Polyurethane Elastomers (eBook)

From Morphology to Mechanical Aspects

Cristina Prisacariu (Autor)

eBook Download: PDF

2011 | 2011
XXIV, 255 Seiten
Springer Wien (Verlag)
978-3-7091-0514-6 (ISBN)

Infos

   A comprehensive account of the physical / mechanical behaviour of polyurethanes (PU´s) elastomers, films and blends of variable crystallinity. Aspects covered include the elasticity and inelasticity of amorphous to crystalline PUs, in relation to their sensitivity to chemical and physical structure. A study is  made of how aspects of the constitutive responses of PUs vary with composition: the polyaddition procedure, the hard segment, soft segment and chain extender (diols and diamines) are varied systematically in a large number of systems of model and novel crosslinked andthermoplastic PUs. Results will be related to: microstructural changes, on the basis of evidence from x-ray scattering (SAXS and WAXS), and also dynamic mechanical analyses (DMA), differential scanning calorimetry (DSC) and IR dichroism. Inelastic effects will be investigated also by including quantitative correlations between the magnitude of the Mullins effect and the fractional energy dissipation by hysteresis under cyclic straining, giving common relations approached by all the materials studied. A major structural feature explored is the relationship between the nature of the hard segment (crystallising or not) and that of the soft segments. Crystallinity has been sometimes observed in the commercial PUs hard phase but this is usually limited to only a few percent for most hard segment structures when solidified from the melt. One particular diisocyanate, 4,4'-dibenzyl diisocyanate (DBDI) that, in the presence of suitable chain extenders ( diols or diamines), gives rise to significant degrees of crystallinity [i-iii] and this is included in the present work. Understanding the reaction pathways involved, in resolving the subtle morphological evolution at the nanometre level, and capturing mathematically the complex, large-deformation nonlinear viscoelastic mechanical behaviour are assumed to bring new important insights in the world basic research in polyurethanes and towards applied industrial research in this area.

Inhalt

 Introduction.The past and the present of polyurethanes (PUs).Chapter 1Chemistry of PUs1.1.Macrodiols1.2.Chain Extenders (diols and diamines)1.3.Diisocyanates1.3.1Conventional model rigid diisocyanates1.3.1.1.Diisocyanates reactivity with alcohols1.3.1..2.Diisocyanates reactivity with diols1.3.1.3. Secondary reactions of diisocyanates group during polyurethane formation1.3.1.4. Methods to investigate the mechanism of polymer crystallization1.3.2. 4ovel flexible diisocyanates: their versatility to polyaddition processes1.4. PUs preparation methods. The effect of reaction conditions on structure heterogeneityChapter 2Hydrogen bonding in polyurethanes2.1. Hydrogen bond influence on polyurethane formation2.2. Effect of hydrogen bonding on phase separation2.3. Effect of the hard segment nature (crystallizing or not) on hydrogen bonding2.4. Effect of hydrogen bonding on mechanical propertiesChapter 3PUs 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 spectroscopy3.4. A comparison between conventional PUs based on rigid, hard segments (not crystallizing) and novelPUs derived from the flexible DBDI giving hard segments of constitutional mobility (crystallizing or not).Chapter 4PUs Mechanical Properties4.1.General considerations4.1.1. Influence of Hydrogen bonding on the mechanical properties. (A comparison between PUs withhydrogen 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) groups4.1.1.2.1. Partial Hydrogen substitution.4.1.1.2.2. Total Hydrogen substitution4.1.1.Influence of the type of soft segment macrodiol4.1.2. 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 effect4.3. Creep and Stress RelaxationChapter 5.Sensitivity of elasticity to PUs chemical and physical structure5.1. Variation of cyclic tensile responses with PUs degree of crystallinity5.2. Variation of cyclic tensile responses with PUs degree of phase separation.Chapter 6.PUs strain induced orientation and crystallization6.1. Orientation of structure under tensile deformation as revealed by WAXS and SAXSmeasurements6.2. Orientation and crystallization of PU microstructure as revealed by dichroic measurementsConclusionsPerspectives

Produkt-Details

• Erscheint lt. Verlag: 3.7.2011
• Zusatzinfo: XXIV, 255 p.
• Verlagsort: Vienna
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Chemie ► Organische Chemie
• Themenwelt: Technik ► Maschinenbau
• Schlagworte: crystallization • DBDI • Diisocyanates • Macrodiols • polyurethanes
• ISBN-10: 3-7091-0514-5 / 3709105145
• ISBN-13: 978-3-7091-0514-6 / 9783709105146