Waste rubber powder

Several authors have discussed the ion exchange potentials and membrane properties of grafted cellulose [135,136]. Radiation grafting of anionic and cationic monomers to impart ion exchange properties to polymer films and other structures is rather promising. Thus, grafting of acrylamide and acrylic acid onto polyethylene, polyethylene/ethylene vinyl acetate copolymer as a blend [98], and waste rubber powder [137,138], allows... 

Hassan, M. M., Badway, N. A., Gamal, A. M., Elnaggar, M. Y, Hegazy E.-S. A., Studies on mechanical, thermal and morphological properties of irradiated recycled polyamide and waste rubber powder blends. Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 2010, 268, 1427-1434. 

G. Markovic, O. Veljkovic, M. Marinovi6-Cincovi6, V. Jovanovi6, S. Samarzija-Jova-novic, J. Budinski-Simendic, Composites based on waste rubber powder and rubber blends BR/CSM, Composites Part B Engineering, ISSN 1359-8368 45 (1) (February 2013) 178-184. http //dx.doi.Org/10.1016/j.compositesb.2012.08.013. 

PROCESSING AND RHEOLOGICAL PROPERTIES OF ACTIVATED WASTE RUBBER POWDER COMPOUNDS... 

The investigations and studies presented in this section are concerned with the blending of waste rubber powder or crumb, which has not been through any devulcanisation processes of the type described in Chapter 4, into rubber compounds to produce new products. The rubber crumb in question may or may not have been surface-activated by one of the processes described in Chapter 6, Section 6.6. The properties of the resulting blends will depend upon whether this activation has taken place or not, as well as upon some of the variables already listed at the start of Section 7.2, namely the origin and type of rubber crumb, the proportion of rubber crumb in the blend, and... 

An example of waste rubber powder being used to produce a new road surface on a public road was reported in 2012 [58]. In that article it was reported that Breedon Aggregates, a UK-based company, had resurfaced a short stretch of a dual carriageway in the UK using asphalt that contained recycled ground rubber. The rubber crumb used had been obtained from a Danish company... 

A number of reviews are already available on the above subject. Rothemeyer [50] discussed the effects of grinding and sieving on the particle size, stmcture, and distribution of powders obtained from waste rubber and also studied the effects of different powders on the physical properties of the... 

Rubber powder from scrap tires readily absorbs oil floating on water and forms a cohesive mass, which can be easily removed. The amount of oil take up and weight of oil absorbed depends on the particle size of waste tire powder, temperature, and type of oil the weight of oil absorbed is directly proportional to the amount of rubber powder [65]. The oil uptake time decreases as the particle size decreases. 

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]. 

Using powdered factory scraps in EPDM compounds, it was found that the cost-effectiveness of this operation depends upon the method of grinding the waste rubber. Also, the size and topography of the particles depend upon the grinding technique, and these characteristics play a vital role in controlling the composite properties [27]. 

Waste ground rubber tire powder was devulcanized and mixed with 30 per hundred rubber (phr) natural rubber to give satisfactory vulcanizate properties. An intermeshing counter-rotating twin-screw extruder with constant root and flight diameters of the screw was designed and installed for waste rubber recycling [31]. 

Waste rubber tire powder from track and passenger tires was treated by various concentrations of nitric acid and 30% hydrogen peroxide (Yehia et al., 2004). Surface-modified rubber powder was used as a filler in NR mixes. The incorporation of rubber powder up to 20phr in combination with a... 

OT-Phenyl bismaleimide was utilized in the waste recovery domain for improvement of the mechanical properties either as a modifier of natural rubber/scrap rubber powder blends (Du et al. 2005) or as a reactive compatibilizer for post-consumer polyolefin waste using Mg(OH)2 as filler (Khunova et al. 2009). 

The study that looked at the economic advantages of re-using waste rubber as an ultra-fine powder (100 mesh and below) in new rubber and plastic products [4] listed three areas of major economic advantage ... 

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 popular reaction vessel to carry out this type of work is an autoclave. Because of its low cost and good health and safety credentials, supercritical (or liquid) CO2 is often used, although its nonpolar nature means that it has its limitations as a solvent, particularly for certain chemical agents. In common with the majority of the other processes that are reviewed in this section, the waste rubber is usually in the form of crumb or powder to present a large surface area to the solvent/reactants in the autoclave. 

A paper was published by Ishiaku and co-workers [11], who investigated the optimum concentration of DeLink to use in the devulcanisation of a sulfur-cured, NR-hased powder that had originated from waste rubber balls and artificial eggs. A solubility test was also developed to assess the degree of crosslink destruction that had taken place. The results obtained showed that the optimum... 

To assist in the marketing of tyre-derived rubber products, a categorisation system has been established as part of the UK Waste Resources Action Programme (WRAP) Quality Protocol (Section 6.4.1.5), which will help avoid possible confusion in the use of terms such as rubber crumb and rubber powder . The categories and definitions that are in the protocol are shown in Table 6.1. 

The results obtained by this WRAP project highlighted that it is possible to produce high-quality rubber powder and crumb products in a consistent way from waste tyres and that these can be used in a wide range of applications. 

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. 

Once it has been commutated into powder, crumb or shred, there are a number of ways in which waste rubber can be re-used to manufacture new products. For example ... 

Workers in India [18] have also blended both waste plastic and waste rubber. In this instance they took scrap computer plastics (e.g., acrylonitrile-butadiene-styrene and styrene-acrylonitrile) and blended them with waste NBR powder. The blends were analysed by TGA in a nitrogen atmosphere and their activation energies of decomposition determined using Friedman and Flynn-Wall-Ozawa methods. 

Yagneswaran and co-workers [25] incorporated mechanically devulcanised waste tyre powder into a vinyl ester resin matrix at various levels of addition and characterised the resulting materials using physical tests, DSC and TGA. As the level of rubber powder increased the composites were found to have reduced heat stability and flexural strength, but increased flexural modulus. 

Adov and co-workers [42] have shown that activated fine waste EPDM rubber powder can be incorporated into EPDM compounds at levels of up to 20% without altering the physical properties. A slight increase in Mooney viscosity was found, but this was compensated... 

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. 

---