Advances in waterborne polyurethane and polyurethane-urea dispersions and their eco-friendly derivatives: a review

Polyurethanes and polyurethane-ureas, particularly their water-based dispersions, have gained relevance as an extremely versatile area based on environmentally friendly approaches. The evolution of their synthesis methods, and the nature of the reactants (or compounds involved in the process) towards increasingly sustainable pathways, has positioned these dispersions as a relevant and essential product for diverse application frameworks. Therefore, in this work, it is intended to show the progress in the field of polyurethane and polyurethane-urea dispersions over decades, since their initial synthesis approaches. Thus, the review covers from the basic concepts of polyure-thane chemistry to the evolution of the dispersion’s preparation strategies. Moreover, an analysis of the recent trends of using renewable reactants and enhanced green strategies, including the current legislation, directed to limit the toxicity and potentiate the sustainability of dispersions, is described. The review also highlights the strengths of the dispersions added with diverse renewable additives, namely, cellulose, starch or chitosan, providing some noteworthy results. Similarly, dispersion’s potential to be processed by diverse methods is shown, evidencing, with different examples, their suitability in a variety of scenarios, outstanding their versatility even for high requirement applications.This research was funded by the University of the Basque Country (UPV/EHU) (GIU18/216 Research Group), the Spanish Ministry of Science, Innovation and Universities and European Union (MICINN/EU/FEDER) (MAT2016-76294-R and PID2019-105090RB-I00). Also, the Foundation for Science and Technology (FCT, Portugal) funded by financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020). National funding by FCT- Foundation for Science and Technology, through the institutional scientific employment program-contract with I.F.info:eu-repo/semantics/publishedVersio

Bioinks functionalized with natural extracts for 3D printing

In the search of materials valid for direct ink writing (DIW) 3D printing and with special interest for the biomedical and pharmaceutical applications, the development of bioactive inks for DIW is of great interest. For that purpose, in this work bioactive waterborne polyurethane–urea inks were prepared by addition of natural extracts (logwood, chestnut, and alder buckthorn) and cellulose nanofibers (CNF). The rheological behavior of the inks proved to be strongly dependent on the extract type and content, and the addition route used. Inks prepared by ex-situ incorporation of the extracts showed a strong gel-like behavior, as did inks prepared with chestnut and alder buckthorn extracts, which, in turn, hindered a continuous flow during the printing process, resulting in 3D printed parts with poor shape fidelity. On the other hand, inks prepared insitu and with logwood extract showed more facility to flow and higher homogeneity, which translated in better printability and better shape fidelity, further enhanced for CNF containing inks. 3D printed composites showed reinforced mechanical behavior, as well as in materials with enhanced antibacterial behavior. Overall, the possibility to successfully prepare bioactive inks valid for 3D printing was proven.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. Financial support from the Basque Government (Grupos Consolidados (IT-1690-22), Elkartek (KK19-00048)) is acknowledged.info:eu-repo/semantics/publishedVersio

Green nanocomposites from Salvia-based waterborne polyurethane-urea dispersions reinforced with nanocellulose

Waterborne polyurethane-urea (WBPUU) dispersions, products having none or low contents of organic solvents, depending on the used synthesis process, can provide suitable environmentally-friendly strategies to prepare novel materials. Moreover, waterborne systems enable the incorporation of aqueous dispersible nanoentities and soluble additives, which provides a strategy to design versatile functional materials with tailored properties. Having demonstrated in previous work the bacteriostatic properties of a 3 wt% Salvia-based WBPUU against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, this work is focused in the preparation of Salvia-based WBPUU added with cellulose nanocrystals (CNC) tackling the preparation of functional green nanocomposite films with increased mechanical properties. Through this strategy, nanocomposites loaded with 1, 3 and 5 wt% of CNC were prepared, showing an effective CNC incorporation avoiding agglomerates. CNC addition is able to modulate soft and hard phase's segregation, inducing enhanced mechanical stiffness, together with improved deformability, while retarding thermomechanical instability to higher temperatures.Financial support from the University of the Basque Country (UPV/ EHU) (GIU18/216 Research Group), the Spanish Ministry of Economy and Competitiveness (MINECO) (MAT2016-76294-R). Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020). National funding by FCT- Foundation for Science and Technology, through the institutional scientific employment program-contract with I.P. Fernandes. We also wish to acknowledge the “Macrobehaviour-Mesostructure- Nanotechnology” SGIker units from the UPV/EHU, for their technical supporinfo:eu-repo/semantics/publishedVersio

The service delivery process : An examination of how consumers evaluate technology-assisted service encounters in the retail banking industry

This study examined consumers\u27 perceptions post-adoption of technology and how these perceptions affect their levels of dis/satisfaction and their continued use of technology·assisted service encounters. To this end, this study investigated the criteria that consumers in Western Australia\u27s retail banking industry are likely to use when evaluating banking transactions involving EFTPOS, ATM, telephone, and Online banking modes. II examined whether these criteria changed with the mode of electronic banking in use and whether the significance of the criteria changed with consumers\u27 demographic characteristics. In addition, this study explored whether consumers who use these modes of electronic banking experience the paradoxes of technology adoption identified by Mick and Foumier (1998). Previous studies have shown that when evaluating the quality of services provided by organizations and their levels of dis/satisfaction with these services. Consumers are likely to base their judgements on their perceptions of the service delivery process (Lehtinen & Lehtinen, 1982; Brogowicz, Delene, & Lyth, 1990; Dllllllher & Mattsson, 1994; Danaher & Mattsson, 1998; Gronroos, 1998; Swam:, 1998). In particular, the studies have shown that the most significant element of the service delivery process is personal contact, that Is the interactions between organisations\u27 personnel and their customers (Sclmeider & Bowen, 1985; LeBIIUic & Nguyen, 1988; Parasuraman, Zeithaml, & Beny, 198fl; Howcroft, 1993; Donner & Dudley, 1997; Nichols, Gilbert, & Roslow, 1998; Tan, Beaumont, \u26 Freeman, 1999; Gabbott & Hogg, 2000). However, technological advancements have meant that some service organisations have changed their service delivery processes by substituting contact personnel with service delivery technologies. Consequently, consumers have been producing and delivering services for themselves by interacting with the service delivery technologies that are available (Bancel-charensol, 1999). Researchers assert that changing the characteristics of the service delivery process can result in changes in how consumers evaluate the quality of services provided by organisations and how they assess their resulting levels of dis/satisfaction (Chase, 1978; Lovelock & Young, 1979; Gronroos, 1984; Zeithaml, Parasuraman, & Beny, 1990). As such, this study examined the effects that retail banking technologies have on consumers\u27 evaluations of the service encounter and how these evaluations translate into usage patterns. Data were collected using qualitative and quantitative research methodologies. The minimum of the qualitative phase of the study was to identify the criteria that consumers are likely to use when evaluating their technology-based banking transactions and the paradoxes of technology adoption that they are likely to experience. Twenty in-depth interviews were conducted with consumers who reported they use at least one of the four modes of electronic banking. The interviews were tape-recorded and analysed using N.U.D.I.S.T. software. The second phase of the study examined consumers\u27 opinions towards relevant criteria identified in the qualitative phase and the effect these criteria have on consumers\u27 use of the four modes of el«1ronic banking. Data for this stage were collected through a mail survey questionnaire that was mailed out to a sample of 1700 Western Australians. In total, 453 useable questionnaires were returned. The data were imported into SPSS v. 10 and analysed using non-parametric statistics. This study showed that consumers are likely to evaluate their electronic banking service encounters on the basis of perceived convenience, transaction aids available, and perceived risk. The findings also indicate that these criteria have sub dimensions. Perceived convenience relates to the perceived ease of transactions, perceived speed of transactions, and accessibility to consumers\u27 transaction accounts from different locations and beyond the bank\u27s traditional operating hours. The transaction aids include the voice prompts available with telephone banking and the visual cues available with Online banking. Perceived risk dimensions include psychological, performance, financial, and physical risks. The present study also showed that some criteria have a greater effect on consumers\u27 use of some modes of electronic banking than others. For instance, in regards to voice prompts, psychological and performance risks appeared to have an effect on the number of tell-phone banking transactions consumers are likely to conduct. Consumers who use electronic banking can experience six of the eight paradoxes of technology adoption identified by Mick and Fournier (199g): freedom/enslavement, control/chaos, engaging/disengaging, efficiency/inefficiency, fulfils/create needs, and competence/incompetence. The findings showed that in most case one side of the paradox dominates. It appears that existing theories, instruments, and techniques of evaluating the service encounter need to be adapted to be applicable to technology-assisted service encounter;. Specifically, these theories, instruments, and techniques need to minimise or exclude elements that require consumers to evaluate their interactions with and perceptions of organisations\u27 customer service personnel and replace them with dimensions relating to consumers’ interactions with the technologies that facilitate the service delivery process. However, an exception needs to be made for technology-assisted service encounters conducted using the telephone because in these service encounters consumers can access organisations\u27 customer service representatives, The findings were used to propose the TASE (technology-assisted service encounters) model, which includes items relating to the three main dimensions of perceived convenience, transaction aids, and perceived risk. The TASE model can be adapted and used to measure consumers’ evaluation of the service delivery processes of organisations in various service industries. The findings of this study have significant managerial applications. Organisations can use these findings to assess the viability of commercial technologies that they intend to implement by examining consumers\u27 perceptions of new technologies based on the relevant criteria and paradoxes identified in this study. In addition, organizations can use these findings to develop promotional strategies that address consumers\u27 concerns about using technology-based service delivery options in order to encourage them to participate more in the service delivery process. In addition the proposed T ASE model can be used to develop an instrument for measuring consumers\u27 levels of dis/satisfaction with technology-based service encounters in general

Phase distribution, composition and disorder in Y2(Hf,Sn)2O7 ceramics : insights from solid-state NMR spectroscopy and first-principles calculations

The authors would like to thank the ERC (EU FP7 Consolidator Grant 614290 “‘EXONMR’”), and EPSRC for support for SS and ASG (EP/L005581/1). SEA would like to thank the Royal Society and Wolfson Foundation for a merit award. We acknowledge support from the Collaborative Computational Project on NMR Crystallography CCP-NC funded by EPSRC (EP/M022501/1).A NMR crystallographic approach, combining 89Y, 119Sn and 17O NMR spectroscopy with X-ray diffraction and first-principles calculations has been used investigate the number and type of phases present, and the local structure and disorder in Y2Hf2–xSnxO7 ceramics. Although a phase change is predicted with increasing Hf content, NMR spectra clearly show the presence of a significant two-phase region, with a Sn-rich pyrochlore and relatively Hf-rich defect fluorite phase co-existing for much of the compositional series. A single-phase pyrochlore is found only for the Sn end member, and a single defect fluorite phase only for x = 0 to 0.2. A solid-solution limit of ~10% is seen for the substitution of Hf into Y2Sn2O7, although no evidence is seen for any cation ordering or antisite disorder in this phase. In the defect fluorite phase there is preferential ordering of oxygen vacancies around Sn, which is only ever seen in a six-coordinate environment. The remaining vacancies are more likely to be associated with Hf than with Y, although this distinction is less apparent at higher Sn concentrations. To acquire 17O NMR spectra samples were post-synthetically exchanged with 17O2(g), although high temperatures (> 900 ºC) were required to ensure uniform enrichment of different chemical species. although these 17O NMR spectra confirm the formation of mixed-metal materials and the presence of two phases, more quantitative analysis is hindered by the overlap of signals from pyrochlore and defect fluorite phases. In all cases, DFT calculations play a vital role in the interpretation and assignment of the NMR spectra, and in understanding the local structure and disorder in these complex multi-phase materials.PostprintPostprintPeer reviewe

Exploiting ¹⁷O NMR and first-principles calculations for the study of disorder in ceramic oxides

Ceramic oxides of the type A₂B₂O₇ (A = La, Y and B = Sn, Ti, Zr and Hf) were investigated in this thesis. Initial work was concerned with the ¹¹⁹Sn NMR study of phase transitions and cation distribution in La₂(Sn,Ti)₂O₇ ceramics, supported by DFT calculations. This study suggested a random distribution of Ti cations in the pyrochlore phase, while a preferential substitution of Sn on to the two bulk perovskite-like sites was observed for La₂Ti₂O₇. However, for most starting compositions a two phase mixture was obtained. ¹¹⁹Sn was also employed to study cation disorder in La₂(Sn,Zr)₂O₇ and La₂(Sn,Hf)₂O₇ pyrochlores. Although well-resolved resonances were obtained these proved difficult to assign and interpret owing to the overlap of signals from different local environments, suggesting an alternative approach is required. ¹⁷O NMR spectroscopy offers an alternative or additional approach for the study structure and disorder, and would be of particular use in systems that lack appropriate spin I = ½ nuclei, such as e.g., La₂Ti₂O₇, La₂Zr₂O₇ and La₂Hf₂O₇. Owing to the low natural abundance of ¹⁷O (~0.037%), samples in this work were enriched post-synthetically with 70% ¹⁷O₂(g). A systematic study of the conditions required to obtain uniform enrichment was performed for a series of end member compositions, before ¹⁷O NMR was applied to more complex materials (e.g., Y₂Hf₂₋ₓSnₓO₇, La₂Sn₂₋ₓTiₓO₇). This work explains in detail how quantitative spectral acquisition can be achieved for ¹⁷O, with emphasis on differences in nutation rates of different O species, differences in longitudinal relaxation (T1) and additional contributions from quadrupolar satellite transitions to the central transition signal. The O sites in the pyrochlore materials showed uniform enrichment with heating at 900 °C for 12 h, while defect fluorite and layered perovskite-like materials enriched uniformly at a relatively lower temperature (i.e., 600 °C for 12h). However, the absolute levels of enrichment in all materials were found to be better at the highest enrichment temperatures. This study proves that ¹⁷O quantitative enrichment can be achieved in a cost-effective manner and ¹⁷O NMR is an informative probe for investigating local structure and disorder in oxides. Although complex spectra can be obtained in some cases, e.g., multi-phase systems, ¹⁷O NMR can provide important information, which would have been difficult to obtain using other approaches and offers great potential for the future

Exploring cation disorder in mixed-metal pyrochlore ceramics using 17O NMR spectroscopy and first-principles calculations

Funding: Royal Society (Grant Number(s): Wolfson Merit Award); FP7 Ideas: European Research Council (Grant Number(s): 614290); Engineering and Physical Sciences Research Council (Grant Number(s): EP/M022501/1).Characterising the local structures (e.g., the cation distribution) of mixed-metal ceramics by NMR spectroscopy is often challenging owing to the unfavourable properties (low γ, large quadrupole moment and/or low abundance) of many metal nuclei. 17O is an attractive option owing to the prevalence of oxygen within ceramics. The moderate γ and small quadrupole moment of 17O mean that the greatest barrier to accessing the information available from this nucleus is isotopic enrichment. We explore the challenges of ensuring uniform isotopic enrichment with 17O2(g) for the pyrochlore solid solutions, Y2SnxTi2–xO7, La2SnxZr2–xO7 and La2SnxHf2–xO7, demonstrating that high enrichment temperatures (900 °C for 12 h) are required. In addition, for sites with very high symmetry (such as the tetrahedral OY4 and OLa4 sites with CQ ≈ 0 present here), we demonstrate that quantitative 17O NMR spectra require correction for the differing contributions from the centreband of the satellite transitions, which can be as high as a factor of ~3.89. It is common to use first-principles calculations to aid in interpreting NMR spectra of disordered solids. Here, we use an ensemble modelling approach to ensure that all possible cation arrangements are modelled in the minimum possible number of calculations. By combining uniform isotopic enrichment, quantitative NMR spectroscopy and a comprehensive computational approach, we are able to show that the cation distribution in Y2SnxTi2–xO7 is essentially random, whereas in La2SnxZr2–xO7 and La2SnxHf2–xO7, OLa2SnZr and OLa2SnHf sites are slightly energetically disfavoured, leading to a weak preference for clustering of like cations.Publisher PDFPeer reviewe

Advances in Waterborne Polyurethane and Polyurethane-Urea Dispersions and Their Eco-friendly Derivatives: A Review

Polyurethanes and polyurethane-ureas, particularly their water-based dispersions, have gained relevance as an extremely versatile area based on environmentally friendly approaches. The evolution of their synthesis methods, and the nature of the reactants (or compounds involved in the process) towards increasingly sustainable pathways, has positioned these dispersions as a relevant and essential product for diverse application frameworks. Therefore, in this work, it is intended to show the progress in the field of polyurethane and polyurethane-urea dispersions over decades, since their initial synthesis approaches. Thus, the review covers from the basic concepts of polyurethane chemistry to the evolution of the dispersion’s preparation strategies. Moreover, an analysis of the recent trends of using renewable reactants and enhanced green strategies, including the current legislation, directed to limit the toxicity and potentiate the sustainability of dispersions, is described. The review also highlights the strengths of the dispersions added with diverse renewable additives, namely, cellulose, starch or chitosan, providing some noteworthy results. Similarly, dispersion’s potential to be processed by diverse methods is shown, evidencing, with different examples, their suitability in a variety of scenarios, outstanding their versatility even for high requirement applications