Properties of crosslinked polyurethanes synthesized from 4,4?-diphenylmethane diisocyanate and polyester polyol

Abstract

Polyurethanes were synthesized using the high functional 4,4′‐diphenylmethane diisocyanate (MDI), polyester polyol, and 1,4‐butane diol. The synthesized polyurethanes were analyzed using differential scanning calorimeter (DSC), dynamic mechanical thermal analysis (DMTA), Fourier transform infrared (FTIR) spectrometer, and swelling measurement using N,N′‐dimethylformamide. From the result of thermal analysis by DSC and DMTA, single Tgs were observed in the polyurethane samples at all the formulated compositions. From this result, it is suggested that the polyurethanes synthesized in this study have crosslinked structure rather than the phase‐separated segmented structure because of the high functionality (f = 2.9) of the MDI. By annealing the polyurethane samples using DSC, the Tgs were increased by 4.7∼16.0°C at the various annealing temperatures. From the results of FTIR and swelling measurement of polyurethanes, it is suggested that the increase of Tg of the polyurethanes by annealing is not due to increase of the hydrogen bond strength but mainly due to the increase of the crosslink density. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 624–630, 2000

Biobased hyperbranched shape‐memory polyurethanes: Effect of different vegetable oils

“…The bands appearing for the hydrogen‐bonded NH stretching vibrations at 3364 cm −1 of HBPU were shifted to 3351, 3359, and 3365 cm −1 for the CHBPU, MHBPU, and SHBPU, respectively. Therefore, the NH stretching frequency shifted to a lower frequency . The band appearing at 2926 cm −1 was assigned to the CH stretching of CH 2 and CH 3 .…”

Supramolecular structure of crosslinked polyurethane elastomers based on well‐defined prepolymers

“…Segmented polyurethane elastomers are composed of soft segments and more rigid, polar hard segments. The soft segments are formed generally from polyethers or polyesters and the hard segments based on diisocyanate and a low‐molecular‐weight chain extender 1–23…”

“…The hard‐segment and soft‐segment units are often crystallizable to form spherulitic structures with a diameter of ∼ 5–10 nm, or randomly oriented cylinders with the comparative diameter and the length of ∼ 100 nm 12, 21. Microdomain crystallinity and crystallite sizes are greatly influenced by the chemical structures of raw materials,7, 18 by the ratio of hard‐block and soft‐block components,2–4 by the average block length employed (including molecular weight distribution),5, 10, 20 by the crosslinking density,11 and by the thermal history of the material.…”

Relationship Between Architecture and Adhesion in Polyurethane‐Based Copolymers, 2

“…On the contrary, for shorter PUR lengths, the integration of PCL hard segments had a negative effect on both tack strength and energy. This fact can be explored by taking into account the hard segment content in the sample,17 which is determined as the ratio of the mass of reactants which bring stiffness to the polymer over the total mass of reactants. Generally, the hard segment (HS) content is composed of diisocyanates and short diols, while long diols give flexibility to the materials.…”

“…PURs are generally prepared by the reaction of diisocyanates (MDI, TDI, …) and two diols, a long one and a short one. The long diol is often a low molar mass polymer, such as an α , ω ‐dihydroxyl‐polydiene or polyester 8,9. The short diols, also called the “chain extender”, are typically 1,4‐butanediol or 1,6‐hexanediol.…”