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[vc_row][vc_column][vc_row_inner][vc_column_inner][vc_separator css=”.vc_custom_1624529070653{padding-top: 30px !important;padding-bottom: 30px !important;}”][/vc_column_inner][/vc_row_inner][vc_row_inner layout=”boxed”][vc_column_inner width=”3/4″ css=”.vc_custom_1624695412187{border-right-width: 1px !important;border-right-color: #dddddd !important;border-right-style: solid !important;border-radius: 1px !important;}”][vc_empty_space][megatron_heading title=”Abstract” size=”size-sm” text_align=”text-left”][vc_column_text]© 2016 by Nova Science Publishers, Inc. All rights reserved.Polyurethanes are commonly prepared from polyols, diisocyanates and chain extenders. The polyols are polyesters, polyethers or polycarbonates, while the chain extenders are low molecular weight diols or diamines. In general only a limited number of diisocyanates are used, such as toluene diisocyanate, methylene diphenyl diisocyanate (MDI), hydrogenated MDI and hexamethylene diisocyanate. Diisocyanates are reactive compounds yielding rapidly polyurethanes after mixing with polyols. Although the high reactivity of isocyanates is generally considered as an advantage, it has also some drawbacks. They can cause health issues since they can react also rapidly with human cell constituents, such as proteins and DNA. Another drawback is that the storage stability is low under wet conditions. Last but not least, due to their high reactivity it is difficult, if not impossible, to introduce functional moieties. Groups like –COOH, -OH and -NH2, which would be extremely helpful to introduce functionalities, are not compatible with free isocyanate groups. Blocked isocyanates are substantially less reactive than unblocked isocyanates. They are, as a result, much more stable, not sensitive for moisture, not toxic, while giving with polyols exactly the same polymers as the corresponding isocyanates. The lower reactivity of blocked isocyanates can in a number of cases advantageously be used, such as in one-pot coating systems in which polyols and the blocked isocyanate are mixed without the risk of premature gelation. For example, powder coatings are solid mixtures of blocked isocyanates and polyols and are stable for years. Perhaps even more interesting, blocked isocyanates allow chemical modifications that are not possible with isocyanates. A prerequisite is then of course that the blocked isocyanates should not be prepared from isocyanates, as the same limitations would be encountered. An alternative pathway that beneficially can be followed is by reacting (di)amines with carbonate moieties, resulting in carbamate (= urethane) segments. Low molecular weight carbonates, such as dimethyl-, diphenyl-, diimidazole- and dicaprolactam-, (cyclic) ethylene- or propylene-carbonate, as well as polycarbonates can be used. The (di)amines can be provided with functional groups yielding functional (di)isocyanates and, as a result, the corresponding functional polyurethanes.[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Author keywords” size=”size-sm” text_align=”text-left”][vc_column_text]Blocked isocyanates,Functional moieties,Hexamethylene diisocyanate,Low molecular weight,Methylene diphenyl diisocyanate,Premature gelation,Propylene carbonate,Toluene diisocyanates[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Indexed keywords” size=”size-sm” text_align=”text-left”][vc_column_text][/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Funding details” size=”size-sm” text_align=”text-left”][vc_column_text][/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”DOI” size=”size-sm” text_align=”text-left”][vc_column_text][/vc_column_text][/vc_column_inner][vc_column_inner width=”1/4″][vc_column_text]Widget Plumx[/vc_column_text][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][/vc_column][/vc_row]