INFLUENCE OF REGRIND ON PROPERTIES OF PLASTICS

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Ľ. Dulebová, F. Greškovič: Influence of regrind on properties of plastics processing by injection moulding
INFLUENCE OF REGRIND ON PROPERTIES OF
PLASTICS PRODUCED BY INJECTION MOULDING
Ľudmila Dulebová1,*, František Greškovič1
1
Department Technologies and Materials, Faculty of Mechanical Engineering, Technical University of Košice,
Mäsiarska 74, 040 01 Košice, Slovak Republic
*
corresponding author: Tel.: +421 55 602 3544, e-mail: ludmila.dulebova@tuke.sk
Resume
The contribution deals with the evaluation of results of selected
mechanical tests. Materials Crastin® PBT (with 30 % glass fibre) and
Celanex® 2004-2 PBT (without filler) were used at tests with various
percentage of added regrind into basic material. The mechanical
properties were obtained by tensile test and Shore hardness test.
Utilization of regrind at the production of new moulded parts is
important from aspect of reduction plastics waste and pollution
abatement of environment.
Available online: http://fstroj.uniza.sk/PDF/2011/08-2011.pdf
1. Introduction
Plastics are nowadays the most important
segment of production and consumption by
volume among the all technical material. Ever
since the emergence of plastics and more
frequent application in all aspects of industry,
this material has the necessary respect and a
unique place on the world market for used
materials [1].
Involvement in the production of this
material also has negative aspects. In
environmental terms, plastic is too burdensome
for the ecosystem. Their decomposition takes a
long time and when burning a very large number
of harmful emissions [2]. Therefore places a
high priority on the ecological and especially
effective recycling of used waste from these
materials. Great development of plastic products
also brought with it the problem of waste
management. In practice, therefore, a need to
make more recycled plastics and this material
was used to production of new products [3].
Article info
Article history:
Received 30 May 2011
Accepted 29 June 2011
Online 14 July 2011
Keywords:
Plastics
Regrind
Injection moulding
Tensile test
Hardness test
ISSN 1335-0803
Mixing the primary material with recycled
material are often occurs, although with an
identical designation as the primary material, but
the value of some of its properties may be
altered [4, 5].
The benefits of plastic recycling:
•
important saving of primary materials,
•
use of recycled
applications,
•
new possibilities for products made from
recycled materials,
•
minimization, mainly communal waste,
•
creation of new employment,
•
conservation of matter (as opposed to
energy assessment).
product
for
new
Restrictions of plastic recycling:
•
not all waste can be reused for the original
use of products - e.g. packages,
Materials Engineering - Materiálové inžinierstvo 18 (2011) 44-48
Ľ. Dulebová, F. Greškovič: Influence of regrind on properties of plastics processing by injection moulding
•
recycled product often has new features,
and recycled once the product becomes
waste,
•
recycling of recycled product may no
longer be effective and justified,
•
plastic parts and products of foreign
production are also on the market, where
recycling in view of their quantity,
specifications may not be effective and
realizable [6,7].
The article aims to investigate the
influence of regrind on selected mechanical
properties of plastics with and without filler.
Materials are used in the automotive industry.
It was further of experiments to determine
whether there was a change in the coefficient of
relationship strength - hardness of materials with
various % regrind.
2. Experimental material and methods
Influence of regrind added into the basic
material on the change of the mechanical
properties of plastic was determined by tensile
test and Shore hardness test. Tests were
conducted on the test specimens with a 0%,
20%, 40%, 70% and 100% regrind in the basic
material.
Material PBT (polybutylentereftalat) was
used for experimental testing:
•
•
DUPONT Crastin® LW9330 PBT – No.
899921002, mineral composite with 30%
glass fibre.
45
Battenfeld, type HM 1000/350 according to
STN EN ISO 294-1 in the Department of
Technologies and Materials, Faculty of
Mechanical Engineering, Technical University
in Košice. The tested samples were made in
multiple ISO injection mould [8].
The experimental verification of the
influence of regrind on mechanical properties
was tested according to STN EN ISO 527 –
tensile test. The tensile machine TIRA- test
2300 was used for the test. Five samples were
tested for each material.
Shore hardness test was done according
to STN ISO 868 (64 0129). The test was
performed on the Shore Hardness Tester type
D producer HARDMATIC Mitutoyo. Shore
hardness was measured on samples with
dimensions 60 mm x 60 mm x 2 mm. It was
used for testing of five pieces of samples of each
material. On the samples were performed for
five measurements in the direction and vertically
to the direction of melt flow.
3. Results and discussion
In the tensile test were evaluated
parameters yield strength and tensile strength. In
the Figure 1 are presented σY for samples with
various % regrind of experimental materials.
Graphic dependence measured values σM of test
samples shown in Figure 2. Average values of
Shore hardness of tested materials shown in
Figure 3.
TICONA Celanex® 2004-2 PBT - No.
899921006 colour NATURAL, without
filler.
Material PBT belong to group of polyester
plastics. It is semicrystalic polymer what utility
properties belong into group of engineering
plastics and both testing materials have used in
the automotive industry [7].
The samples were made by injection
moulding, with using of the injection press type
Fig. 1. Average values of yield strength
of tested material
Materials Engineering - Materiálové inžinierstvo 18 (2011) 44-48
46
Ľ. Dulebová, F. Greškovič: Influence of regrind on properties of plastics processing by injection moulding
Fig. 2. Average values of tensile strength
of tested material
Fig. 5. Structure of testing material Crastin® PBT
matrix of material with 100% regrind
Structure of material Crastin® PBT after
tensile test is shown in the Figure 6 and failure
of glass fibre is shown in Figure 7.
Fig. 3. Shore hardness of tested materials
with various % regrind
Break planes of testing samples were
observed on scanning electron microscope JEOL
JSM – 7000F, Japan. Structure of polymeric
material Crastin® PBT after tensile test is
shown in the Figure 4 (basic material). Structure
of material with 100% regrind is shown in
Figure 5.
Fig. 4. Structure of testing material Crastin® PBT
matrix of basic material (0 % regrind)
Fig. 6. Structure of testing material Crastin® PBT
after tensile test, failure of basic material (0 %
regrind)
Fig. 7. Structure of testing material Crastin® PBT
after tensile test, - detail (100 % regrind)
Materials Engineering - Materiálové inžinierstvo 18 (2011) 44-48
Ľ. Dulebová, F. Greškovič: Influence of regrind on properties of plastics processing by injection moulding
Hardness tests are effective and simple
means for estimating the mechanical strength of
materials. The paper studied the relationship
between hardness and strength of experimental
material. The ratio of tensile strength to
hardness of experimental materials as a factor
“k” is shown in Table 1 and Table 2.
Tab. 1
(material with glass fibre). For the material
without glass fibre there wasn´t found
change of this value.
•
Shore hardness test hasn’t determined the
influence of added regrind into the basic
material (scilicet in the direction and
vertically to the direction of melt flow).
•
On the basis of compared values of
measurements listed in Table 1 and Table 2,
we can conclude that the hardness of the
surface
•
layers of moulded samples of tested
materials showed no variation depending on
the percentage of regrind.
Comparison of the values of strength and hardness
of material Crastin® PBT
Material Crastin® LW 9330 PBT
regrind
(%)
0
20
40
70
100
σM (MPa)
47
50
50
50
50
ShD
85
85
85
85
84
k
0.55
0.59
0.59
0.59
0.59
Tab. 2
Comparison of the values of strength and hardness of
material Celanex® PBT
Material Celanex® 2004-2 PBT
regrind
(%)
0%
20%
40%
70%
100%
σM (MPa)
119
119
112
108
110
ShD
79
79
80
79
78
k
1.51
1.51
1.4
1.37
1.41
On the basis of experimental tensile test
and Shore hardness test of tested materials were
reached the following conclusions:
•
•
The value σY of tested material with glass
fibre has tendency to decline about 8%. For
the material without glass fibre there wasn´t
found change of this value.
At evaluation of the parameter σM we draw
conclusion to similar results i.e. with
increasing the percentage of regrind to
material there was the decrease of value σM
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4. Conclusion
Requirements that are imposed for
plastic products can only be met with a good
knowledge of mechanical, physical, electrical,
chemical, optical and biological properties.
Anisotropy of mechanical and physical
properties of molding products of fiberreinforced plastics is considerably greater than
the unreinforced. The presence of different
additives in the basic material, for example
glass fibers can sometimes completely change
dependence that apply for unreinforced plastics.
Growing applications of plastics for
technically demanding parts ever put greater
demands on the level of knowledge about the
behavior of these materials, particularly in
conditions of mechanical stress.
Before application of completed parts
moulded with regrind it is necessary to verify
technological moulding conditions with
additional technological tests in conditions of
application in praxis.
Acknowledgements
This contribution is the result of the
project implementation: Center for research of
control of technical, environmental and human
risks for permanent development of production
Materials Engineering - Materiálové inžinierstvo 18 (2011) 44-48
48
Ľ. Dulebová, F. Greškovič: Influence of regrind on properties of plastics processing by injection moulding
and products in mechanical engineering ( ITMS:
26220120060) supported by the Research
&Development Operational Programme funded
by the ERDF.
[4] L.Běhálek: Acta Mechanica Slovaca 12(3a)
(2008) 39-44.
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Materials Engineering - Materiálové inžinierstvo 18 (2011) 44-48