Polymer-filler interaction, silicone

A silicone oil plasticiser is desirable to facilitate dispersion and to prevent undesirable polymer-filler interaction prior to vulcanisation. 

Another example of the effect of fillers on improving bond strength is reported for a silicone RTV-1 sealant formulated with Cabot Corporation s Cab-O-Sil LM-130 and TS-720 materials. Cab-O-SU fumed silicas are very effective reinforcing agents due to the very-large surface area available for polymer/filler interactions. The very low, 45 psi, tensile strength of the unfilled silicone increased to 210 psi with 14 phr of LM-130 fumed silica and to 150 psi with the same level of TS-720 fumed sUica. ... 

Silicone Rubber RTV-1 Sealants (Cabot, 1994) - The superior rheology control and reinforcement properties of fumed silica compared to a similar stuface area grade of preeipitated silica has already been shown in Figure 5 and Table 4. The more open ehained structure of the frmred sihea allows the formation of a much more effective silica network with more of the sihea srrrface available for polymer/filler interaction, resulting in superior eured physical properties. 

In recent years it has been demonstrated that NMR methodologies can be effectively utilized in the development and vahdation of predictive models of silicone networks. The information made available on a silicone network though the use of various NMR methodologies such as molecular weight distribution (MWD), effective crosslink density, modahty, polymer-filler interactions and the presence of localized stresses, defects and inhomogeneities, can be used to both test and refine theoretical models, which predict both network dynamics and degradation in sihcone systems. 

Reduced blood-polymer interaction (Filler-free silicone surface reduces thrombogenic response.)... 

Both the Japanese Synthetic Rubber Company and Nippon Zeon have reported that anionically prepared elastomers that are functionally terminated by active lithium can be chain terminated with Michler ketone, benzophenone, and a variety of enamide groups. Moreover, these chains can be terminated with silicone or tin metals. Chain end functionalization did not change the viscoelasticity of the polymer chains but rather dramatically improved the elastomer-filler interaction and, therefore, reduced its hysteretic properties. 

The main applications, by far, are as reinforcing fillers in hydrocarbon elastomers. Organo-silanes, such as the mercapto, polysulfides, amino and vinyl are used to improve filler to polymer interactions and reinforcement. Particnlarly important uses are in tyres and in footwear. There is also significant use as a reinforcing filler in silicone elastomers. 

Since most technical applications require better mechanical properties than those displayed by pure polydimethylsiloxane polymer/crosslinker networks, liquid silicone systems also contain fillers. These are classified as inert, i.e. nonreinforcing, or active, i.e. reinforcing. Inert fillers such as quartz powder, diatomaceous earths, calcium silicates, calcium carbonates, and iron oxides interact neither chemically nor physically with the polydimethylsiloxane netwoflr. They mainly influence the silicone rubber s hardness and swelling properties. 

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