Morphology–properties relationship in high‐renewable content polyurethanes

Abstract

The effect of diisocyanate nature and hard segment content on the morphology and properties of high‐renewable content segmented thermoplastic polyurethanes was studied. Vegetable oil‐based polyether diol and corn sugar derived chain extender were used as renewable reactants together with an aliphatic (1,6‐hexamethylene diisocyanate, HDI) or aromatic (4,4′‐diphenylmethane diisocyanate, MDI) diisocyanate as hard segment. Segmented thermoplastic polyurethanes were synthesized by two‐step bulk polymerization. Morphology and physicochemical, thermal and mechanical properties were analyzed by Fourier‐transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, atomic force microscopy, and mechanical testing. The effect of mechanical deformation over the microstructure was also analyzed. Changes in crystallinity and hard segment hydrogen bonding after mechanical testing were evaluated by Fourier‐transform infrared spectroscopy and differential scanning calorimetry. The increase of physical crosslinking sites by aromatic diisocyanate and chain extender ratio in the polyurethane results in hard segment crystalline domains with spherulitic morphology, which enhance the stiffness and hardness whereas percentage elongation at break diminish. The flexible, linear aliphatic nature of HDI favors the arrangement of urethane groups thus creating strong hard segment interactions and hard segment crystal microdomains composed of fibrillar morphology are observed. POLYM. ENG. SCI., 54:2282–2291, 2014. © 2013 Society of Plastics Engineers

Thermally-responsive biopolyurethanes from a biobased diisocyanate

“…Besides, biopolyurethanes show a band around 1728 cm À1 which encompasses LDI and CO3 carbonyl groups. In the same way, a shoulder ascribed to the carbonyl of urethane group was seen between 1705 and 1682 cm À1 [31], which becomes more intense as diisocyanate content increases, due to a higher amount of urethane groups per volume unit.…”

“…It was seen that M w and M n decreased with the increase of LDI/PD content, due to the lower proportion of CO3 (the reagent with the higher molar mass) involved in the synthesis of the biopolyurethanes with higher LDI/PD content. In addition, the increase observed in PI can be attributed to vitrification, which hinders chain extension [31]. In any case, the variations on the molecular weight can be ascribed to segment architecture [32].…”

Relationship between reagents molar ratio and dispersion stability and film properties of waterborne polyurethanes

“…TgSS peaks [25] like in blocks based on HDI or MDI [5,26]. Soft domain glass transition temperature (T gSS ), melting temperature (T mSS ) and enthalpy ( H mSS ) of the synthesized WBPUs are summarized in Table 3.…”

Effect of molar ratio [NCO]/[OH] groups during prepolymer chains extending step on the morphology and selected mechanical properties of final bio‐based thermoplastic poly(ether‐urethane) materials

“…The authors confirmed that aliphatic diisocyanate‐based polyurethanes showed more phase separation than the polyurethanes obtained with the use of aliphatic diisocyanates. Ugarte et al produced poly(ether‐urethane)s with the use of two different diisocyanates, for example, HDI and MDI. The authors found that the polyurethane prepared by using aromatic diisocyanate and a chain extender displayed enhanced stiffness and hardness, and lower elongation at break.…”

“…This was due to the increased number of physical crosslinking sites and spherulitic morphology of HS crystalline domains. However, materials prepared with the use of linear aliphatic diisocyanates exhibited fibrillary morphology of HS crystal microdomains . To investigate hydrogen bonding distribution and microphase separation, researchers used DSC and FTIR spectroscopy .…”