46
and insects. One of the methods commonly used to deal with a high volume of waste
tires is their application as a cheap substitute for coal in cement kilns or power
plants. It should be noted, however, that the energy equivalent of 1 kg of a passenger
car tire is around 128 MJ, while its combustion allows recover only 30 MJ. On the
other hand, about 6.8 MJ of additional energy is required to produce 1–1.5 kg of
ground tire rubber (GTR) (Schulman 2002). Waste tires and other waste rubber are
made from high quality materials (elastomers and reinforcement fillers), which
could be considered a valuable source of secondary raw materials. Therefore, the
search for new methods of recycling and application of waste tires in the industry is
totally reasonable.
In this chapter, the recent progress in the recovery and modification strategies of
the waste rubber will be discussed, paying special attention to the structureproperties relationships of the products obtained in order to better understand the
mechanism of waste rubber modification and/or functionalization and its impact on
the efficiency of the process.
4.2 Reactive Sintering of GTR
One of the possibilities for the direct application of GTR on an industrial scale is
reactive sintering. This simple and environmentally friendly process allows the
molding of waste rubber into simple shapes by applying high pressure and
temperature.
Arastoopour et al. (1999) patented the method of sintering of wasterubber followed by compression molding at a temperature of at least 200 °C by applying a
compression force of at least 10 tons to the rubber powder for a period of at least one
hour. According to the patent claims, this technology ‘results in the formation of a
single piece of the rubber, elastomeric, or thermoset material, with no change in
chemical structure’.
Morin et al. (2002) indicated that reactive sintering makes it possible to convert
commercially available rubber powder into new rubber products with tensile
strength in the range of 4–7 MPa and an elongation at break of 150–250%. The
scheme of the reactive sintering process of rubber wastes is shown in Fig. 4.4.
Hrdlicka et al. (2011) indicated that rubber recycling by reactive sintering is suitable for natural rubber and styrene-butadiene rubber vulcanized with sulfur-based
curing systems, while it is not recommended for vulcanizates cured with sulfur
donors or peroxides.
Reactive sintering can be done without additives and with the use of curing systems or adhesive binders. It should be noted that this method is limited to the production of low-cost products with simple shapes and low quality requirements. The
application of additives and/or binders during reactive sintering usually improves
the processing and final performance properties of the prepared products. This is
related to additional physical interactions (e.g. by reinforcing fillers) and chemical
reactions (e.g. crosslinking), which have a beneficial impact on interfacial adhesion
between GTR particles.
Ł. Zedler et al.
and insects. One of the methods commonly used to deal with a high volume of waste
tires is their application as a cheap substitute for coal in cement kilns or power
plants. It should be noted, however, that the energy equivalent of 1 kg of a passenger
car tire is around 128 MJ, while its combustion allows recover only 30 MJ. On the
other hand, about 6.8 MJ of additional energy is required to produce 1–1.5 kg of
ground tire rubber (GTR) (Schulman 2002). Waste tires and other waste rubber are
made from high quality materials (elastomers and reinforcement fillers), which
could be considered a valuable source of secondary raw materials. Therefore, the
search for new methods of recycling and application of waste tires in the industry is
totally reasonable.
In this chapter, the recent progress in the recovery and modification strategies of
the waste rubber will be discussed, paying special attention to the structureproperties relationships of the products obtained in order to better understand the
mechanism of waste rubber modification and/or functionalization and its impact on
the efficiency of the process.
4.2 Reactive Sintering of GTR
One of the possibilities for the direct application of GTR on an industrial scale is
reactive sintering. This simple and environmentally friendly process allows the
molding of waste rubber into simple shapes by applying high pressure and
temperature.
Arastoopour et al. (1999) patented the method of sintering of wasterubber followed by compression molding at a temperature of at least 200 °C by applying a
compression force of at least 10 tons to the rubber powder for a period of at least one
hour. According to the patent claims, this technology ‘results in the formation of a
single piece of the rubber, elastomeric, or thermoset material, with no change in
chemical structure’.
Morin et al. (2002) indicated that reactive sintering makes it possible to convert
commercially available rubber powder into new rubber products with tensile
strength in the range of 4–7 MPa and an elongation at break of 150–250%. The
scheme of the reactive sintering process of rubber wastes is shown in Fig. 4.4.
Hrdlicka et al. (2011) indicated that rubber recycling by reactive sintering is suitable for natural rubber and styrene-butadiene rubber vulcanized with sulfur-based
curing systems, while it is not recommended for vulcanizates cured with sulfur
donors or peroxides.
Reactive sintering can be done without additives and with the use of curing systems or adhesive binders. It should be noted that this method is limited to the production of low-cost products with simple shapes and low quality requirements. The
application of additives and/or binders during reactive sintering usually improves
the processing and final performance properties of the prepared products. This is
related to additional physical interactions (e.g. by reinforcing fillers) and chemical
reactions (e.g. crosslinking), which have a beneficial impact on interfacial adhesion
between GTR particles.
Ł. Zedler et al.