چكيده به لاتين
Controlled rheology polypropylene or abbreviated CRPP is one of the polypropylene grades with high flowability which is suitable for processes such as thin wall injection molding, electrospinning, melt spinning, etc. This grade can be produced by controlling the molecular weight of polypropylene during polymerization or by polypropylene chain scission in post-reactor processes with optical, thermal and chemical modification methods. In the meantime, the chemical modification method using organic peroxides is one of the most common in the industry. In this research, the effectiveness of two types of organic peroxides, peroxyesters called t-butylperoxybenzoate (TBPB) and peroxyketals called 1,1-di(t-butylperoxy)-5,3,3-trimethylcyclohexane (TMCH) ), in three amounts of 0.5, 1.0 and 1.5% by weight, were investigated for the degradation of two grades of polypropylene with different melt flow indexes in the internal mixer. Also, considering the selection of peroxides with low half-life in The process temperature, efficiency and improvement of their mixing with polypropylene in the form of 0.5% by weight solution in paraffin oil were also investigated under the same conditions of the process. Finally, the rheological, mechanical, thermal properties and crystallization behavior of the prepared samples were studied and compared with industrial samples. The results of the melt flow index have shown the good performance of both peroxides in the degradation of polypropylenes, especially the grade with higher flowability. Also, increasing the concentration of TBPB peroxide has a greater effect on increasing this index and has increased its value to 909 g/10 min. In addition, it was observed that with increasing in the degradation of polypropylene, the mechanical properties of the samples dropped sharply and their molecular weight distribution increased. In the continuation of the project, it was also observed for the samples degraded with 0.5% solution of peroxides in paraffin oil, in addition to reducing their consumption, the melt flow index increased up to 807.5 g/10min, and the homogeneous degradation of polypropylene caused a decrease in the molecular weight distribution of CRPP and As a result, the ultimate strength has increased and the elongation at break has increased.
