TY - JOUR
T1 - Urea hard segment morphology in flexible polyurethane foam
AU - Neff, Raymond
AU - Adedeji, Adeyinka
AU - Macosko, Christopher W.
AU - Ryan, Anthony J.
PY - 1998/3
Y1 - 1998/3
N2 - A series of flexible polyurethane slabstock foam samples were prepared with varying water content and studied using transmission electron microscopy (TEM), video-enhanced optical microscopy (VEM), and small-angle X-ray scattering (SAXS). A new TEM sample preparation technique was developed in which the foam is impregnated with water, frozen, and microtomed, and the polyether soft segment is selectively degraded in the electron beam. Structures of two size scales were detected. A texture with grains ("urea aggregates") 50-200 nm in size was imaged using both VEM and low-magnification TEM for foams with formulations containing more than 2 pphp water. For the first time, images of urea hard segment microdomains in polyurethane foam (approximately 5 nm in size) were obtained using high-magnification TEM. A microdomain spacing of approximately 6-8 nm was estimated from the SAXS scattering profiles. Glycerol was added to one of the formulations in order to modify the urea microphase separation and to give insight into morphology development in molded polyurethane foam systems. No structure was observed in low-magnification TEM images of the glycerol-modified foam, although smaller structures (hard segments) were detected at high magnification and by SAXS.
AB - A series of flexible polyurethane slabstock foam samples were prepared with varying water content and studied using transmission electron microscopy (TEM), video-enhanced optical microscopy (VEM), and small-angle X-ray scattering (SAXS). A new TEM sample preparation technique was developed in which the foam is impregnated with water, frozen, and microtomed, and the polyether soft segment is selectively degraded in the electron beam. Structures of two size scales were detected. A texture with grains ("urea aggregates") 50-200 nm in size was imaged using both VEM and low-magnification TEM for foams with formulations containing more than 2 pphp water. For the first time, images of urea hard segment microdomains in polyurethane foam (approximately 5 nm in size) were obtained using high-magnification TEM. A microdomain spacing of approximately 6-8 nm was estimated from the SAXS scattering profiles. Glycerol was added to one of the formulations in order to modify the urea microphase separation and to give insight into morphology development in molded polyurethane foam systems. No structure was observed in low-magnification TEM images of the glycerol-modified foam, although smaller structures (hard segments) were detected at high magnification and by SAXS.
KW - Block-segmented copolymers
KW - Microphase separation
KW - Optical microscopy
KW - Polyether polyol
KW - Polyurethane foam
KW - Small-angle X-ray scattering
KW - Transmission electron microscopy
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U2 - 10.1002/(SICI)1099-0488(199803)36:4<573::AID-POLB4>3.0.CO;2-Q
DO - 10.1002/(SICI)1099-0488(199803)36:4<573::AID-POLB4>3.0.CO;2-Q
M3 - Article
AN - SCOPUS:0032024697
SN - 0887-6266
VL - 36
SP - 573
EP - 581
JO - Journal of Polymer Science, Part B: Polymer Physics
JF - Journal of Polymer Science, Part B: Polymer Physics
IS - 4
ER -