5th International DAAAM Baltic Conference
"INDUSTRIAL ENGINEERING – ADDING INNOVATION CAPACITY OF LABOUR
FORCE AND ENTREPRENEURS"
20–22 April 2006, Tallinn, Estonia
REUSE OF REINFORCED ACRYLIC PLASTIC WASTE IN NEW
COMPOSITE MATERIAL DEVELOPMENT
Kers, J., Kulu, P., Goljandin, D. & Mikli,V.
¶ Abstract: This study had two aims: to
develop prospective techniques for
recycling of composite plastic wastes and
to find a potential application area for
secondary raw materials. The method of
collision was selected for the treatment of
composite
plastic
wastes
and
a
disintegrator mill was used. In our
experiments, the particle size of acrylic
plastic was reduced and glass fibers intact
were separated. The paper describes the
results of materials separation, granularity
of the milled material and morphology of
the plastic powder particles.
To develop new filler materials for fillerresin systems, plastic powders with
different granularity were used. The
mechanical properties of the new
composite materials were examined.
The developed new acrylic powder filler
materials are prospective for use in the
filler-resin systems as reinforcement
acrylic cells.
Key words: environmental friendly
technology, waste management, composite
plastic waste, recycling, disintegrator mill
2002/96/EC on WEEE, the producers are
responsible for environment protection
during their product lifecycle. The
producers should form the producers
responsibility organizations to manage the
collection and recycling of post-consumer
products. To meet these requirements, two
solutions can be proposed. Firstly, to
extend the lifecycle of the product in
combination of durable materials and a
durable design. Secondly, to extend the
lifecycle of the materials to reduce
environmental impacts related to materials
manufacturing and transportation. Finding
a solution for the reuse of production waste
will help to recycle post consumer products
in future.
The interest of this study lies with Estonian
bathroom equipment manufacturing companies. In their point of view, the
composite plastic wastes (vacuum formed
acrylic plastic with glass fiber reinforcement) have low volume weight and thus
have to be precrushed to save transportation and landfilling costs.
2. EXPERIMENTAL
1. INTRODUCTION
2.1 Plastics to be recycled
Industrial polymethylmetacrylate (PMMA)
wastes can be divided into two groups:
acrylic
plastic
wastes,
without
technological additives form about 20 %
and reinforced acrylic plastic wastes about
80 % of the total amount.
The acrylic plastic wastes without
technological additives could not be
recycled and re-extruded to produce the
new PMMA sheet material, because of the
Wastes
are
produced
in
each
manufacturing plant. Every producer
should manage its waste effectively to
protect
the
environment
against
contamination. According to EU waste
directives, hierarchy of waste management
is: 1) prevention, 2) reuse, 3) recycling, 4)
energy recovery, 5) incineration without
energy recovery, 6) landfill. As it follows
from directives 2000/53/EC on ELV and
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amorphous structure of this thermoplastic
material. Heating up the acrylic plastic
material over the glass transition
temperature (100 °C) converts the plastic
in to a rubber-like state, which makes this
material ideal for vacuum forming.
Continued heating will cause thermal
degradation instead of melting the material.
Physical and mechanical properties of the
plastics to be recycled are given in Table 1.
disintegrator to separate the GFP pieces
from the milled acrylic plastic sieves were
used;
– intermediate milling in the DSA-2
disintegrator to reduce the size of GFP
pieces for a feed of DSL-115;
– final milling in the DSL-115
disintegrator, using the direct and selective
milling system to remove glass fiber from
the milled material.
Table 1. Physical properties of milled
plastics
2.3 Granularity and morphology study
In this study, particle size of acrylic plastic
powder was characterized by sieving
analysis (SA) and image analysis (IA). To
characterize particle shape, the image
analysis was used. To evaluate coarse
powder granularity (particle size more than
50 m), the sieve analysis ensuring
sufficiently good results was used. Particle
size distribution is adequately described by
the modified Rosin-Rammler distribution
function, and the method may be used to
characterize
powders
produced
by
collision. Particle size data obtained by the
image analysis method was primarily
described through the arithmetical mean
diameter dm of the measured values. The
values of dm depend on the number of
particles. To characterize particle shape the
IA method was used and the following
shape factors were calculated:
– the elliptic parameter;
to characterize ellipticity, aspect ratio AS
(similar to elongation in literature) was
calculated by
AS = a/b,
(1)
where a and b are the axes of the Legendre
ellipse (ellipse is an ellipse with the centre
in the object’s centroid and with the same
geometrical moments up to the second
order as with the original object area).
– the irregularity or surface smoothness;
the shape factor roundness RN value was
calculated by
RN=P2/4A (2)
where P is perimeter and A is area of the
particle. Roundness of the circle is equal to
1. In all other cases, roundness it is greater
than 1 [4].
Material
(23 °C)
PMMA
PE-resin
GFP
Tensile
strength
N/mm2
78
50
75
Tensile
modulus
MN/mm2
3.33
4.60
7.70
Impact
strength
kJ/m2
12
5
9
Density
kg/m3
1200
1200
1700
PMMA sheet material, vacuum-formed and
reinforced with glass fiber plastic (GFP) in
the matrix of polyester resin, was used as
the composite plastic waste.
2.2 Retreatment technology
For the milling of the composite plastic
waste, different disintegrator types
developed at Tallinn University of
Technology were used [1]. As a result of
our previous study the 20 %wt. of the
industrial acrylic plastic wastes was
retreatable by high energy disintegrator
mills [2]. Thus, we assumed that we made
assumption that the high energy mill can be
used for the remaining 80% wt. To recycle
the composite plastic waste, we then
focused on the size reduction of the acrylic
plastic constituent and the separation of the
glass fiber constituent.
Disintegrator milling offers the possibility
of milling with a simultaneous separation
of components with low toughness
properties [3]. Composite plastic stripes
(PMMA+GFP) with dimensions of 500
mm length, 100-150 mm of width, and a
thickness of 5 mm were retreated by the
mechanical method – milling by collision.
The retreatment technology consisted of
three steps: – preliminary milling of
reinforced acrylic stripes in the DSL-158
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were obtained using an image processing
system, which consisted of a Nikon
Microphot-FX, an optical microscope
(OM) and a video transferring system.
Measurements were performed in the
transmission regime of OM, because of
more accurate results of particle size
obtained as compared to a reflected regime.
The size and shape parameters were
determined using image analysis – ImagePro Plus 3.0 system.
Morphology studies of acrylic plastic
powder particles showed the roundness
parameter RN 1.32 for powders with a
mean particle 600 m and the specific
energy of treatment 12 kWh/t and RN 1.31
for powders 300 m and the specific
energy of treatment 50 kWh/t.
3. RESULTS AND DISCUSSION
3.1 Recycling of composite plastic waste
As it follows from Fig. 1, an intensive size
reduction (80% of particles less than 25
mm) of composite plastic takes place by
the preliminary milling in the DSA-158
disintegrator.
90
Precrushing 0.2
kWh/ T
f( m) , %
80
2.4 4.8
kWh/ T
70
7.2
12
50
60
50
40
30
20
3.3 Reuse of the milled product
Preliminary tests to find the application
areas of acrylic powder as a new filler
material were made by using the Solid
Surface casting technology. For example,
most of bathroom washbasins are produced
by casting technology. Commonly,
washbasins are made from a composite
material consisting of a binder agent
(unsaturated polyester resin), a filler
material (dolomite powder) and a catalyst
agent added to resin to accelerate
hardening. The mixing ratios of the binder
agent and the filler material are 25/75 wt%.
The traditional filler material used in the
casting technology is a high-white
dolomite filler with the chemical
composition of CaMg (CO3)2 with a
density of 2850 kg/m3 and particle sizes of
coarse fractions (0.2-0.6 mm), (0.1-0.3
mm) and fine fraction (less than 0.1 mm).
For this purpose, the composites were
designed with different mixing ratios of
the binder (unsaturated polyester resin) and
the filler (acrylic powder). The filler
volume varied from 50 to 65 wt%. The
filler consists of 50 wt% of coarse fraction
(0.7-1.4 mm) and 50 wt% of fine fractions
(0.2-0.4 mm) of acrylic powder material. 1
wt% of peroxide catalyst was added to
accelerate
the
polymerization,
for
10
0
100.000
10.000
1.000
0.100
Size d ( mm)
0.010
Fig. 1. Dependence of the distribution
function of composite plastic particle size
on the specific energy of treatment
The results of the separation of glass fiber
plastic from the composite plastic waste
are given in Table 2.
Table 2. Results of separated GFP
Milling
stages
Milling
device
Separation
method
I
II
III
DSA-158
DSA-2
DSL-115
Sieves
Sieves
Air classifying
Separated
GFP,
wt%
16.3
12.2
16.5
As it follows from Table 2, the total
amount of separated GFP was 45 wt%. As
a result, we can reuse 55 wt% of acrylic
plastic from the composite plastic waste. It
is important to find a future application for
GFP. One of the possible areas for reuse of
GFP is in the production of polymeric
concrete products as reinforcement.
3.2 Study of the particles shape
The data necessary in a particle size study
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transforming from liquid to solid state with
maximum physical properties; The liquid
mixture of the composite was cast into a
plate shape mould (500 x 500 mm2) with a
layer thickness of 15 mm. We assumed that
by increasing the acrylic filler content the
mixed polyester resin will ensure the
hardness and good wear resistant properties
of the working surface of the washbasin.
The hardening time of the composite was
four hours. The best flow characteristics of
the mixture were with 50 wt% of acrylic
filler and 50 wt% of resin, but the best
surface quality and hardness after polishing
was achieved by the mixture of 66 wt% of
acrylic filler and 33 wt% of resin. The flow
characteristics of the mixture 66/33 could
be improved by using a lower viscosity
binder agent .
1B. To compare the test results, specimens
of acrylic sheet material were made. The
tensile test of the new composite materials
33/66 gave an average tensile strength 15
N/mm2. The tensile strength of an acrylic
plastic specimen was 42 N/mm2. We
assumed that the pores inside the material
influence the tensile strength of the new
composite material. To determine the
percentage and the size of the pores, the
microsection of the composite material was
prepared.
3.4 Porosity of the composite material
To study the porosity of the cast composite
material, specimens (50 mm length, 50 mm
width, and thickness 10 mm) were made.
The surfaces of the specimens (top, bottom
and cross section) were ground and
polished. The photos of the surfaces of the
specimen were taken and the pictures were
processed (see Fig.3).
3.4 Mechanical testing of the new
composite material
Mechanical properties of the new
composite materials were determined.
Using specimens of plastic composites (in
different compositions of the filler and
binder agent) were made according to ISO
and DIN standards. Mechanical properties
of the plastic are primarily defined by the
tensile strength of the material. Unlike
metals, the utmost influencing factor for
plastics is temperature. Therefore it is
important to know the minimum and
maximum working temperatures of the
plastic which are not entailing the changes
in physical and mechanical properties of
the material.
The tensile strength of composite plastic
materials mainly depends on the adhesion
strength between the resin matrix and
reinforcement. For glass fiber plastics, the
direction of reinforcement is important
(uni-axial, bi-axial, multi-axial). In our
case, the new composite plastic material
consists of polyester resin matrix and
granular reinforcement (acrylic plastic),
instead of fibers.
Test specimens were machined from cast
plate material in accordance with ISO 5272/1A/50 standard and specimen type was
Fig. 3. Porosity of the composite material
The images were analyzed with Image-Pro
Plus 3.0. Firstly, the surface areas of the
matrix and the pores were calculated. The
total area of the pores was 6.5 %. The pore
size data obtained by the image analysis
method were primarily described through
the arithmetical mean diameter dm of the
measured values (see Fig. 4). The mean
diameter of the pores was 97 m.
As it was mentioned above an increase in
the acrylic filler content in mixed polyester
resin ensures strength and hardness of
material, good wear resistance properties
for the surface of the materials.
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2. The retreated material can be reused in
the same production process where they
are generated.
3. The aim of further study is to design a
composite
material
for
washbasin
production. Washbasins made from the
designed new composite material, using
retreated plastics, would have a good wear
resistance of the working surface because
of the hardness of the acrylic material. At
the same time they will weight two times
less than produced of the dolomite filler.
16
14
Percent
12
10
8
6
4
2
0
60
70
80
90
100 110 120 130 140 150 160 170
Mean diameter dm,  m
Fig. 4 Mean diameter of the pores
Therefore it is important to determine the
optimal size and shape of particles in the
composite.
5. REFERENCES
1. Tamm, B. and A. Tymanok, Impact
grinding and disintegrators. Proc.
Estonian Acad. Sci. 1996, Eng., 2/2,
209-223,
2. Kers, J. and P. Kulu, Retreatment of
industrial plastic wastes by high energy
disintegrator mills, In proc. of Global
Symposium on Recycling, Waste
Treatment and Clean Technology,
Madrid 2004 Vol. 3, 2795-2797
3. Kulu, P. and A. Tymanok, 1999,
Treatment of different materials by
disintegrator systems, Proc. Estonian
Acad. Sci. Eng. 1999, 5/3, 222-242
4. Wojnar,
L.,
Image
analysis:
applications in materials engineering.
CRC Press LLC, Boca Raton, 1999
Fig. 5 Particle size and shape inside the
composite matrix.
As it follows from Fig. 5. the mean
diameter of the particle in surface was 105
m. The mean roundness parameter RN of
particles was 1.56 and the mean aspect AS
was 1.67.
6. CORRESPONDING AUTHOR
4. CONCLUSION
J. Kers
Department of Materials Engineering
Tallinn University of Technology
Ehitajate tee 5, Tallinn 19086, Estonia.
E-mail: j.kers@mail.ee
1. The existing advanced technologies for
size reduction mostly using 1 to 4 rotor(s)
with knives and the resulting size of the
final product (20-40 mm) not applicable as
a filler material in the casting technology,
however it suits for further size reduction
by milling in disintegrators. A high-energy
powder with a particle size of about 1-2
mm by two-step milling and 95 wt% glass
fiber content can separate by final selective
milling.
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