Fillers enhancement function

Further insight into the nature of the interaction between irreversibly adsorbed species and the filler surface can be gained from DRIFTS analysis of the filler sample taken from the FMC cell after completion of the adsorption - desorption cycle. DRIFTS is described in more detail in Section 3.5.4, but in summary, it is an infrared spectroscopic technique, that by virtue of a significant proportion of glancing angle reflections, affords enhanced resolution of filler surface functional groups. The authors have found this technique particularly useful when studying competitive adsorption of polymer stabilisers and carboxylic acids onto silica and metal hydroxides, respectively. 

Developed to provide improved thermal management for today s smaller, faster electronic devices, silica coated aluminum nitride is a highly thermally conductive filler material used in semiconductor molding compounds. Molding compounds filled with this material provide the potential to improve reliability when compared to standard and non-metal-enhanced packages. Silica coated aluminum nitride also provides the potential to enhance functionality, power, heat dissipation and performance, while lowering system costs. 

Early reports and patent applications of Stonehart and Watanabe [22], Antonucci et al. [23], and Antonucci and Arico [24] claim the advantage of the introduction of small amounts of sihca particles to Nafion to ino-ease the retention of water and improve the membrane performance above 100°C. The effect is believed to be a result of water adsorption on the oxide surface. As a consequence the back-diffusion of the cathode-produced water is enhanced and the water electro-osmotic drag from anode to cathode is reduced [3]. A recent report of the group of Arico et al. [25] confirms the effect of water retention with the inclusion of oxide particles in Nafion and the importance of the acidity of the particle surface. An increase in both strength and amount of add surface functional groups in the fillers enhances the water retention in the membrane SiO -PWA (modified with phosphotungstic acid) > SiOj > neutral-AljOj > basic-AI2O3 > ZrO. ... 

Papermaking additives can be categorized either as process additives or as functional additives. Process additives are materials that improve the operation of the paper machine, such as retention and drainage aids, biocides, dispersants, and defoamers they are primarily added at the wet end of the paper machine. Functional additives are materials that enhance or alter specific properties of the paper product, such as fillers (qv), sizing agents, dyes, optical brighteners, and wet- and dry-strength additives they may be added internally or to the surface of the sheet. 

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. 

Of course, the rates of reaction are dependent on the accessibility of the functional groups of the polymer to the reactant. This accessibility is enhanced by the presence of solvents and plasticizers and hindered by crystallization, fillers, and cross-links. In general, the rate of attack of a polymer molecule by a corrosive is dependent on the rate of diffusion of the attacking molecule, and the temperature. Polymers are more readily attacked by corrosives at temperatures above the glass transition temperature Tt and when stiffening groups are not present in the polymer molecule. 

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... 

Tseng et al. (51) reported the epoxy nanocomposites in which the nanotubes were functionalized by maleic anhydride by using plasma treatment. The thermal decomposition temperature was reported to increase with increasing the extent of the nanotubes in the composites as shown in Figure 2.16a. Untreated nanotubes were also used to reinforce the polymer and the increase in the decomposition temperature was also observed in this system as a function of filler content, but the enhancement was more significant using the functionalized nanotubes. This was attributed to... 

Figure 2.16. Enhancement of (a) decomposition temperature as well as (b) glass transition temperature as a function of filler content in epoxy nanocomposites. Reproduced from reference 51 with permission from American Chemical Society.

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