NEW TRENDS IN THE SYNTHESIS AND PROPERTIES OF POLYURETHANE AND POLYURETHANE-UREA ELASTOMERS BASED ON DIBENZYL DIISOCYANATE

摘要

Polyurethanes (PUs) and polyurethane-ureas (PUUs) were prepared by the polyaddition reaction between a macrodiol (MD) like polyester-diol, polyethylene adipate (PEA), or polyether-diol, polytetrahydrofuran (PTHF), a diisocyanate (DI) e.g. 4,4'-dibenzyl diisocyanate (DBDI) or 4,4'-methylene bis (4-phenyl isocyanate) (MDI), and as chain extenders (CE), like ethylene glycol (EG) or an aromatic diamine like 4,4'-dibenzyl diamine (DAB), 4,4'-methylene dianiline (MDA), or a heterocyclic diamine, like 2,5-bis-(4-amino-phenylene)-l,3,4-oxadiazole (DAPO) or 2,6-diaminopyridine (DAPy). The resulting polymers were characterized by means of the IR spectra, inherent viscosity measurements, and wide angle X-ray scattering (WAXS). PUs mechanical properties were investigated. Special consideration was given mainly to the study concerning the PUs energy loss. The study of the relationships between structure and properties reveals the influence of the nature of starting materials, macrodiols, diisocyanates and chain extenders on the mechanical properties of the polymers. The great number of hydrogen bonding that formed between urea and urethane groups of polyurethane-ureas (PUUs) and the presence of oxadiazole or pyridine rings in the polymer chain induced an improved thermal stability in these polymers. PUUs mechanical behavior was discussed by comparison with those of polyurethanes based on DBDI or MDI and chain-extended with EG.