Preparation and characterization of magnesium stearate,cobalt stearate,and copper stearate and their effects on poly(vinyl chloride) dehydrochlorination

Preparation and characterization of pure metal soaps and investigation of their effects on poly(vinyl chloride) (PVC) dehydrochlorination were the objectives of the present study. Magnesium stearate (MgSt₂), cobalt stearate (CoSt₂), and copper stearate (CuSt₂) were prepared by a precipitation method. An aqueous sodium stearate (NaSt) solution was mixed at 500 rpm with respective metal salt solutions at 75^oC. The precipitates that formed were collected by filtration, washed with water, and ultimately dried at 105^oC under reduced pressure. Lamellar crystals that melted on heating were obtained. Solid‐liquid phase transitions were observed by optical microscopy at 160^oC, 159^oC, and 117^oC for MgSt₂, CoSt₂, and CuSt₂, respectively. However, the melting points of MgSt₂, CoSt₂, and CuSt₂ were determined as 115^oC, 159^oC, and 111^oC, respectively, by analysis by differential scanning calorimetry. The onset temperature of the mass loss was the lowest at 255^oC for CuSt₂ and the lowest activation energy for thermal decomposition was 18 kJ/mol for CuSt₂. CoSt₂ was effective in extending the induction time of PVC dehydrochlorination at both 140^oC and 160^oC. The activation energy calculated from stability time decreased from 175 kJ/mol for a blank PVC sample to 114, 105, and 107 kJ/mol for MgSt₂, CoSt₂, and CuSt₂‐containing PVC samples, respectively. All three metal soaps accelerated the dehydrochlorination of PVC. J. VINYL ADDIT. TECHNOL., 21:235–244, 2015. © 2014 Society of Plastics Engineers