Polyurethane Elastomers

Introduction. The past and the present of polyurethanes (PUs). Chapter 1 Chemistry of PUs 1.1.Macrodiols 1.2.Chain Extenders (diols and diamines) 1.3.Diisocyanates 1.3.1Conventional model rigid diisocyanates 1.3.1.1.Diisocyanates reactivity with alcohols 1.3.1..2.Diisocyanates reactivity with diols 1.3.1.3. Secondary reactions of diisocyanates group during polyurethane formation 1.3.1.4. Methods to investigate the mechanism of polymer crystallization 1.3.2. 4ovel flexible diisocyanates: their versatility to polyaddition processes 1.4. PUs preparation methods. The effect of reaction conditions on structure heterogeneity Chapter 2 Hydrogen bonding in polyurethanes 2.1. Hydrogen bond influence on polyurethane formation 2.2. Effect of hydrogen bonding on phase separation 2.3. Effect of the hard segment nature (crystallizing or not) on hydrogen bonding 2.4. Effect of hydrogen bonding on mechanical properties Chapter 3 PUs morphology and thermal behaviour. Crystallinity and phase segregation as revealed by: 3.1. Structural studies (WAXS, SAXS, SANS) 3.2. Thermal methods (DCS, DMA, TGA, thermal creep) 3.3. Morphology (IR dichroism; SEM) 3.4.IR spectroscopy 3.4. A comparison between conventional PUs based on rigid, hard segments (not crystallizing) and novel PUs derived from the flexible DBDI giving hard segments of constitutional mobility (crystallizing or not). Chapter 4 PUs Mechanical Properties 4.1.General considerations 4.1.1. Influence of Hydrogen bonding on the mechanical properties. (A comparison between PUs with hydrogen bonding and analogous structures but achieved without hydrogen bonding) 4.1.1.1. Hydrogen substitution with Deuterium. Deuterated PUs. 4.1.1.1.1 Deuterated PUs achieved with deuterated chain extenders. 4.1.1.1.2.Deuterated PUs achieved with deuterated macrodiols. 4.1.1.2. Hydrogen substitution with inert (-CH3) groups 4.1.1.2.1. Partial Hydrogen substitution. 4.1.1.2.2. Total Hydrogen substitution 4.1.1.Influence of the type of soft segment macrodiol 4.1.2. Influence of hard segment nature (crystallizing or not) 4.1.3. Influence of the type chain extender. 4.1.4. Influence of the polyaddition procedure. 4.2. Elasticity and inelasticity. Inelasticity measures. 4.2.1 Tensile Modulus. 4.2.2 Hysteresis: work input and unrecovered strain. 4.2.3.Mullins effect 4.3. Creep and Stress Relaxation Chapter 5. Sensitivity of elasticity to PUs chemical and physical structure 5.1. Variation of cyclic tensile responses with PUs degree of crystallinity 5.2. Variation of cyclic tensile responses with PUs degree of phase separation. Chapter 6. PUs strain induced orientation and crystallization 6.1. Orientation of structure under tensile deformation as revealed by WAXS and SAXS measurements 6.2. Orientation and crystallization of PU microstructure as revealed by dichroic measurements Conclusions Perspectives