Controlled Branching of Industrially Important Polymers: Modeling and Multi-objective Optimization

Mogilicharla, A and Majumdar, Saptarshi (2014) Controlled Branching of Industrially Important Polymers: Modeling and Multi-objective Optimization. PhD thesis, Indian Institute of Technology, Hyderabad.

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Abstract

Long chain branching (LCB) in any polymerization is of profound importance. It helps in improving certain properties such as melt strength and strain hardening. Branched polymers are, therefore, having different characteristics than linear polymers. In addition to having good end use properties, they are well suited for various processing applications such as blow molding, thermoforming, extrusion coating etc. As real world applications demand different extents of branching of polymers for different applications, this study aims to perform an investigation for a controlled way of long chain branching of polymers with enhanced properties. The main goal of this research is, therefore, three fold; viz. i) Finding the optimal process conditions for the desired combination of conflicting objectives, ii) Development of a kinetic model for long chain branched polypropylene system based on the available experimental data from open literature and simultaneously performing the multi objective optimization for the desired combination of conflicting performance objectives within experimental limits, and iii) Development of Kriging based surrogate model to replace the first principles based computationally expensive model to save execution time, while performing the multi objective optimization task for a highly non-linear, multi-modal search space. First, a batch optimization study for the bulk polymerization of vinyl acetate has been considered to find optimal process conditions for imparting LCB in polymer architecture. A theoretical study has been conducted with a validated model to observe the effect of live radical concentration on long chain branching as this is an important factor for branching in polymer molecule via ‘chain transfer to polymer’ route.

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