Fillers, active inactive

The use of OEA for rubber crosslinking opens new possibilities for the use of all kinds of fillers [111[. Inactive fillers intensify the strengthening process of rubber by means of OEA. Active filler materials participate, however, in the strengthening process, and OEA contributions to improved physicochemical properties of the cured product become less important. 

With increasing MM the swelling increases faster in systems with a more active filler and is also somewhat greater by an absolute value than in systems with an inactive filler [183]. 

Fillers are solid materials that are dispersed in plastics and elastomers. One distinguishes between inactive fillers that are used in the first place to make the plastics less expensive and active fillers (reinforcing fillers) that improve specific mechanical properties and thus effect a reinforcement . With the aid of these fillers, the elastic modulus, hardness, and thermostability are enhanced predominantly, whereas the impact strength of thermoplastic niaterials is re-... 

Formulation design is based on the physical, chemical, and biopharmaceutical properties of a drug substance. A formulation for direct compression is composed of active pharmaceutical ingredients and other inactive ingredients such as fillers, binders, dis-integrants, flow aids, and lubricants. Simplicity is the basis of good formulation design. Minimally, a direct compression tablet formulation must meet requirements for manufacturability, uniformity of dose, physical and chemical stability, appropriate dmg release profiles, and bioavailability. In addition, the formulation must meet many quality standards and special requirements to ensure the efficacy and safety of the product. 

Besides the active ingredients, antacid tablets also contain inactive ingredients, such as starch, which act as a binder or filler. The efficacy of an antacid tablet is its ability to neutralize HC1. The more HC1 that is neutralized, the more effective the antacid pill. (You must have heard the competing advertisement claims of different commercial antacids Turns neutralizes one-third more stomach acid than Rolaids. )... 

The N 300 series is characterized by a wide variety of rubber blacks, covering about 10 different types. As mentioned above, fme-particle active blacks are used for rubber components that need to withstand significant levels of mechanical stress, e.g. tire treads. Semi-active blacks, on the other hand, are used in the tire carcass but also in technical rubber components, from screen and door seals to floor mats. Tires also contain other special carbon blacks, for instance, so-called adhesion blacks for improving radial steel belt adhesion, conductive blacks or inactive blacks for higher filler load rates [4.26]. 

A distinction between inactive and active fillers is at present hardly relevant, since the properties of the final product depend more or less strongly upon all the fillers utilized and their use has for a long time not been primarily determined in terms of cost reduction. The efforts of the fdler producers in the direction of improved processing methods and dedicated manufacturing processes take this development into account. The surface treatment of natural and synthetic fillers has also acquired great importance. For years there have been products which in the classic sense are not fillers at all, but are in fact active substances (e.g. silica aerosols). Apart from any cost reduction considerations, fillers have essentially the following functions ... 

Corrosion protection coatings also contain inactive corrosion protection pigments as additives (Ti02, Fe203, fillers, CaC03 etc.), which support the operation of the active pigments. 

Sample preparation of anaerobic adhesives for metal content is an important step, be it by destructive or non-destructive methods. Inactive metal salts are added directly to anaerobic formulations as fillers or for thixotropic reasons. Generally, active transition metals are not added directly to anaerobic adhesives but are prepared as activators in aerosol solvents to be applied to inactive surfaces as part B of an adhesive formulation. In the majority of cases trace metal analysis of anaerobic adhesives is only required for batches with problematic stability and is best done using destructive methods. 

NanofiUers are often added to enhance one or more of the properties of polymers. Inactive fillers or extenders raise the quantity and lower the cost price, while active fillers bring about targeted improvements in certain mechanical or physical properties. Common nanofillers include calcium carbonate, ceramic nanofiUers, carbon black, carbon nanotubes (CNTs), carbon... 

The embedded material should reinforce the matrix, e.g., with respect to flexural strength. Because this effect is absent with interpenetrating networks, these are often not classed as composites, although, according to structure, they are composites with a zero-dimensional dispersed phase. Polymers reinforced with active or inactive particulate fillers are also not classed as composites. 

As particle size grows, the specific surface area of the carbon blacks diminishes. A distinction is made between active rubber blacks with a specific area from 70 to 150 mVg, which are commonly used in the production of tire treads, and semi-active blacks, used for tire carcasses, which have a specific surface area of 15 to 70 mVg. Inactive carbon blacks have a specific surface area of <15 mVg they are commonly used as fillers in the production of industrial rubber goods. 

Liquids. Liquid enzyme formulations usually contain a significant amount of stabilizing agents, such as carbohydrates, polyols and inactive (filler) proteins. In addition, side-products from the fermentation may be present. In general, they tend to stabilise enzymes and thus their removal (e.g., by dialysis) is not recommended. The same apphes to dilution, as concentrated protein solutions are usually more stable. Liquid formulations should be stored in the cold (0 to +4°C), but avoid freezing If long-term storage is required, two options are possible (if in doubt, test both methods on a sample first and check for any loss of activity) ... 

As an example of the use of equation (4.5) to determine the viscosity of suspensions, one can refer to e works of Mullins [94] and Feldman and Boiesan [95] on rubbers containing fillers which are chemically inactive like wood flour or chemically active like carbon black. When the filler introduced is chemically inactive (with any ) or chemically active (with < 0.10), the quadratic form of equation (4.5) with aj = 2.5 and X2 = 14.1 could be used to give a good estimate of the viscosity of the suspension. For higher concentrations of the chemically active filler (carbon black), particle interaction begins and the viscosity of the suspension increases markedly and equation (4.5) as such cannot then be used for an estimate. However, if particle interaction leads to agglomeration, then Mullins [94] and Feldman and Boiesan [95] recommend the use of aj = 0.67 , and 02 = 1.62 in equation (4.5), where a, is the index of asymmetry of the elastomer macromolecules. 

Based on the mutual interaction between fillers and polymers, it is possible to classify fillers into two groups, active and inactive [22]. This classification is rather arbitrary [24], since it is based not only on differences in chemical composition but also on characteristics of filler particles surfaces, particle shape and size, and treatment of the surface by coupling agents (see Section 4.4). 

The possibility of galvanic corrosion must be considered when filler metals are selected for brazing titanium-base metals. While titanium is an active metal, its activity tends to decrease in an oxidizing environment, because its stirface undergoes anodic polarization similar to that of aluminum. Thus, in many environments, titanium becomes more chemically inactive than most structural alloys. The corrosion resistance of titanium is generally not affected by contact with structural steels, but other metals, such as copper, corrode rapidly in contact with titanium xmder oxidizing conditions. Thus, filler metals must be chosen carefully to avoid preferential corrosion of the brazed joint. 

Introduction of these definitions is veiy important to rmderstand the processes of reinforcement of pol3rmers, although they cannot be used for quantitative description of filler influence. The degree of this influence, as shown below, depends not only on the chemical nature of a fiUer but on its concentration in a polymer matrix. In such away, the same fiUer may be active in one polymer and inactive in another. The influence of a filler may be related to the change in properties per unit content of fiUer, which is another quantitative characteristic of filler. However, this assessment is very arbitrary, because the reinforcement is not linearly related to the fiUer concentration. Reinforcement can be related to the energy. A, used to rupture pol3rmer rmder standard conditions, as measured by the area rmder the stress-strain cruve ... 

To bring the polymer into the state of a surface layer on the filler particles, it is necessary to contribute work to overcome the forces of surface tension. This work is expended for increasing the surface of the polymer, and it is a measure of the additional work necessary for rupture. The increase in the work of rupture, per unit of volume, by the incorporation of the filler, may be taken as a basic characteristic of the reinforcing action of fillers in polymers which are in the rubber-like state. Fillers which do not increase work of rupture are considered inactive, those which do increase are considered active. The magnitude of effect depends on the nature of the filler. To assess the reinforcement, one may use the relative reinforcement ... 

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