Filler surface activity

Applications. Bound rubber is a measure of filler surface activity to the matrix, and it is considered as a factor in the estimation of filler reinforcement. 

The particle size of the filler as discussed earlier may be considered as a physical contribution to reinforcement, while filler surface activity provides the chemical contribution. The ability of the filler to react with the polymer results in chemical bonding, which increases strength significantly. In the absence of strong coupling bonds, the polymer is physically absorbed on the surface of the... 

Resin Viscosity. The flow properties of uncured compounded plastics is affected by the particle loading, shape, and degree of dispersion. Flow decreases with increased sphericity and degree of dispersion, but increases with increased loading. Fillers with active surfaces can provide thixotropy to filled materials by forming internal network stmctures which hold the polymers at low stress. 

The metal fillers act as a reinforcing material that results in added strength and stiffness (126). They color the plastic gray for nickel, 2inc, stainless steel, and aluminum, and brown for copper. Metal additives are more expensive than carbon black or surface-active agents, but they get extensive use in EMI shielding appHcations. 

This relatively new trend in PCM manufacturing business amounts to creating a polymeric matrix out of the liquid or gaseous phase directly on the filler surface which has previously undergone special conditioning aimed at generating active polymerization sites on it. 

I — the filler was activated in the liquid phase via reaction of the organoaluminum compounds fixed on the surface with VOCl3 II — activation of filler by previous securing on the surface of VOCl3 from the gas phase particles of less than 5-10microns in size amount to 96% ... 

Silica is unique among nonblack fillers. Its reinforcing ability is comparable to that of carbon black, especially when mixed with a suitable coupling agent, and its transparency affords many products. Additionally, it is chemically synthesized, which means that a wide range of silica (in terms of diameter, surface area, or surface activity) may be produced depending on the reaction routes and reaction conditions. 

Sodium silicate wetting, emulsifying, penetrating, and other surface-active properties do not appear to impact ink removal efficiency in flotation (36). Flotation can also remove some of the paper filler and coating particles dispersed in the pulp. Addition of certain cationic oiganic polymers such as poly(dia11yldimethylammonium chloride) to pulp improves the removal efficiency of these particles during flotation (37,38). 

As Table 2 shows, non-treated fillers and reinforcements have high energy surfaces. During the almost exclusively used melt mixing procedure, the forces discussed in the previous section lead to the adsorption of polymer chains onto the active sites of the filler surface. The adsorption of polymer molecules results in the development of a layer which has properties different from those of the matrix polymer [43-47]. Although the character, thickness and properties of this interlayer or interphase are much discussed topics, its existence is now an accepted fact. 

Kodama and co-workers [58] have reported TG-DSC curves for the analysis of the interaction between vulcanisation accelerators (tetramethylthiuram disulphide, dibenzothiazolyl disulphide, diphenylguanidine and N-cyclohexyl-2-benzothiazolyl-sulphenamide) and fillers (carbon black, white carbon, hard clay and CaC03). The initial melting point (MP) of the accelerators was largely influenced by the fillers. The higher the surface activity of the filler is, the lower and wider the melting range becomes. 

It should be pointed out that diluents are not the only way to lower the viscosity of filled epoxy resins systems. Surface active agents can also be added to the system. They provide better wetting of the filler by the epoxy resin matrix. This can lead to substantial viscosity reduction for systems having equivalent filler concentration. The surface active agent, in turn, could also be used to produce formulations with higher filler loading at equivalent viscosity. These surface active agents are discussed in Chap. 10. 

Both of these effects refer to a high surface activity and specific surface of the filler particles [26, 27, 47]. In view of a deeper understanding of such structure-property relationships of filled rubbers it is useful to consider the morphological and energetic surface structure of carbon black particles as well as the primary and secondary aggregate structure in rubber more closely-... 

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