Structure and thermal properties of polyether polyurethaneurea elastomers

Abstract

SYNOPSISThree series of polyether polyurethaneurea ( PEUU) elastomers based on poly-(tetramethylene glycol) (PTMG, MW = 1000 or 2000), 4,4'-diphenylmethane &isocyanate (MDI ) , and three kinds of diamine chain extenders, i.e., 4,4'-diaminodiphenylmethane ( DAM ) , rn-phenylenediamine ( MPD ) , and p -phenylenediamine ( PPD ) were synthesized in dimethylformamide or DMF-LiCl solvent by the prepolymer method. The degree of phase separation was higher in the samples with PTMG-2000 than in those with PTMG-1000. Three-dimensional hydrogen bonding between hard segments led to strong harddomain cohesion, but solubilized soft segment and the remaining LiCl within hard domains interfered with microstructural ordering of hard segments. According to the TG/DTA analyses, as-cast PEUU elastomers showed two-stage degradation behavior at a heating rate of 20°C /min in a nitrogen atmosphere. Initial degradation temperature was closely related with both hard-segment content and microstructural ordering, i.e., most of the hard segments were degraded in the first stage and samples with less ordered hard segments degraded at a lower temperatures.

Study on shape-memory behavior of polyether-based polyurethanes. I. Influence of the hard-segment content

“…The hard-segment domain of A1 could not form for lack of a chain extender, Morphology of the PUs BD, and the thermal behavior of the hard segment Differential Scanning Calorimetry was not observed. 12 In the spectrum of A2, MDI bonded with BD to form the hard segment, but it All the thermal properties and characteristic temperatures such as the glass transition temperadid not show the same thermal behavior as that of the HS. Therefore, it could be thought that most ture (T g ), recrystallizing temperature ( T c ), and crystal melting temperature ( T m ) were measured of the short hard segment were mixed with the soft segment.…”

“…The former was based on the aliMaterials phatic polydiol, and the later, on the aromatic diisocyanate and the chain extender that was diol Reagent-grade poly(tetramethylene oxide)glycol (PTMO, MW Å 650 and 250, Aldrich Chemical with the small molecular weight. 10,11 Repulsive interaction between the dissimilar segments 10 and Co., Wisconsin, USA) and 1,4-butanediol (BD, Aldrich Chemical Co.) were dehydrated under a the thermodynamical incompatibility 12 led to the phase separation and formed the hard-and softvacuum at 65ЊC before using. Reagent-grade 4,4 -diphenylmethane diisocyanate (MDI, Tokyo segment domains.…”

Modification of polyurethaneurea with PEG and YIGSR peptide to enhance endothelialization without platelet adhesion

“…The CH stretch peaks of the soft segment, PTMO, appeared at 2850 and 2940 cm Ϫ1 , and the hydrogen-bonded NH peak also appeared at 3310 cm Ϫ1 . 6,21,22 Thermal behaviors from DSC indicate successful incorporation of PEG as a soft segment. The glass transition temperature (T g ) of PUUPPD was observed at 9°C.…”

Investigation of the thermal degradation of polyurea: The effect of ammonium polyphosphate and expandable graphite

“…It is worth noting that the thermal decomposition of polyurethane has received considerable attention in the literature [23], [24], [25], [26] and [27], but very little attention has been given to the thermal decomposition of polyurea. It is generally believed that the thermal degradation and stability of polyurethane is related to the hard segment and soft segment structures.…”