Synthesis and thermal deblocking of blocked diisocyanate adducts

Toward Microcapsule-Embedded Self-Healing Membranes

“…More than 24 h after the damage, the defect sites filled up with a newly formed material (Figure c,d) and the depth of the damage became shallower [from ∼37 μm for the damaged membrane to ∼10 μm for the healed membrane (Figure d)], effectively healing the damage site. We presume that this efficient plugging of the large damage area is a result of the expansion of the polyurea matrix due to CO 2 evolution as diisocyanate and water react to form urea linkages. ,,, A similar phenomenon of healing matrix expansion has previously been reported in other self-healing materials. − , The self-healing restored the water flux to 93.7 ± 5.6 L m –2 h –1 and rejection to 90.0 ± 1.7%, which correspond to 103.2 and 90.4% performance recovery, respectively, compared to the undamaged membrane. A faster self-healing was observed when the temperature during the self-healing period was increased to 50 °C …”

“…We presume that this efficient plugging of the large damage area is a result of the expansion of the polyurea matrix due to CO 2 evolution as diisocyanate and water react to form urea linkages. 14,17,18,28 A similar phenomenon of healing matrix expansion has previously been reported in other self-healing materials. [14][15][16]18 The selfhealing restored the water flux to 93.7 ± 5.6 L m −2 h −1 and rejection to 90.0 ± 1.7%, which correspond to 103.2 and 90.4% performance recovery, respectively, compared to the undamaged membrane.…”

Evaluation of Cashew Nut Shell Liquid Derived Isocyanate Blocking Agents

“…Triethylenediamine (TEDA) in dipropyleneglycol and potassium-octoate in diethylene glycol show the highest effect/deblocking efficiency within the series, while other options are still suitable, but showing a slightly lower contribution. The high efficiency of these two catalyst can be explained considering both the nucleophilicity of the catalysts as well as the present of a polar solvent (dipropylene glycol and diethylene glycol) both catalysts are dispersed in [15,16].…”

Blocked isocyanates: from analytical and experimental considerations to non-polyurethane applications

“…Noted by both Griffin and Willwerth, and by Mohanty and Krishnamurti, the higher the solubility of the adduct, the lower the observed deblocking temperature, with it being widely acknowledged that liquid blocked isocyanates deblock at lower temperatures than solids. 57,115 Catalysts It should be noted that for the synthesis of blocked isocyanates, no catalyst is necessary in the majority of instances, with Sankar and Yan noting that the aromatic secondary amines present in their system were sufficiently reactive without the addition of a catalyst. 116 In spite of this, dibutyltin dilaurate (DBTL) is frequently used to ensure both a successful reaction and that the reaction goes to completion, with catalysis proposed to proceed via a four-membered transition state.…”