Polymer modification reinforced with silicas

Modification of the polymer backbone by the incorporation of trifluoropropyl groups leads to substantial decreases in swelling. In vulcanized systems reinforced with hydrophilic silica (30 phr) the swelling decreased with increasing CH2CH2CF3 content as shown in Table III. 

Silica particles do not induce any modification of the stress state in the material, and so no extended plasticity in the matrix. Naiiosized silica particles can be considered as a modifier of polymer chain displacement, and not as a reinforcement filler. There is adsorption of PP on silica surface and consequent reduction of molecular mobility with a large increase of elastic modulus. We do not observe any process zone, and mechanisms as particle/matrix decohesion as well as crack pinning or blunting are not effective. 

A new area of development is to incorporate the filler permanently into the polymer matrix, by use of coupling reactions. This can increase impact strength and thermal properties of polyamides and modify the anisotropy of partially crystalline plastics, such as polyamides and polyesters. In polypropylene, bonding with kaolin can also improve scratch resistance, which is a useful benefit for automobile interior applications. Surface modification of fillers such as silica, mica, and wollastonite allows these to penetrate markets that were formerly the province of reinforcements such as carbon black and glass fibre. 

Cesium acid heteropolys alts (CsHPA) One interesting modification of the HPA is the partial substitution with Cs, especially in the case of 2.5 atoms, where the surface acidity achieves its maximum [39, 48, 49]. The water solubility of the salt is reduced and the surface area increased, maximizing the interaction with the polymer matrix. The use of a phosphorous-based salt of this type maximizes the membrane conductivity, whereas the silica-based salt reinforces the mechanical properties. Very interesting results are also obtained when W was replaced by Mo [49]. 

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