Particulate fillers filler

It is clear that ab will be extremely large for inclusions of small radius r, even if the level of adhesion, represented by Ga, is relatively small, only of the order of magnitude of van der Waals attractions. For example, when E is assumed to be 2 MPa, representative of soft elastomers, and Ga is given the relatively low value of 10 J/m, then the critical applied stress for detachment is predicted to reach a magnitude similar to E when the radius of the inclusion is reduced to about 20 ixm, even if the initially debonded zone is as large as feasible, 6 — 45°. These considerations appear to account for some features of reinforcement of elastomers by particulate fillers Fillers (140). 

Particulate fillers are divided into two types, inert fillers and reinforcing fillers. The term inert filler is something of a misnomer as many properties may be affected by incorporation of such a filler. For example, in a plasticised PVC compound the addition of an inert filler will reduce die swell on extrusion, increase modulus and hardness, may provide a white base for colouring, improve electrical insulation properties and reduce tackiness. Inert fillers will also usually substantially reduce the cost of the compound. Amongst the fillers used are calcium carbonates, china clay, talc, and barium sulphate. For normal uses such fillers should be quite insoluble in any liquids with which the polymer compound is liable to come into contact. 

There has also been some interest in polymers containing particulate mineral fillers. 

Commercial grades of polymer may contain, in addition to glass fibre, fire retardants, impact modifiers and particulate reinforcing fillers. Carbon fibre may be used as an alternative to glass fibre. 

Fibrous fillers are now gaining more importance over particulate fillers due to the high performance in mechanical properties. The influence of fiber diameter on the tensile behavior of short glass fiber on polyimide was reported [95], At higher concentrations thick fibers seem to be more advantageous probably because of the... 

Particulate fillers provide better creep resistance than unfilled plastics but are less effective than fibrous reinforcements. 

In general adding reinforcing fibers significantly increases mechanical properties. Particulate fillers of various types usually increase the modulus, plasticizers generally decrease the modulus but enhance flexibility, and so on. These RPs can also be called composites. However the name composites Utterly identifies thousands of different combinations with very few that include the use of plastics (Table 6-18). In using the term com-... 

Modulus Rigid minerals Ductility Ductility produces a more rigid composite. Particulate fillers severely degrade impact strength. 

Table 7.1 The effect of particulate fillers on tensile properties of poly(ethylene) (filler concentration 25 parts/lOO of polymer by weight)...

Carbon blacks are the most widely used fillers for elastomers, especially vulcanised natural rubber. They cause an improvement in stiffness, they increase the tensile strength, and they can also enhance the wear resistance. Other particulate fillers of an inorganic nature, such as metal oxides, carbonates, and silicates, generally do not prove to be nearly so effective as carbon black. This filler, which comes in various grades, is prepared by heat treatment of some sort of organic material, and comes in very small particle sizes, i.e. from 15 to 100 nm. These particles retain some chemical reactivity, and function in part by chemical reaction with the rubber molecules. They thus contribute to the crosslinking of the final material. 

Report 79 Rubber Compounding Ingredients - Need, Theory and Innovation, Part I Vulcanising Systems, Antidegradants and Particulate Fillers for General Purpose Rubbers, C. Hepburn, University of Ulster. 

Report 141 Particulate Fillers for Polymers, Professor R.N. Rothon, Rothon Consultants and Manchester Metropolitan University. 

The most important approach was to use poly(methyl methacrylate), PMMA, in formulations, either as a particulate filler or as a coating on zinc oxide particles (Jendresen Phillips, 1969 Jendresen et al., 1969 Civjan et al., 1972). It is claimed that such materials can be used for permanent as well as temporary cementation. 

Aid in the uniform dispersion of additives. Make powdered solids (e.g. particulate fillers with high energy and hydrophilic surface) more compatible with polymers by coating their surfaces with an adsorbed layer of surfactant in the form of a dispersant. Surface coating reduces the surface energy of fillers, reduces polymer/filler interaction and assists dispersion. Filler coatings increase compound cost. Fatty acids, metal soaps, waxes and fatty alcohols are used as dispersants commonly in concentrations from 2 to 5 wt %. 

As already mentioned, a network can be obtained by linking polymer chains together, and this linkage may be either physical or chemical. Physical linking can be obtained by (i) absorption of chains onto the surface of finely divided particulate fillers, (ii) formation of small crystallites, (iii) coalescence of ionic groups, or (iv) coalescence of glassy sequences in block copolymers. 

Particulate composites, 26 754-755 ceramics processing, 5 653-654 extensional modulus of, 26 777 fabrication of, 26 766 Particulate emission limits, 13 183 Particulate emissions, reducing, 11 689 Particulate fillers, ll 302t, 303 for rubber, 21 772, 773 Particulate fluidized-bed regime, 11 801 Particulate impurities in gases, 13 464 in high purity gases, 13 466 Particulate matter (PM), 1 798-801 ... 

Alumina-Filled Edoxv. A different interfacial geometry and failure mechanisms are provided by particulate fillers. Alumina and silica are incorporated into plastics primarily because of their low cost, and may also improve properties to some extent. In our studies, the EE, phE and RE from neat and alumina-filled Epon 828... 

Crosslinked polymers are widely used as dental materials (1-31. Perhaps the most challenging application is in the restoration of teeth (4). The monomers must be non-toxic and capable of rapid polymerization in the presence of oxygen and water. The products should have properties comparable to tooth enamel and dentin and a service life of more than a few years. In current restorative materials such properties are sought using so-called "dental composites" which contain high volume fractions of particulate Inorganic fillers (5-71. However in the present article attention is concentrated on one commonly used crosslinked polymeric component, and on the way in which some of its properties are influenced by low volume fractions of fillers. 

Maximum volume fraction of a particulate filler that can be added to a polymer while maintaining the polymer as the continuous phase domains. 

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