Application Modes for Coupling Agents

To obtain composites with good high-temperature properties and better creep performance, a cross-linked coating has to be formed between fibers and the polymer matrix [3]. 

Isopropyltri(dioctylpyrophosphato) titanate Isopropyltriacryl titanate Dioctylphosphito titanate Isopropyltri(ethylamino-ethanolamino) titanate 

Coupling agents are used at a rate of 0.3-3% by weight of filler. They are applied in a solution in water or in nonpolar solvents (hexane, benzene). In practice the solution concentration varies between 0.1 and 0.3 g Hydrolysis of coupling agents is done at pH between 3.5 and 5 [69,78]. It is also necessary to clean fibers from impurities and lubricants by washing with solvents or by firing at 250-600°C [81]. 

Silanes form a 10-20-nm thick layer but they may also form a 0.5-1-nm thick layer that corresponds to a trimolecular layer [21]. It all depends under which form the filler is used, in the form of roving, mat, or fiber. 

Adsorption equilibrium of coupling agents from aqueous solutions is very rapid. For example, it is attained in 30 sec in the case of a glass E filler. For this reason the treatment takes about 1 min in practice [68,78] and the solution is quickly removed after that time to avoid any excess of coupling agent then the treated filler is dried [69,78]. 

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