New soluble, thermally stable poly(amide-imide)s containing cardo anthraquinone unit

Preparation of new types of polyimides with high thermal stability and improved solubility was considered. In this way, two new amide diamines containing bulky pendant units were prepared in two steps: nucleophilic substitution reactions of 1- and 2-aminoanthraquinone with 3,5-dinitrobenzoyl chloride to form amide containing dinitro compounds, and then reduction of resulted dinitro compounds with hydrazine monohydrate in the presence of palladium/activated carbon. Two series of new poly(amide-imide)s were prepared from the reactions of these two diamines with various dianhydrides by one step polyimidation process. All poly(amide-imide)s were characterized by FTIR and ¹H-NMR spectroscopies and elemental analysis. The polymers were obtained in high yields with inherent viscosities of 0.54-0.69 dl g⁻¹. X-ray diffraction patterns (XRD) showed that all the polymers were amorphous and therefore this factor in addition to the introduction of bulky anthraquinone group led to good solubility of the polymers in most common organic solvents especially in N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and dimethylsulfoxide (DMSO). Thermal analysis showed glass transition temperature between 204 and 226 °C. Decomposition temperatures were more than 293 °C, also 10% weight loss were in the range of 387-419 °C in air.     

New Approach in Modeling of Metallocene‐Catalyzed Olefin Polymerization Using Artificial Neural Networks

A new approach for the estimation of kinetic rate constants in olefin polymerization using metallocene catalysts is presented. The polymerization rate has been modeled using the method of moments. An ANN has been used and trained to behave like the mathematical model developed before, so that it gets polymerization rate at different reaction times and predicts reaction rate constants. The network was trained using modeling results in desired operational window. The polymerization rates were normalized to make the network work independent of operational conditions. The model has also been applied to real polymerization rate data and the predictions were satisfactory. This model is specially useful in comparing different new metallocene catalysts.

     

The Influence of Copolymerization Condition on Rheology,Morphology and Thermal Behavior of Polypropylene Heterophasic Copolymers

In this work, the polypropylene impact copolymers were synthesized by a modified sequential polymerization process. The copolymerization of ethylene and propylene was carried out between two homopolymerization stages at two different pressures and temperatures and the rheology, morphology and thermal properties of reactor alloys were studied. It is found that the ethylene propylene rubber (EPR) content increased up to 32 wt% by increasing the copolymerization time to 20 min. At a fixed copolymerization time of 10 min, the addition of 50 ppm hydrogen (H₂), increased the EPR content from 9.7 to 12.8 wt%. By doubling H₂ concentration, no considerable change in EPR wt% was observed. It is found that the zero shear viscosity of the alloys is significantly under the influence of EPR wt%, not the molecular weight of matrix. The molecular weight of PP matrices determined by rheological data, mildly decreased from 463000 to 458000 g/mol by increasing the copolymerization time from 10 min to 15 min. At high copolymerization time/high H₂ concentration, a melting peak in the differential scanning calorimetry test around 165°C for isotactic PP and also an endothermic peak around 127°C for the block copolymer with long ethylene segments, is observed. The study of interfacial strength by theoretical emulsion models showed that 15 min copolymerization time is optimum considering EPR wt%.