Fillers economic importance

During the last two decades probably no other class of nanomaterials has been associated with such a tremendous broad field of potential application like carbon nanotubes. However, despite considerable advances which have emerged from intense worldwide activities in the corresponding fields of research, their commercial use still turns out relatively sparse. Within the near future, the application as filler for polymeric materials could become of significant economic importance. Recently, some producers of CNTs made massive investments to expand their production capacities and the decreasing price level for industrial grades of CNTs has already caused an increased attention to other branches of industry. 

In addition to their economic importance, carbon blacks exhibit extreme forms of some of the most difficult characterisation issues in the particulate fillers area, especially regarding size and shape determinations, and surface chemistry. However, largely because of their commercial value, more has been done to make advances in these fields than with most other fillers and this pioneering work has much to teach us in a general sense. 

A few numbers allow underlining the economical importance of filled polymers. According to recently published market research reports (2007), the worldwide consumption of fillers is more than 50 million tons with a global value of approximately 25 billion. Many application areas are concerned. 

In consequence of strain crystallisation even vulcanisates without fillers have high tensile strength. The elasticity and low-temperature flexibility values are considerably inferior to those of NBR. NIR has been commercially available for several years but the various grades have not yet acquired much economic importance. 

In evaluating the economics of a filler it is important to consider the volume of filler that can be added bringing the processing and service properties below that which can be tolerated. Thus in some cases it may be more economical to use a filler with a higher volume cost because more can be incorporated. To judge the economics of a filler simply on its price per unit weight is of little merit. 

Each of these additives plays an important role in either the processing or service life of the finished goods. In addition, fillers and pigments are two larger scale additives that play an important role in product economics and aesthetics. 

Composite-based PTC thermistors are potentially more economical. These devices are based on a combination of a conductor in a semicrystalline polymer—for example, carbon black in polyethylene. Other fillers include copper, iron, and silver. Important filler parameters in addition to conductivity include particle size, distribution, morphology, surface energy, oxidation state, and thermal expansion coefficient. Important polymer matrix characteristics in addition to conductivity include the glass transition temperature, Tg, and thermal expansion coefficient. Interfacial effects are extremely important in these materials and can influence the ultimate electrical properties of the composite. 

It is important at this point to give due consideration to the various ways in which a plastics material may be applied. 1. The material may be strengthened with additives to afford specialized properties such as hardness, abrasion resistance, lubricity or tensile strength. 2. The material may be extended either by fillers or by foaming (that is, filling with air) to overcome perceived economic... 

Thermal blacks are used for mechanical rubber goods with high filler contents. Cheaper products (clays, milled coals, and cokes), however, have become increasingly important as substitutes for economic reasons. The total production of thermal blacks is, therefore, decreasing. 

Just as in the manufacture of sheet natural rubber and the asphaltic sheet linings, the basic material as the sheet lining manufacturer receives it from the plantation (rubber) or from the refiner or importer (asphalt), the manufacturer of the synthetic lining materials will receive his synthetic elastomer, thermoplastic or other basic resin from the company that produces it-and will have to blend it with fillers, stabilizers, plasticizers, and other materials to make a suitable compound which will-as a lining—perform its function satisfactorily under the anticipated conditions, and for an economical length of time. The actual amount of the basic resinous material in the compound may be as low as 70% of the total weight. 

Fumed silicas are not only essential fillers in relatively new economically expanding polymers like special silicone rubber [70], they are also of importance in natural and synthetic rubber for applications, where outstanding properties regarding mechanical strength and temperature stability or reduced permeability for gases and liquids are required. 

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