|M.Sc Student||Hasson Gil|
|Subject||Structure-Property Relationships for Polypropylene,|
Catalyzed by Organo-Metallics Complexes
|Department||Department of Materials Science and Engineering||Supervisors||Professor Emeritus Arnon Siegmann (Deceased)|
|Professor Moris Eisen|
This research was based on previous results, received in our research group, where the activity of several benzamidinate complexes was studied and some of them produced an elastomeric PP. The main goal hereby was to receive elastomers in the high pressure polymerization of propylene and study their properties.
The benzamidinate ligand was synthesized and characterized by 1H-NMR and X-ray. It was used in the next step, the synthesis of bis(benzamidinato)titanium dichloride complex, which was later converted to bis(benzamidinato)titanium dimethyl complex, in the last synthetic step. The desired complex was characterized by 1H-NMR, 13C-NMR (different methods) and X-rays.
This complex was used, together with MAO (MethylAlumOxane) as co-catalyst, to polymerize propylene in small reactors. Different solvents were used and their influence examined. The more polar solvents lowered the activity of the complex. Furthermore, all studied solvents gave rise to a totally amorphous (elastomeric) PP, except for CH2Cl2.
The most active catalytic systems were chosen for the larger scale polymerizations. These included polymerization in the presence of either hexane as solvent or without a solvent. The polymers received in those polymerizations were characterized by 1H-NMR, 13C-NMR, X-ray, DSC, GPC, MFI and Instron. The results were compared with another PP, made in our group, using a different catalytic system.
Elastomeric PP's have high molecular weights, very low MFI, an isotactic percent of 8-13% and small crystalline regions, not detectable by DSC. The polymer, made without a solvent, showed the lowest mechanical properties and the highest MFI but had a very high strain to break (~3000%). This elastic nature of PP is explained by physical crosslinks, such as the small crystalline regions, mentioned above, and entanglements, caused by the high molecular weights, allowing high values of strain and a resilience property as well.