Carbon filler-rubber adhesion

The reinforcing effects of fillers cannot be overlooked while specifjring the performance requirements of an O ring or a seal for oil field use. Briscoe et al [4], in one of their many papers, gave additional insight into the carbon filler-rubber adhesion during reinforcement. They observed that the degree of adhesion of a filler in a rubber influences the carbon dioxide gas uptake, as indicated in Table 5.1. 

Aromatic amines are the most effective primary antioxidants (Fig. 34) but they are discolouring and can only be used where the darker colours are acceptable (for instance in rubber adhesive formulations containing carbon blacks as fillers). The... 

Biopolymers have diverse roles to play in the advancement of green nanotechnology. Nanosized derivatives of polysaccharides like starch and cellulose can be synthesized in bulk and can be used for the development of bionanocomposites. They can be promising substitutes of environment pollutant carbon black for reinforcement of rubbers even at higher loadings (upto SOphr) via commercially viable process. The combined effect of size reduction and organic modification improves filler-matrix adhesion and in turn the performance of polysaccharides. The study opens up a new and green alternative for reinforcement of rubbers. 

Camel-CARB . [Genstar Stone Prods.] Cdcium carbonate filler/extender used in interior flat paint and exterior house paints, rubber compds., putty and caulk, ceramics, adhesives, linoleum, floor tile, and textile coatings. 

Camel-FIL. [Genstar Stone Prods.] Cdcium carbonate filler for high loadings in glass-reinforced polyester, in PVC, PP, rubber automotive goods and floor tiles, caulks, sedants, and adhesives. 

Camel-TEX . [Genstar Stone Prods.] Calcium carbonate filler for pdnts, primers, seders, polyester-fiberglass premixes, preforms, and hand lay-up gel coats, rubber automotive prods., household prods., tubing, medical prods., closures, putty, caulk, adhesives. 

Gama-FIL [Georgia Marble] Calcium carbonate filler for use in plastics, BMC/SMC, paint, caulks, sealants, adhesives, paper, foam urbane, niodi-fied acrylics, filled thermosets/thermo-plastics, and rubber. 

Hubercarb . [JAl. Huber] Calcium carbonate fillers and extenders for plastics, caulks, sealants, rubber, adhesives, paints, coatings, ceramics, paper, nonabrasive cleaners. 

Chem. Descrip. Calcium carbonate (99.7%) coated by stearine acid CAS 471-34-1 EINECS/ELINCS 207-439-9 Uses Filler for paints (primers, undercoats), plastics (PVC rigid extrusion, PVC foam extmsion, PVC calendered sheet, PVC inj. molding), rubber, adhesives, sealing compds., and fire extinguishers Properties Spherical crystals 30% < 2 p sp.gr. 2.7 bulk dens. 1.1 g/ml (packed) surf, area 3.5 m /g oil absorp. 14/100 g dry brightness 93% pH 9 ref. index 1.58 hardness (Mohs) 3 < 0.2% moisture MT Binder ENB 02 [Bayer AG]... 

Chem. Desaip. Carbon black CAS 1333-86-4 EINECS/ELINCS 215-609-9 Uses Conductive filler for elec, conductive and antistatic compds., incl. thermoplastics, rubber, adhesives, sealants, inks, coatings, putties, floor pavements, concrete, mortar, paper for conductor insulation Features Porous results in lower compding. vise., easier processing, lower moisture pickup during compding., storage, and transportation, improved physical props. 

In solvent-borne rubber adhesives, a variety of solvents can be chosen to control drying rate, adjust viscosity and dissolve important ingredients. Resins can be added to improve tack, wetting properties, heat resistance, bond strength and oxidation resistance. The most common resins nsed in rubber-based adhesives are rosins, rosin esters, and terpene, coumarone-indene, hydrocarbon and phenobc resins. Plasticizers and softeners reduce hardness, enhance tack and decrease cost of rubber adhesive formulations. Paraffinic oils, phthalate esters and polybutenes are typical plasticizers. Fillers are not often added to rubber adhesive formulations because they reduce adhesion. However they are sometimes used because they decrease cost and increase solution viscosity. Carbon black and titanium dioxide are also used to provide colour to the adhesives. Clays, calcium carbonate and silicates are also common fillers in rubber adhesive formulations. For water-borne adhesives, typically protective colloid, preservative, defoamers, wetting agents and emulsifiers are included in the formulations. 

In the rubber industry the distribution of particle size is considered to be important as it affects the mechanical properties and performance. Aggregate size also varies with particle size. Aggregates can have any shape or morphology. The fundamental property of the filler used in a filled elastomer is the particle size. This affects the reinforcement of elastomer most strongly. One of the sources of reinforcement between the carbon black surface and the rubber matrix is the van der Waals force attraction. Also, rubber chains are grafted onto the carbon black surface by covalent bonds. The interaction is caused by a reaction between the functional group at the carbon black particle surface and free radicals on polymer chains. Hence, filler-rubber interface is made up of complex physical-chemical interaction. The adhesion at the rubber-filler interface also affects the reinforcement of rubber. When the polymer composites are filled with spherical filler (aspect ratio of the particle is equal to unity), the modulus of the composite depends on the modulus, density, size, shape, volume ratio, and number of the incorporated particles. 

Butyl rubber is a copolymer of isobutylene with a minor amount of isoprene (0.8-2 mole %). Unlike PIB, butyl can be crosslinked to improve the otherwise poor cohesive properties of this class of adhesive. The major use for BR is in anticorrosion wrap for gas nd oil transmission pipes. The backing for this tape consists of a thick polyethylene or PVC film, loaded with carbon black. The adhesive mass, which is quite thick (up to 12 mils) not only contains the usual tackifiers, of which many can be used, but also a high concentration of particulate filler. This tape lends itself favorably to calendar manufacture. A typical formulation for a pipewrap adhesive is given in Table 6. 

Generally, natmal rubber and synthetic rubber elastomers do not have enough natmal stick and tack to adhere to many substrates. Tackify resins are added to improve the adhesive strength. Rubber adhesive formulations also contain plasticizers, antioxidants, carbon black, fillers, and colorants. 

The purposes to mix fillers with adhesives are (1) viscosity control, (2) suppression of resin invasion into porous adherends, and (3) strengthen the cured adhesive layer. Commonly used materials for fillers are minerals such as calcium carbonate, clay, talc, and diatom earth. Cellulose powders and recycled rubber powders are also used for the purpose. 

One way of improving the adhesion between polymer and filler is to improve the level of wetting of the filler by the polymer. One approach, which has been used for many years, is to coat the filler with an additive that may be considered to have two active parts. One part is compatible with the filler, the other with the polymer. Probably the best known example is the coating of calcium carbonate with stearic acid. Such coated or activated whitings have been used particularly with hydrocarbon rubbers. It is generally believed that the polar end attaches itself to the filler particle whilst the aliphatic hydrocarbon end is compatible with the rubbery matrix. In a similar manner clays have been treated with amines. 

Colour. The colour of resins ranges from water-white to dark brown. Colour may be an important factor in resin choice depending on end use. Pale colours are necessary in some types of adhesives, whereas darker colours may be tolerated in rubber formulations, especially where carbon black filler is incorporated. Medium-coloured resins can be used in most adhesive formulations. 

In the literature, there are several reports that examine the role of conventional fillers like carbon black on the autohesive tack (uncured adhesion between a similar pair of elastomers) [225]. It has been shown that the incorporation of carbon black at very high concentration (>30 phr) can increase the autohesive tack of natural and butyl rubber [225]. Very recently, for the first time, Kumar et al. [164] reported the effect of NA nanoclay (at relatively very low concentration) on the autohesive tack of BIMS rubber by a 180° peel test. XRD and AFM show intercalated morphology of nanoclay in the BIMS rubber matrix. However, the autohesive tack strength dramatically increases with nanoclay concentration up to 8 phr, beyond which it apparently reaches a plateau at 16 phr of nanoclay concentration (see Fig. 36). For example, the tack strength of 16 phr of nanoclay-loaded sample is nearly 158% higher than the tack strength of neat BIMS rubber. The force versus, distance curves from the peel tests for selected samples are shown in Fig. 37. 

It appears from the evolution of the adhesion index that a distinction has to be made between the interactions carbon blacks are able to have with unsaturated or with saturated (or near-to-saturated) elastomers. Thus, the adhesion index of butyl rubber is enhanced upon oxidation of the black, while the reverse is observed with polybutadiene 38). The improvement of the reinforcing ability of carbon black upon oxidation, in the former case, has been interpreted by Gessler 401 as due to chemical interactions of butyl rubber with active functional groups on the solid surface. Gessler, relating the reinforcing characteristics of the oxidized carbon black for butyl rubber to the presence of carboxyl groups on the surface of the filler, postulated a cationic... 

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