A Comparative Study of In Situ and Ex Situ Impregnation for LLDPE/Silica Composites Production
The two different kinds of impregnation (in situ and ex situ were used in the heterogeneous copolymerization of ethylene and 1-hexene for production of LLDPE/silica composite. For the ex situ impregnation, MMAO cocatalyst was immobilized firmly onto the silica support through washing and drying step before introducing the powder of MMAO/silica support into the copolymerization system. For the in situ impregnation, MMAO was only contacted with silica support for the short period of time before bringing all of the slurry of MMAO/silica support into the copolymerization system. By comparing the catalytic activity between two methods, it was found that the in situ impregnation provided the higher one beneficial from the lower interaction between MMAO and silica due to lower contacting time. The lower interaction enhanced the reactivity of MMAO toward zirconocene catalyst during activation process thus leading to the higher catalytic activity. The said interaction can be proven by thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) analysis. In addition, the obtained polymers were further characterized by means of scanning electron microscopy (SEM), 13C-NMR spectroscopy (NMR) and differential scanning calorimetry (DSC).