of non-wovens, either with or
without a thermoplastic binder. The photograph below shows the
roof of a BMW i3 made from secondary carbon fibre.
In addition to the individual fibre properties, the textile structure
is also very important. The non-woven properties are still low
when compared with their primary unidirectional or textile-based
composites. This is only because of the orientation potential of the
primary fibres. For this reason, primary carbon fibres are used for
guaranteeing rigidity where this plays a crucial role. Therefore the
orientation of short, recycled fibres is an important study subject
found in literature. Studies are carried out using air flows in the
production of yarn for example. The results will definitely make a
difference where fibres are concerned and will widen the design
opportunities of the recycled material. The latest step in the search
for high quality recyclate.
Example of carbon fibre recycling by the SGL Group in Germany: on the left is the non-woven produced with secondary carbon fibre - on the right the roof of the BMW i3 [2]
©Sirris
9
3. RECYCLING GLASS FIBRE COMPOSITES: WHAT IS THE CHEAPEST WAY OF DISPOSING OF THIS ENORMOUS WASTE MOUNTAIN?
The composites market is heavily dominated by glass fibre
composites (more than 90 percent). The largest volume of composite
waste comes from glass fibre composites based on thermosets.
In Belgium alone that is around 10,000 tons of waste annually.
These flows of waste originate principally from the transport
and construction sectors. Although the largest part of fibre glass
composite production is for export, a lot of composites are imported.
A recent study instigated by OVAM, concluded that the greatest
challenge lies in the analysis of all the various material flows.
Companies are often not particularly clear about either their
production or associated waste figures. Apart from that, many
manufacturers have no idea of what happens at the end of life-cycle
stage of their products. It is also difficult to make estimates about
the imports.
Though it is clear that the volumes being released are growing rapidly.
For example the operational wind turbine capacity in Belgium is
currently approximately 2,300 MW, which is roughly equivalent to
about 28,000 tons of composite material. Taking account of the annual
increase in generation capacity, this could mean that from 2030 on,
3,000 tons of wind turbine blades are released each year. Polyester
boats are being released in great numbers too. Old boats in Belgian
harbours and marinas are already creating a problem, particularly as
some neglected boats and yachts start sinking after a while and the
©Sirris
10
harbour authorities are unable to take the initiative to remove them.
In addition, there are several thousand tons of composite water
sports equipment stored in gardens, sheds and garages that are fast
approaching the end of life-cycle stage. According to a Dutch study,
about 4,000 tons of composite material will be released annually
over the next 15 years. These figures demonstrate that wind turbine
blades and boats are ideal candidates for recycling, particularly as
they produce relatively pure waste flows. Other waste flows such as
swimming pools and printed circuit boards are usually smaller and
often more contaminated.
The ambiguous volumes and quality of these waste flows makes
it difficult to provide suitable collection channels. A reasonable
number of recycling centres for separately collecting glass fibre
waste could be the solution here. However transporting lightweight,
voluminous glass fibre composites is expensive and processing
(i.e. removing contaminates, chopping up, etc.) is an intensive task.
Nonetheless, because of current legislation, landfilling and burning
will no longer be a feasible option.
Boats, wind turbine blades and pultrusion sections: examples of pure glass fibre waste flows for which the first recy-cling options exist. [12a,b,c]
©Sirris
11
Pyrolysis
Although pyrolysis is the most convenient processing method for
carbon, it is actually more difficult to apply to glass. The figure below
[3] shows just how much glass fibres lose their strength during
thermal processing. The high temperatures degrade the sizing of
the glass fibre and the glass fibre structure.
The ReCoVeR research project, which ended in 2015, claimed to be
able to recover 80 percent of the strength of thermally treated glass
using an economically feasible recovery process. The recyclate
can be used in existing process chains for glass fibre products that
include injection moulding applications and GMT. This patented
process is currently one of the few recycling routes that retains
so much added value from the fibre and therefore has a lot of
commercial potential.
Typical results from the litterature on residual fibre strength after heat conditioning. [3]
©Sirris
12
Cement industry
Studies show that the current and most efficient way of valorising
glass fibre composites is by processing them in cement ovens.
Milled material is mixed with other raw materials in which 30 percent
of the composite is used as the source of energy and 70 percent
as the raw material. Processing 1,000 tons of pultrusion profiles for
example saves 450 tons of coal, 200 tons of lime, 200 tons of sand
and 150 tons of aluminium oxide. [1] This recognised and developed
process is however not so economically attractive in countries
where landfilling is still permitted.
Glass fibre composite waste to be milled for the cement industry at the Fiberline company [1]
©Sirris
13
Mechanical milling
Mechanical milling technologies are commercially available, but
only on a small scale. The price of primary glass fibre is very low
and recyclate is generally of low quality.
There are examples of companies that have made technologies
available that produce mechanically functional fibres. But
contamination of these fibres along with the remaining resin
sometimes prevents proper fibre resin matrix adhesion in the new
composite. Deploying this type of recyclate fibre is going to demand
intensive testing and quality control.
Composites can be finely milled into filler, however standard
fillers are currently cheaper. Despite these setbacks, a number of
companies are actively working on this, as can be seen from the
examples below.
AB-VAL (France) processes production waste (left) by way of compressing a mixture of recyclate and thermoplastic materials (right). [13]
©Sirris
14
CONCLUSION
The development and implementation of recycling technologies is
rapidly growing at both research and commercial levels. Important
motivation includes a ban on landfilling composites, a lowering of
the environmental impact and dropping cost prices. The latter is
currently giving the recycling of carbon fibre composites a substantial
boost in commercial applications.
With respect to glass fibre, developments are taking longer, because
the economic value of it tends to be limited for now. Nonetheless,
various studies indicate a substantially strong recycling potential.
Reprocover (which applied for bankruptcy earlier this year) converts BMC for example from the automotive indus-try (left) into cable channel covers (right). [14]
©Sirris
15
SOURCES
[1] Fiberline, fiberline.com[2] BMW[3] Thomason, J.; Jenkins, P.; Yang, L. Glass Fibre Strength—A Review with Relation
to Composite Recycling. Fibers 2016, 4, 18.[4] OVAM[5] AVK Market research[6] Current status of recycling of fibre reinforced polymers; University of
Birmingham; 2015[7] ELG CF[8] SGL Group[9] Procotex[10] Cranfield University, Nick Rawle Photography[11] Composites World: Recycled koolstof fiber: Comparing cost and properties, 2014[12a] © Ssuaphoto | Dreamstime.com[12b] © Gary Parker | Dreamstime.com[12c] © Alexander Sorokopud | Dreamstime.com[13] AB-VAL, France[14] ReprocoverComposites recycling: where are we now?, CompositesUK, 2016OVAM; market research into the reuse of high quality recycling for fibre reinforced thermosets, 2016
AUTHORSLinde De Vriese (Sirris)
Thomas Vandenhaute (Sirris)
©Sirris
16
‘Eco-compliance as a competitive weapon’, a collaborative
project with Sirris and Agoria, gives active support to companies
including manufacturing companies, where the impact lies on
production or production design in order to take advantage
of innovation opportunities presented by eco-compliance:
cost savings, improved market access, extended production
life-cycles, lower total costs of ownership and the design of
new ecological products. This acts as leverage for sustainable
innovation by adopting a proactive approach towards changing
environmental legislation and standards, and market demands.
This is how the barriers to innovation are lowered and the
technology choices for participating companies become clearer.
Thomas Vandenhaute (Sirris) is project leader for sustainability
and engaged in the areas of sustainable material management and
ecological production. He is also co-author of the book, ‘Innoveren
met materialen’ [innovating with materials] and an approved
OVAM SIS Toolkit coach. He also contributed to the TWOL study
for OVAM (http://www.ovam.be/kunststofcomposieten), which
involved visiting and interviewing many companies. Together
with Agoria he supports companies wanting to make the move
towards the circular economy with activities such as setting
up learning networks, as well as providing support in bringing
together partners for specific materials or material flows.
ECO-COMPLIANCE AS A COMPETITIVE WEAPON
This white paper was written within the scope
of two projects: ‘CompositeBoost’ and
‘Eco-compliance as a competitive weapon’.
©Sirris
17
‘CompositeBoost’ is a collaborative project involving the Sirris
SLC-Lab, UGent and KU Leuven. Based on these six highly
relevant issues, the project partners want to use these essential
tools and methodologies to allow designers and OEMs to make
the right choices. The masterclasses, demonstrations and
exploratory case studies will help transform the composites
processor into a reliable production company and partner. This
will mean that our companies will retain their competitiveness over
foreign competitors.
COMPOSITEBOOST
Markus Kaufmann, PhD (Sirris)
is the program manager of the composites division of Sirris and head
of the SLC-Lab since April 2012. Before that he acquired experience
in design and cost estimation of composite structures. Markus is
responsible for coordinating CompositeBoost.
Linde De Vriese (Sirris)
is the team member specialising in material characterisation, press
forming of thermoplastic composites, and bio-composites. Linde re-
ceived her Master’s in Materials Engineering at KU Leuven in 2010,
specialising in polymers and composite materials.
©Sirris
18
Bart Waeyenbergh (Sirris)
works at SLC-Lab on prototyping, product development, mould
design and processing of thermoset composites. He graduated
with a Master’s in industrial sciences at Group T in Leuven in 2008,
specialising in advanced manufacturing.
Tom Martens (Sirris)
is the senior technician at SLC-Lab, with 18 years of experience
in the plastics industry. He is responsible for the production
of prototypes and demonstrators in both thermoplastics and
thermoset composites.
Katleen Vallons, PhD (KU Leuven)
is a post-doctoral researcher at SLC-Lab. She has worked with the
Composite Materials Group at KU Leuven since 2005, mostly on
projects in collaboration with industrial partners. Her expertise is in
the material behaviour of composites.
Geert Luyckx, PhD (UGent)
is a post-doctoral researcher at SLC-Lab. He has worked at
UGent, Mechanics of Materials and Structures, since 2003 and is
involved in the experimental validation of new optical measuring
technologies for measuring shape distortion in composite
components.
©Si
rris
PARTNERS
SIRRIS LEUVEN-GENT COMPOSITES APPLICATION LABCelestijnenlaan 300C3001 Heverlee+32 498 91 94 [email protected]
SirrisLeuven-GentCompositesApplication Lab