Application of blocked isocyanate in preparation of polyurethane(urea) elastomers

Sang, Shilin; Li, Yuanyuan; Wang, Kaijie; Jia-ling, Tang

doi:10.1002/app.50582

Cited by 9 publications

(7 citation statements)

References 72 publications

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“…There was a strong absorption band near 1732–1708 cm −1 , which is a benzene-type flood frequency peak [ 31 ]. At 1054 cm −1 , there was a clear strong absorption band, which was the polyether polyurethane ether group (-O-) absorption band, and this is the characteristic peak of polyether polyol [ 32 , 33 ], which is similar to the characteristic peak of commercially available polyether polyol. It can be concluded that the degradation product was the mixed product of polyether polyol and aromatic polyol.…”

Section: Resultsmentioning

confidence: 88%

Study and Characterization of Regenerated Hard Foam Prepared by Polyol Hydrolysis of Waste Polyurethane

et al. 2023

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In this paper, four different kinds of diols were used for the alcoholysis of waste thermoplastic polyurethane elastomers. The recycled polyether polyols were used to prepare regenerated thermosetting polyurethane rigid foam through one-step foaming. We used four different kinds of alcoholysis agents, according to different proportions of the complex, and we combined them with an alkali metal catalyst (KOH) to trigger the catalytic cleavage of the carbamate bonds in the waste polyurethane elastomers. The effects of the different types and different chain lengths of the alcoholysis agents on the degradation of the waste polyurethane elastomers and the preparation of regenerated polyurethane rigid foam were studied. Based on the viscosity, GPC, FT-IR, foaming time and compression strength, water absorption, TG, apparent density, and thermal conductivity of the recycled polyurethane foam, eight groups of optimal components were selected and discussed. The results showed that the viscosity of the recovered biodegradable materials was between 485 and 1200 mPa·s. The hard foam of the regenerated polyurethane was prepared using biodegradable materials instead of commercially available polyether polyols, and its compressive strength was between 0.131 and 0.176 MPa. The water absorption rate ranged from 0.7265 to 1.9923%. The apparent density of the foam was between 0.0303 and 0.0403 kg/m3. The thermal conductivity ranged from 0.0151 to 0.0202 W/(m·K). A large number of experimental results showed that the degradation of the waste polyurethane elastomers by the alcoholysis agents was successful. The thermoplastic polyurethane elastomers can not only be reconstructed, but they can also be degraded by alcoholysis to produce regenerated polyurethane rigid foam.

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Section: Resultsmentioning

confidence: 88%

Study and Characterization of Regenerated Hard Foam Prepared by Polyol Hydrolysis of Waste Polyurethane

et al. 2023

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“…3,61−63 Additionally, the presence of heteroatomic hydrogen bonding between urea and urethane groups in PUU dispersion further enhances the hydrogen bonding interactions, 64,65 resulting in the formation of pseudo-cross-linked network structures. 62,66,67 These structures impart physical properties similar to those of covalent cross-linked networks, 62,66,67 resulting in thicker aqueous dispersions. This hypothesis was also confirmed with FTIR analysis, which showed the presence of free NCO residuals in the analyzed samples before the water addition (Figure S4 of the Supporting Information).…”

Section: Rheological Behavior Of Heurs Produced Via the One-mentioning

confidence: 99%

One-Step versus Two-Step Synthesis of Hydrophobically Modified Ethoxylated Urethanes: Benefits and Limitations

Tzortzi,

Xiouras,

Choustoulaki

et al. 2023

Ind. Eng. Chem. Res.

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Associative thickeners, such as hydrophobically modified ethoxylated urethanes (HEURs), are an important class of rheological modifiers allowing precise control and optimization of the rheology of waterborne coatings. In this work, we present a novel, comprehensive investigation of one-step and two-step HEUR synthesis processes, highlighting their impact on the final HEUR properties. In the conventional one-step process (current industrial practice), there are inherent limitations in producing high molecular weight polymers due to the complex competition between end-capping and polymerization. We show that the two-step method allows for much higher molecular weight polymers than the one-step method while using less amounts of toxic diisocyanates. Additionally, using the two-step method, the polymerization can be simply and efficiently controlled by the addition timepoint of the end-capping agent, which can be tailored to provide HEURs with a wide range of molecular weight and polydispersity index. However, the efficient end-capping of high molecular weight polymers remains a challenge when using conventional mixing equipment in batch reactors due to mass transfer and mixing limitations associated with the significant increase in the bulk viscosity of the reaction mixture. To overcome these limitations, alternative and more efficient mixing technologies, such as reactive extruders, should be considered for the efficient end-capping of high molecular weight polymers.

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“…Furthermore, hydrogen bondaccepting solvents lower the deblocking temperature because recombination of the isocyanate with the blocking agent is impeded during deblocking process. [17][18][19][20] For these reasons, deblocking temperatures given in the literature should only be regarded as guide values. Nevertheless, to get an overview of common blocking agents and their deblocking temperature range, a short selection is shown in Table 1.…”

Section: Introductionmentioning

confidence: 99%

Vanillin as low-temperature isocyanate-blocking agent and its use in one-component aqueous coatings

et al. 2022

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Mainly because of the high sensitivity of the isocyanate group to atmospheric moisture, it is blocked with a blocking agent for many applications and thus kept as inert as possible at room temperature (Zhang et al. in Langmuir ACS J Surf Colloids 37:12705, 2021, Meier-Westhues in Polyurethane: Lacke, Kleb-und Dichtstoffe, Vincentz Network, Hannover, p 36, 2007). When exposed to temperature, the protective group unblocks, and the isocyanate group reacts with the reactant that was previously present together with the blocked isocyanate (Meier-Westhues in Polyurethane: Lacke, Kleb- und Dichtstoffe, Vincentz Network, Hannover, p 36, 2007, Goldschmidt and Streitberger in BASF handbook on basics of coating technology, Vincentz Network, Hannover, pp 96–99, 2007). Many of the substances which are used today as blocking agents have toxicological concerns or unblock at high temperatures, which limits their application areas (Guillem Parra et al. in Blocked isocyanate polyurethane compositions using a new blocking agent, method of manufacture and uses thereof: European patent application, 2019, https://data.epo.org/publication-server/document?iDocId=6506253&iFormat=0). In this work, vanillin is presented as an effective deblocking agent at low temperatures and is compared with similar structures. The process of deblocking from an hexamethylene diisocyanate trimer (HDI-trimer) is followed by means of IR-spectroscopic measurements at different temperatures and thermogravimetric analysis. Temperature-dependent oscillation measurements using a rheometer are suitable for measuring onset temperatures and for qualitatively tracking the unblocking process. The combination of the results is used to draw conclusions about the existing deblocking mechanism. The comparatively low deblocking temperature of vanillin enables the formulation of an HDI-trimer modified with sulfonate groups and blocked with vanillin, which is dispersed in the aqueous phase and then reacted with OH-functional binders. Deblocking and subsequent reaction with the binder are followed by means of IR spectroscopy, and the mechanical properties of the coating films are examined. Vanillin is therefore suitable as a toxicologically harmless blocking agent for isocyanates and enables the production of crosslinkers for one-component water-based coatings (Arya et al. Adv Tradit Med (ADTM) 21:1, 2021).

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Application of blocked isocyanate in preparation of polyurethane(urea) elastomers

Cited by 9 publications

References 72 publications

Study and Characterization of Regenerated Hard Foam Prepared by Polyol Hydrolysis of Waste Polyurethane

Study and Characterization of Regenerated Hard Foam Prepared by Polyol Hydrolysis of Waste Polyurethane

One-Step versus Two-Step Synthesis of Hydrophobically Modified Ethoxylated Urethanes: Benefits and Limitations

Vanillin as low-temperature isocyanate-blocking agent and its use in one-component aqueous coatings

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