Influence of the Epoxy/Acid Stoichiometry on the Cure Behavior and Mechanical Properties of Epoxy Vitrimers.

Bisphenol A epoxy resin cured with a mixture of dimerized and trimerized fatty acids is the first epoxy vitrimer and has been extensively studied. However, the cure behavior and thermal and mechanical properties of this epoxy vitrimer depend on the epoxy/acid stoichiometry. To address these issues, epoxy vitrimers with three epoxy/acid stoichiometries (9:11, 1:1 and 11:9) were prepared and recycled four times. Differential scanning calorimetry (DSC) was used to study the cure behavior of the original epoxy vitrimers. The dynamic mechanical properties and mechanical performance of the original and recycled epoxy vitrimers were investigated by using dynamic mechanical analysis (DMA) and a universal testing machine. Furthermore, the reaction mechanism of epoxy vitrimer with different epoxy/acid stoichiometry was interpreted. With an increase in the epoxy/acid ratio, the reaction rate, swelling ratio, glass transition temperature and mechanical properties of the original epoxy vitrimers decreased, whereas the gel content increased. The recycling decreased the swelling ratio and elongation at break of the original epoxy vitrimers. Moreover, the elongation at break of the recycled epoxy vitrimers decreased with the epoxy/acid ratio at the same recycling time. However, the gel content, tensile strength and toughness of the original epoxy vitrimers increased after the recycling. The mechanical properties of epoxy vitrimers can be tuned with the variation in the epoxy/acid stoichiometry.

Waste Cooking Oil-Modified Epoxy Asphalt Rubber Binders with Improved Compatibility and Extended Allowable Construction Time.

The application of crumb rubber from end-of-life tires and waste cooking oil (WCO) in road pavements is of significant importance from an economic and environmental viewpoint. However, the incorporation of crumb rubber greatly shortens the allowable construction time of epoxy asphalt binders due to the high viscosity of the epoxy asphalt rubber (EAR) binder and poor compatibility between crumb rubber and asphalt binder. To lower the viscosity of asphalt rubber, extend the allowable construction time and improve the compatibility of EAR binder, waste cooking oil (WCO) was introduced. The effect of WCO on the viscosity-time behavior, thermal stability, dynamic modulus, glass transitions, crosslink density, damping ability, compatibility, mechanical properties and phase separation of WCO-modified EAR binders was investigated by using the Brookfield viscometer, thermogravimetric analysis, dynamic mechanical analysis, universal testing machine and laser confocal microscopy. The test results demonstrated that the incorporation of WCO declined the viscosity and extended the allowable construction time of the unmodified EAR binder. The inclusion of WCO improved the compatibility between asphalt and crumb rubber and the damping ability and elongation at the break of the unmodified EAR binder. The presence of WCO had a marginal effect on the thermal stability of the unmodified EAR binder. Confocal microscopy observation revealed that asphalt rubber particles aggregated in the epoxy phase of the unmodified EAR binder. With the inclusion of WCO, co-continuous asphalt rubber particles became more spherical.

Enhancement of Bonding and Mechanical Performance of Epoxy Asphalt Bond Coats with Graphene Nanoplatelets.

Improving bonding and mechanical strengths is important for the application of bond coats used in the construction of steel deck bridges. Graphene nanoplatelets (GNPs) are attractive nanofillers for polymer modification because of their low cost, ultra-high aspect ratio, and extraordinary thermal and mechanical performance. In this paper, GNPs were used to reinforce the epoxy asphalt bond coat (EABC). The morphology, viscosity-time behavior, contact angle, dynamic mechanical properties, and mechanical and bonding strengths of GNP-reinforced EABCs were investigated using laser confocal microscopy, a Brookfield rotational viscometer, a contact angle meter, dynamic mechanical analysis, a universal test machine, and single-lap shear and pull-off adhesion tests. GNP dispersed non-uniformly in the asphalt phase of EABC. The viscosity of the neat EABC was lowered with the inclusion of GNPs and thus the allowable construction time was extended. The existence of GNPs enhances the hydrophobicity of the neat EABC. When adding more than 0.2% GNP, the storage modulus, crosslinking density and glass transition temperatures of both asphalt and epoxy of the neat EABC increased. The mechanical and bonding properties of the neat EABC were greatly enhanced with the incorporation of GNPs. Furthermore, the mechanical and bonding strengths of the modified EABCs increased with the GNP content. GNP-reinforced EABCs can be utilized in the pavement of long-span steel bridges with long durability.

Graphene Oxide-Modified Epoxy Asphalt Bond Coats with Enhanced Bonding Properties.

The bonding strength of the bond coat plays an important role in the composite action between the wearing surface and the deck plate of the orthotropic steel deck system. Poor bonding results in the delamination of the wearing surface from the deck plate. Graphene oxide (GO) possesses outstanding mechanical and thermal properties, as well as impressive multifunctional groups, which makes it an ideal reinforcement candidate for polymer matrices. In this study, graphene oxide was used to improve the bonding strength and toughness of the epoxy asphalt bond coat (EABC). The dispersion, hydrophobicity, viscosity-time behavior, phase-separated morphology, dynamic mechanical properties, pull-off strength, shear strength and mechanical performance of GO-modified EABCs were investigated using various techniques. The inclusion of GO improved the hydrophobicity of the unmodified EABC. The viscosity of the unmodified EABC was lowered with the addition of GO during curing. Moreover, the allowable construction time for the modified EABCs was extended with the GO loading. The incorporation of GO enhanced the stiffness of the unmodified EABC in the glassy and rubbery states. However, graphene oxide lowered the glass transition temperature of the asphalt of the unmodified EABC. Confocal microscopy observations revealed that GO was invisible in both the asphalt and epoxy phases of the EABC. The inclusion of GO improved the bonding strength, particularly at 60 °C, and mechanical properties of the unmodified EABC.

Designing Self-Sustainable Icephobic Layer by Introducing a Lubricating Un-Freezable Water Hydrogel from Sodium Polyacrylate on the Polyolefin Surface.

A convenient, environment-friendly, and cost-effective method to keep anti-icing for a long time was highly desirable. Slippery lubricant layers were regarded to be effective and promising for anti-icing on different surfaces, but the drought-out of lubricants and the possible detriments to the environment were inevitable. By combining super-high molecular weight sodium polyacrylate (H-PAAS) with polyolefin through a one-pot method, a self-sustainable lubricating layer with extremely low ice adhesion of un-freezable water hydrogel was achieved at subzero conditions. The lubricant hydrogel layer could auto-spread and cover the surface of polyolefin after encountering supercooled water, frost, or ice. Due to the reduction of storage modulus in the interface, the ice adhesion of the specimen surfaces was far below 20 kPa, varying from 5.13 kPa to 18.95 kPa. Furthermore, the surfaces could preserve the fairly low adhesion after icing/de-icing cycles for over 15 times and thus exhibited sustainable durability. More importantly, this method could be introducing to various polymers and is of great promise for practical applications.

Evidence summary for nonsurgical prevention and management of parastomal hernia in patients with enterostomy.

OBJECTIVE: To select and obtain the best evidence for parastomal hernia (PH) prevention in patients with enterostomy so as to provide reference for clinical practice to decrease the rate of PH. METHODS: Based on the method of evidence-based nursing, this paper proposes the prevention and management of PH in patients with enterostomy. The literature was checked according to the "6S" model, and literature evaluation standards (2016 edition) of JBI Evidence-based Health Care Center in Australia were adopted to evaluate the literature quality and evidence level of various studies. RESULTS: Combined with the judgment of professionals, 24 pieces of relevant evidence from 7 dimensions were summarized, including related controllable risk factors, diagnosis and identification, nutrition, the strength of abdominal wall muscle around the stoma, reduction of abdominal pressure, the use of belt on treatment of PH, and the prevention of complications related to PH. CONCLUSIONS: This study summarized the best evidence of nonsurgical prevention and management of PH in patients with enterostomy, and provided an evidence-based basis for nurses to carry out clinical work, so as to use scientific methods to manage and prevent the occurrence of PH in patients with enterostomy and improve the quality of care.

Reinforcement of Castor Oil-Based Polyurethane with Surface Modification of Attapulgite.

Polyurethane/attapulgite (PU/ATT) nanocomposites derived from castor oil were prepared by incorporation of 8 wt % ATT, acid-treated ATT, and KH560-treated ATT. The effects of three ATTs (ATT, acid-ATT, and KH560-ATT) on the comprehensive properties of PU/ATT nanocomposites were systematically investigated. The results showed that the incorporation of 8 wt % of three ATTs could produce an obvious reinforcement on the castor oil-based PU and that the silane modification treatment, rather than the acid treatment, has the more effective reinforcement effect. SEM images revealed the uniform dispersion of ATT in the PU matrix. DMA confirmed that the storage modulus and glass transition temperature (Tg) of PU/ATT nanocomposites were significantly increased after blending with different ATTs. For PU/KH560-ATT8 nanocomposites, the thermal stability of the PU was obviously enhanced by the addition of KH560-ATT. In particular, 8 wt % KH560-ATT loaded castor oil-based PU nanocomposites exhibit an obvious improvement in tensile strength (255%), Young's modulus (200%), Tg (5.1 °C), the storage modulus at 25 °C (104%), and the initial decomposition temperature (7.7 °C). The prepared bio-based PU materials could be a potential candidate to replace petroleum-based PU products in practical applications.

Translation Initiation Factor eIF4E and eIFiso4E Are Both Required for Peanut stripe virus Infection in Peanut (Arachis hypogaea L.).

Peanut stripe virus (PStV) belongs to the genus Potyvirus and is the most important viral pathogen of cultivated peanut (Arachis hypogaea L.). The eukaryotic translation initiation factor, eIF4E, and its isoform, eIF(iso)4E, play key roles during virus infection in plants, particularly Potyvirus. In the present study, we cloned the eIF4E and eIF(iso)4E homologs in peanut and named these as PeaeIF4E and PeaeIF(iso)4E, respectively. Quantitative real-time PCR (qRT-PCR) analysis showed that these two genes were expressed during all growth periods and in all peanut organs, but were especially abundant in young leaves and roots. These also had similar expression levels. Yeast two-hybrid analysis showed that PStV multifunctional helper component proteinase (HC-Pro) and viral protein genome-linked (VPg) both interacted with PeaeIF4E and PeaeIF(iso)4E. Bimolecular fluorescence complementation assay showed that there was an interaction between HC-Pro and PeaeIF4E/PeaeIF(iso)4E in the cytoplasm and between VPg and PeaeIF4E/PeaeIF(iso)4E in the nucleus. Silencing either PeaeIF4E or PeaeIF(iso)4E using a virus-induced gene silencing system did not significantly affect PStV accumulation. However, silencing both PeaeIF4E and PeaeIF(iso)4E genes significantly weakened PStV accumulation. The findings of the present study suggest that PeaeIF4E and PeaeIF(iso)4E play important roles in the PStV infection cycle and may potentially contribute to PStV resistance.

A multi-needle-assisted transformation of soybean cotyledonary node cells.

A new and simple method for wounding cotyledonary node cells of soybean [Glycine max (L) Merrill] was developed for obtaining a high frequency of transformants. Soybean seeds were germinated for 1 day, and the cotyledonary node cells of half-seeds were wounded mechanically by using a multi-needle consisting of thin 30 fibers. The wounded half-seeds were inoculated with Agrobacterium tumefaciens cells harboring a recombinant DNA that contained the bar and sgfp genes conferring phosphinothricin (PPT)-resistance and green fluorescent protein (GFP) activity, respectively. The inoculated explants were selected on medium containing 5 or 3 mg PPT/l. The transformation efficiency of soybean was up to 12%. Polymerase chain reaction and genomic Southern blot analysis confirmed stable integration of the transgenes in the genome of the PPT-resistant plants. GFP analysis revealed that the transgenes were highly expressed in the plantlets. Adult plants were resistant to 100 mg PPT/l applied on the leaves, demonstrating their herbicide-resistance.