Tetramethylene oxide-based polyurethanes

A. T. Chen, and co-workers, "Comparison of the Dynamic Properties of Polyurethane Elastomers Based on Low Unsaturation Polyoxypropylene Glycols and Poly(tetramethylene oxide) Glycols," Polyurethanes World Congress 1993, Vancouver, B.C., Canada, Oct. 10—13,1993. 

Figure 4. Comparison of the tensile behavior of polydimethylsiloxane and poly(tetramethylene oxide) based segmented polyurethanes with similar compositions and structure. (A) PSU-8, (A) PEU-3, (o) PSU-7 and ( ) PEU-2.

Poly(tetramethylene oxide) polyols (PTMEG) are high performance polyethers that are crystalline waxes at molecular weights above 650 and liquids at lower molecular weights. They are only available as diols, but they produce adhesives with good hydrolysis resistance and moisture resistance, which is why these adhesives are even used in medical devices, blood bags, catheters, and heart-assist devices [25]. Certain thermoplastic polyurethane adhesives and solvent-borne adhesives are also based on PTMEG s. 

Segmented polyurethane elastomers, prepared from diisocyanates, macrodiols and chain extenders, are frequently used in the construction of implantable medical devices, such as cardiac pacemakers, heart valves, catheters, and heart assist devices, because of their excellent mechanical properties and haemocompatibility. Polyether macrodiols, such as poly(tetramethylene oxide) (PTMO), are used to prepare polyurethanes for implant, since they offer an increased resistance to enzymatic hydrolysis compared with polyester-based polyurethanes. 

The polyurethanes chosen for this study are based on 1,4-cyciohexane-diisocyanate (CHDI, 99 % trans isomer. Elate 166, Akzo Chemie America), poly(tetramethylene oxide) soft segment diol of different molecular weights (PTMO), chain extender 1,4-butanediol (BD) and crosslinker tri-... 

Recentfy McGrath and coworkers reported the preparation and characterization of polyurethanes based on 4,4 -diphenylmethanediisocyanate (MDI) and mixed poly(tetramethylene oxide) (PTMO) and PDMS soft segments, where 1,4-butanediol was used as the chain exteiuler (12). They used toluene/DMF (50/50) mixture as the reaction solvent. They reported number average molecular weights of 10,000 to 12,000 g/mole for the copolymers obtained. 

On the other hand, the photodegradation of segmented polyurethanes based on methylene 4,4 -diphenyldiisocyanate (MDI) is dependent on the physical structure of the polymer. Such segmented polyurethanes are formed from poly(ethylene oxide) (PEO) or poly(tetramethylene oxide) (PTMO) with various polyether polyols, which are chain extended with 1,4-butanediol (EDO) [680-682, 1006, 1321]. 

Although these polyethers produced good foams they were rather expensive and were soon displaced by the cheaper propylene oxide-based polyethers. However, these polymers of tetrahydrofuran (commonly called poly(oxy-tetramethylene)glycol) now find use in the preparation of polyamide, polyester and polyurethane thermoplastic elastomers (see sections 10.3, 11.8 and 16.6.3). 

Conditions are established for the preparation of hydrophilic and water-soluble polyurethane elastomers based on ADMH and other hydrazine derivatives, 1,6-hexamethylene diisocyanate and poly(tetramethylene oxide) (MW 1000 g/mole)... 

Polyurethane elastomers based on ADMH. All samples of the polyurethane elastomers studied (for synthesis see Section 2.6.1) are amorphous, since the poly(tetramethylene oxide) used in their synthesis loses its recrystallization ability within the urethane-containing polymers. For this reason, the areas of heterogeneity existing in the bulk of polyurethane elastomers are domains of hard blocks. As it follows from the small-angle X-ray scattering (SAXS) data (Table 5), sample PU(H) 1/1, which is characterized by structural heterogeneity. 

Esters and ethers based on poly(tetramethylene glycol) and propylene oxide or a combination of propylene and ethylene oxides commonly are used in reactive processing. The chemistry of leading to polyurethane formation, has been analyzed in many publications 15 7 however, the practical problems of processing real initial oligomers and molding compounds based on them into articles for different applications have received less attention. 

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