Polycaprolactone strengthening keratin/bioactive glass composite scaffolds with double cross-linking networks for potential application in bone repair

In this study, we aimed at constructing polycaprolactone (PCL) reinforced keratin/bioactive glass composite scaffolds with a double cross-linking network structure for potential bone repair application. Thus, the PCL-keratin-BG composite scaffold was prepared by using keratin extracted from wool as main organic component and bioactive glass (BG) as main inorganic component, through both cross-linking systems, such as the thiol-ene click reaction between abundant sulfhydryl groups of keratin and the unsaturated double bond of 3-methacryloxy propyltrimethoxy silane (MPTS), and the amino-epoxy reaction between amino groups of keratin and the epoxy group in (3-glycidoxymethyl) methyldiethoxysilane (GPTMS) molecule, along with introduction of PCL as a reinforcing agent. The success of the thiol-ene reaction was verified by the FTIR and 1H-NMR analyses. And the structure of keratin-BG and PCL-keratin-BG composite scaffolds were studied and compared by the FTIR and XRD characterization, which indicated the successful preparation of the PCL-keratin-BG composite scaffold. In addition, the SEM observation, and contact angle and water absorption rate measurements demonstrated that the PCL-keratin-BG composite scaffold has interconnected porous structure, appropriate pore size and good hydrophilicity, which is helpful to cell adhesion, differentiation and proliferation. Importantly, compression experiments showed that, when compared with the keratin-BG composite scaffold, the PCL-keratin-BG composite scaffold increased greatly from 0.91 ± 0.06 MPa and 7.25 ± 1.7 MPa to 1.58 ± 0.21 MPa and 14.14 ± 1.95 MPa, respectively, which suggesting the strong reinforcement of polycaprolactone. In addition, the biomineralization experiment and MTT assay indicated that the PCL-keratin-BG scaffold has good mineralization ability and no-cytotoxicity, which can promote cell adhesion, proliferation and growth. Therefore, the results suggested that the PCL-keratin-BG composite scaffold has the potential as a candidate for application in bone regeneration field. Graphical Abstract

Effect of interaction from the reaction of carboxyl/epoxy hyperbranched polyesters on properties of feedstocks for metal injection molding

The purpose of this study is to improve the properties of the feedstocks and shape retention of debinded parts by the reaction between 17-4PH stainless steel powders. Carboxyl-terminated hyperbranched polyester (CTHP) and epoxy-terminated hyperbranched polyester (ETHP) were used to treat the powders, and termed as CTHP-m and ETHP-m with carboxyl and epoxy group, respectively. Comparing with pristine, CTHP-m and ETHP-m, feedstock prepared from equal amount of CTHP-m and ETHP-m (CTHP-m/ETHP-m) possessed more excellent properties. The experimental results showed that the critical solids loading, flexural modulus, density and melt flow index of CTHP-m/ETHP-m feedstock were 63.8 vol.%, 2800 Mpa, 5.06 g/cm3 and 62 g/10min, respectively, which were obviously higher than that of others. Also, the shape retention of CTHP-m/ETHP-m debinded parts was the best of all the samples. The improved properties of CTHP-m/ETHP-m feedstock were attributed to the powder interaction between CTHP-m and ETHP-m formed by the chemical reaction between epoxy and carboxyl group.

Synthesis and Evaluation of Acridone and Xanthone Epoxides with Anti-MRSA and Anti-MSSA Activity

A series of acridone and xanthone-based compounds bearing 1,2-epoxypropyl or 1,2-propanediol substituents were synthesized and evaluated for activity against MRSA and MSSA bacterial strains. The results indicate a correlation exists between the number of epoxide groups and activity, with peak MIC values observed for bis-epoxy derivatives. Both activity and heathy cell toxicity was shown to decrease with the addition of a third epoxy group. The corresponding ring-opened diol analogs were devoid of activity, demonstrating the critical function of the epoxide in mediating antimicrobial activity. The most active compounds were also screened using a regulated antisense RNA expression library. The results show no increase in activity against cells sensitized by down-regulation of the most common drug targets, including DNA gyrase, DNA topoisomerase, tRNA synthetase, and the fatty acid biosynthesis pathway. The compounds are postulated to function as membrane disrupting agents, similar to the xanthone natural product α-mangostin.

A Novel Epoxy Resin Composition as a Lost Circulation Material: Formulation, Lab Testing and Field Execution

The novel resin composition described in this paper has been designed to treat moderate to severe losses. The resin composition comprises an epoxy resin and a chemical activator that undergo a polymerization reaction without any addition of water. The polymerization was designed to delay and successfully controlled to gel up and form the target resin composition after the fluid goes inside the wellbore. This is very important to avoid early setting of the fluid. The objective of this paper is to discuss the formulation of epoxy resin as a lost circulation material and also detail the lab testing and field execution. In this study, we used two different epoxy resins to study the development of the novel loss circulation material. One contains two epoxy groups and the other contains only one epoxy group. Two different chemical activators have been used in this study as well; each of them differs in the number of amine groups and geometry. The effect of these differences on the polymerization in terms of time and properties were investigated. In addition, the effect of the chemical activator concertation on the setting time of the resin composition was investigated to accomplish a controlled and a delayed polymerization. Also, the chemical conditions were evaluated to simulate a variety of downhole conditions to prove the effectiveness of this novel resin composition as a loss circulation treatment. The lab testing includes thickening time measurements. The novel resin composition is designed to have a controlled thickening time under a variety of downhole conditions. This is important to have an accurate placement of the fluid inside the wellbore; thus, avoiding an early setting of the fluid. We found that the thickening time of the resin composition can be controlled by mainly varying the concertation of the chemical activator. We found as well that changing the type of epoxy resin or chemical activator produce different gelling time and properties. We designed the loss circulation composition to provide a predictable and controlled pumping time. This novel resin composition can remain in a liquid phase from a few minutes to several hours based on the desired conditions. This is favorable in order to have an accurate placement of the fluid inside the wellbore over a predictable and controlled period of time. The final and target resin composition, will appear and gel as a solid thereby preventing loss circulation. The resin was pumped from the BHA in a single stage which helped mitigate and reduce the dynamic losses from 260 bbl./hr. to 200 bbl./hr. using only 25 bbls and eventually to zero.

Internal Polymerization of Epoxy Group of Epoxidized Natural Rubber by Ferric Chloride and Formation of Strong Network Structure

In this work, studies are carried out to understand the crosslinking reaction of epoxidized natural rubber (50 mol% epoxy, ENR-50) by metal ion namely ferric ion (Fe3+, FeCl3, ferric chloride). It is found that a small amount of FeCl3 can cure ENR to a considerable extent. A direct interaction of the ferric ion with the epoxy group as well as internal polymerization enable the ENR to be cured in an efficient manner. It was also found that with the increased concentration of FeCl3, the crosslinking density of the matrix increased and therefore, the ENR offers higher mechanical properties (i.e., modulus and tensile strength). In addition, the glass transition temperature (tg) of ENR vulcanizate is increased with increasing concentration of FeCl3. Moreover, the thermal degradation temperature (Td) of the ENR-FeCl3 compound was shifted toward higher temperature as increasing concentration FeCl3.

Preparation of Ionic Conductivity Polymer Electrolyte Film Based on Epoxidized Deproteinized Natural Rubber

Ionic conductivity polymer electrolyte film based on epoxidized deproteinized natural rubber (EDPNR) and lithium salt lithium triflate (LiCF3SO3) were prepared by solution casting technique. The EDPNR was prepared from deproteinized natural rubber latex (DNR) epoxidized in the latex stage with fresh peracetic acid 33%, which was deproteinized by incubation of the latex with 0,1 wt% urea and 1 wt% surfactant. The ionic conductivity of EDPNR mixed with lithium salt was investigated through impedance analysis. The results show that the conductivity of EDPNR/ LiCF3SO3 mixture was dependent on LiCF3SO3 salt concentration and amount of epoxy group. The highest ionic conductivity at room temperature obtained is 1,71 x 10-5 S.cm-1 at 35 wt% LiCF3SO3 and 45 mol% epoxy groups. Fourier transform infrared spectroscopy (FTIR) spectra showed evidence of complexation between EDPNR and LiCF3SO3. Glass transition temperature, Tg displayed an increasing trend in which are the increase in salt concentration and the increase in epoxy group concentration.

Thermal Stability, Smoke Density, and Flame Retardance of Ecotype Bio-Based Flame Retardant Agricultural Waste Bagasse/Epoxy Composites

In the study, agricultural waste bagasse was used as a bio-based flame retardant for reducing the flammability of epoxy. Specifically, an interpenetrating network (IPN) was formed through a ring opening reaction between the hydroxyl functional group of bagasse and the epoxy group of triglycidyl isocyanurate (TGIC), forming Bagasse@TGIC. Next, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) was mixed with Bagasse@TGIC, inducing a reaction between the active hydrogen of DOPO and the epoxy group of TGIC, ultimately forming Bagasse@TGIC@DOPO with an IPN structure. Finally, the novel flame retardant was added to epoxy to create a composite. The integral procedural decomposition temperature (IPDT) of pure epoxy is 619 °C; after the introduction of the 30 wt% flame retardant, the IPDT of the resultant composite material increased to 799 °C, greatly increasing the thermal stability by 29%. After the addition of the Bagasse@TGIC@DOPO flame retardant, the limiting oxygen index increased from 21% for the pure epoxy to 29% for the composite, and the UL-94 rating improved from failing rating for the pure epoxy and V-0 rating for the composite. The Raman spectrum indicated that the addition of Bagasse@TGIC@DOPO IPN substantially increased the biochar yield during the burning process, increasing thermal stability. These results confirmed that the epoxy/Bagasse@TGIC@DOPO composite had substantial flame retarding effects.

An Efficient and Sustainable Approach to Prepare Carboxylated Cellulose Nanocrystals for Rubber Reinforcement Featuring Dual Crosslinking Networks

The surface functionalization of CNCs and the construction of strong interfacial adhesion between CNCs and rubber matrix are effective way to achieve high performance rubber/CNCs nanocomposites. Herein, carboxylation of sulphated cellulose nanocrystals (CNC-OSO3H) was conducted in aqueous medium by using citric acid as modifier. Large amount of carboxyl groups was successfully grafted on the surface of CNC-OSO3H, which endows the carboxylated CNC-OSO3H (abbreviate as CNC-CA) with higher chemical reactivity and thermal stability. Subsequently, carboxylated styrene butadiene rubber (XSBR)/CNC-CA nanocomposites with dual crosslinking design were prepared by using polyethylene glycol diglycidyl ether (PEGDE) as the crosslinking agent and CNC-CA as the reinforcing fillers. FTIR investigation found that in the obtained nanocomposites, the carboxyl groups on CNC-CA and XSBR formed hydrogen bonds (physical crosslinking) with each other, and the carboxyl groups formed covalent bond with the epoxy group on PEGDE simultaneously. The coexistence of physical and chemical crosslinking improved the interface compatibility between CNC-CA and XSBR matrix, accelerated the homogenous dispersion of CNC-CA and realized the crosslinking of the matrix itself. As expected, XSBR/CNC-CA nanocomposites with dual crosslinking network showed remarkable enhancement in tensile strength (up to 500%), modulus (up to 151%), work of fracture (up to 348%). This work provides both a facile and green approach to obtain carboxylated CNCs and a convenient method for the preparation of high-performance rubber nanocomposites with multiple interactions.

Combining Renewable Eleostearic Acid and Eugenol To Fabricate Sustainable Plasticizer and Its Effect of Plasticizing on PVC

The recent studies on sustainable plasticizer mainly focus on raw material source, synthesis method and plasticization, but the effect of chemical functional groups (epoxy group and ester group) of sustainable plasticizer on compatibility and thermal stability of plasticized polyvinyl chlorid (PVC) materials has been ignored. In this study, we synthesized two kinds of sustainable plasticizer, eleostearic acid eugenol ester(EAEE) and epoxidized EAEE. PVC films plasticized with EAEE were investigated and compared with epoxidized EAEE. PVC plasticized with epoxidized EAEE showed more flexible and thermal stability than EAEE. More hydrogen bonds were formed between PVC chains and epoxidized EAEE than that of PVC chains and EAEE, which caused the that epoxidized EAEE played more efficient plasticizing effect on PVC than EAEE. Epoxidized EAEE containing the flexible alkane chains and polar group (ester groups and epoxy groups) has stronger intermolecular interaction force than EAEE, causing homogeneous and smooth surface of plasticized PVC films.