Synthesis and Properties of Moisture-Cured Reactive Polyurethane Containing Castor Oil and Oxime Compounds

Abstract

Reactive polyurethane hot-melt resin (moisture-cured reactive polyurethane, PUR) could successfully be prepared from poly(tetramethylene ether) glycol (PTMG), castor oil and dimethylglyoxime (DMG) by one or two-stage synthesis. Fourier-transform infrared spectroscopy (FTIR) analysis showed that the synthesis resins belonged to NCO-capped castor oil-based polyurethane. The thermal behaviors of the cured PUR were analyzed by differential scanning calorimeter (DSC) and dynamic mechanical analyzer (DMA) instruments. The results showed that the cured resin provided remeltable properties under the dosages of 3 wt% DMG. Furthermore, the phenomenon could be proved by FTIR analysis according to the characteristic absorption peak of NCO groups after the cured resin was heated. Comparing different syntheses, the resin prepared by one-stage synthesis showed random distribution of DMG with PUR structure and that prepared by two-stage synthesis had distribution of DMG with branching structure in the prepolymer. The former obtained lower remeltable temperatures from 90 to 130 °C than the latter temperatures, which had temperatures above 125 °C. The tensile test showed that all of the PUR films exhibited typical tough behavior. Thus, the cured resin with DMG dosages of 3 wt% provided remeltable and mechanical properties at the same time. Overall, the crosslinking density and numbers of dynamic bonds should be kept in balance for preparation of remeltable PUR.

New Star-Shaped Polyether-Pentols (PEPOs) for Fabrication of Crosslinked Polyurethanes—Synthesis and Characterization

“…In the case of the PUR2 sample, the 2nd thermal response is visible at 363.5 °C with 39.22% weight loss, followed by 3rd step at 393.9 °C with 36.10% of weight loss. A similar two-stage thermal decomposition was reported for PURs [ 37 , 38 ].…”

Concise and Efficient Self-Healing Cross-Linked Polyurethanes via the Blocking/Deblocking Reaction of Oxime Urethanes

“…On the other hand, its hydroxyl group activity is higher than that of the phenolic hydroxyl group, so it is possible to achieve more efficient blocking and deblocking. , Compared to aromatic monomers and extenders, flexible aliphatic chains may enhance the healing. Besides, we have also noticed the application of some oximes in PU self-healing. − Liu et al first used the thermal reversibility of oxime urethanes to prepare self-healing polyurethane. The polyurethane can be re-compressed within 30 min at 120 °C and 10 MPa.…”

“…The team of You et al used the coordination properties of oxime for metal ions for the first time and used the reversible properties and coordination bonds of oxime urethanes in self-healing materials, but the modified materials rely more on metal ions. The introduction of heavy metal ions deviates from the original intention of the concise structure, cost, and environmental friendliness; in addition, the rigidity of isocyanates also reduces the healing efficiency of oxime urethanes. − In addition, we have noticed that many self-repair systems now require external assistance to improve the efficiency of self-repair (such as external pressure, external weight, molds, and so forth). In summary, relying on the characteristics of the flexible polyurethane chain and the oxime urethane itself along with a Lewis base cross-linking agent, it is in line with the concept of simple and efficient self-healing polyurethane structure design.…”

Eco-Friendly Polyurethane Reactive Hot-Melt Adhesive Derived from Poly(ε-caprolactone-co-lactic acid) Diols

“…DTG curves showed that the pyrolysis of PURHAs underwent three main steps. The first step between 186 and 380 °C was linked with the decomposition of urethane and urea bonds. , The weight loss was relatively low at 186–240 °C, associated with the pyrolysis of a few urethane bonds. Moreover, most urethane and urea linkages pyrolyzed at 240–380 °C.…”