RESUMO
Only 0.1% of polyurethanes available on the market are from renewable sources. With increasing concern about climate change, the substitution of monomers derived from petrochemical sources and the application of eco-friendly synthesis processes is crucial for the development of biomaterials. Therefore, polyhydroxyurethanes have been utilized, as their synthesis route allows for the carbonation of vegetable oils with carbon dioxide and the substitution of isocyanates known for their high toxicity, carcinogenicity, and petrochemical origin. In this study, polyhydroxyurethanes were obtained from carbonated soybean oil in combination with two diamines, one that is aliphatic (1,4-butadiamine (putrescine)) and another that is cycloaliphatic (1,3-cyclohexanobis(methylamine)). Four polyhydroxyurethanes were obtained, showing stability in hydrolytic and oxidative media, thermal stability above 200 °C, tensile strength between 0.9 and 1.1 MPa, an elongation at break between 81 and 222%, a water absorption rate up 102%, and contact angles between 63.70 and 101.39. New formulations of bio-based NIPHUs can be developed with the inclusion of a cycloaliphatic diamine (CHM) for the improvement of mechanical properties, which represents a more sustainable process for obtaining NIPHUs with the physicochemical, mechanical, and thermal properties required for the preparation of wound dressings.
RESUMO
Microencapsulation of curing agents is a major strategy for the development of self-healing polymers. Isocyanates are among the most promising compounds for the development of one-part, catalyst free, self-healing materials, but their microencapsulation is challenging due to their high reactivity. To keep the healing agent intact in the liquid state and containing free-NCO groups, the monitoring of several synthesis parameters is essential. This review aims to summarise the outcomes in the microencapsulation of isocyanates, emphasising the efforts reported in the literature to modulate the microcapsule properties. In this regard, the main synthesis procedures are presented, followed by the most relevant characterisation methods used to assess microcapsule properties. The correlation between these properties and synthesis parameters is also discussed, and finally the main potential and challenges for industrial applications are highlighted.
Assuntos
Cápsulas , Isocianatos/química , Compostos de Epóxi/química , Indústrias , NanoestruturasRESUMO
Carbonation of epoxidized linseed oil (CELO) containing five-membered cyclic carbonate (CC5) groups has been optimized to 95% by reacting epoxidized linseed oil (ELO) with carbon dioxide (CO2) and tetrabutylammonium bromide (TBAB) as catalysts. The effect of reaction variables (temperature, CO2 pressure, and catalyst concentration) on the reaction parameters (conversion, carbonation and selectivity) in an autoclave system was investigated. The reactions were monitored, and the products were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), carbon-13 nuclear magnetic resonance (13C-NMR) and proton nuclear magnetic resonance (1H-NMR) spectroscopies. The results showed that when carrying out the reaction at high temperature (from 90 °C to 120 °C) and CO2 pressure (60-120 psi), the reaction's conversion improves; however, the selectivity of the reaction decreases due to the promotion of side reactions. Regarding the catalyst, increasing the TBAB concentration from 2.0 to 5.0 w/w% favors selectivity. The presence of a secondary mechanism is based on the formation of a carboxylate ion, which was formed due to the interaction of CO2 with the catalyst and was demonstrated through 13C-NMR and FT-IR. The combination of these factors makes it possible to obtain the largest conversion (96%), carbonation (95%), and selectivity (99%) values reported until now, which are obtained at low temperature (90 °C), low pressure (60 psi) and high catalyst concentration (5.0% TBAB).
RESUMO
Abstract There is credible evidence that the 1984-Bhopal-methyl isocyanate (MIC)-gas-exposed long-term survivors and their offspring born post-exposure are susceptible to infectious/communicable and non-communicable diseases. Bhopal's COVID-19 fatality rate suggests that the MIC-gas tragedy survivors are at higher risk, owing to a weakened immune system and co-morbidities. This situation emboldened us to ponder over what we know, what we don't, and what we should know about their susceptibility to COVID-19. This article aims at answering these three questions that emerge in the minds of public health officials concerning prevention strategies against COVID-19 and health promotion in the Bhopal MIC-affected population (BMAP). Our views and opinions presented in this article will draw attention to prevent and reduce the consequences of COVID-19 in BMAP. From the perspective of COVID-19 prophylaxis, the high-risk individuals from BMAP with co-morbidities need to be identified through a door-to-door visit to the severely gas-affected regions and advised to maintain good respiratory hygiene, regular intake of immune-boosting diet, and follow healthy lifestyle practices.
Resumo Há evidências plausíveis de que os sobreviventes a longo prazo da exposição a gás de 1984 e isocianato de metila (CIM), em Bhopal, e seus filhos nascidos após esse fato estão suscetíveis a doenças infecciosas/transmissíveis e não transmissíveis. A taxa de fatalidade COVID-19 de Bhopal sugere que os sobreviventes da tragédia do gás MIC estão em maior risco, devido a um sistema imunológico enfraquecido e comorbidades. Essa situação nos encorajou a refletir sobre o que sabemos, o que não sabemos e o que devemos saber sobre a suscetibilidade deles ao COVID-19. Este artigo objetiva responder a essas três perguntas que surgem na mente dos funcionários de saúde pública sobre estratégias de prevenção contra o COVID-19 e promoção da saúde na população afetada pelo Bhopal MIC (BMAP). Nossas visões e opiniões apresentadas neste artigo chamam a atenção para prevenir e reduzir as consequências do COVID-19 no BMAP. Da perspectiva da profilaxia com COVID-19, os indivíduos de alto risco do BMAP com condições comórbidas precisam ser identificados por meio de uma visita de porta em porta nas regiões severamente afetadas por gases e aconselhados a manter uma boa higiene respiratória, ingestão regular de dieta que estimule o sistema imunológico e seguir práticas de estilo de vida saudáveis.
Assuntos
Humanos , Pneumonia Viral/prevenção & controle , Sobreviventes , Isocianatos/toxicidade , Infecções por Coronavirus/prevenção & controle , Suscetibilidade a Doenças , Exposição Ambiental/efeitos adversos , Pandemias/prevenção & controle , Pneumonia Viral/transmissão , Pneumonia Viral/epidemiologia , Autocuidado , Controle de Doenças Transmissíveis , Hospedeiro Imunocomprometido , Infecções por Coronavirus , Infecções por Coronavirus/transmissão , Infecções por Coronavirus/epidemiologia , Populações Vulneráveis , Desastres , Betacoronavirus , Índia/epidemiologiaRESUMO
The reaction of cyclic carbonates with amines is the most attractive among the synthesis methods for isocyanate-free polyurethane. Non-isocyanate polyurethane films with SiO2 NPs fabricated by a sol-gel process are reported, where cyclic carbonates (CC) were produced under mild conditions by CO2 insertion in an epoxide complex in the presence of LiCl. A reaction of CC and polyamines was carried out in a low concentration polymer matrix of PVA. The materials were characterized by 1H-NMR, FTIR, UV-Vis, SEM, TGA, DTG, and a KD2 pro technique. polymer FTIR results are consistent with the literature, even with the use of a non-conventional methodology, where the found chemical interactions values were 3330, 2930 and 1637 cm-1. There are differences in the polymers' morphologies due to the presence and absence of SiO2 NPs according to SEM, where the spherical morphology and homogenous particle size distribution of NPs around 100 nm. According to TGA results, all polymers showed their last stage decomposition after 300 °C and polymers with higher concentration of NPs showed even better stability. Due to the obtained results, the polymers have the potential to be used for thermal insulation without negative effect on the environment.