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In the present paper, a dynamic optimization problem regarding grade transitions in bulk poly(propylene) polymerization processes is formulated and solved for the first time. Initially, a detailed dynamic process model is presented and implemented, comprising mass and energy balances, some of the polymer properties (such as the melting flow index and the xylene solubles) and regulatory control loops. Additionally, the effects of cocatalyst and electron donor on the propagation rate constant are taken into account. Then, the dynamic optimization problem is formulated and an evolutionary algorithm is used to solve the resulting nonlinear programming problem. It is shown that there is significant coupling among the manipulated variables and the controlled performance and polymer property variables, which adds complexity to the grade transition problem and demands the simultaneous manipulation of multiple variables during transitions. Despite the inherent open‐loop unstable nature of the analyzed process, it is shown that smooth grade transition trajectories can be accomplished through proper adjustment of the objective function weights. Finally, it is shown that the obtained optimum trajectories can significantly diminish the transition time, which can be of paramount importance for the plant economics. [ABSTRACT FROM AUTHOR]

Long chain branched polypropylene/clay‐supported calcium pimelate (LCBPP/CaHA‐OMMT) composites and their foams were prepared using self‐made CaHA‐OMMTs. The CaHA‐OMMT showed high β‐nucleation efficiency, especially that with larger initial interlayer distance could induce 89% of β crystal in LCBPP with a dosage of 0.5%. Clay layers were mostly exfoliated in the composites with low CaHA‐OMMT content, while intercalated structure was dominant and agglomeration occurred when the content of CaHA‐OMMT was higher than 2%. The composite foams were prepared with improved compression molding. The cell structure of the composite foams is improved, that is, the density, cell size, and cell size distribution decreased, and the cell density increased compared with that of LCBPP foam. The minimum average cell size of LCBPP/CaHA‐OMMT foams was 77 μm and the maximum cell density was 2.8 × 106 cells/cm3 with the CaHA‐OMMT content of 2%. It is concluded that there are two requirements for high nucleation efficiency: the CaHA was supported on OMMT layers, and the OMMT platelets were dispersed well and exfoliated. The compression properties of the composite foams, including compression modulus, energy absorption density and failure strength increased first and then decreased with the increase of CaHA‐OMMT content. [ABSTRACT FROM AUTHOR]