47
Kowalska et al. (2010) patented mixtures of waste rubber (especially GTR) with
sulfur in the range of 0.1–5.0 wt.% with possible addition of dithiocarbamate up to
5.0 wt.%, which was subsequently revulcanized in a temperature range between
150–210 °C, under pressure of 5–50 MPa and for 0.1–5.0 min/mm of product thickness. Products obtained with tensile strength between 0.9 and 2.7 MPa could, for
example, be used as rubber floor coverings, wipers or car floor mats.
Crespo et al. (2012) studied the impact of latex and polychloroprene as binders
during the reactive sintering of ground ethylene-propylene-diene-monomer rubber.
It was found that the increase in pressure and temperature improved mechanical
properties of the material, however, the tensile strength of the prepared materials
was relatively low (in the range of 0.3–0.9 MPa). The authors noted that, regardless
of the compression temperature, the addition of 5% latex adhesive leads to a 50%
reduction in tensile strength and elongation at break. A higher content of latex adhesive results in a more visible deterioration of mechanical properties. On the other
hand, for polychloroprene adhesive an opposite tendency was observed, the
mechanical properties of reactively sintered rubber wastes increase with an increase
in the content of this binder.
Polyurethane (PU) adhesives are commonly used as binders during waste rubber
recycling (Tan et al. 2008; Sułkowski et al. 2010, 2012), which is related to their
relatively simple processing and a broad spectrum of properties. Perfromance can
be easily tailored by changing the chemical structure of the PU matrix or the application of a specific modifier.
Balas et al. (2014) patented composition of PU waste rubber crosslinked with
unsaturated compounds. As could be expected, a higher content of waste rubber into
PU matrix caused a significant deterioration of mechanical properties, which is
illustrated in Fig. 4.5. This is related to the low compatibility between the PU matrix
and the crosslinked rubber particles.
The examples presented by Balas et al. (2014) also confirmed that the isocyanate
index has a significant impact on the mechanical properties of PU/waste rubber
composites, which is related to the efficiency of the reactions between the isocyanate component and the active sites present in waste rubber, as presented in Fig. 4.6.
Fig. 4.4 Reactive sintering process of rubber wastes. Based on data presented by Morin
et al. (2002)
4 Reactive Processing and Functionalization of Ground Tire Rubber
Kowalska et al. (2010) patented mixtures of waste rubber (especially GTR) with
sulfur in the range of 0.1–5.0 wt.% with possible addition of dithiocarbamate up to
5.0 wt.%, which was subsequently revulcanized in a temperature range between
150–210 °C, under pressure of 5–50 MPa and for 0.1–5.0 min/mm of product thickness. Products obtained with tensile strength between 0.9 and 2.7 MPa could, for
example, be used as rubber floor coverings, wipers or car floor mats.
Crespo et al. (2012) studied the impact of latex and polychloroprene as binders
during the reactive sintering of ground ethylene-propylene-diene-monomer rubber.
It was found that the increase in pressure and temperature improved mechanical
properties of the material, however, the tensile strength of the prepared materials
was relatively low (in the range of 0.3–0.9 MPa). The authors noted that, regardless
of the compression temperature, the addition of 5% latex adhesive leads to a 50%
reduction in tensile strength and elongation at break. A higher content of latex adhesive results in a more visible deterioration of mechanical properties. On the other
hand, for polychloroprene adhesive an opposite tendency was observed, the
mechanical properties of reactively sintered rubber wastes increase with an increase
in the content of this binder.
Polyurethane (PU) adhesives are commonly used as binders during waste rubber
recycling (Tan et al. 2008; Sułkowski et al. 2010, 2012), which is related to their
relatively simple processing and a broad spectrum of properties. Perfromance can
be easily tailored by changing the chemical structure of the PU matrix or the application of a specific modifier.
Balas et al. (2014) patented composition of PU waste rubber crosslinked with
unsaturated compounds. As could be expected, a higher content of waste rubber into
PU matrix caused a significant deterioration of mechanical properties, which is
illustrated in Fig. 4.5. This is related to the low compatibility between the PU matrix
and the crosslinked rubber particles.
The examples presented by Balas et al. (2014) also confirmed that the isocyanate
index has a significant impact on the mechanical properties of PU/waste rubber
composites, which is related to the efficiency of the reactions between the isocyanate component and the active sites present in waste rubber, as presented in Fig. 4.6.
Fig. 4.4 Reactive sintering process of rubber wastes. Based on data presented by Morin
et al. (2002)
4 Reactive Processing and Functionalization of Ground Tire Rubber