Standards for rubber powders.With the manufacturing of rubber products, waste streams from production errors and end of life materials are generated. These wastes are dumped dump v. dumped, dump·ing, dumps v.tr. 1. To release or throw down in a large mass. 2. a. , burned, re-used and recycled. Recycling recycling, the process of recovering and reusing waste products—from household use, manufacturing, agriculture, and business—and thereby reducing their burden on the environment. of tires for instance (whereby tire components or whole tires are physically recycled), can take place by several processes (table 1).
Table 1
Process Example
Retreading Retreaded truck tires and
passenger car tires
Use of tires as a whole Artificial rafts; farmer foil
weights
Use of tires in parts Tiles and building blocks
from cut treads (sometimes
with steel belt); wipers from
inner liners
Grinding Granulated and powder for
e.g. tiles (with PU) or for use
in fresh rubber compounds
Back to feedstock process Pyrolysis: to monomers or
carbon black, steel and oil
(TDF, tire derived fuel)
Physical reclaiming Reclaim for mixing into fresh
rubber compounds, like
(under)tread, bead, apex,
inner linner, etc.
Grinding grinding, process by which surface material is removed from an object, usually metal, by the abrasive action of a rotating wheel or a moving belt that contains abrasive grains. rubbers to a granulate gran·u·late v. gran·u·lat·ed, gran·u·lat·ing, gran·u·lates v.tr. 1. To form into grains or granules. 2. To make rough and grainy. v.intr. or a rubber powder is being done on an industrial scale, largely from tires, since they represent about 60 to 70% of all rubber being consumed con·sume v. con·sumed, con·sum·ing, con·sumes v.tr. 1. To take in as food; eat or drink up. See Synonyms at eat. 2. a. . Therefore, a wide variety of ground rubber powders is being offered on the market that differ in properties due to feed stock, grinding process, sieving process, defibering/deironing steps and logistics. At this moment, as far as we know, there is only one standard prescribing how to characterize the rubber powders: ASTM ASTM abbr. American Society for Testing and Materials D5603. According to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. this standard, the ground rubber powders (denoted as "particulate par·tic·u·late adj. Of or occurring in the form of fine particles. n. A particulate substance. particulate composed of separate particles. rubber") are to be classified with respect to feed stock and sieve analysis A sieve analysis is a practice or procedure used to assess the particle size distribution of a granular material. The size distribution is often of critical importance to the way the material performs in use. . The rubber powder should then comply to a range of chemical properties and a maximum allowable concentration of fibers and metal. Discussion This standard cannot be used on the European European emanating from or pertaining to Europe. European bat lyssavirus see lyssavirus. European beech tree fagussylvaticus. European blastomycosis see cryptococcosis. continent in its present form, however. The materials used and the composition of rubber compounds in the U.S. are different from those in Europe Europe (y  r`əp), 6th largest continent, c.4,000,000 sq mi (10,360,000 sq km) including adjacent islands (1992 est. pop. 512,000,000). . Due to
different road conditions, constructions of cars, trends in tires (e.g.
use of run-flat tires A run-flat tire is a pneumatic vehicle tire that is designed to resist the effects of deflation and to enable the vehicle to continue to be driven, although depending on the type of tire, at reduced speeds (i.e. 80 km/h or 50 mph) and for limited distances. ) and traffic laws, for instance, the chemical
compositions of tire compounds are different.In table 2, an overview is given of different rubber powders produced by Vredestein Vredestein Banden B.V. is a Dutch manufacturer of tyres for cars, commercial vehicles, tractors, motorcycles and bicycles. The company is independent of other large tyre manufacturers and describes itself as "middle-sized". Rubber Resources. In Maastricht Maastricht (mäs`trĭkht'), city (1994 pop. 118,102), capital of Limburg prov., SE Netherlands, on the Maas (Meuse) River and on the Albert Canal system. It is an important rail and river transportation point and an industrial center. , the Netherlands Netherlands (nĕth`ərləndz), Du. Nederland or Koninkrijk der Nederlanden, officially Kingdom of the Netherlands, constitutional monarchy (2005 est. pop. 16,407,000), 15,963 sq mi (41,344 sq km), NW Europe. , powders are produced from truck tire tread tread injury to the coronet of the horse's hoof by treading on it by the opposite hoof, or by another horse when they are being worked in a team. If the coronary matrix is injured there may be a subsequent crack or deformity. peelings peelings Noun, pl strips of skin or rind that have been peeled off: potato peelings peelings npl → pelures fpl, épluchures fpl . In Lommel, Belgium, whole truck tires are ground to a range of powders and granulates. As can be seen from the chemical specification of these materials, the concentrations of acetone acetone (ăs`ĭtōn), dimethyl ketone (dīmĕth`əl kē`tōn), or 2-propanone (prō`pənōn), CH3COCH3 extractables, carbon black, polymer and ash are different from ASTM D5603. The data show that, in general, acetone extracts are lower, and ash and polymer content are higher than in the U.S., while the amount of natural rubber used in treads and the tire as a whole is considerably higher.
Table 2 - standard spec 2000
Orgin (region:WE)
Truck tread
Truck buffing
Truck whole tire
Grinding technology
Ambient
Chemical composition
Acetone extract % ASTM D 297
Ash % ASTM D 297
Carbon black % ASTM E 1131
Rubber content % ASTM E 1131
NR/synthetic composition % ASTM D 3452
Heat loss % ASTM D 1278
Particle distribution
3 mesh/6.700 mm % ASTM D 5644
4 mesh/4.750 mm % ASTM D 5644
5 mesh/4.000 mm % ASTM D 5644
7 mesh/2.800 mm % ASTM D 5644
10 mesh/2.000 mm % ASTM D 5644
12 mesh/1.700 mm % ASTM D 5644
20 mesh/0.850 mm % ASTM D 5644
30 mesh/0.600 mm % ASTM D 5644
35 mesh/0.500 mm % ASTM D 5644
40 mesh/0.425 mm % ASTM D 5644
50 mesh/0.300 mm % ASTM D 5644
60 mesh/0.250 mm % ASTM D 5644
80 mesh/0.180 mm % ASTM D 5644
100 mesh/0.150 mm % ASTM D 5644
140 mesh/0.106 mm % ASTM D 5644
200 mesh/0.075 mm % ASTM D 5644
Physical properties
Specific surface (rough/edgy) Microscopy
Specific gravity of material g/[cm.sup.3] ASTM D 297
Pour density g/[cm.sup.3] ISO 1306
Compacted density g/[cm.sup.3] ISO 787
Impurities
Steel % ASTM D 5603
Textile % ASTM D 5603
Other % ASTM D 5603
Leaching to environment([dagger])
RWM0002 RWM0005
Orgin (region:WE)
Truck tread
Truck buffing
Truck whole tire X X
Grinding technology
Ambient X X
Chemical composition
Acetone extract 7 [+ or -] 3 7 [+ or -] 3
Ash 17 [+ or -] 3 14 [+ or -] 3
Carbon black 28 [+ or -] 3 28 [+ or -] 3
Rubber content 48 [+ or -] 3 50 [+ or -] 3
NR/synthetic composition ca. 55/45 ca. 55/45
Heat loss <1 <1
Particle distribution
3 mesh/6.700 mm
4 mesh/4.750 mm
5 mesh/4.000 mm
7 mesh/2.800 mm
10 mesh/2.000 mm
12 mesh/1.700 mm
20 mesh/0.850 mm
30 mesh/0.600 mm
35 mesh/0.500 mm <1
40 mesh/0.425 mm
50 mesh/0.300 mm
60 mesh/0.250 mm <1
80 mesh/0.180 mm
100 mesh/0.150 mm
140 mesh/0.106 mm
200 mesh/0.075 mm
Physical properties
Specific surface (rough/edgy) Rough Rough
Specific gravity of material 1.23
Pour density ca. 0.37 ca. 0.40
Compacted density ca. 0.44 ca. 0.47
Impurities
Steel <0.1 <0.1
Textile <0.5 <0.5
Other 0 0
Leaching to environment([dagger])
RWM0208 RWM0508
Orgin (region:WE)
Truck tread
Truck buffing
Truck whole tire X X
Grinding technology
Ambient X X
Chemical composition
Acetone extract 7 [+ or -] 3 7 [+ or -] 3
Ash 10 [+ or -] 3 9 [+ or -] 3
Carbon black 30 [+ or -] 3 30 [+ or -] 3
Rubber content 53 [+ or -] 3 54 [+ or -] 3
NR/synthetic composition ca. 55/45 ca. 55/45
Heat loss <1 <1
Particle distribution
3 mesh/6.700 mm
4 mesh/4.750 mm
5 mesh/4.000 mm
7 mesh/2.800 mm
10 mesh/2.000 mm
12 mesh/1.700 mm
20 mesh/0.850 mm <1 <1
30 mesh/0.600 mm
35 mesh/0.500 mm >40
40 mesh/0.425 mm
50 mesh/0.300 mm
60 mesh/0.250 mm <70
80 mesh/0.180 mm
100 mesh/0.150 mm
140 mesh/0.106 mm
200 mesh/0.075 mm
Physical properties
Specific surface (rough/edgy) Rough Rough
Specific gravity of material 1.18
Pour density ca. 0.38 ca. 0.38
Compacted density ca. 0.44 ca. 0.43
Impurities
Steel <0.1 <0.1
Textile <0.5 <0.5
Other 0 0
Leaching to environment([dagger])
RWM0816 RWM1625
Orgin (region:WE)
Truck tread
Truck buffing
Truck whole tire X X
Grinding technology
Ambient X X
Chemical composition
Acetone extract 7 [+ or -] 3 7 [+ or -] 3
Ash 7 [+ or -] 3 7 [+ or -] 3
Carbon black 30 [+ or -] 3 31 [+ or -] 3
Rubber content 55 [+ or -] 3 55 [+ or -] 3
NR/synthetic composition ca. 55/45 ca. 55/45
Heat loss <1 <1
Particle distribution
3 mesh/6.700 mm
4 mesh/4.750 mm
5 mesh/4.000 mm
7 mesh/2.800 mm <1
10 mesh/2.000 mm
12 mesh/1.700 mm <1 >50
20 mesh/0.850 mm >80
30 mesh/0.600 mm
35 mesh/0.500 mm
40 mesh/0.425 mm
50 mesh/0.300 mm
60 mesh/0.250 mm
80 mesh/0.180 mm
100 mesh/0.150 mm
140 mesh/0.106 mm
200 mesh/0.075 mm
Physical properties
Specific surface (rough/edgy) Rough Rough
Specific gravity of material 1.22
Pour density ca. 0.42 ca. 0.45
Compacted density ca. 0.46 ca. 0.49
Impurities
Steel <0.1 <0.1
Textile <0.5 <0.5
Other 0 0
Leaching to environment([dagger])
RWM2545 RWM4070
Orgin (region:WE)
Truck tread
Truck buffing
Truck whole tire X X
Grinding technology
Ambient X X
Chemical composition
Acetone extract 9 [+ or -] 3 7 [+ or -] 3
Ash 6 [+ or -] 3 6 [+ or -] 3
Carbon black 31 [+ or -] 3 31 [+ or -] 3
Rubber content 55 [+ or -] 3 56 [+ or -] 3
NR/synthetic composition ca. 55/45 ca. 55/45
Heat loss <1 <1
Particle distribution
3 mesh/6.700 mm <2
4 mesh/4.750 mm <1
5 mesh/4.000 mm >90
7 mesh/2.800 mm >50
10 mesh/2.000 mm
12 mesh/1.700 mm
20 mesh/0.850 mm
30 mesh/0.600 mm
35 mesh/0.500 mm
40 mesh/0.425 mm
50 mesh/0.300 mm
60 mesh/0.250 mm
80 mesh/0.180 mm
100 mesh/0.150 mm
140 mesh/0.106 mm
200 mesh/0.075 mm
Physical properties
Specific surface (rough/edgy) Rough Rough
Specific gravity of material
Pour density ca. 0.46 ca. 0.42
Compacted density ca. 0.48 ca. 0.46
Impurities
Steel <0.1 <0.1
Textile <0.5 <0.5
Other 0 0
Leaching to environment([dagger])
PNM80 PNM60
Orgin (region:WE)
Truck tread X X
Truck buffing
Truck whole tire
Grinding technology
Ambient X X
Chemical composition
Acetone extract <13 <13
Ash <6 <6
Carbon black 31 [+ or -] 2 31 [+ or -] 2
Rubber content 56 [+ or -] 4 56 [+ or -] 4
NR/synthetic composition ca. 70/30 ca. 70/30
Heat loss <1 <1
Particle distribution
3 mesh/6.700 mm
4 mesh/4.750 mm
5 mesh/4.000 mm
7 mesh/2.800 mm
10 mesh/2.000 mm
12 mesh/1.700 mm
20 mesh/0.850 mm
30 mesh/0.600 mm
35 mesh/0.500 mm
40 mesh/0.425 mm
50 mesh/0.300 mm
60 mesh/0.250 mm <16
80 mesh/0.180 mm <2 <45
100 mesh/0.150 mm <15
140 mesh/0.106 mm <75
200 mesh/0.075 mm <90
Physical properties <98
Specific surface (rough/edgy) Rough Rough
Specific gravity of material 1.19 1.19
Pour density ca. 0.41 ca. 0.33
Compacted density ca. 0.46 ca. 0.39
Impurities
Steel <0.1 <0.1
Textile <0.5 <0.5
Other 0 0
Leaching to environment([dagger])
RNM45
Orgin (region:WE)
Truck tread X
Truck buffing
Truck whole tire
Grinding technology
Ambient X
Chemical composition
Acetone extract <13
Ash <6
Carbon black 31 [+ or -] 2
Rubber content 56 [+ or -] 4
NR/synthetic composition ca. 70/30
Heat loss <1
Particle distribution
3 mesh/6.700 mm
4 mesh/4.750 mm
5 mesh/4.000 mm
7 mesh/2.800 mm
10 mesh/2.000 mm
12 mesh/1.700 mm
20 mesh/0.850 mm
30 mesh/0.600 mm
35 mesh/0.500 mm <0.8
40 mesh/0.425 mm
50 mesh/0.300 mm <16
60 mesh/0.250 mm <52
80 mesh/0.180 mm <66
100 mesh/0.150 mm
140 mesh/0.106 mm
200 mesh/0.075 mm <85
Physical properties
Specific surface (rough/edgy) Rough
Specific gravity of material 1.15 [+ or -] 0.02
Pour density ca. 0.37
Compacted density ca. 0.45
Impurities
Steel <0.1
Textile <0.5
Other 0
Leaching to environment([dagger])
ASTM D5603
Orgin (region:WE) Grade 2
Truck tread Grade 3
Truck buffing Grade 1
Truck whole tire
Grinding technology Not used in D5603
Ambient
Chemical composition Grade 1-4 5-6
Acetone extract 8-22 -
Ash <8 -
Carbon black 26-38 -
Rubber content >42 -
NR/synthetic composition
Heat loss NR: 10-35% -
Particle distribution <1
3 mesh/6.700 mm Grades 1-6
4 mesh/4.750 mm
5 mesh/4.000 mm
7 mesh/2.800 mm
10 mesh/2.000 mm
12 mesh/1.700 mm
20 mesh/0.850 mm
30 mesh/0.600 mm 15 # 0% en 20 # max 5
35 mesh/0.500 mm 20 # 0% en 30 # max 10
40 mesh/0.425 mm
50 mesh/0.300 mm 30 # 0% en 40 # max 10
60 mesh/0.250 mm
80 mesh/0.180 mm 50 # 0% en 60 # max 10
100 mesh/0.150 mm 60 # 0% en 80 # max 10
140 mesh/0.106 mm 80 # 0% en 100 # max 5
200 mesh/0.075 mm
Physical properties
Specific surface (rough/edgy) Not
Specific gravity of material used in
Pour density ASTM
Compacted density D5603
Impurities
Steel <0.1
Textile <0.5
Other 0
Leaching to environment([dagger]) Not used
([dagger]) No PBN PBN Paint By Number PBN Procurement Business Number PBN Pyrolytic Boron Nitride PBN Policy-Based Networking PBN Performance-Based Navigation PBN Progressive Bengali Network PBN Paintball Nation PBN Permanent Background Notices , PCBs detected in powder itself; leaching leaching, method of extraction in which a solvent is passed through a mixture to remove some desired substance from it. A simple example is the passage of boiling water through ground coffee to dissolve and carry out the chemicals necessary for producing the beverage. of metals in water under government limits (building treaty) The second classification aspect that is mentioned in ASTM D5603 is the sieve analysis. This can be performed on a mechanical sieve shaker Shaker Member of the United Society of Believers in Christ's Second Appearing, a celibate millenarian sect. Derived from a branch of the radical English Quakers (see Society of Friends), the movement was brought to the U.S. , such as the ro-tap sieve shaker. According to the standard, the powder is denoted to be of a certain mesh Refers to an interconnect architecture that cross- connects several devices. See mesh network, wireless mesh network and switch fabric. (character) mesh - The INTERCAL name for hash. size if less than 10% (5% for 10 and 20 mesh size) is retained on the designation screen and nothing on the foregoing sieve, the zero percent retained screen. This is a simple and quick test method and can be used for most powders and granulates that are produced by grinding all or most of the material to a certain size. However, in many operations, materials are produced by separating a single stream of ground materials on consecutive sieves, or in a cascade sieve, to create a wider product range. These materials have sieve limits both at the top as well as at the bottom end of the sieve fractions. If these materials were to be denoted with ASTM D5603, the performance of the materials can be quite different from powders which have been sifted on one top sieve. An example where this might lead to problems is where bulky bulk·y adj. bulk·i·er, bulk·i·est 1. Having considerable bulk; massive. 2. Of large size for its weight: a bulky knit. 3. Clumsy to manage; unwieldy. equipment with relatively large clearances in bearings is used to handle the material. A granulate without fines (i.e., sieved on top and bottom sieves) with appropriate dimensions will not clog the bearings, whereas the one-sieve powders might lead to enhanced maintenance (and thus costs). Vredestein in Maastricht itself separates the fines after the first rough breaker breaker: see wave, in oceanography. step to avoid problems. Another area where this is of importance can be found among manufacturers of crumb-polyurethane products. These products are made by mixing the crumb with a PU system and pressing the end product in a mold mold, name for certain multicellular organisms of the various classes of the kingdom Fungi, characteristically having bodies composed of a cottony mycelium. The colors of molds are caused by the spores, which are borne on the mycelium. . Examples of products that can be made this way include stable mats and tiles; tiles for playgrounds; noise dampening tiles or mats; speed ramps; road furniture; railroad railroad or railway, form of transportation most commonly consisting of steel rails, called tracks, on which freight cars, passenger cars, and other rolling stock are drawn by one locomotive or more. crossing blocks; sport track/hall or tennis court underground; and playground Playground - A visual language for children, developed for Apple's Vivarium Project. OOPSLA 89 or 90? furniture. For these applications, the amount of PU used depends on the amount of fines present in the powder. More fines mean more PU must be used to create the products, and thus the costs increase with the amount of fines present. For these particular applications, the specific raw material source of the powders is less important than for other applications, as long as it is a consistent stream. Also, a small concentration of e.g. fibrous fibrous /fi·brous/ (fi´brus) composed of or containing fibers. fi·brous adj. Composed of or characterized by fibroblasts, fibrils, or connective tissue fibers. material is not likely to cause major problems, since it will be embedded Inserted into. See embedded system. in a PU matrix. A quick method that will give some indication on the amount of PU needed to coat an amount of powder is the determination of the pour density and the compacted density. The compacted density, in combination with the specific gravity specific gravity, ratio of the weight of a given volume of a substance to the weight of an equal volume of some reference substance, or, equivalently, the ratio of the masses of equal volumes of the two substances. of the rubber, can be used as an indication of what is needed to fill up a certain volume, i.e., how much powder and PU is needed to make the end product. Apart from the powders differing in origin and sieve analysis, the grinding technology also can have an influence on the performance of the material in end products. In a comparative test, several different powders with different mesh sizes, origins and grinding techniques were used to produce surface activated activated a state of being more than usually active. In biological systems this is usually brought about by chemical or electrical means. Commonly said of pharmaceutical and chemical products. crumb, according to a technique developed by Vredestein. From figure 1 it can be seen that the properties primarily are determined by the raw material source, while sieve analysis and grinding technique do not play a role in this case. In another test, however, SBR SBR - Spectral Band Replication rubber scrap material was ground cryogenically and ambiently. Here it was found that the cryogenic cryogenic /cry·o·gen·ic/ (-jen´ik) producing low temperatures. cry·o·gen·ic adj. 1. Relating to or producing low temperatures. 2. material performed less (had a lower tensile stress tensile stress See under axial stress. and elongation elongation, in astronomy, the angular distance between two points in the sky as measured from a third point. The elongation of a planet is usually measured as the angular distance from the sun to the planet as measured from the earth. ) than the ambient Surrounding. For example, ambient temperature and humidity are atmospheric conditions that exist at the moment. See ambient lighting. material. [Figure 1 ILLUSTRATION OMITTED] In an article by Gibala et al. (ref. 1) a single cryogenic and ambiently ground rubber particle particle /par·ti·cle/ (pahr´ti-k'l) a tiny mass of material. Dane particle an intact hepatitis B viral particle. was embedded in a tensile tensile, adj having a degree of elasticity; having the ability to be extended or stretched. test bar. After rupturing the test bar, the break surface was investigated. It was found that the crack had passed through the ambiently ground particle, whereas it had followed the boundary between the cryogenic particle and the rubber matrix, thereby exposing the clean surface of the cryogenic particle. This indicates that the ambient powders usually will be the best choice for high performance applications. The surface of powders can be measured analogously a·nal·o·gous adj. 1. Similar or alike in such a way as to permit the drawing of an analogy. 2. Biology Similar in function but not in structure and evolutionary origin. to carbon black. In the literature, some articles have described the use of these techniques as applied to rubber powders (refs. 2 and 3). It appears that the CTAB CTAB Clear to auscultation bilaterally, see there technique is one of the best suited techniques to use in practice. From a comparison of literature data, it can be concluded that the cryogenic powders have lower surface/mass ratios, roughly up to half that of ambient powders (compared at equal mesh size). In a comparison done by Vredestein, a 40 mesh ambient powder and an 80 mesh wet ground powder gave values of 14 and 17 [m.sup.2]/g, respectively. The ambient powder value compared close to a literature value on another ambiently ground 40 mesh powder: 12 [m.sup.2]/g. By multiplying mul·ti·ply 1 v. mul·ti·plied, mul·ti·ply·ing, mul·ti·plies v.tr. 1. To increase the amount, number, or degree of. 2. Mathematics To perform multiplication on. these values with the median particle size Particle size, also called grain size, refers to the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. , a comparison between different techniques can be made (since equally processed material with half the particle diameter must have twice the surface per gram). By this method, an 80 mesh cryogenic, 80 mesh wet and 40 mesh ambient powder gave values of 2, 3 and 6, respectively, reflecting the difference in the process. Another technique to discern dis·cern v. dis·cerned, dis·cern·ing, dis·cerns v.tr. 1. To perceive with the eyes or intellect; detect. 2. To recognize or comprehend mentally. 3. between different processes and surface/mass ratios is microscopy microscopy /mi·cros·co·py/ (mi-kros´kah-pe) examination under or observation by means of the microscope. mi·cros·co·py n. 1. The study of microscopes. 2. . Cryogenic powders will have a more edgy, flat surface as compared to the rough, undefined surface of ambient powders. In some laboratory trials, indeed, we saw differences between rough or brittle (jargon) brittle - Said of software that is functional but easily broken by changes in operating environment or configuration, or by any minor tweak to the software itself. Also, any system that responds inappropriately and disastrously to abnormal but expected external stimuli; e. surfaces. A further quantification quan·ti·fy tr.v. quan·ti·fied, quan·ti·fy·ing, quan·ti·fies 1. To determine or express the quantity of. 2. is difficult to achieve, although some literature does describe techniques with computers (ref. 4). If a qualifying scheme could be set up, it might lead to a quick method to classify clas·si·fy tr.v. clas·si·fied, clas·si·fy·ing, clas·si·fies 1. To arrange or organize according to class or category. 2. To designate (a document, for example) as confidential, secret, or top secret. materials. Another aspect of powders that will influence its application range is concerned with the degree of contamination by metals, fibers and others. Applications with higher demands on the properties will generally ask for materials with very low levels of contamination, whereas other applications are not so meticulous me·tic·u·lous adj. 1. Extremely careful and precise. 2. Extremely or excessively concerned with details. [From Latin met . An example where it is not so important that the rubber powder is completely free of textile is the road building industry. Here, rubber powders are used to incorporate elastomeric properties in rubberized asphalt Rubberized asphalt is pavement material that consists of regular asphalt concrete mixed with crumb rubber -- ground, used tires that would otherwise be discarded or take up space in landfills. . The material is completely immersed im·merse tr.v. im·mersed, im·mers·ing, im·mers·es 1. To cover completely in a liquid; submerge. 2. To baptize by submerging in water. 3. in a tacky compound and a small (though consistent) amount of textile and metal can be allowed for, thus leading to a better price/performance ratio In economics and engineering, the price/performance ratio refers to a product's ability to deliver performance, of any sort, for its price. For instance, if you have a whole day to travel 100 km, spending $50 to do the journey in two hours is a better price/performance ratio than . However, the handling conditions of the material will determine the requirements for the allowable concentrations of (especially) fibers. If big bags of materials are to be handled in free air, risk will have to be avoided that fibrous material pollutes air or ends up in the lungs of employees. It is therefore open to discussion if a standard should incorporate materials with lower contamination levels but which are safe to handle. Another example where contaminations are less important is the cement cement, binding material used in construction and engineering, often called hydraulic cement, typically made by heating a mixture of limestone and clay until it almost fuses and then grinding it to a fine powder. industry. Here, the rubber is used for its calorific value calorific value n. The calories or thermal units contained in one unit of a substance and released when the substance is burned. and the iron even is needed in the process. A defined sieve analysis hardly is needed for this material, while fibrous material will simply be burned. However, the same rules for a safe handling of the powder will still apply to this application (although the problems are probably not big, since the cement industry can handle roughly ground granulate that will have fibers embedded in larger rubber chunks, that will not float around as in finer mesh materials). Last, but not least, there is the matter of the possible leaching of detrimental det·ri·men·tal adj. Causing damage or harm; injurious. det  ri·men chemicals from the powders to the environment, for
certain applications. Examples could be the use of ground rubber mixed
with soil to create a certain structure, the use of tires cut in half
under golf fields to serve as water carriers and the use of crumb in dry
processed road constructions (where crumb replaces part of the
aggregate). In these applications, the crumb has contact with water that
might leach leach v. leached, leach·ing, leach·es v.tr. 1. To remove soluble or other constituents from by the action of a percolating liquid. 2. out some of the hazardous ingredients in the powders. As was shown in the table, the Vredestein powders are free from nitrosamines nitrosamines highly hepatotoxic compounds formed in the rumen by the combination of amines and nitrite. They do not appear to occur naturally in large quantities. Nitrosamine poisoning has also been caused by feeding nitrite-treated fishmeal and Solanum incanum. , PCBs and PBN and did not leach heavy metals heavy metals, n.pl metallic compounds, such as aluminum, arsenic, cadmium, lead, mercury, and nickel. Exposure to these metals has been linked to immune, kidney, and neurotic disorders. above government limits in a test conducted for possible use in aforementioned a·fore·men·tioned adj. Mentioned previously. n. The one or ones mentioned previously. aforementioned Adjective mentioned before Adj. 1. applications. Since the raw materials used by Vredestein primarily are gathered in Western Europe Western Europe The countries of western Europe, especially those that are allied with the United States and Canada in the North Atlantic Treaty Organization (established 1949 and usually known as NATO). , this most likely will not be true for other parts of the world, yet. Obviously, this will have an impact on usability How easy something is to use. Both software and Web sites can be tested for usability. Considering how difficult applications are to use and Web sites are to navigate, one would wish that more designers took this seriously. See user interface and usability lab. of powdered material in other parts of the world. The ASTM standard does not give any limits for concentrations of hazardous chemicals. Nitrosa-mine free recipes, for instance, most likely will be developed in the western hemisphere Western Hemisphere Part of Earth comprising North and South America and the surrounding waters. Longitudes 20° W and 160° E are often considered its boundaries. first. For certain applications, e.g. back into rubber compounds, powder from regions where these developments have not yet taken place are not suitable. Since it is costly and difficult to analyze this, it is probably best to specify the originating region for an indication of its usability. Suggestions for standardization standardization In industry, the development and application of standards that make it possible to manufacture a large volume of interchangeable parts. Standardization may focus on engineering standards, such as properties of materials, fits and tolerances, and drafting In the discussion above, some rubber powder properties have been linked with their impact on the processing of the powders and the end properties of several products. Based upon this review we would like to make some suggestions for a standardization of rubber powders. ASTM D5603 can serve as a starting point Noun 1. starting point - earliest limiting point terminus a quo commencement, get-go, offset, outset, showtime, starting time, beginning, start, kickoff, first - the time at which something is supposed to begin; "they got an early start"; "she knew from the for a European standard. We feel it should be modified and expanded with the following: * We propose D5603 to be modified with respect to the classification by parent compound. Rather than using a grade 1 to 6 classification, we feel it would be clearer to make a distinction in truck versus passenger car tire versus other rubber sources (table 3). Table 3 Proposed grade ASTM D5603 grade Grade 1: Truck tire tread (Part of) grade 2 Grade 2: Truck tire buffing (Part of) grade 3 Grade 3: Whole truck tire (Part of) grade 1 Grade 4: Passenger car tire tread (Part of) grade 2 Grade 5: Passenger car tire buffing (Part of) grade 3 Grade 6: Whole passenger car tire (Part of) grade 1 Grade 7: Other tire (e.g. full rubber tire) Grade 5 Grade 8: Technical rubber goods Grade 6 * Due to the fact that tires from different areas will have different compositions, we feel that the region from which the tires originate o·rig·i·nate v. 1. To bring into being; create. 2. To come into being; start. should be mentioned when materials are specified as well. As discussed, this will also give some indication on the concentrations of hazardous chemicals present in the powder, that might leach to the environment. * We propose D5603 to be modified with respect to the chemical composition for proposal grades 1, 2 and 3 (and possibly 4, 5 and 6, but data is lacking at the moment and should be gathered to fill the gaps) (table 4). Table 4 Proposed limits for grades 1, 2 and 3 Acetone extract 4-13% Ash content 3-20% Carbon black 25-34% Polymer content 45-60% NR % of total RHC 45-80% (or NR % of total compound) (20-50%) * D5603 should further be expanded with sieve limits for top and bottom sieve for powders produced in a cascading sieving procedure. For top and bottom sieves, the same sort of classification scheme can be used as mentioned in D5603. * The mesh size of the powders will give an indication of the surface/mass ratio, i.e., that finer powders ground with the same technology will have higher ratios. As discussed, this ratio differs between techniques. Since this is of importance for applications where the powder should be firmly embedded in a (rubber) matrix, we propose that the grinding technology is mentioned in the standard. A proposal for a distinction in categories is shown in table 5. Table 5 Proposal for classification of grinding techniques Cryogenic grinding Ambient grinding (<130 [degrees] C) High temperature grinding (>130 [degrees] C) Wet grinding Buffing (sieving, without further grinding) Other techniques As discussed, it is possible to measure the surface of the powder directly with a CTAB technique. Since it is not a simple and cheap technique, it would have to be discussed whether or not this should be part of a standard. Concerning allowable concentrations of contamination present in the powders, we feel that D5603 could have more stringent limits. It is logical that the tread grades should not be allowed to have any fibrous content. The limits mentioned for the other grades, namely 0.5%, seems to be rather high. Surely, with modern processing equipment, this limit can be set to 0.1% or even lower. Several market investigations have shown this to be possible. As mentioned in the discussion above, some applications are not that meticulous about contamination, as long as it can be handled safely. It is probably best if a broader industrial debate is set up, to discuss the need for a proposal incorporating grades with broader limits. Materials with higher concentrations of contaminating con·tam·i·nate tr.v. con·tam·i·nated, con·tam·i·nat·ing, con·tam·i·nates 1. To make impure or unclean by contact or mixture. 2. To expose to or permeate with radioactivity. adj. agents, that can be used for specific applications, can then be included as well. Conclusion Standardization is necessary for a better understanding between suppliers of rubber powders and producers of rubber end products that use these powders (ref. 5). In this presentation, data on commercially available rubber powders from Vredestein were discussed in comparison to the ASTM standard. With this, suggestions for a standard were given that will help set up a European standard. References (1.) D. Gibala, G.R. Hamed and J. Zhao, "Tensile behavior of an SBR vulcanizate containing a single rubber particle," Rubber Chem. & Technol. 71, 861-865 (1998). (2.) R.P. Burford and M. Pittolo, "Characterization A rather long and fancy word for analyzing a system or process and measuring its "characteristics." For example, a Web characterization would yield the number of current sites on the Web, types of sites, annual growth, etc. and performance of powdered rubber," Rubber Chem. & Technol. 55, 1,233-1,249 (1982). (3.) G.W. Holland, B. Hu and S. Holland, "Surface measurement of ground rubber using the BET surface area analyzer analyzer /ana·ly·zer/ (an´ah-li?zer) 1. a Nicol prism attached to a polarizing apparatus which extinguishes the ray of light polarized by the polarizer. 2. ," Rubber World, May 1994, 29-33. (4.) A. Spittel & R.H. Schuster, "Lichtmikroscopisches Verfahren zur Charakterisierung von Gummimehlen," Kautsch. Gummi, Kunstst. 47, 896-902 (1994). (5.) J.L.B. de Groot, C.N. Smit, E. Mot and B.L. van der Ven, "Certificeren kunststofregranulaat," Kunststof en Rubber 4-1994, 51-56. Henk Jan Manuel joined Vredestein in 1992 as Manager of Product Development, Vredestein Rubber Recycling. He is currently Manager of Research and Development for Vredestein Rubber Resources, a position he assumed in 1998. |
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