Adhesion properties and phase separation behavior of glycidyl‐terminated polyurethanes

Abstract

2,3-Epoxy-l -propano1 has been introduced into isocyanate-terminated polyurethane to form glycidyl-terminated polyurethane resins. A series of glycidyl-terminated polyurethanes based on hydroxyterminated poly(oxypropy1ene) (poly(oxypropylene)glycol, PPG), toluene diisocyanate (TDI), and 1 ,4-butanediol (BD) was synthesized with various PPG soft segment lengths (MW 700, 1000 and 2000) and soft segment concentrations (30, 50 and 70 wt.-Vo). The effect of glycidyl-terminated polyurethane on the adhesion properties and the phase separation were investigated. The adhesion properties at liquid nitrogen temperature coincide with the phenomenon observed in the phase separation behavior of polyurethane. Differential scanning calorimetry (DSC) and infrared technique (IR) were used to assess the phase separation content. The enthalpy jump at the glass transition temperature (AC,) and the unique spectroscopic features in the N-H and C=O stretching regions were applied to characterize the phase separation behavior. It was found that the modified resins do not only show superior adhesion at liquid nitrogen temperature but also exhibit some unique properties, e. g., room temperature curing and good storage stability. ZUSAMMENFASSUNG:Die Klebeeigenschaften und das Phasentrennungsverhalten von Polyurethanen aus ,,weichen" Poly(oxypropy1en)-Einheiten (PPG) und ,,harten" Segmenten aus Toluoldiisocyanat (TDI) und 1,4-Butandiol (BD) wurden untersucht. Die Lange der PPG-Weichsegmente (PPG mit MW 700, 1 OOO bzw. 2000) sowie deren Konzentration (30, 50 and 70 Gew.-Vo) wurden variiert. Die Isocyanat-Endgruppen dieser PU-Harze wurden mit 2,3-Epoxy-l-propanol zu Glycidyl-Endgruppen umgesetzt. Die Klebeeigenschaften bei der Temperatur flussigen Stickstoffs folgen dem Phasentrennungsverhalten der Polyurethane. Die Phasentrennung wurde mit DSC-(Enthalpiesprung bei der Glasternperatur) und IR-Messungen (Veranderungen im Bereich der N-H-und C=O-Streckschwingungen) untersucht. Die rnodifizierten PU-Harze weisen neben verbesserter Haftung bei tiefen Temperaturen auch gute Lagerungseigenschaften sowie die Fahigkeit der Hartung bei Raumtemperatur auf.

Glycidyl carbamate functional resins and their applications: a review

“…Chen and colleagues further reported a series of glycidyl terminated polyurethanes based on PPG soft segments of a range of molecular weights and also a range of soft segment contents, with the hard segment derived from the incorporation of 1,4-butanediol. 28 As before, the cured systems demonstrated good adhesion at liquid nitrogen temperatures as well as good room temperature curing and good storage stability.…”

Influence of diisocyanate, glycidol and polyol molar ratios on the mechanical and thermal properties of glycidyl-terminated biobased polyurethanes

“…To overcome this limitation, end capping of NCO groups of PU with 2,3‐epoxy‐1‐propanol is a most promising method. The free isocyanate groups of PU can be capped or blocked with hydrogen‐donating groups of epoxy which can improve the moisture resistivity and other core properties of PUs …”

“…Several authors have synthesized epoxy‐terminated PUs (EPUs) and evaluated their various properties. Hsia et al . prepared glycidol‐terminated PUs with varied lengths of soft segments.…”

Characterization of the relaxation transitions in toluene diisocyanate-based polyurethanes with poly(propylene glycol) as the soft segment by thermally stimulated current depolarization with relaxation mapping analysis

“…16 -19 Consequently, the segmented PU with variations in the widely distributed soft aliphatic chains and the hard aromatic TDI-MOCA segment in the backbone, often observed with a broadened glass transition (T g ), appeared in the differential scanning calorimeter (DSC) thermogram. 17,20 Thermal analyzers such as the thermal mechanical analyzer (TMA) 21,22 and dynamic mechanical analyzer (DMA) [23][24][25][26][27][28] are also being used for the measurements of the T g data. Schneider and Paik Sung used thermal analyzers in their studies of hydrogen bonding in PUs in association with data measured by the infrared spectroscopy, 29,30 and by the small angle X-ray scattering (SAXS).…”