Valorisation of Chitosan Natural Building Block as a Primary Strategy for the Development of Sustainable Fully Bio-Based Epoxy Resins.

The non-toxic and biodegradable nature of chitosan makes it a valuable resource offering promising opportunities in the development of bio-based materials with enhanced mechanical and thermal properties. In this work, the combination of epoxidized linseed oil, oxalic or citric acids, and chitosan (CHI) as a curing accelerator presents an attractive strategy to create bio-based and sustainable thermosetting materials. This article aims to provide a comprehensive exploration of the systems reactivities, characteristics, and performance evaluation of the designed bio-thermosets. Both the nature of the two carboxylic acids and the presence of chitosan are shown to have a big impact on the thermomechanical properties of the developed networks. While oxalic acid favours the formation of elastic networks, with low Tg values (increasing with CHI content between 0.7 and 8.5 °C) and relatively low Young's modulus (~2.5 MPa), citric acid promotes the formation of very dense networks with lower mass of the segments between the crosslinks, having 20 times higher Tg values (from 36 to 45 °C) and ~161 times higher Young's modulus (from 94 MPa up to 404 MPa in these systems). The CHI has a strong impact on the curing reaction and on the overall properties, by increasing the materials' performance.

Development of Sustainable High Performance Epoxy Thermosets for Aerospace and Space Applications.

There is an imperative need to find sustainable ways to produce bisphenol A free, high performance thermosets for specific applications such as the space or aerospace areas. In this study, an aromatic tris epoxide, the tris(4-hydroxyphenyl)methane triglycidyl ether (THPMTGE), was selected to generate high crosslinked networks by its copolymerization with anhydrides. Indeed, the prepared thermosets show a gel content (GC) ~99.9% and glass transition values ranged between 167-196 °C. The thermo-mechanical properties examined by DMA analyses reveal the development of very hard materials with E' ~3-3.5 GPa. The thermosets' rigidity was confirmed by Young's moduli values which ranged between 1.25-1.31 GPa, an elongation at break of about 4-5%, and a tensile stress of ~35-45 MPa. The TGA analyses highlight a very good thermal stability, superior to 340 °C. The Limit Oxygen Index (LOI) parameter was also evaluated, showing the development of new materials with good flame retardancy properties.

Physico-Chemical Properties and Principal Component Analysis of Biobased Thermosets Developed with Different Batches of Industrial Humins.

Humins have already shown their potential as thermosetting resins to produce crosslinked networks and composites, with a large variety of properties depending on the used macromolecular approach. Our group has shown that a very interesting class of materials with tunable flexibility can be made by humins co-polymerization with glycerol diglycidyl ether (GDE). To create a clearer picture on structure-reactivity-properties-application interdependent relationship, a principal component analysis (PCA) was applied on several humins batches. The PCA allowed to obtain a clear discrimination between the humins/GDE resins samples in 3 groups which correlate very well with the results of copolymerization reactivity (DSC) and thermosets properties: crosslink density, thermal stability, tan δ, Shore D hardness values, etc.

Hydrothermal Carbon as Reactive Fillers to Produce Sustainable Biocomposites with Aromatic Bio-Based Epoxy Resins.

Thiswork is focused on the development of sustainable biocomposites based on epoxy bioresin reinforced with a natural porous material (hydrochar, HC) that is the product of spruce bark wastes subjected to hydrothermal decomposition. To identify the influence of hydrochar as a reinforcing material on the designed composites, seven formulations were prepared and tested. An aromatic epoxy monomer derived from wood biomass was used to generate the polymeric matrix, and the formulations were prepared varying the filler concentration from 0 to 30 wt %. The reactivity of these formulations, together with the structural, thermal, and mechanical properties of bio-based resin and biocomposites, are investigated. Surprisingly, the reactivity study performed by differential scanning calorimetry (DSC) revealed that HC has a strong impact on polymerization, leading to an important increase in reaction enthalpy and to a decrease of temperature range. The Fourier Transform Infrared Spectroscopy (FT-IR) investigations confirmed the chemical bonding between the resin and the HC, while the dynamic mechanical analysis (DMA) showed increased values of crosslink density and of storage moduli in the biocomposites products compared to the neat bioresin. Thermogravimetric analysis (TGA) points out that the addition of hydrochar led to an improvement of the thermal stability of the biocomposites compared with the neat resorcinol diglycidyl ether (RDGE)-based resin (T5% = 337 °C) by ≈2-7 °C. Significantly, the biocomposites with 15-20 wt % hydrochar showed a higher stiffness value compared to neat epoxy resin, 92SD vs. 82SD, respectively.

Polyhydroxybutyrate Bioresins with High Thermal Stability by Cross-linking with Resorcinol Diglycidyl Ether.

The development of sustainable materials by employing natural and nontoxic resources has been attracting much attention over the previous years. In this work, we discuss for the first time the chemical combination between resorcinol diglycidyl ether (RDGE), an aromatic biobased thermosetting monomer, and polyhydroxybutyrate (PHB), a bioderived and biodegradable thermoplastic polyester. By this combination, we aimed to associate the high thermal stability of RDGE with a toughening effect by the aliphatic chains of PHB. The investigations on the mechanism of the cross-linking reaction and on the structural connectivity between the two components were realized by Fourier transform infrared (FTIR) and NMR spectroscopies. We found that the epoxide polymerization catalyzed by tertiary amines triggers the formation of crotonyl species by polyhydroxybutyrate cleavage. Two-dimensional NMR experiments show that polyhydroxybutyrate fragments covalently bind as side chains to the rigid aromatic network of the epoxide frame. The cross-linking between the two systems entails the formation of new ester and ether bonds. The obtained structures show a network homogeneity confirmed by a single Tg, from 85 to 47 °C, as a function of the formulation, and tan δ values from 87 to 53 °C. The combination of the two comonomers showed a positive effect. The PHB increased the toughness of RDGE-based thermosets, improving the material elasticity by increasing the chain length between the cross-links. An important result of this study is the high thermal stability of RDGE/PHB bioresins, with the T5% varying between 330 and 310 °C as a function of the PHB ratio.

Biorefinery Byproducts and Epoxy Biorenewable Monomers: A Structural Elucidation of Humins and Triglycidyl Ether of Phloroglucinol Cross-Linking.

The need for thermosets from renewable resources is continuously increasing to find eco-friendly alternatives to petroleum-derived materials. Products obtained from biomass have shown to play an important role in this challenge. Here, we present the structural characterization of new biobased thermosets made of humins, a byproduct of lignocellulosic biorefinery, and glycidylated phloroglucinol coming from the biomass phenolic fraction. By employing attenuated total reflection-Fourier transform infrared and NMR spectroscopies, we elucidated the connections between these two systems, contributing to clarify their molecular structures and their reactivities. We demonstrated that the resin curing takes place through ether bond formation between humin hydroxyl functions and phloroglucinol epoxides. Besides cross-linking, humins show a complex rearrangement of their furanic structure through different concomitant chemical pathways depending on the reaction conditions.

Synthesis of Resins Using Epoxies and Humins as Building Blocks: A Mechanistic Study Based on In-Situ FT-IR and NMR Spectroscopies.

The combination of eco-respectful epoxy compounds with the humins, a by-product of biomass chemical conversion technologies, allow the obtention of materials with high added value. In this work, we propose a chemical connection study of humins with two aliphatic bis-epoxides through copolymerization reactions to synthesize sustainable, bio-based thermosets. The mechanism insights for the crosslinking between the epoxides and humins was proposed considering the different functionalities of the humins structure. Fourier Transform InfraRed (FT-IR), one dimensional (1D) and two-dimensional (2D) Nuclear Magnetic Resonance (NMR) spectroscopy techniques were used to build the proposed mechanism. By these techniques, the principal chain connections and the reactivity of all the components were highlighted in the synthesized networks.

Usefulness of virtual chromoendoscopy in the evaluation of subtle small bowel ulcerative lesions by endoscopists with no experience in videocapsule.

BACKGROUND AND STUDY AIMS: In videocapsule endoscopy examination (VCE), subtle variations in mucosal hue or pattern such as those seen in ulcerations can be difficult to detect, depending on the experience of the reader. Our aim was to test whether virtual chromoendoscopy (VC) techniques, designed to enhance the contrast between the lesion and the normal mucosa, could improve the characterization of ulcerative mucosal lesions. PATIENTS AND METHODS: Fifteen trainees or young gastroenterologists with no experience in VCE were randomly assigned to evaluate 250 true ulcerative and 100 false ulcerative, difficult-to-interpret small bowel lesions, initially as white light images (WLI) and then, in a second round, with the addition of one VC setting or again as WLI, labeling them as real lesions or artifacts. RESULTS: On the overall image evaluation, an improvement in lesion characterization was observed by adding any chromoendoscopy setting, especially Blue mode and FICE 1, with increases in accuracy of 13 % [95 %CI 0.8, 25.3] and 7.1 % [95 %CI - 17.0, 31.3], respectively. However, when only false ulcerative images were considered, with the same presets (Blue mode and FICE 1), there was a loss in accuracy of 10.7 % [95 %CI - 10.9, 32.3] and 7.3 % [95 %CI - 1.3, 16.0], respectively. The interobserver agreement was poor for both readings. CONCLUSIONS: VC helps beginner VCE readers correctly categorize difficult-to-interpret small bowel mucosal ulcerative lesions. However, false lesions tend to be misinterpreted as true ulcerative with the same presets. Therefore care is advised in using VC especially under poor bowel preparation.

Rapid Fecal Calprotectin Testing Predicts Mucosal Healing Better than C-reactive Protein and Serum Tumor Necrosis Factor α in Patients with Ulcerative Colitis.

BACKGROUND AND AIMS: Serum and fecal biomarkers have been used as noninvasive methods for assessing disease activity in ulcerative colitis. C-reactive protein, serum tumor necrosis factor-α and fecal calprotectin are among the most promising such biomarkers. However, their role in the management of ulcerative colitis patients remains to be clarified. We aimed to evaluate the accuracy of C-reactive protein, fecal calprotectin and tumor necrosis factor-α in detecting clinical and endoscopic activity and predicting disease outcome. METHODS: A cohort of ulcerative colitis patients was prospectively evaluated for clinical and endoscopic disease activity using the Mayo score. Serum C-reactive protein and tumor necrosis factor-α levels were measured and a point-of-care method was used for determining Calprotectin levels. RESULTS: Fifty-three patients with ulcerative colitis were followed for a median of 12 months. Fecal calprotectin and C-reactive protein levels were significantly higher in patients with clinically active disease at baseline, but only calprotectin levels correlated with endoscopic activity. Calprotectin values over 300 µg/g had 60% sensitivity and 90% specificity for detecting active endoscopic disease and 61% sensitivity and 89% specificity for predicting mucosal healing. CONCLUSION: Rapid calprotectin testing is a better predictor of mucosal healing than serum biomarkers and it could improve the management of ulcerative colitis patients by decreasing the need for invasive investigations.

Factors Influencing Complication Rates at Colonic Polypectomy: A Prospective Study from a Tertiary-Referral Center.

BACKGROUND AND AIMS: Colon polypectomy decreases the incidence of colorectal cancer and related mortality. Several factors such as the size, location and type of polyp as well as endoscopist experience have been shown to correlate with the risk of ensuing procedure-related complications. This study aims to evaluate the impact of polyp and endoscopist-related factors on the rate of postpolypectomy complication in a real-life setting. METHODS: During the study period all polypectomies performed in our unit were reported on a standard form that included data on polyp type (flat, sessile, pedunculated), size, location in the colon, resection method, endoscopist volume and procedure-related complications arising up to 30 days. The main outcome was the complication rate of polypectomies. The factors that associated with a higher risk of complications were assessed on univariate and multivariate analysis. RESULTS: 244 polyp resections from 95 patients were included in the analysis. 199 polyps were resected by low-volume endoscopists (44.7%) and 135 polypectomies were performed by high-volume endoscopists (55.3%). On multivariate analysis only polyp size correlated with the risk of procedure-related complications. CONCLUSION: Polyp size is the most important risk factor for procedure-related complications. Both high and low-volume endoscopists have a low overall rate of serious complications.

Current Stance of Magnetic Resonance Imaging in the Diagnosis and Monitoring of Hepatic Encephalopathy.

OBJECTIVES: Hepatic encephalopathy is a complex of neuropsychiatric manifestations in patients with acute or chronic liver insufficiency and/or porto-systemic shunts. MATERIAL AND METHODS: The diagnostic can be sustained by various elements, clinical and paraclinical. Selected patients with hepatic encephalopathy have been investigated by Magnetic Resonance, in parallel with specific biochemical analysis. OUTCOMES: This paper emphasizes the importance of Magnetic Resonance Imaging in an accurate diagnosis and patient monitoring after treatment. CONCLUSIONS: Magnetic Resonance Spectroscopy has a substantial role, showing even minute metabolite ratio changes, with a potential in investigating minimal hepatic encephalopathy.

Rapid fecal calprotectin level assessment and the SIBDQ score can accurately detect active mucosal inflammation in IBD patients in clinical remission: a prospective study.

BACKGROUND AND AIMS: Mucosal healing is an important predictor of disease-related outcome in patients with inflammatory bowel disease (IBD) patients, including those in clinical remission. However, colonoscopy is an invasive procedure and many patients decline repeated endoscopic examinations. We aimed to assess whether noninvasive biomarkers could accurately detect endoscopic mucosal inflammatory activity in IBD patients in clinical remission. METHODS: We conducted a prospective observational cohort study on IBD patients in clinical remission at Colentina Hospital, Bucharest. Clinical activity was assessed using the Mayo score and Crohn's Disease Activity Index (CDAI), quality of life was assessed using the Short Inflammatory Bowel Disease Questionnaire (SIBDQ). Serum C-reactive protein (CRP) and fecal calprotectin (FC) levels were determined. All patients underwent ileo-colonoscopy to assess mucosal inflammatory activity. RESULTS: 48 patients were included in this study, with 67% showing endoscopic disease activity. SIBD questionnaire and FC performed well as noninvasive markers of intestinal inflammation (AUROC 0.78 and 0.77, respectively), while CRP could not accurately predict endoscopic disease activity. Fecal calprotectin levels > 30 µg/g showed a 93% sensitivity and a 50% specificity for detecting inflammatory changes of the mucosa while a combined test using FC > 30µg/g and a SIBDQ score < 6 achieved 81.2% sensitivity and 75% specificity, respectively, in detecting active endoscopic disease. CONCLUSION: Fecal calprotectin and SIBDQ have good diagnostic accuracy in detecting mucosal inflammatory changes in IBD patients in clinical remission. Combining simple, noninvasive tests such as the SIBDQ and FC levels appears to be a practical method for monitoring disease activity in these patients, possibly reducing the need for repeat endoscopic examinations.