Investigasi Pengaruh Pluronik 473 Pada Stabilitas Shellac 321Istiqomah1, Khairuddin2, Nanik Dwi NurhayatiJurusan Fisika FMIPA Universitas Sebelas MaretDosen Jurusan Fisika FMIPA Universitas Sebelas MaretDosen Jurusan Pendidikan Kimia FKIP Universitas Sebelas MaretJl. Ir. Sutami No. 36A, Kentingan, Jebres, Surakarta  ABSTRACT3 The effect of pluronic 473 on stability of had been investigated in this study. The films were preparedusing solvent casting  method. The shellac stability related to polymerization of shellac moleculescould be identified through insoluble solid test. The polymerization was occured by humidityatmosphere or by heating.. The insoluble solid test was then performed after the samples were 1).placed in 85 % relative humidity, 2). heated at 1250 C for 10, 30, 60, 90, and 180 minutes, a test called“life under heat”. The result showed that percentage of insoluble solid by both humidity and heatingtreatment increased with increasing of time from 2 % to 5 %, and from 20 to 82 %, respectively. Theaddition of pluronic reduced the amount of insulible solid of samples at 85 % RH after 1st and 2ndmonth, but no effect of the 3rd month. For the heated samples, the amount of insoluble solid increasedsignificantly from 10 to 90 minutes, then increased steadly untill 180 minutes.The addition of pluronicalso reduced the insoluble solid. These results suggested that pluronic 473 improved stability ofshellac, altought could not stop the polymerization. Keyword: Shellac, pluronic, insoluble solid testing, polymerization.