Effect of chain extender structure on the properties and morphology of polyurethanes based on H12MDI and mixed macrodiols (PDMS–PHMO)

Abstract

ABSTRACT:The effect of chain extender structure on properties and morphology of ␣,-bis(6-hydroxyethoxypropyl) polydimethylsiloxane (PDMS) and poly(hexamethylene oxide) (PHMO) mixed macrodiol-based aliphatic polyurethane elastomers was investigated using tensile testing, differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA). All polyurethanes were based on 50 wt % of hard segment derived from 4,4Ј-methylenecyclohexyl diisocyanate (H 12 MDI) and a chain extender mixture. 1,4-Butanediol was the primary chain extender, while one of 1,3-bis(4-hydroxybutyl)tetramethyldisiloxane (BHTD), 1,3-bis(3-hydroxypropyl)tetramethyldisiloxane (BPTD), hydroquinonebis(2-hydroxyethyl)ether (HQHE), 1,3-bis(3-hydroxypropyl)tetramethyldisilylethylene (HTDE), or 2,2,3,3,4,4-hexafluoro-1,5-pentanediol (HFPD) each was used as a secondary chain extender. Two series of polyurethanes containing 80 : 20 (Series A) and 60 : 40 (Series B) molar ratios of primary and secondary chain extenders were prepared using one-step bulk polymerization. All polyurethanes were clear and transparent and had number-average molecular weights between 56,000 and 122,100. Incorporation of the secondary chain extender resulted in polyurethanes with low flexural modulus and high elongation. Good ultimate tensile strength was achieved in most cases. DSC and DMTA analyses showed that the incorporation of a secondary chain extender disrupted the hard segment order in all cases. The highest disruption was observed with HFPD, while the silicon-based chain extenders gave less disruption, particularly in Series A. Further, the silicon chain extenders improved the compatibility of the PDMS soft segment phase with the hard segment, whereas with HFPD and HQHE, this was not observed.

Effect of polydimethylsiloxane macrodiol molecular weight on properties and morphology of polyurethane and polyurethaneurea

“…Tan ␦ peak temperatures and glass-transition temperatures estimated from EЈ-versus-temperature plots are summarized in Table VI. As we previously observed for other systems, 12 the T g values estimated from DMTA were higher than those determined by DSC. However, the general trend was similar.…”

“…The molecular weights observed are typical of what is normally achieved with this class of polymers and should not have significantly affected their mechanical properties. 12 The films cast from polymers in each series showed different degrees of transparency, as measured using a Gardner UX10 Hazemeter with a PG5500 digital photometer attachment. The results are summarized in Figure 1.…”

Study of thermal stability and degradation kinetics of polyurethane–ureas by thermogravimetry

“…They have unique combination of properties, which is related to their chemical structure and macromolecular architecture [8][9][10].…”

Coating of Polyester with Poly(dimethylsiloxane)- and Poly(tetramethylene oxide)-based Polyurethane

“…Siloxanes can be incorporated into polyurethanes to obtain new hydrophobic formulations. Several studies have been carried out on the synthesis of PDMS-PU [2][3][4][5][6][7]. In some of these studies [2][3][4], the diisocyanate used was 4,4 0 -diphenylmethane diisocyanate (MDI) and they made use of PDMS as the polyol, the polycondensation being performed in solution.…”

“…This is very interesting for the industry because bulk synthesis does not affect the environment much and has low energy cost. Three studies have used this method [5][6][7]. In a previous study [7] the authors used isophorone diisocyanate (IPDI) as the isocyanate.…”