Waste rubber with thermoplastics blending

A company called Innovative Polymer Technologies has developed a solid state shear pulverisation process for powder production, intimate mixing and compatibilisation of polymer blends, including waste rubber-thermoplastic blends [14]. The process creates powders with a large surface area and complicated morphologies. In addition to waste rubber, the process is also capable of producing powders from thermoplastic rubbers, and waste rubber-thermoplastic blends. The resulting powders can be used for a variety of applications. 

Further information in particular areas can be obtained by using recent reviews. For example, readers who would like to obtain more information on the use of waste rubber in blends with thermoplastics, thermosets and virgin rubber compounds can obtain it in an extensive review that has been produced recently by Karger-Kocsis, Meszaros and Barany [1], This review also surveyed the methods available to reclaim waste rubber, the surface treatment of rubber particles to improve interfacial adhesion in blends, and the principals underlying the compatibilisation of waste rubber within the host matrix. 

A considerable amount of work has been carried out to establish if it is possible to produce good-quality rubber/thermoplastic blends by incorporating waste rubber crumb, whether surface-activated or not, into thermoplastics matrices. This work has often been carried out using commodity semi-crystalline thermoplastics, such as low-density polyethylene (LDPE), high-density polyethylene (HOPE) and polypropylene (PP), with the aim to produce final products that are either modified (e.g., improvements in impact strength) or have properties that are usually associated with thermoplastic rubbers. 

The possibility of preparing thermoplastic rubbers by blending PP with dynamically vulcanised waste butyl rubber has been reported by a group of Chinese workers [7]. They carried out a series of tests on the blends using a range of techniques to characterise their mechanical, processing and solvent resistance properties. 

The ductility of GRT-polyethylene blends drastically decreases at ground rubber concentration in excess of 5%. The inclusion of hnely ground nitrile rubber from waste printing rollers into polyvinyl chloride (PVC) caused an increase in the impact properties of the thermoplastic matrix [76]. Addition of rubber powder that is physically modihed by ultrasonic treatment leads to PP-waste ethylene-propylene-diene monomer (EPDM) powder blends with improved morphology and mechanical properties [77]. 

Rubber matrices have commonly been used as a second phase to improve the toughness of brittle thermoplastic materials, such as polypropylene and polyethylene. These systems, commonly referred to as polyolefin thermoplastic elastomers (TPOs), are a special class of thermoplastic elastomers that combine the processing characteristic of plastics at elevated temperatures with the physical properties of conventional elastomers at service temperature, playing an increasingly important role in the polymer material industry. Polyolefin blends attract additional interest due to the possibility of recycling plastic wastes, avoiding the complex and expensive processes of separation of the different components. 

S. Satapathy, A. Nag, G. B. Nando, Thermoplastic elastomers from waste polyethylene and reclaim rubber blends and their composites with fly ash. ProcessSaf. Environ. Prot. 88 (2), 131-141 (2010). 

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