Influencia de la molienda en la energía superficial de fritas para esmaltes

espanolSe ha estudiado el proceso de molienda en dos fritas de la industria ceramica. Las dos fritas, de composiciones similares pero en una se ha sustituido parte de la silice por 5% de oxido de boro, fueron molidas por via seca o humeda y se caracterizaron mediante FT-IR, valoracion Karl-Fischer e IGC-ID. Mediante valoracion se han determinado los contenidos en moleculas de agua e hidroxilos. El mayor contenido en hidroxilos lo posee la frita sin boro seguida de la de boro ambas molidas en humedo, poseyendo 28 y 26 grupos OH por cada 100 A2, respectivamente. Estos resultados coinciden con IGC-ID, sin embargo es la frita sin boro molida en seco la de mayor energia superficial (44 mJ.m-2) y constante acida (0.13 kJ.mol-1). Aunque las dos fritas tienen centros acidos y basicos, la que no contiene boro presenta mayor basicidad que la de boro. La molienda influye de forma diferente en las dos fritas aumentando la basicidad en la que no tiene boro y disminuyendo en la que lo contiene. Esto se debe a la localizacion de los grupos hidroxilo en la superficie de la frita, poseyendo mayor interaccion con los grupos hidroxilo la frita sin boro molida en humedo. EnglishIn this work has been studied the influence of the milling process of two ceramic frits used in the ceramic tile industry. Both glass frits were of similar chemical composition changing SiO2 by 5% of B2O3 and both of them were water or dry milled. Glass frit surfaces were characterized by FT-IR, Karl-Fischer (K-F) titration and Inverse Gas Chromatography at Infinite Dilution (IGC-ID). By K-F titration it was observed that water milled frits presented 28 and 26 OH groups for 100 A2 if they do not contain or contain boron, respectively. These surface changes are also observed by IGC-ID. Thus, the glass frit without boron and dry milled presented the highest dispersive surface energy (44 mJ.m-2) and the less acidic constant (0.13 kJ.mol-1). Both glass frits are amphoteric with acidic and base surface active sites, and that frit without boron presents the higher basicity. Milling process influences in the acid-base surface characteristics of both frits by increasing the basicity for the one without boron and increasing for the other one. This has been assigned to the different location of hydroxyl groups where the higher interaction is the one that does not contain boron and dry milled as K-F results.