Objectives of the Course are: (i) to pass to students the basic concepts of composites based on polymer melts and elastomers: the polymers’ molecular structure and the structure-property correlation, selection oof materials and preparation, rheological aspects, mechanical reinforcement, crosslinking, (ii) to examine with students main applications of elastomer composites, such as the one in tyre compounds, correlating the design of the material with the needs of the performance (iii) to discuss with students basic concepts of composite materials which go beyond the elastomer matrix (v) to correlate concepts learn in the course with the actual industrial practice, by visiting major players in the field.  

The Course will allow the students to:

• learn, discuss about and use the basic concepts of elastomer composites
• understand and discuss about the correlation between composition, structure and performances of main elastomer goods
• approach the selection of materials for preparing elastomer composites in view of a target performance

Organic chemistry and polymers

Short background on main concepts of organic chemistry and polymers.

Organic chemistry: alkanes and alkenes: nomenclature, conformational and configurational isomers, reactivity.

Polymers. The polymeric nature of solids. Introduction to polymers. Origin. Nomenclature. Chemical composition. Structure. Dimension. Average molar mass. Synthesis of polymers: stoichiometry, thermodynamics, kinetics. Catalysis for polymerization and types of polymerizations. Intermolecular and intramolecular bonds in polymers. Stereochemistry. Organization of polymers at the solid state: amorphous and crystalline polymers. Thermodynamic origin of melting point. Main types of polymers.

Transitions of polymers and thermodynamics.

Elastomers and Rubbers

Elastomers and rubbers. Definitions. Worldwide production. Trends.

Design of an elastomer: from molecular structure to elasticity.

Main types of rubbers. Poly-isoprene rubber: natural and synthetic. Butadiene and styrene-butadiene, butyl and halo-butyl rubber. Polyolefin elastomers. Special elastomers: poly(chloroprene), nitrile, fluorinated, silicon elastomers

Elasticity

Enthalpic and entropic elasticity: classical and statistical thermodynamics.

Elasticity and Moduli.

Viscosity and viscoelasticity

Viscosity. Definition. Newton law. Viscosity as a function of shear rate. Newtonian fluids. Non Newtonian fluids: Plastic, pseudoplastic, dilatant flow. The power law. Rheological behaviour of polymers: viscosity as a function of molar mass, temperature, pressure. WLF equation.

Viscoelasticity. Definition. The creep curve of a viscoelastic polymer. Relaxation test. Compliance and relaxation modulus. Linear viscoelasticity.  Maxwell model. Kelvin-Voigt model.

Boltzmann, time temperature superposition principles. The master curve

Tensile and dynamic-mechanical properties of polymers, in particular of elastomers

Tensile properties: stress, modulus, ultimate properties. Stiffness and toughness. Deformation and fracture.

Dynamic-mechanical properties: storage and loss moduli, tan delta. Effect of chemical composition, crosslinking, glass transition temperature.

Reinforcement of elastomers

Reinforcing fillers. Carbon black and Silica as nanostructured fillers. Main features: surface area and activity, structure, aggregates and agglomerates.

Contributions to modulus. Einstein-Guth-Gold equation. The behaviour at low, medium and large strain. Filler network and non linearity of modulus: Payne Effect. Theories to explain the Payne effect. The Mullins effect. The paradox of elastomers.

The behaviour of elastomeric composite materials containing (i) carbon black (ii) silica.

Rheological properties and Processing of elastomers and elastomeric composites

Measurements of viscosity: Mooney viscosity and capillary rheometry. Bagley and Rabinowitch corrections. Elongational viscosity.

Distributive and dispersive mixing. Mixing technologies: roll mill, internal mixer: Banbury® type, with tangential and intermeshing rotors. Mixing cycles.

Twin screw extruder: co-rotating and counter-rotating.

Crosslinking of elastomers

Monitoring the crosslinking of elastomers: rheometry and calorimetry. Effects of crosslinking on elastomer properties. Crosslinking systems: peroxides, phenolic resins, sylanes. Vulcanization: crosslinking with sulphur based systems. Fil rouge of crosslinking chemistry. Mechanism of sulphur based vulcanization.

Formulation of elastomeric composites

Polymer blends: few concepts of thermodynamics.

Ingredients for an elastomeric composite: role and behaviour of ingredients. Typical formulations for tyre compounds: correlation with properties and applications.

Tyre and tyre compounds

Tyre: definition and structure. Fundamental parts of a tyre. Tyre compounds and materials. Examples from patent literature. A tyre compound as a multi-transition material.

Tyre compound for green tyres: silica based compounds: how to control the chemistry to achieve lower dissipation of energy. Coupling agent. The chemistry and the effect of sylanization reaction.

Elastomer nanocomposites

Nano-fillers: clay, carbon nanotubes, graphene, nanographite. Comparison with nanostructured fillers.

Visit to major industrial players.

Example: Pirelli Tyre

Students are required to know the basic concepts of chemistry. Particularly useful is the knowledge of basic concepts of organic chemistry and polymers.

At the end of the Course, a written exam will assess the knowledge of the contents of the Course. There will be the chance for the student to take also an oral exam.