Page 51 from: April 2015

51April 2015

A U T O M O T I V E

Upgrading and
application
ARN has conducted extensive research into puri-
fying the plastics concentrates from unwanted
elements, especially rubber and wood. Invest-
ments have been made to integrate new screen-
ing and bouncing machines for removal of inter-
fering elements.
At the ARN plant, three plastics concentrates are
produced: heavier than 1.3 kg/l (50%); 1.1-1.3
kg/l (20%); and a floating fraction of < 1.1 kg/l
(30%). These are separated from the raw ASR
fraction through grinding, magnetics and air
separation. Actual separation of the plastics is
achieved via two sink-float steps using calcium
carbonate as a medium.
The heavier than 1.3 kg/l fraction contains valu-
able metals such as copper wire and stainless
steel which can be further separated with balling
of the metals and air tables for metal-plastic
separation. The remaining plastic-rubber mixture
is high in chlorine (10%) and therefore difficult
to process in an incineration plant.
The plastic mixture within a density of 1.1-1.3
kg/l contains a broad spectrum of plastics which
are still difficult to separate for material recy-
cling. Normally, this fraction is used as a reducing
agent in a blast furnace. ARN is investigating
innovative material recycling applications.
The floating fraction of < 1.1 kg/l contains the most
interesting plastics for material recycling, which are
the polyolefins (PP/PE) and styrenics (ABS/PS).
Further upgrading of these fractions into single
plastic streams can be achieved by introducing
additional sink-float steps, electrostatic separa-
tion, and NIR and colour sorting. The melt filtra-
tion after the extrusion line will take away the
final impurities such as rubber. This downstream
separation and compounding of plastics is con-
ducted by specialist plastics recycling companies
which have access to other plastics for blending,
in order to achieve the right qualities and prod-
uct specifications.

About the author
Allard Verburg is business development man-
ager at ARN Recycling. This post-shredding tech-
nology plant in the Netherlands is one of the
world’s most advanced facilities for handling
automotive shredder residue. The PST plant is
supported by a European LIFE+ subsidy.
This article represents the second and penultimate
part of a series, with
the third and final fea-
ture to appear in the
May issue of Recycling
International. The first
part was published in
our March issue.
www.arn.nl/recycling

and the one which will improve the recycling

rate and quality of plastics – relates to the pro-

duction of components in the product supply

chain. A lack of a true incentive and essential

knowledge exists among product designers to

create materials and products which, at the very

least, will not dent overall vehicle recyclability.

Synergy with other complex waste streams is

also essential to reach a true market scale.

The following are worthy of note:

• Spectral imaging. Innovation is taking place

to improve the speed and quality of sen-

sor-based X-ray, colour, near infrared and

laser sorting. Latest developments are com-

bining several sorting tasks.

• Organic-based plastics. Use of sugar cane and

corn starch – within polylactic acid or PLA –

may sound like an environmentally preferable

alternative to petroleum-based plastics. But

for a recycling process, organic-based plastics

deliver an adverse impact because the melt

flow temperature is totally different.

• Recycling of composites. Although their use

is very limited within the automotive sector,

composite structures will have significant

technical, economic and organisational

impact on the existing recycling chain. The

practical recyclability of novel plastic combi-

nations is becoming increasingly important.

Composite structures
The best-known example of extensive plastics

composite usage dates back to the 1950s when

the Trabant motor car was launched in eastern

Germany. It followed a simple design that could

be easily maintained and repaired. To limit the

use of expensive metals, the car’s body was

manufactured using Duroplast, a thermoset-

ting plastic-containing resin strengthened by

recycled wool or cotton.

Thermoset structural composites, as previous-

ly used in Trabant body panels, are now

employed in the aviation sector and some mod-

ern car equivalents such as electric vehicles that

boast a thermoset carbon reinforced frame and

body work. Lightweight vehicles provide excel-

lent environmental characteristics as they are

reducing greenhouse gas emissions along the

use phase. But for recyclers, thermosets are infa-

mous for their irreversible characteristics, unlike

thermoplastic composites, which cannot be

returned to their original matrix. Electric vehi-

cles with carbon composite structures are also

iconic for the recycling sector, and not only

because of high-voltage battery packs and high

levels of gluing instead of welding: an ‘end-of-

life’ composite car requires a totally different

recycling approach. Indeed, these could become

the first vehicles to be recovered for their poly-

meric value rather than for their metal content.

Adaptive by nature
To an increasing extent, the car manufacturing

chain is investigating thermoplastic composites,

not least because they are more easily recyclable

and because carbon (or other) fibres can be

recovered and reintroduced into lower-quality

applications. The recycling sector has always

been adaptive by nature, learning to transform

a threat into an opportunity. ‘Economic value’

within production and recycling has always been

the pillar supporting recycling chains. Therefore,

all operators along the value chain should col-

laborate to create a circular model for innovative

plastics against best ecological standards.

tures such as railway sleepers. Fractions not

suitable for material recycling are directed to

co-combustion within cement kilns or to ener-

gy recovery thanks to their high calorific value.

Fields of innovation
There are plenty of fields of innovation within

the ASR processing chain, especially in the

recovery of plastics. But the key innovation –

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