• 096241 - PRINCIPLES OF POLYMER CHEMISTRY

The first objective of the course is the description and classification of the main classes of monomers and polymerization processes of industrial interest.

A second objective of the course is a quantitative description of the general principles of polymerization, including a detailed statistical and kinetic analysis of the mechanisms of polymer chain formation, growth and gelation, vulcanization and crosslinking.

The third objective is the derivation of molecular theory of entropic elasticity of rubbers, highlighting the limitations of the model by comparison with the real elastomer behaviour.

After attending the course and after the final examination, the student will: 

• know the main types of available industrial monomers and polymers, and understand how to classify them according to their structure
• know and understand the kinetics and statistics of chain formation and growth in both step and chain polymerization processes
• know and understand how to control composition and sequence in copolymerization
• know and understand the mechanism of network formation in polyfunctional polymerization processes
• know and understand the role of catalysis in polymerization
• know the features of homogeneous and heterogeneous polymerization processes, with application to the most relevant industrial cases
• know and understand the molecular basis of the entropic elasticity model 
• know the main chemical technologies for rubber vulcanization, and the behaviour of real elastomers
• be able to apply the above described knowledge to the quantitative control of process variables in polymerization, solving numerical problems aimed at the control of rate of reaction, conversion, and molecular weight 
• be able to apply the above described knowledge to the prediction of the gel point / gel time in polyfunctionl process
• be able to apply the entropic elasticity model to the modeling of the mechanical behavior of elastomers

 These learning outcomes are expected to provide the student with the needed knowledge tools necessary for successfully performing their future activities in an industrial environment, with particular reference to the polymer industry

The course is divided in two parts, with the following programme

Part 1: Polymerization

Classification of monomers and polyreactions, correlation with polymer microstructure.

Step polyreactions, kinetic and thermodynamic aspects of polycondensations, most probable distribution of molecular weights, control of polymerization.

Chain polyreactions, phases of free-radical poyadditions, kinetic and thermodynamic aspects of free radical polyadditions, distribution of molecular weights, chain transfer and control of molecular weight, effect of temperature. Some hints on controlled radical polymerizations.

Chain polyreactions, ionic processes, phases of cationic and anionic polymerizations, living anionic polymerizations and block copolymers. Ziegler-Natta catalysis and stereospecific polymerization. Control of the polymer microstructure.

Copolymerization, derivation of the kinetic model, reactivity ratios and Lewis-Mayo equation, F1-f1 diagrams, Alfrey-Price parameters, yield and control of compositional drift in copolymerization. Determination of composition in copolymers.

Crosslinking ad thermoset polymers. Carothers and Flory's statistical models for the estimation of the gel point in crosslinking processes. Experimental monitoring of the gel time.

Industrial production of polymers: batch and continuous processes, homogeneous and heterogeneous processes. Bulk polymerization, suspension polymerization, emulsion polymerization. Production of PET, PA6, PVC, SBR.

Part 2: Rubber science and technology

Structural requirements of elastomeric materials, correlation with intra and intermolecular parameters. Definition of entropic elasticity.

Classical thermodynamics of rubber elasticity, derivation of the equation of state of elasticity at constant pressure and constant volume; thermoelastic inversion.

Molecular (statistical) theory of rubber elasticity; gaussian chain and elastic retraction force, Kuhn model and ideal rubber, affine deformation and derivation of the constitutive law for ideal rubber.

Behavior of real elastomers; hysteresis and dissipation, strain-induced crystallization of stereoregular rubbers, Mooney-Rivlin plot.

Vulcanization of rubbers; sulfur, peroxy and ionic vulcanization processes. Process monitoring by rheological and thermal methods. Isothermal kinetic modelling of rubber vulcanization.

Mechanical reinforcement of real elastomers; reinforcing fillers, small deformation behavior and Payne effect; large deformation behavior.

A background in mathematics, chemistry and physics is needed

The examination will be a written test about all the course topics, chosen by the examiner. The test will consist in 5 or 6 questions, typically some 2-3 questions concerning theoretical aspects, derivation of mathematical models, graphical representation of data and physical interpretation of results, and 2-3 questions in form of numerical exercises to be solved.

The student is required to be able to write clearly and critically discuss the proposed topics, highlighting hypotheses, assumptions, critical points, the physical meaning and its consequences, including a correct mathematical approach where needed.

The final evaluation will be averaged with the results of the module "Structural Chemistry of Materials". The 10 CFU exam is passed is the average mark is at least 18/30. The evalution of the single module (5 CFU exam) must be at least 15/30 in order to be valid.