Coupling Agents or Surface Modifiers

Coupling agents improve the adhesion between polymer and filler, particularly inorganic. Providing a chemical bridge. 

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In addition to the raw material cost, one also has to take into account compounding costs, the cost of any coupling agent or surface modifier that is not already present on the filler and the cost of additional stabilisers that might be re-... 

For the encapsulation of hydrophilic magnetic nanoparticles, the surfaces have to be converted into more hydrophobic by functionalization with a surfactant having a low hydrophilic/lipophilic balance (HLB) value, with coupling agents or surface modifiers. Apart from the enhancement of the surface hydrophobicity of the inorganic particles, in some cases different reactive groups are introduced for polymerization with the hydrophobic monomer... 

The amount of additives reduction maintains the mechanical standards but negatively affects the flame resistance of the materials [37]. In a flame retardant compound, addition of coupling agents or surface modifiers reduces its flame retardancy. 

The probe compounds may be chosen as model acids (for example, carboxylic acids or chloroform) and bases (for example, pyridine or ether), with which to measure the acid-base character of the filler surface. However, the probes may be actual interfacial modifiers used in the composite system under investigation, for example an organosilane coupling agent or fatty acid dispersant. Furthermore other interesting interactions have been studied by the authors and include stabiliser - filler interactions during evaluation of controlled release/displacement effects. 

Many silane coupling agents can be applied to substrates by volatilization in an enclosed chamber under heat or vacuum. In this approach, the substrate is placed within the chamber in a fashion to allow for vapor phase molecules to access all areas that are to be derivatized. This method is commonly used for silanizing glass slides or substrates that are difficult to suspend in a silane solution. Slides are often placed in racks within the chamber and all surfaces get modified... 

Spectroscopic techniques are extremely useful for the characterization of filler surfaces treated with surfactants or coupling agents in order to modify interactions in composites. Such an analysis makes possible the study of the chemical composition of the interlayer, the determination of surface coverage and possible coupling of the filler and the polymer. This is especially important in the case of reactive coupling, since, for example, the application of organofunctional silanes may lead to a complicated polysiloxane interlayer of chemically and physically bonded molecules [65]. The description of the principles of the techniques can be found elsewhere [15,66-68], only their application possibilities are discussed here. 

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