Fillers, active

Reinforcing fillers (active) Fumed Silica (Si02) precipitated calcium carbonate (CaCOi) carbon black Thixotropic reinforcing agents (non-slump), adjustment of mechanical properties (cohesion) provide toughness to the elastomer as opposed to brittle materials. 

Elastomer-plastic blends without vulcanization were prepared either in a two roll mill or Banbury mixer. Depending on the nature of plastic and rubber the mixing temperature was changed. Usually the plastic was fed into the two roll mill or an internal mixer after preheating the mixer to a temperature above the melting temperature of the plastic phase. The plastic phase was then added and the required melt viscosity was attained by applying a mechanical shear. The rubber phase was then added and the mixture was then melt mixed for an additional 1 to 3 min when other rubber additives, such as filler, activator, and lubricants or softeners, were added. Mixing was then carried out with controlled shear rate... 

Note that, apart from the filler particle shape and size, the molecular mass of the base polymer may also have a marked effect on the viscosity of molten composites [182,183]. The higher the MM of the matrix the less apparent are the variations of relative viscosity with varying filler content. In Fig. 2, borrowed from [183], one can see that the effect of the matrix MM on the viscosity of filled systems decreases with the increasing filler activity. In the quoted reference it has also been shown that the lg r 0 — lg (MM)W relationships for filled and unfilled systems may intersect. The more branches the polymer has, the stronger is the filler effect on its viscosity. The data for filled high- (HDPE) and low-density polyethylene (LDPE) [164,182] may serve as an example the decrease of the molecular mass of LDPE causes a more rapid increase of the relative viscosity of filled systems than in case of HDPE. When the values (MM)W and (MM)W (MM) 1 are close, the increased degree of branching results in increase of the relative viscosity of filled system [184]. 

Silica fillers also react with the rubber causing an increase in viscosity and dry and unmanageable processing behaviour. Filler activators need to be added to silica-reinforced compounds to overcome these problems. The usual filler activators used are diethylene glycol, polyethylene glycol and amines such as triethanolamine. Some of these activators not only overcome the problems of processing and accelerator absorption, but depending on the cure system used, will also act as vulcanisation activators. 

Precompounded grades are optimized by the supplier to provide the best combination of accelerator and cross-linker for a given application [43]. Then, the final compounding consists of only the addition of fillers, activators, and other ingredients needed to achieve the required physical properties and processing characteristics. 

Bound rubber is the fraction of polymer which is not extracted by a good solvent from a rubber-filler mix. It is a measure of rubber reinforcement as well as of filler activity towards the rubber. This concept was introduced in 1925 by Twiss. Although, the traditional term bound rubber is commonly used for rubber compounds, the concept can also be applied to other macromolecular materials. The amount of bound rubber is given by the following equations ... 

For the protection of the light sensitive IC devices, pigments are usually incorporated into the RTV encapsulant (such as low level of the carbon black and titanium dioxide). The main parameter that affects the RTV rheology may be filler incorporation and filler activity. Through the RTV silicone study, we have learned that the rheology of the RTV silicone is closely related to its coating performance. 

These are accelerators and crosslinking agents with which in particular heat-resistant vulcanizates can be produced based on natural and synthetic rubber, as well as filler activators based on amines. 

Sihca and silicates are usually rather passive fillers. Active fillers able to contribute also for the proton conductivity include zirconium [203, 237-250] and boron phosphates [251-253] and heteropolyacids [254-264]. 

Dubois, P. et al., Macromol. Symp., Filler Activated filler... 

Additives used in finai products Fillers activated carbon, glass fiber, carbon fiber, aramid fiber, montmorlllonite, PTFE, silica, titanium dioxide Plasticizers benzyl butyl phthalate, diethyl phthalate, methyl phthalyl ethyl glycolate, tricresyl phosphate Release silicone oil, zinc stearate ... 

The filler activity is conditioned by the mutual adhesion of the polymer and the filler it corresponds to the physicochemical character of the polymer-filler interface, which determines the extent of sorption processes on the solid surface as well as the type of polymer-filler bonds. 

The filler activity in this case is determined by the molecular interaction between media and filler and by formation of solvated shells. This means that some part of the dispersion medium (polymer) forms these shells and transits... 

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