R. Striani

Microgel Modified UV-Cured Methacrylic-Silica Hybrid: Synthesis and Characterization

An innovative photopolymerizable microgel modified UV-cured acrylic-silica hybrid formulation was developed and characterized for possible use as protective coating for different substrates. A deep investigation, aiming at providing a strong scientific basis for the production of organic-inorganic (O-I) hybrids exhibiting phase co-continuity, was firstly carried out. The O-I hybrid first proposed in this study was obtained from organic precursors with a high siloxane content, which are mixed with tetraethoxysilane (TEOS) in such a way to produce co-continuous silica nanodomains dispersed within the crosslinked organic phase, as a result of the sol-gel process. The first part of the research deals with the selection and optimization of suitable systems through appropriate chemical modifications, in order to ensure that curing reactions can be carried out at room temperature and in the presence of UV radiation. Firstly, the silica domains are formed, followed by crosslinking reactions of the acrylic groups in the oligomer via a free radical polymerization. The crosslinking reaction was controlled with the use of a suitable photoinitiator. Most of the experimental work was devoted to understanding the morphology of the hybrid system, both in uncured and cured states, and to assess its final thermal and optical properties, using different experiential techniques.

Morphological characterization of silica obtained by calcination of methacrylic and epoxy – silica hybrid systems

The work is addressed to investigating the potentiality of calcination of organic-inorganic (O-I) hybrids as a feasible approach to produce silica particles, at mild temperature conditions and with tailored morphology. Two different innovative hybrid systems were obtained through sol-gel process with a siloxane content ranging from 6 to 26wt%. The two O-I hybrids differed for i) the organic matrix (methacrylic or epoxy), ii) its crosslinking mechanism (photopolymerization for methacrylic systems or thermal cold-cure for epoxy systems) and iii) the rate ratio between sol-gel and crosslinking reactions. Different characterization techniques were used to understand the effect of composition and curing method on the morphology of the silica obtained from O-I hybrids after calcination in air. The results confirm the morphology and properties of silica particles in terms of surface and porosity may be tailored over a wide range by varying the composition and nature of organic and inorganic precursors of hybrids.

Novel hydrophobic photopolymerizable nano-structured protective coating for porous stones

In order to guarantee a very high preservation of stone artworks from water actions, an innovative super hydrophobic photopolymerizable organic–inorganic (O-I) nano-structured hybrid system has been developed and applied on a calcarenitic stone characteristic of Apulia Region (Italy), i.e. Pietra Leccese (PL). This novel system avoids the use of harmful solvents and is able to quickly set and harden at room temperature. Different analytical techniques (contact angle, colorimetric measurements, water absorption measurements, liquid water and water vapor transmission) have been employed to fully characterize the product in terms of hydrophobicity, protective efficacy, water penetration resistance and transpiring capability. The results obtained evidenced that the coating is able to equal the performance of high quality commercial products.