Characterization of the properties of thermoplastic elastomers containing waste rubber tire powder
Introduction
With an ever increasing number of automobiles in the world, the disposal of used rubber tires has been a significant problem in recent years. The ever increasing stockpile of waste rubber tires is a potential environmental hazard. One way of utilizing waste rubber tires is to recycle them. The recycling of waste rubber tires consists of three parts: heat utilization, processing and original utilization. The generation and utilization of waste rubber tires in Korea is shown in Table 1. From Table 1, it can be observed that the majority of waste rubber tires produced in Korea are used as fuel in cement kilns, which is ecologically unviable since it is well known that the combustion of waste rubber tires leads to emission of greenhouse gases like COx and NOx.
Our laboratory has been focusing considerable attention on the development of technologies to effectively recycle waste rubber tires (Kim and Burford, 1999, Kim and Park, 1999, Shanmugharaj et al., 2007). Recycling of waste rubber tires requires special techniques, because waste rubber tires are a thermoset material, which cannot be reprocessed like thermoplastics. Powder utilization is one of the most attractive techniques for its effective utilization. A promising way of ‘recycling’ waste rubber tire powder (WRT) is to incorporate it into thermoplastics to obtain thermoplastic elastomers (TPEs). However, the adhesion between the WRT and the polymer matrix is usually very weak due to the crosslinked structure of WRT. In order to solve the problem, some attempts were made to produce thermoplastic rubbers by adding WRT to the corresponding recipes (Lee et al., 2007, Shanmugharaj et al., 2005). It was recognized early that the WRT should be devulcanized, or at least partially devulcanized, to facilitate the molecular entanglement between the WRT and the polymer matrix. For devulcanization, various routes were attempted, such as thermomechanical and thermochemical treatments (Kim et al., 2006, Radeshkumar and Karger-Kocsis, 2002).
Following the above guidance, special attention has been focused on the effective utilization of WRT in TPEs. In the first stage of this 10-year project (2000–2002), we developed technologies to produce ultra fine powders from waste rubber tires. In the second stage (2003–2005), we developed technologies to manufacture thermoplastic elastomers from WRT. Some products, like the brake pedal and rubber wheels, have been developed and commercialized successfully. In the third stage (2006–2009), we are developing technologies for mass production based on WRT.
In order to achieve this target and produce TPEs which contain WRT and exhibit competitive properties, bitumen and compatibilizer were incorporated into polypropylene/WRT composites due to their devulcanized, plasticized and compatibilized effect on the composites. In this work, the influence of bitumen content and different compatibilizers on the properties of polypropylene/WRT/bitumen composites is discussed.
Section snippets
Materials
Polypropylene (PP, H360F), manufactured by SK Corporation in Korea, was obtained. Styrene–ethylene–butylene–styrene (SEBS, Kraton G1652) and maleic anhydride-grafted styrene–ethylene–butylene–styrene (SEBS-g-MA, Kraton FG-1901X) were obtained from Shell Chemical Co. Ltd. Maleic anhydride-grafted ethylene–propylene–diene monomer (EPDM-g-MA, KEPA1130B) was supplied by Kumho Polychem Co. Ltd in Korea. Bitumen (X-4) was obtained from Waterproofbank Company in Korea. WRT was produced by Hongbok
Influence of bitumen and compatibilizer on the tensile mechanical properties of the composites
One of the major criteria for a thermoplastic elastomer is that elongation at break is more than 100%. This is the primary reason why we focus on the tensile mechanical response of composites in this work. The influence of bitumen and compatibilizer on the tensile mechanical properties of composites is shown in Table 2. Comparing sample 1 with sample 2, it can be found that the elongation of the composite increases in the presence of bitumen, due to the devulcanizing effect of the bitumen. The
Conclusion
In this work, waste rubber tire powder was treated with bitumen. It was proven that the presence of bitumen can improve the elongation at break, thermal stability and processing flowability of PP/WRT composites due to the devulcanizing and plasticizing effects of bitumen. Moreover, the presence of compatibilizer (SEBS-g-MA) can also enhance the elongation at break and thermal stability of PP/WRT composites, whereas it decreases the processing flowability. This originates from the
Acknowledgement
The authors are grateful to the support from the BK21 program in Korea.
References (11)
- et al.
Blends of bitumen with various polyolefins
Polymer
(2000) - et al.
UV surface modification of waste tire powder: Characterization and its influence on the properties of polypropylene/waste powder composites
Polymer Testing
(2005) - et al.
Study on powder utilization of waste tires as a filler in rubber compounding
Rubber Chemistry and Technology
(1999) - et al.
The biological and chemical desulfurization of crumb rubber for the rubber compounding
Journal of Applied Polymer Science
(1999) - et al.
A comparative study of effect of compatibilization agent on untreated and ultrasonically treated waste ground rubber tire and polyolefin blends
Polimeros
(2006)
Cited by (71)
Screw extrusion process used in the polymer modified asphalt field: A review
2024, Journal of Cleaner ProductionMacro- and micro- mechanisms associated with valorization of waste rubber in cement-based concrete and thermoplastic polymer composites: A critical review
2023, Construction and Building MaterialsEffect of binder dosage and the use of waste rubber fiber on the mechanical and durability performance of geopolymer concrete
2022, Journal of Building EngineeringAn overview on the recycling of waste ground tyre rubbers in thermoplastic matrices: Effect of added fillers
2021, Resources, Conservation and RecyclingSustainable mobility: The route of tires through the circular economy model
2021, Waste ManagementRecycling waste thermoplastic for energy efficient construction materials: An experimental investigation
2019, Journal of Environmental Management