A randomized-controlled trial of ischemia-free liver transplantation for end-stage liver disease.

BACKGROUND & AIMS: Ischemia-reperfusion injury (IRI) has thus far been considered as an inevitable component of organ transplantation, compromising outcomes, and limiting organ availability. Ischemia-free organ transplantation is a novel approach designed to avoid IRI, with the potential to improve outcomes. METHODS: In this randomized-controlled clinical trial, recipients of livers from donors after brain death were randomly assigned to receive either an ischemia-free or a 'conventional' transplant. The primary endpoint was the incidence of early allograft dysfunction. Secondary endpoints included complications related to graft IRI. RESULTS: Out of 68 randomized patients, 65 underwent transplants and were included in the analysis. 32 patients received ischemia-free liver transplantation (IFLT), and 33 received conventional liver transplantation (CLT). Early allograft dysfunction occurred in two recipients (6%) randomized to IFLT and in eight (24%) randomized to CLT (difference -18%; 95% CI -35% to -1%; p = 0.044). Post-reperfusion syndrome occurred in three recipients (9%) randomized to IFLT and in 21 (64%) randomized to CLT (difference -54%; 95% CI -74% to -35%; p <0.001). Non-anastomotic biliary strictures diagnosed with protocol magnetic resonance cholangiopancreatography at 12 months were observed in two recipients (8%) randomized to IFLT and in nine (36%) randomized to CLT (difference, -28%; 95% CI -50% to -7%; p = 0.014). The comprehensive complication index at 1 year after transplantation was 30.48 (95% CI 23.25-37.71) in the IFLT group vs. 42.14 (95% CI 35.01-49.26) in the CLT group (difference -11.66; 95% CI -21.81 to -1.51; p = 0.025). CONCLUSIONS: Among patients with end-stage liver disease, IFLT significantly reduced complications related to IRI compared to a conventional approach. CLINICAL TRIAL REGISTRATION: chictr.org. ChiCTR1900021158. IMPACT AND IMPLICATIONS: Ischemia-reperfusion injury has thus far been considered as an inevitable event in organ transplantation, compromising outcomes and limiting organ availability. Ischemia-free liver transplantation is a novel approach of transplanting donor livers without interruption of blood supply. We showed that in patients with end-stage liver disease, ischemia-free liver transplantation, compared with a conventional approach, led to reduced complications related to ischemia-reperfusion injury in this randomized trial. This new approach is expected to change the current practice in organ transplantation, improving transplant outcomes, increasing organ utilization, while providing a clinical model to delineate the impact of organ injury on alloimmunity.

Clinical Impacts and Outcomes With Possible Donor-Derived Infection in Infected Donor Liver Transplantation: A Single-Center Retrospective Study in China.

BACKGROUND: Information on possible donor-derived transmission events in China is limited. We evaluated the impacts of liver transplantation from infected deceased-donors, analyzed possible donor-derived bacterial or fungal infection events in recipients, and evaluated the etiologic agents' characteristics and cases outcomes. METHODS: A single-center observational study was performed from January 2015 to March 2017 to retrospectively collect data from deceased-donors diagnosed with infection. Clinical data were recorded for each culture-positive donor and the matched liver recipient. The microorganisms were isolated and identified, and antibiotic sensitivity testing was performed. The pathogens distribution and incidence of possible donor-derived infection (P-DDI) events were analyzed and evaluated. RESULTS: Information from 211 donors was collected. Of these, 82 donors were infected and classified as the donation after brain death category. Overall, 149 and 138 pathogens were isolated from 82 infected donors and 82 matched liver recipients, respectively. Gram-positive bacteria, Gram-negative bacteria, and fungi accounted for 42.3% (63 of 149), 46.3% (69 of 149), and 11.4% (17 of 149) of pathogens in infected donors. The incidence of multidrug-resistant bacteria was high and Acinetobacter baumannii was the most concerning species. Infections occurred within the first 2 weeks after liver transplantation with an organ from an infected donor. Compared with the noninfection recipient group, the infection recipient group experienced a longer mechanical ventilation time (P = .004) and intensive care unit stay (P = .003), a higher incidence of renal dysfunction (P = .026) and renal replacement therapy (P = .001), and higher hospital mortality (P = .015). Possible donor-derived infection was observed in 14.6% of cases. Recipients with acute-on-chronic liver failure were more prone to have P-DDI than recipients with other diseases (P = .007; odds ratio = 0.114; 95% confidence interval, .025-.529). CONCLUSIONS: When a liver recipient receives a graft from an infected deceased-donor, the postoperative incidence of infection is high and the infection interval is short. In addition, when a possible donor-derived, drug-resistant bacterial infection occurs, recipients may have serious complications and poor outcomes.

Identification and partial purification of thuricin 4AJ1 produced by Bacillus thuringiensis.

Thuricin 4AJ1, produced by Bacillus thuringiensis strain 4AJ1, showed inhibition activity against Bacillus cereus 0938 and ATCC 10987. It began to appear in the stationary phase and reached its maximum activity level of 209.958 U at 18 h against B. cereus 0938 and 285.689 U at 24 h against B. cereus ATCC 10987. Tricine-SDS-PAGE results showed that the partly purified thuricin 4AJ1 was about 6.5 kDa. The molecular weights of the known B. thuringiensis bacteriocins and the ones obtained by the two mainstream websites for predicting bacteriocins were inconsistent with the size of the thuricin 4AJ1, indicating that the bacteriocin obtained in this study may have a novel structure. Based on the biochemical properties, the thuricin 4AJ1 activities increased after treatment with proteinase K and lipase II, and were not affected by a-amylase, catalase, α-chymotrypsin VII and α-chymotrypsin II. It was heat tolerant, being active up to 90º C. In the pH 3-10 range, it maintained most of its activity. Finally, the sensitivity of the strain 4AJ1 to commonly used antibiotics was tested. In view of its stability and antibacterial activity, thuricin 4AJ1 may be applied as a food biopreservative.

Global evolution of glycosylated polyene macrolide antibiotic biosynthesis.

Antibiotics are the most marvelous evolutionary products of microbes to obtain competitive advantage and maintain ecological balance. However, the origination and development of antibiotics has yet to be explicitly investigated. Due to diverse structures and similar biosynthesis, glycosylated polyene macrolides (gPEMs) were chosen to explore antibiotic evolution. A total of 130 candidate and 38 transitional gPEM clusters were collected from actinomycetes genomes, providing abundant references for phenotypic gaps in gPEM evolution. The most conserved parts of gPEM biosynthesis were found and used for phylogeny construction. On this basis, we proposed ancestral gPEM clusters at different evolutionary stages and interpreted the possible evolutionary histories in detail. The results revealed that gPEMs evolved from small rings to large rings and continuously increased structural diversity through acquiring, discarding and exchanging genes from different evolutionary origins, as well as co-evolution of functionally related proteins. The combination of horizontal gene transfers, environmental effects and host preference resulted in the diversity and worldwide distribution of gPEMs. This study is not only a useful exploration on antibiotic evolution but also an inspiration for diversity and biogeographic investigations on antibiotics in the era of Big Data.

Distribution of metal and metalloid elements in human scalp hair in Taiyuan, China.

This study investigated the levels of metal and metalloid elements (As, Ca, Cd, Cr, Cu, Fe, Hg, Mg, Ni, Pb, and Zn) in scalp hair samples collected from 161 people of different age and gender groups living in the six districts of Taiyuan, an industrial city with rich coal reserve in Shanxi province in China. Levels of most elements in the hair were high in the 26-40 age groups and increased with the length of residence. Calcium, Cr, Mg, Ni and Zn levels in the females' hair were significantly higher than those in the males' (p < 0.05). Element levels in the hair didn't have significantly differences between industrial and non-industrial districts because most of industry factories are in the upper wind position in Taiyuan, and contamination is prone to spread to non-industrial districts. The principal component analysis indicates that the main sources of these elements are mining activities, the neighboring stainless steel industry, and coal combustion. These results indicate that the industrial activities primarily contribute to the metal and metalloid pollution in Taiyuan, whereas numerous factors caused the metals accumulation in hair.

First principle structural determination of (B2O3)n (n = 1-6) clusters: from planar to cage.

The structure of (B2O3)n clusters (n = 1-6) are investigated using the method combining the genetic algorithm with density functional theory. Benchmark calculations indicate that TPSSh functional is reliable in predicting the energetic sequences of different isomers of (B2O3)n cluster compared to the high-level coupled cluster method. The global minimum (GM) structures of (B2O3)n clusters are planar up to n = 3, and cages at n = 4-6. A Td fullerene is found in the GM structure at n = 6. The stability of three-dimensional structures increases with the size of the cluster according to the analysis of the calculated atomization energy. Natural bonding analysis given by adaptive natural density partitioning reveals delocalized π-bonding in the 4-membered and 6-membered rings, and it is aromatic at the centers of cages and rings.

Benzene analogues of (quasi-)planar M@B(n)H(n) compounds (M = V(-), Cr, Mn+): a theoretical investigation.

The stability of M@B(n)H(n) (M = V(-), Cr, Mn(+); n = 5-8) is investigated by density functional theory. For n = 6-8, the isomers possess (quasi-)planar local minima showed by geometry optimization at TPSSh/6-311+G** level. All the optimized structures are thermodynamics stable according to the large HOMO-LUMO gap, binding energy, vertical ionization potential, and vertical electron affinity analysis. The peripheral and central atomic radius fit each other best at n = 7 confirmed by the variation of the binding energy values. The availability of d atom orbitals in M for participation in the π-delocalized bonding with the peripheral ring leads to the aromaticity of the (quasi-)planar structures and makes them the benzene analogues. This work establishes firmly the metal-doped borane rings as a new type of aromatic molecule.

Two new species of the sac-spider genus Clubiona Latreille, 1804 (Araneae, Clubionidae) and the female of C. subcylindrata from China.

Two new species of the genus Clubiona Latreille, 1804 are described: C. tianpingshan sp. nov. (♂♀) and C. flammaforma sp. nov. (♂♀) from central and south China. The female of C. subcylindrata Wang et al., 2018 is described for the first time. Detailed descriptions, photographs of somatic features and copulatory organs, as well as a distribution map of these three species, are provided.

Mechanical Properties Variation in Wood-Plastic Composites with a Mixed Wood Fiber Size.

In this study, the influence of fiber particle size on the mechanical properties of a wood--plastic composite (WPC) was investigated using a combination of experimental measurements and numerical modeling. Four different sizes of wood fibers (10-20 mesh, 20-40 mesh, 40-80 mesh, and 80-120 mesh) were used to reinforce high-density polyethylene (HDPE), either separately or in combination. The different sizes of fibers produced varying properties in the resulting composites. The smallest fiber size (80-120 mesh) resulted in the lowest flexural and tensile properties, but the highest impact strength (15.79 kJ/m2) compared to the other three sizes (12.18-14.29 kJ/m2). Using a blend of fiber sizes resulted in improved mechanical properties. Composites containing a mix of 20-40 mesh and 40-80 mesh fibers exhibited the best flexural (strength 74.16 MPa, modulus 5.35 GPa) and tensile performance (strength 48.27 MPa, modulus 4.30 GPa), while composites containing a mix of all four fiber sizes had the highest impact-resistant strength (16.08 kJ/m2). Several models, including the Rule of Mixtures (ROM), the Inverse Rule of Mixtures (IROM), and the Hirsch models, were used to predict the performance of WPCs. The ROM model was found to be the most accurate in describing the mechanical properties of WPCs reinforced with multi-size wood fibers, based on the sum squared error (SSE) analysis.

Endoplasmic reticulum stress response mediated by the PERK-eIF2α-ATF4 pathway is involved in odontoblastic differentiation of human dental pulp cells.

OBJECTIVE: RNA-activated protein kinase-like ER-resident kinase (PERK) was a major transducer of Endoplasmic reticulum (ER) stress response and it directly phosphorylated α-subunit of eukaryotic initiation factor 2 (eIF2α), which specifically promoted the translation of activating transcription factor 4 (ATF4), an important transcription factor in cells' differentiation. The purpose of this study was to establish whether ER stress mediated by PERK-eIF2α-ATF4 pathway was involved in odontoblastic differentiation of human dental pulp cells (DPCs). METHODS: DPCs were isolated from extracted teeth and cultured in odontogenic medium. A recombinant lentiviral vector was constructed to transfect DPCs for PERK knockdown. Alkaline phosphatase (ALP) and Alizarin red S staining were used to characterize the odontoblastic differentiation. Real-time polymerase chain reactions (RT-PCR) were performed to analyze the genes' expressions in DPCs' odontoblastic differentiation. The mRNA and protein levels of ER stress markers were examined by RT-PCR and western blot. RESULTS: DPCs cultured in odontogenic media showed increased ALP activity and mineralized nodule formation. Notably, treatment with differentiation medium resulted in the up-regulation of genes, such as osteocalcin (OCN), bone sialoprotein (BSP), dentin sialophosphoprotein (DSPP), splicing x-box binding protein-1 (sXBP1), ATF4 and glucose-regulated protein 78 (GRP78). Meanwhile, the expressions of PERK-eIF2α-ATF4 pathway proteins, phosphorylated PERK, phosphorylated eIF2α and ATF4, increased in odontoblastic induction cells compared with controls. Furthermore, inhibition of PERK (PERK knockdown) decreased ALP activity and matrix mineralization in DPCs accompanied by the decrease expression of phosphorylated eIF2α and ATF4. CONCLUSION: These results suggested that PERK-eIF2α-ATF4 pathway was involved in the odontoblastic differentiation of DPCs.

Surface Characteristics of Thermally Modified Bamboo Fibers and Its Utilization Potential for Bamboo Plastic Composites.

Bamboo fibers are considered as a more attractive option for the reinforcement of wood plastic composites as compared to wood fiber due to its fast growth rate and good toughness. Heat treatment is an environment-friendly method of improving the integrated performance of bamboo materials. This paper highlights the heat treatment of bamboo fiber for suitable properties as reinforcements in bamboo plastic composites. The effects of vacuum heat treatment on the surface characteristics of bamboo fibers and the properties of bamboo plastic composites were analyzed by studying the chemical composition, surface elements and polarity of bamboo fiber before and after treatment, and the physical and mechanical properties of bamboo plastic composite. The results showed that after vacuum heat treatment, the bamboo fibers became darker and experienced a transition from green to red. Moreover, FTIR, XPS and contact angle analysis indicated that the hemicellulose content, the oxygen/carbon ratio and the polar component of the bamboo fiber had a decreasing trend as the treatment temperature increased. In addition, the 24 h water absorption and the 24 h thickness expansion rate of the water absorption showed a trend of first decreasing and then increasing as the treatment temperature increased, while the bending performance of bamboo plastic composite showed a trend of increasing first and then decreasing as a result of increased treatment temperature. Therefore, a combined process of vacuum heat treatment and the addition of MAPE could improve the physical and mechanical properties of bamboo plastic composites to a certain extent.

A two-photon fluorescence probe with endoplasmic reticulum targeting ability for turn-on sensing photosensitized singlet oxygen in living cells and brain tissues.

Endoplasmic reticulum (ER) is an indispensable organelle responsible for protein synthesis, transportation, and maintenance of Ca2+ homeostasis in eukaryotic cells. Recent studies highlighted that ER-targeted photosensitizers with high yield of singlet oxygen (1O2) are effective in selectively disrupting ER function and are promising candidates for anticancer therapy. Unfortunately, no ER targetable fluorescent probes for determining 1O2 photosensitized in this photodynamic therapy process is available. In this work, we synthesized an ER-targetable, two-photon fluorescence probe, ER-1O2, for fluorescence turn-on sensing of 1O2. ER-1O2 demonstrated high sensitivity to 1O2 sensing with a wide detection range (0-2.75 µM) and a low detection limit (0.11 µM). ER-1O2 also displayed excellent selectivity toward 1O2 out of other ROS and metal ions. Notably, ER-1O2 exhibited low cytotoxicity but with specific ER targetable capability. On account of these advantageous features, fluctuations of 1O2 in living cells and brain tissues were effectively visualized by ER-1O2.

Engineering the CuO-HfO2 interface toward enhanced CO2 electroreduction to C2H4.

We report significantly enhanced electrochemical CO2 reduction (ECR) to C2H4 by tuning the interface of a metal oxide composite (CuOx/HfO2), enabling a C2H4 faradaic efficiency as high as 62.6 ± 1.3% at 300 mA cm-2, in contrast to only 11.6 ± 1.6% over pure CuO. Collective knowledge from multiple control experiments, density functional theory calculations, and operando Raman study reveals that the CuOx-HfO2 interface greatly strengthens CO2 adsorption and the binding of *CO for further C-C coupling to yield C2H4.

Acute pancreatitis as a rare complication of gastrointestinal endoscopy: A case report.

BACKGROUND: Acute pancreatitis is an uncommon complication of gastrointestinal endoscopy, especially if the patient has none of the common risk factors associated with pancreatitis; such as alcoholism, gallstones, hypertriglyceridemia, hypercalcemia or the use of certain drugs. CASE SUMMARY: A 56-year-old female patient developed abdominal pain immediately after the completion of an upper gastrointestinal endoscopy. The pain was predominantly in the upper and middle abdomen and was persistent and severe. The patient was diagnosed with acute pancreatitis. Treatment included complete fasting, octreotide injection prepared in a prefilled syringe to inhibit pancreatic enzymes secretion, ulinastatin injection to inhibit pancreatic enzymes activity, esomeprazole for gastric acid suppression, fluid replacement and nutritional support. Over the next 3 d, the patient's symptoms improved. The patient remained hemodynamically stable throughout hospitalization and was discharged home in a clinically stable state. CONCLUSION: Pancreatitis should be considered in the differential diagnosis of abdominal pain after upper and lower gastrointestinal endoscopy.

A New Wood Adhesive Based on Recycling Camellia oleifera Cake-Protein: Preparation and Properties.

In order to improve the initial viscosity and stability of Camellia oleifera cake-protein adhesive, Camellia oleifera cake-protein was blended with defatted soybean protein (DSP), soybean protein isolate (SPI), and casein, followed by adhesive preparation through degradation and crosslinking methods. The performance of Camellia oleifera cake-protein adhesive was investigated by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), scanning electron microscopic (SEM), and thermogravimetric (TG) and X-ray diffraction (XRD). The results showed that DSP, SPI, and casein likely promoted the effective degradation of Camellia oleifera cake-protein, and, thus, more active groups were formed in the system, accompanied by more reactivity sites. The prepared adhesive had a lower curing temperature, and higher initial viscosity and stability, but the storage time was shortened. Moreover, DSP, SPI, and casein, themselves, were degraded into peptide chains with lower molecular weights; thus, improving the overall flexibility of the adhesive, facilitating a better elastic contact and regular array between crosslinking products, and further strengthening the crosslinked structure and density of the products. After curing, a compact and coherent reticular structure was formed in the adhesive layer, with both bonding strength and water resistance being significantly improved. According to the results obtained, the next step will be to study the DSP-modified Camellia oleifera cake-protein adhesive in depth.

Boosting CO2 methanation on ceria supported transition metal catalysts via chelation coupled wetness impregnation.

The incipient wetness impregnation (IWI) method is widely used in the preparation of supported transition metal catalysts for its high throughput and cost-effective synthesis, yet suffers from poor metal-support interaction, restricting its further application at an industrial scale. Herein, a universal strategy of chelation coupled impregnation (CCI) is presented. The as-prepared Ni/CeO2(CCI) showed superior catalytic performance for CO2 conversion (84.3%) and CH4 selectivity (100%) under the experimental conditions (WGHSV = 24,000 mL g-1 h-1 and H2/CO2 = 4:1) even at low temperatures (T = 275 °C). The surface characterization results confirmed that the agglomeration of metal active sites in Ni/CeO2(CCI) was restricted and more surface oxygen vacancies were generated on CeO2. Further, the in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) analysis suggested that the surface oxygen vacancies that served as active sites could facilitate the direct dissociation of CO2 more favorably than the associative route, thus significantly promoting CO2 methanation activity.

Changes of monocyte human leukocyte antigen-DR expression as a reliable predictor of mortality in severe sepsis.

INTRODUCTION: Many studies have shown that monocyte human leukocyte antigen-DR (mHLA-DR) expression may be a good predictor for mortality in severe septic patients. On the contrary, other studies found mHLA-DR was not a useful prognostic marker in severe sepsis. Few studies have taken changes of mHLA-DR during treatment into consideration. The objective of this study was to estimate the prognostic value of changes of mHLA-DR to predict mortality in severe sepsis. METHODS: In this prospective observational study, mHLA-DR was measured by flow cytometry in peripheral blood from 79 adult patients with severe sepsis. mHLA-DR levels were determined on day 0, 3, 7 after admission to the surgical intensive care unit (SICU) with a diagnosis of severe sepsis. ΔmHLA-DR3 and ΔmHLA-DR7 were defined as the changes in mHLA-DR value on day 3 and day 7 compared to that on day 0. Data were compared between 28-day survivors and non-survivors. Receiver operating characteristic (ROC) curves were plotted to measure the performance and discriminating threshold of ΔmHLA-DR3, ΔmHLA-DR7, ΔmHLA-DR7-3, mHLA-DR0, mHLA-DR3 and mHLA-DR7 in predicting mortality of severe sepsis. RESULTS: ROC curve analysis showed that ΔmHLA-DR3 and ΔmHLA-DR7 were reliable indicators of mortality in severe sepsis. A ΔmHLA-DR3 value of 4.8% allowed discrimination between survivors and non-survivors with a sensitivity of 89.0% and a specificity of 93.7%; similarly, ΔmHLA-DR7 value of 9% allowed discrimination between survivors and non-survivors with a sensitivity of 85.7% and a specificity of 90.0%. Patients with ΔmHLA-DR3 ≤ 4.8% had higher mortality than those with ΔmHLA-DR3 > 4.8% (71.4% vs. 2.0%, OR 125.00, 95% CI 13.93 to 1121.67); patients with ΔmHLA-DR7 ≤ 9% had higher mortality than those with ΔmHLA-DR7 > 9% (52.9% vs. 2.0%, OR 54.00, 95% CI 5.99 to 486.08). The mean change of mHLA-DR significantly increased in the survivor group with the passage of time; from day 0 to day 3 and day 7, changes were 6.45 and 16.90 (P < 0.05), respectively. CONCLUSIONS: The change of mHLA-DR over time may be a reliable predictor for mortality in patients with severe sepsis.

Engineering of anatase/rutile TiO2 heterophase junction via in-situ phase transformation for enhanced photocatalytic hydrogen evolution.

Constructing effective interphase boundary is one of the efficient approaches for improving photocatalytic performances of semiconductor materials. In this work, an anatase/rutile-TiO2 (AR-TiO2) heterophase junction with appropriate carbon content was successfully fabricated via an in-situ phase transformation process. The phase transformation started from the inner core of the nanoparticles and the area of phase interface between anatase and rutile was carefully controlled by regulating the activation temperature. The well-established type-II band alignment between two TiO2 phases with residual carbon as additional charge transfer intermediary which significantly improved the light-harvesting and photoinduced electron-hole pair separation. As a result, the optimal AR-TiO2-550 catalyst (without adding commonly used Pt as co-catalyst) remarkably enhanced photocatalytic H2 generation (201 µmol h-1 g-1), which was about 12-fold to that of P25. The AR-TiO2-550 heterophase junction also showed long-term stability under simulated solar light irradiation. This research provides a new phase engineering route for developing high-efficient photocatalysts.

[Prenatal diagnosis of a fetus in a family with mandibulofacial dysostosis].

OBJECTIVE: To measure the feasibility of application of comparative genomic hybridization technique in the prenatal diagnosis of fetus with mandibulofacial dysostosis. METHODS: A pregnant woman having a fetus with mandibulofacial dysostosis diagnosed by prenatal ultrasound test was selected. The amniotic fluid and blood of the pregnant and blood of her husband were collected and conventional cytogenetic analysis was performed. The whole genome was scanned by array comparative genomic hybridization assay (array-CGH). Reverse transcription fluorescence quantitative PCR (RT-qPCR) analysis was used to verify the result of array-CGH. RESULTS: No abnormality was found in conventional cytogenetic analysis while a duplicated region in 1p36.33 was detected by array-CGH assay. The region spans 722 kb and contains two genes, VWA1 and PYGO2, which play roles in the development of cartilage. The result of array-CGH was confirmed by the RT-qPCR assay. The diagnosis of mandibulofacial dysostosis was confirmed after birth. CONCLUSION: Author diagnosed a fetus with mandibulofacial dysostosis by array-CGH assay and found two candidate genes related to the development of craniofacial bone: VWA1 and PYGO2.

Influence of Single/Collective Use of Curing Agents on the Curing Behavior and Bond Strength of Soy Protein-Melamine-Urea-Formaldehyde (SMUF) Resin for Plywood Assembly.

Soybean protein hydrolysate, melamine, urea, and concentrated formaldehyde were used to synthesize an environmentally friendly soybean protein-melamine-urea-formaldehyde (SMUF) co-condensation resin. (NH4)2SO4, (NH4)2HPO4, (NH4)2HPO4 + (NH4)2SO4, (NH4)2HPO4 + (NH4)2S2O8, and (NH4)2HPO4 + (NH4)2SO4 + (NH4)2S2O8 were employed as curing agents for SMUF resin. The curing and thermal behaviors of the SMUF resin were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results revealed the following: (1) (NH4)2SO4 alone could not cure the SMUF resin completely; thus, the final shear strength accomplished plywood with the resin was low, and its water resistance was poor, while the adhesive section was loose and porous/brittle after curing. (2) (NH4)2HPO4 could be hydrolyzed to generate H+ and promote SMUF curing, but it could also form polyphosphoric acids, resulting in crosslinking reactions with SMUF in parallel; thereby, the curing properties were improved. (3) When (NH4)2HPO4 + (NH4)2SO4 + (NH4)2S2O8 were engaged collectively as curing agent, the shear strength, water resistance, and heat resistance of SMUF attained were the best possible whereas the curing temperature was decreased and the heat released by curing was elevated substantially, which signifies maximized extent of crosslinking was achieved. Further, the adhesive section exhibited mostly a crosslinking intertexture as demonstrated by means of SEM. Accordingly, this study may serve as a guide for the curing of amino resins, with low-molar ratio of formaldehyde to amine in adhesives, which are applied to plywood production.