The NHSG condensation reaction of methacryloxypropyl trimethoxysilane and DPSD was exploited in order to synthesize nano-structured units for the preparation of organic/inorganic hybrid coatings in the presence of suitable thermal and photoinitiators .
This result suggested that both "active chain end" and "activated monomer" mechanisms (see Scheme 1) occurred during the propagation step in the cationic ring-opening polymerization leading to a covalent incorporation of BzOH (and corresponding by-products of NHSG reaction) within epoxy network.
In other words, titania nanoparticles generated by NHSG process acted not only as rigid reinforcing filler but also as cross-linking points, increasing the cross-linking density of the composite material with respect to the pristine epoxy matrix.
The NHSG method is here proposed as an alternative synthetic way with respect to the hydrolytic route.
A very simple procedure (few parameters to control), significantly higher crystallinity and the absence of water can be mentioned as major advantages of the NHSG.
On this basis, in the present work titania nanoparticles were in situ generated by using an NHSG process from Ti[Cl.
After stirring for 15 min, the resulting sol was mixed with a previously prepared EPDM solution in a round-bottom flask and heated in an oil bath at 70[degrees]C for 24 h in order to complete the NHSG reaction in the presence of the organic matrix.
In order to characterize the powders embedded in the EPDM, the NHSG reaction was performed following the same procedure described above, except for the presence of EPDM in the reaction media.
In order to evaluate the amount of organic phase on the particles' surfaces and calculate the reaction yields of the NHSG, thermogravimetric analysis (TG) was performed by a Perkin-Elmer TGA7 thermogravimetric analyzer under nitrogen flow, from 30 up to 700[degrees]C at a heating rate of 10[degrees]C [min.
Moreover, the NHSG reaction yield was calculated taking into account the mass loss found by TG analysis.
In all the cases, the actual filler contents were very near to the expected values, indicating that the NHSG process was appropriate to induce an almost complete conversion of Ti[Cl.
This comparison, even if concerning different filler particles, can suggest that the generation of titania particles by NHSG in the presence of the rubber matrix was able to enhance the mechanical properties typical of filled systems in the presence of coupling agents, that is a strong filler-matrix interface was created due to the NHSG process.