Reclaim rubber, properties

Al-Malaika, S. and Amir, E.J., Thermoplastic elastomers Part III—Ageing and mechanical properties of natural rubber-reclaimed rubber/polypropylene systems and their role as solid phase dispersants in polypropylene/polyethylene blends, Polym. Degrad. Stab., 26, 31, 1989. 

Reclaim rubber tends to lose its elastic properties during processing and, therefore, is no longer extensively used in tires because of the flex needed. That is, it does not become like new rubber. Howeyer, some new tires routinely contain one to 2 percent crumb rubber (5). 

In the Tirecycle process, first developed in 1982, finely ground scrap rubber is treated with a liquid polymer to form a reclaimed rubber product. RRE literature claims superior bonding properties and suggests use in tread rubber and other products including washers, mats, car parts, and tiedowns. The Tirecycle product is claimed to be useful with thermoplastics such as polypropylene, polyethylene, and polystyrene, as well as polyvinyl chloride, polyesters, and urethanes. 

Ultrasonic reclaiming of NR was reported by Okuda and Hatano in 1987, which was also patented. They subjected the NR vulcanizate to 50 kHz ultrasonic energy for 20 min to achieve devulcanization followed by revulcanization and obtained reclaimed rubber with similar properties to those of original rubber. Isayev and coworkers reported in a number of publications the phenomenon of devulcanization by ultrasound energy and they also patented their developments. ... 

As can be seen from Table 6, the physical properties of some of the cured blends made with the surface devulcanized reclaimed rubber crumb samples were equivalent to those made with only virgin rubber. For instance, the 100% modulus, 300% modulus, and percent elongation measured in Examples 19 and 20 were very similar to those found in the control using only virgin rubber (the series labeled None ). 

Castello and Dixon74 find that staining of light-colored rubber products is often caused by the incorporation of reclaimed rubber. They correct this condition with activated carbon the staining substances are fixed by the char remaining in the rubber and are unable to migrate. Rubber so reclaimed is similar in appearance and in physical properties to ordinary reclaimed rubber except that it is nonstaining. 

In another study, the ground reclaim rubber was blended with stirene-butadiene rubber and cured under pressure at 160°C. The cured sheets were silica-reinforced by soaking in tetraethyl ortho silicate, then in an aqueous solution of n-butyl amine catalyst, followed by heat treatment at 50°C. The tensile properties of the blends containing conventionally incorporated silica, with no coupling agent, were superior to those containing silica incorporated by the sol-gel reaction [21]. 

TPV nanocomposites of LLDPE/reclaimed rubber with nanoclay and 1 wt.% MA-grafted PE and curative were prepared using a Brabender internal mixer at 170°C (Razmjooei et al., 2012). Contents of the reclaimed rubber, nanoclay, and compatibilizer were varied up to 30, 7, and 21 wt.%, respectively. The blends without the compatibilizer were also prepared. Morphological, thermal, and mechanical properties of the nanoclay-reinforced TPV nanocomposites indicated intercalation and partial exfoliation by the high-shear stress during mixing with the reclaimed rubber. Vulcanization of rubber phase led to an increase of viscosity. The size of rubber particles in TPV was reduced with the addition of nanoclay and compatibilizer. 

NR composites and nanocomposites can be fabricated by three main techniques, namely latex compounding, solution mixing and melt blending. A variety of nanofillers, such as carbon black, silica, carbon nanotubes, graphene, calcium carbonate, organomodified clay, reclaimed rubber powder, recycled poly(ethylene terephthalate) powder, cellulose whiskers, starch nanocrystals, etc. have been used to reinforce NR composites and nanocomposites over the past two decades. In this chapter, we discuss the preparation and properties of NR composites and nanocomposites from the viewpoint of nanofillers. We divide nanofillers into four different types conventional fillers, natural fillers, metal or compound fillers and hybrid fillers, and the following discussion is based on this classification. 

The requirement for ease of processing demands that the rubber behave as a plastic material. While the effect of heating will aid in converting the tough elastic polymer into a plastic, the process is far from complete. Many grades of polymer are available in a pre-crosslinked form to assist in this respect. These polymers have usually been crosslinked prior to coagulation of the emulsion from which they were derived. The three-dimensional network helps to reduce the elastic component of the compound but at the expense, usually, of mechanical strength. Reclaimed rubbers form a supply of polymer with similar properties because of the residual crosslink structure from the parent material. 

Tread. Tread is the wear resistance component of the tyre and is in direct contact with the road. It must provide traction, wet skid and good cornering characteristics with minimum noise generation and also low heat build-up. Tread components can consist of blends of NR, polybutadiene (BR) and SBR, compounded with carbon black, silica, oils and vulcanizing chemicals." Among recently reported formulations for tyre tread with economic and environmental merits is the work of Rattanasom, in which a blend of NR and tyre tread reclaimed rubber (RR) was prepared and mechanically characterized. Their results showed that the blends prepared with different curing systems, i.e. conventional vulcanization (CV) and efficient vulcanization (EV), exhibit an increase in their hardness and modulus with increasing RR content, while other mechanical properties were adversely affected. ... 

Medhat M. Hassan, Raouf O. Aly, Jehan A. Hasanen, and El Sayed F. El Sayed, The effect of gcunma irradiation on mechcmical, thermal and morphological properties of glass fiber reinforced polyethylene waste/reclaim rubber composites. /. Ind. Eng. Chem. 27 (2013) (in press). 

In addition to the two reviews that are mentioned at the beginning of this section, a number of other relatively recent reviews of the processes and methods that have been developed and evaluated for the devulcanisation of waste rubber are available. For example, Majumdar published an overview in 2009 in the Chemical Weekly journal [4], which covered the challenges that face workers in this field and covered the main types of systems that have been developed (i.e., chemical, microwave, ultrasonic and so on). This article also covered the production and use of rubber crumb from waste rubber. In another article [5], Majumdar reviews the three main sources of reclaimed rubber that are available in the marketplace (rubber crumb, rubber powder and chemically digested reclaimed sheet) and describes their properties and uses. 

A standard production thermo-mechanical reclaiming machine , designated MRR-031, has been developed by Elast-Tekhologii LLC in Russia [20,21]. This machine is capable of reclaiming rubber from scrap tyres and GRG based on SBR, polyisoprene, EPDM and butyl rubber. The reclaimed rubber has been incorporated back into new rubber compounds at a replacement level of up to 90% of virgin rubber polymer. The physical properties that are reported for various... 

Workers in Sri Tanka [24] reclaimed waste rubber by utilising a readily available, low-cost and environmentally friendly amino compound and then carried out an extensive study comparing the properties of a compound produced by blending virgin NR with this reclaimed rubber at a ratio of 85 15 (designated Novel reclaim) with two other rubber compounds ... 

Wu and Chen [84] blended reclaimed rubber powder from waste tyres with fly ash and a coupling agent (aminopropyl triethoxysilane) and investigated the physical and morphological properties of the resulting blends. In addition to investigating the influence that the amount of fly ash had on these properties, they also evaluated the effect of adding different cure systems (peroxide and sulfur types) and the temperature of cure. The results showed that the fly ash was an excellent filler and could be used as a replacement for silica fillers in reclaimed rubber powder composites of this type. 

ELASTOPffiRS,SYNTHETic-POLYcm.OROPRENE Elastop rs, SYNTHETIC-ETHYLENE-PROPYLENE-DIENE RUBBER). Tires, hoses, belts, molded and extmded goods, and asphalt products consume ca 80% of the reclaimed mbber manufactured. Typical properties of reclaimed mbbers are shown in Table 5. 

In 1839, Charles Goodyear discovered that sulfur could cross-link polymer chains and patented the process in 1844 [1]. Since then rubber became a widely usable material. By the year 1853, natural rubber (NR) was in short supply. So attempts were made to undo what Goodyear had accomplished. Goodyear himself was involved in trying to reclaim vulcanized rubber to overcome the shortage of NR. Later, as a consequence of World War I, Germany introduced synthetic rubbers, namely the Buna rubbers, which raised the curiosity of polymer chemists all over the world. Subsequently, synthetic rubbers with tailor-made properties were born. This was followed by the discovery of new methods and chemicals for vulcanization and processing. It is obvious... 

The product resulting from the treatment of waste rubber (flash, used tyres, etc.) by heat and chemical agents, which effect sufficient break down and softening so that the reclaim may be used as a compounding ingredient in fresh compound without excessive degradation of physical properties. 

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