Original Article
Saman Damavandi, Gholam Hossei
Abstract
Rubber formpolyethylene with crystallinity of about 1 to 14%was prepared using a late transition metal catalyst of bis(2,6-isopropyl phenyl) 1,4- diazobutadine Nickel(II) dibromide, [(2,6-i-prph)2 DABMe2]NiBr2. Methylaluminoxan (MAO) and triisobuthylaluminum (TIBA) were used as cocatalyst and scavenger respectively. The optimum activity of the catalyst was observed at [Al]:[Ni]=3333:1 molar ratio and polymerization temperature of 25°C. Higher concentration of MAO than the optimum value not only decreased the activity of the catalyst but also produced polyethylene-wax (PE-Wax). The rate/time profile of the polymerizationwas a decay type with an acceleration period of about 60 min at polymerization temperature of 25°C. However, the higher the temperature to 65°C, the lower the acceleration period and the higher decay rate were observed. The polyethylene produced at temperature up to 55°C showed rubbery form while the reaction at 65°C produced PE-Wax. Activity of the catalyst was increased with monomer pressure to 5 bars. The viscosity average molecular weight (Mv) of the polymer obtained was 7.5 ×104 at the monomer pressure of 3 bars and 35°C temperature.