DMA behaviour of polyurethane elastomers based on single diisocyanates

1 DMA behaviour of polyurethane elastomers based on single diisocyanates 

Both the mechanical and thermal PUs properties are affected dramatically by phase mixing. Interaction between HS and SS may increase the Tg of the SS and decrease the Tg of the HS. The Tg of the polyether polymer was found to be lower 

Eceiza et al investigated a series of thermoplastic PUs synthesized in bulk by two-step polymerization, obtained with the isocyanate-chain extender couple MDI-BG and various SS macrodiols. The chemical structure, the SS molecular weight and the HS content were varied. The effects on the thermal and mechanical properties were investigated [77]. The changes in the macrodiols in the case of PUs based on MDl-BG, resulted in a modulus curve that showed a plateau indicating the existence of physical crosslinks because of the increase in the size and inter-connectivity 

Christenson et al [208] reported research on a series of PUs synthesized with the couple MDI/BDO. The SS macrodiols were PTMO (molar mass 1000 g/mol) or a mixture ofSS based on ethylene oxide (EO) / propylene oxide (PO). The MDI/BDO polymers were compared with a MDI based material extended with mixed diamines [208,218]. 

A systematic DMA study was carried out by Marcos et al on a series of aromatic and aliphatic PUs chain extended with diamine functionalised poly(oxypropylene)-tipped poly(oxyethylene) of various molar masses [224]. Four diisocyanates, MDI, 2,4-toluene (TDI), hexamethylene (HMDI) and isophorone (IPDI) were employed. The symmetry/asymmetry of the diisocyanate strongly influenced the dynamic mechanical properties. The symmetric diisocyanates (MDI, HMDI) had more phase 

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