Leta 1961 se je Bratina vpisal na fakulteto za inženirstvo v Trstu. Tu je med drugim obiskoval zavod, ki ga je vodil monsinjor Edoardo Marzari in se ravno po njegovi zaslugi začel zanimati za sociologijo. Leta 1972 se je ponovno vrnil v Trst, kjer je poučeval ekonomsko sociologijo na fakulteti za politične vede. Istočasno je bil zelo dejaven v slovenskih zamejskih organizacijah v Italiji. Bil je član upravnega odbora SKGZ, od leta 1976 je sodeloval s slovenskim raziskovalnim inštitutom Slori, med letoma 1982 in 1992 pa je bil direktor tega inštituta.

Bratina enrolled in 1961 at the Faculty of Engineering in Trieste, where he attended the college directed by Monsignor Edoardo Marzari, thanks to whom he began to mature an interest in sociology. In 1972 he returned to Trieste to teach Economic Sociology at the Faculty of Political Science. At the same time he became an active member in the organizations of the Slovenian community in Italy. In addition to being on the board of the SKGZ, from 1976 he collaborated with the Slovenian Research Institute (Slori), which he directed from 1982 to 1992.