Nanocomposites of Rigid Polyurethane Foam and Graphene Nanoplates Obtained by Exfoliation of Natural Graphite in Polymeric 4,4'-Diphenylmethane Diisocyanate.

The influence of graphene nanoplates (GNPs) obtained by the ecofriendly exfoliation of natural graphite has been addressed on the mechanical and thermal insulating properties of rigid polyurethane foams (RPUFs). Few-layer GNPs with few defects were prepared in polymeric 4,4'-diphenylmethane diisocyanate (pMDI) under ultrasonication to obtain a GNP/pMDI dispersion. GNP/pMDI dispersions with different GNP concentrations were used to prepare RPUF nanocomposites via in situ polymerization. An important finding is that the GNP/pMDI dispersion exhibits lyotropic liquid crystalline behavior. It was found that the unique orientation of GNPs above the concentration of 0.1 wt% in the dispersion affected the mechanical and thermal insulation properties of the RPUF nanocomposites. GNP/RPUF nanocomposites with GNP concentrations at 0.2 wt% or more showed better thermal insulating properties than neat RPUF. The lyotropic liquid crystalline ordering of GNPs provides stable nucleation for bubble formation during foaming and prevents bubble coalescence. This decreases the average cell size and increases the closed cell content, producing GNP/RPUF nanocomposites with low thermal conductivity. Furthermore, GNPs incorporated into RPUF act as a barrier to radiant heat transfer through the cells, which effectively reduces the thermal conductivity of the resulting nanocomposites. It is expected that the nanocomposite of RPUF investigated in this study can be applied practically to improve the performance of thermal insulation foams.

Rationally Designed Eugenol-Based Chain Extender for Self-Healing Polyurethane Elastomers.

Bio-based polyurethane (PU) has recently drawn our attention due to the increasing interest in sustainability and the risks involved with petroleum depletion. Herein, bio-based self-healing PU with a novel polyol, i.e., eugenol glycol dimer (EGD), was synthesized and characterized for the first time. EGD was designed to have pairs of primary, secondary, and aromatic alcohols, which all are able to be involved in urethane bond formation and to show self-healing and antioxidant effects. EGD was incorporated into a mixture of the prepolymer of polyol (tetramethylene ether glycol) and 4,4'-methylene diphenyl diisocyanate to synthesize PU. EGD-PU showed excellent self-healing properties (99.84%), and it maintained its high self-healing property (84.71%) even after three repeated tests. This dramatic self-healing was induced through transcarbamoylation by the pendant hydroxyl groups of EGD-PU. The excellent antioxidant effect of EGD-PU was confirmed by 2,2-diphenyl-1-picrylhydrazyl analysis. Eugenol-based EGD is a promising polyol chain extender that is required in the production of bio-based, self-healing, and recyclable polyurethane; therefore, EGD-PU can be applied to bio-based self-healable films or coating materials as a substitute for petroleum-based PU.

Characterization of Extended-Spectrum ß-Lactamase-Producing and AmpC ß-Lactamase-Producing Enterobacterales Isolated from Companion Animals in Korea.

The emergence of extended-spectrum cephalosporin (ESC)-resistant Gram-negative bacteria is of great concern in both human and veterinary medicine. The aim of this study was to investigate ESC-resistant bacterial isolates from companion animals in South Korea between 2017 and 2019. Isolates with ESC resistance genes, which were identified by PCR, were assessed for genetic relatedness by multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). In total, 91 ESC-resistant Escherichia coli, Klebsiella spp., Serratia spp., and Enterobacter cloacae isolates harbored the blaTEM gene. Among other ESC resistance genes, blaCTX-M-15, blaCIT, and blaCTX-M-55 were predominantly detected in E. coli isolates, whereas blaSHV and blaDHA were more frequently detected in Klebsiella pneumoniae isolates. In addition, all blaEBC-positive isolates were classified as E. cloacae. From the MLST results, blaCTX-M-9-carrying ST131, blaCIT-carrying ST405, and blaCTX-M-1-carrying ST3285 strains were dominant among E. coli isolates. ST273 and ST275 strains harboring blaSHV were frequently detected in K. pneumoniae isolates. Various sequence types were obtained in E. cloacae and Klebsiella oxytoca isolates. All isolates demonstrated unique PFGE profiles (<57-98% similarity) and were unlikely to be derived from a single clone. The present study reveals the presence and wide genetic distribution of ESC-resistant bacterial species in South Korean companion animals.

Distribution and antimicrobial resistance profiles of bacterial species in stray dogs, hospital-admitted dogs, and veterinary staff in South Korea.

Transferring antimicrobial-resistant bacteria from companion animals to human hosts has become increasingly common. Data regarding antimicrobial susceptibility could help veterinarians to select the most appropriate antibiotic treatment. However, standardized and ongoing surveys regarding antimicrobial resistance remain limited. In this study, we investigated the antimicrobial-susceptibility patterns and trends of bacteria isolated from stray dogs, hospital-admitted dogs, and veterinary staff in South Korea from 2018 to 2019. The minimum inhibitory concentrations of different antimicrobials for Staphylococcus spp., Enterobacterales, and Enterococcus spp. were determined to establish representatives of different antibiotic classes relevant for treatment or surveillance. For coagulase-positive and -negative Staphylococci, resistance to gentamicin was <27 %, while that to ampicillin and penicillin was high (33-80 %). The mecA-detection rates among staphylococcal isolates were 28.5 %, 42.6 %, and 32 % from stray dogs, hospital-admitted dogs, and veterinary staffs, respectively. For Enterobacterales, resistance to carbapenems was low (0-6%). A total of 31.2 % and 18.9 % of Enterobacterales isolates from stray dogs and hospital-admitted dogs were confirmed to possess at least one of blaCTX-M, blaSHV, or blaTEM. Additionally, Enterococcus spp. isolates showed no resistance to vancomycin. These results demonstrate that dogs are commonly colonized with antimicrobial-resistant bacteria and highlight the need for further investigation.

Self-Healing and Mechanical Properties of Thermoplastic Polyurethane/Eugenol-Based Phenoxy Resin Blends via Exchange Reactions.

The possibility of exchange reactions and thermal self-healing in blends of thermoplastic polyurethane (TPU) and phenoxy resin was investigated herein. The analyses were based on characterization obtained via differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), and tensile test. A new phenoxy resin was synthesized from eugenol, and blends with different types of TPU were prepared to investigate the exchange reaction, thermal self-healing, and mechanical properties. The influence of phenoxy resin content on the mechanical behavior and healing efficiency was studied. Improvement of storage modulus owing to the increase of phenoxy resin content was observed. Results suggest that the exchange reaction between phenoxy- and ester-type TPU occurred during thermal treatment. However, little exchange occurred between phenoxy resin and ether-type TPU. Specifically, only ester-type TPU exhibited a significant exchange reaction in the phenoxy resin blend. Furthermore, in the presence of a catalyst (e.g., zinc acetate), the exchange reaction readily occurred, and the healing efficiency improved by the addition of the catalyst and increase in the phenoxy content.

Characteristics of Self-Healable Copolymers of Styrene and Eugenol Terminated Polyurethane Prepolymer.

With limited biomass that can be currently utilized as a renewable resource, it is important to develop a method to convert biomass into materials that can replace fossil fuel product. In this paper, eugenol, a bio-based allyl chain-substituted guaiacol, was used to synthesize self-healable copolymers. Eugenol terminated polyurethane prepolymer (ETPU) was synthesized from eugenol and polyurethane prepolymers terminated with isocyanate groups. ETPU contained two allyl groups. Self-healing copolymer networks were obtained by copolymerization of ETPU and styrene monomer via free radical polymerization. Effects of ETPU content on the properties of copolymers were then studied. These copolymers containing ETPU exhibited good thermal stability and mechanical properties. These copolymers showed higher tensile strength and elongation at break than PS. Their maximum tensile strength reached 19 MPa. In addition, these copolymers showed self-healing property at elevated temperature due to the reversible nature of urethane units in ETPU.

Effects of Isosorbide Incorporation into Flexible Polyurethane Foams: Reversible Urethane Linkages and Antioxidant Activity.

Isosorbide (ISB), a nontoxic bio-based bicyclic diol composed from two fuzed furans, was incorporated into the preparation of flexible polyurethane foams (FPUFs) for use as a cell opener and to impart antioxidant properties to the resulting foam. A novel method for cell opening was designed based on the anticipated reversibility of the urethane linkages formed by ISB with isocyanate. FPUFs containing various amounts of ISB (up to 5 wt%) were successfully prepared without any noticeable deterioration in the appearance and physical properties of the resulting foams. The air permeability of these resulting FPUFs was increased and this could be further improved by thermal treatment at 160 °C. The urethane units based on ISB enabled cell window opening, as anticipated, through the reversible urethane linkage. The ISB-containing FPUFs also demonstrated better antioxidant activity by impeding discoloration. Thus, ISB, a nontoxic, bio-based diol, can be a valuable raw material (or additive) for eco-friendly FPUFs without seriously compromising the physical properties of these FPUFs.

Thermal Healing, Reshaping and Ecofriendly Recycling of Epoxy Resin Crosslinked with Schiff Base of Vanillin and Hexane-1,6-Diamine.

A bio-derived dihydroxylimine hardener, Van2HMDA, for the curing of epoxy resin was prepared from vanillin (Van) and hexamethylene-1,6-diamine (HMDA) by Schiff base formation. The epoxy resin of diglycidyl ether of bisphenol A was cured with Van2HMDA in the presence of the catalyst, 2-ethyl-4-methylimidazole (EMI). The crosslinked epoxy resin showed thermal-healing properties at elevated temperatures. Moreover, the crosslinked epoxy resin can be reshaped by heating via imine metathesis of the hardener units. The imine metathesis of Van2HMDA was confirmed experimentally. Stress-relaxation properties of the epoxy resin crosslinked with Van2HMDA were investigated, and the activation energy obtained from Arrhenius plots of the relaxation times was 44 kJ/mol. The imine bonds in the epoxy polymer matrix did not undergo hydrolysis after immersing in water at room temperature for one week. However, in the presence of acid, the crosslinked polymer was easily decomposed due to the hydrolysis of imine bonds. The hydrolysis of imine bonds was used for the ecofriendly recycling of crosslinked polymer. It is inferred that thermal-healing, reshaping, and reprocessing properties can be implemented in the various crosslinked epoxy resins with the bio-derived dihydroxylimine hardener, albeit the recycled epoxy resin is of inevitably lower quality than the original material.

Sorbitol as a Chain Extender of Polyurethane Prepolymers to Prepare Self-Healable and Robust Polyhydroxyurethane Elastomers.

A self-healable polyhydroxyurethane (S-PU) was synthesized from sorbitol, a biomass of polyhydric alcohol, by a simple process that is suitable for practical applications. In the synthesis, only two primary hydroxyl groups of sorbitol were considered for the chain extension of the polyurethane (PU) prepolymers to introduce free hydroxyl groups in PU. As a control, conventional PU was synthesized by hexane diol mediated chain extension. Relative to the control, S-PU showed excellent intrinsic self-healing property via exchange reaction, which was facilitated by the nucleophilic addition of the secondary hydroxyl groups without any catalytic assistance and improved tensile strength due to the enhanced hydrogen bonding. We also investigated the effect of the exchange reaction on the topological, mechanical, and rheological properties of S-PU. The suggested synthetic framework for S-PU is a promising alternative to the conventional poly hydroxyurethane, in which cyclic carbonates are frequently reacted with amines. As such, it is a facile and environmentally friendly material for use in coatings, adhesives, and elastomers.

Benefit of negative pressure drain within surgical wound after cytoreductive surgery for ovarian cancer.

OBJECTIVE: The objective of this study was to investigate the efficacy of subcutaneous negative-pressure wound drains on wound healing after cytoreductive surgery for ovarian cancer. METHODS: A retrospective study was performed on patients who underwent cytoreductive surgery for epithelial ovarian cancer, between 2012 and 2013. The patients were divided into 2 groups, according to using (n = 163) and not using (n = 37) of subcutaneous wound drains, and wound outcomes were analyzed. RESULTS: Patients' characteristics were not statistically different, except for the prolonged operative time in patients with wound drains (median, 395 vs 240 minutes; P = 0.001). A lower rate of wound infection (12.9% vs 27.0%; P = 0.032) was observed in the drain group. In the multivariate analysis, placement of subcutaneous wound drain was an independent prognostic factor for reducing wound complications: disruption (odds ratio [OR], 0.367; 95% confidence interval [CI], 0.145-0.929; P = 0.034) and wound infection (OR, 0.198; 95% CI, 0.068-0.582; P = 0.003). Bowel surgery at the time of cytoreductive surgery and prolonged operative time (≥360 minutes) were also associated with higher rates of disruption (OR, 2.845; 95% CI, 1.111-7.289; P = 0.029) and wound infection (OR, 4.212; 95% CI, 1.273-13.935; P = 0.019), respectively. CONCLUSIONS: Installation of subcutaneous negative-pressure wound drain is an effective method to achieve clearer wound healing and less wound complications after cytoreductive surgery for ovarian cancer.