Rubber blends thermoplastic-recycled

Dynamic vulcanization is the process of vulcanizing the elastomer during its melt-mixing with the molten plastic (Coran and Patel, 1996). 

The use of GRT instead of virgin elastomers, however, results in significant deterioration in the mechanical properties of these composites. It was reported (Hilyward et al., 1983 Phadke et al., 1984 Phadke and De, 1986) that the GRT has a detrimental effect on most of the physical properties of cured rubber, the extent of deterioration increasing with the amount and size of the GRT. There have been many investigations with the aim to improve the adhesion between the GRT and polymer matrix. 

Blend Tensile Strength (MPa) Young s Modulus (MPa) Elongation at Break (%) 

Blends of GRT and recycled HDPE from used milk containers were studied and patented (Coran and Howard, 1999 Howard and Coran, 2000). Effects of GRT particle size and concentration on mechanical and rheological properties were determined. The blend systems were optimized by a soft rubber-plastic binder produced from a mixture of HDPE and EPDM, wherein EPDM is dynamically vulcanized during its mixing with the HDPE. It was concluded that the softening of the HDPE binder provides compositions of improved ultimate mechanical properties. 

The solid-state mechanochemical milling of PP/GRT blends was carried out, leading to the improved dispersion, as confirmed by the fluorescence microscopy and polarized optical microscopy (POM) observations (Zhang et al., 2012b). After 20 cycles of milling, the tensile strength and elongation at break of PP/GRT blends at a ratio of 100/40 were increased by 13.8% and 

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Ismail, H. and Suryadiansyah, S., Thermoplastic elastomers based on polypropylene/natural rubber and polypropylene/recycle rubber blends. Polymer Test., 21, 389, 2002. 

Michael, H., Scholz, H., and Mennig, G., Blends from recycled rubber and thermoplastics, Kautsch. Gummi Kunst., 52, 510, 1999. 

Polypropylene (PP) in various forms (filled, unfilled, reinforced, rubber blended) finds the greatest usage of all automotive plastics. Its consumption is likely to accelerate as a result of new laws requiring recyclability, and because of the weight and cost reductions it offers. New fabrication techniques may also contribute to growth. For example, the monomaterial sandwich construction techniques developed by fabricators yield rugged and lightweight PP-based instrument and door panels. These parts consist of a sandwich of reinforced or neat PP substrate, a cross-linked PP foam, and a thermoplastic polyolefin elastomer (TPO) cover. 

A number of methods [11,13-17] have been applied in an attempt to solve the problem and to find more effective ways of tire rubber recycling and waste rubber utilization. These methods include retreading, reclaiming, grinding, pulverization, microwave and ultrasonic processes, pyrolysis, and incineration. Processes for utilization of recycled rubber are also being developed, including the use of reclaimed rubber to manufacture rubber products and thermoplastic-rubber blends and the use of GRT to modify asphalt and cement. 

Thermoplastic elastomer (TPE) blends have been broadly studied as a new class of materials. TPEs offer various advantages and require no state-of-the-art processing machinery, while scrap and rejects are recyclable. Blends can be homogeneous, phase separated or both. TPEs are multi-phase polymer systems consisting of hard and soft domains that can be copolymers or mechanical blends. This phase separation leads to materials having unique and viable commercial physical properties. TPEs exhibit the thermoplastic characteristics of the hard thermoplastic phase, and resilience as a result of the rubbery domains. TPEs based on natural rubber (NR) and thermoplastic blends are known as thermoplastic natural rubber (TPNR) blends. There are two types of TPNR, namely thermoplastic polyolefin (TPO) and thermoplastic vulcanizate (TPV).3... 

Kuriakose et al. mentioned that the reduction of the molecular weight of NR by mastigation" improved the processability of NR/PP thermoplastic blends. It was also observed that quinoline imparts better ageing resistance than imidazole when used as antioxidants in the blend. Another study observed that the highest thermal stability is attained with the addition of ethylene-propylene diene rubber to the NR/PP blend." TPEs can also be developed from recycled rubber (PP/RR) and Ismail and Suryadiasnsyah observed that its thermal stability was higher than that of PP/NR." " ... 

PE/PP Recycled tire rubber Thermoplastic vulcanizate described (Syman-T NRI Industries) based on recycled tire rubber blend with PE/PP mixtures 169... 

Murphy and co-workers [3] have looked into the effect on physical properties of blending ultrafine rubber particles into thermoplastics. A large range of blends were produced using a munber of recycled thermoplastics and recycled rubbers in a batch process. The influence that the particle size of the rubber, the total amount of recycled rubber, and the degree of compatibilisation had on the physical properties was determined and reported. 

The market of PP/EPDM blends has grown dramatically because of its recycling abihty and processability by conventional thermoplastic processing equipment. The unique characteristics of thermoplastic elastomer made it an attractive alternative to conventional elastomers in a variety of markets. Liu et al. showed from the experimental blends (53) that materials cost reduction of between 30% to 50% is possible in comparison to commercial products if one applies the PP/EPDM blends to the construction of a basketball court, a tennis court, and a roller hockey rink, which were estimated around 7000, 14,000, and 40,000, respectively. The cost comparison took into account the percentage of rubber or PP used in experimental blend, the exponential factor for a scale-up process and the overall surface area of the specific applications. Among many possible application of this blend two readily feasible applications are roofing and flooring. 

Starting in the 1980 s, a number of governmental recycling policies created a demand for recycled thermoplastic olefin (TPO) for post-consumer applications. Since polystyrenes and TPOs are not miscible, polystyrene-TPO diblock copolymers are being developed to reduce the interfacial tension in PS/TPO blends. TPOs are tough materials with low stififiiess properties. If blended with polystyrene, they improve the toughness of polystyrenes. If compatibilized, the properties of PS/TPO should be similar to styrene-hydrogenated polybutadiene rubbers. 

Thermoplastic elastomers (TPEs) combine the physical properties of vulcanized rubber with the ease and economy of conventional thermoplastic processing. They are also well suited to reprocessing and recycling and minimize toxicity issues. Many types of thermoplastic elastomers are polymer blends cranprising a thermoplastic continuous phase in combination with a discontinuous vulcanized or unvulcanized elastomeric phase, which in the latter case could also be co-continuous. 

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. 

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