Preparation of High-Performance Composite Hydrogel Reinforced by Hydrophilic Modified Waste Rubber Powder.

In order to reduce the environmental pollution caused by waste rubber and to realize the recycling of resources, we proposed a facile method for the hydrophilic modification of waste rubber powder (HRP) and used it to reinforce a composite hydrogel. In the presence of toluene, dibenzoyl peroxide (BPO) diffused into the waste rubber powder. After the solvent was removed, BPO was adsorbed in the rubber powder, which was used to initiate the grafting polymerization of the acrylamide monomer on the rubber-water interface. As a result, the polyacrylamide (PAM) molecular chains were grafted onto the surface of the rubber powder to realize hydrophilic modification. The success of the grafting modification was confirmed by FTIR, contact angle testing, and thermogravimetric analysis. The hydrophilic modified waste rubber powder was used to reinforce the PAM hydrogel. Mechanical tests showed that the tensile strength and elongation at the break of the composite hydrogel reached 0.46 MPa and 1809%, respectively, which was much higher than those of pure PAM hydrogel. Such a phenomenon indicates that the waste rubber particles had a strengthening effect.

TEMPO oxidized cellulose nanofiber-reinforced sodium alginate encapsulated poly(acrylamide) microcapsules and its releasing behaviours for enhancing oil recovery.

Poly(acrylamide) (PAM) has excellent thickening ability as a conventional flooding agent. However, PAM confronts the problems of high injection pressure and high shear loss in the process of oil extraction, which have limited its application in this field. In this work, 2, 2, 6, 6-Tetramethylpiperidinooxy oxidized cellulose nanofibers (TOCNFs) enhanced sodium alginate (SA) shell was used to encapsulate PAM to form microcapsule. The composition, morphology, structure and the releasing behaviours of TOCNFs enhanced microcapsules was tested. Mechanical stirring was used to simulate the state of polymer subjected to shear during stratigraphic transport. The release performance of the microcapsules was characterized by measuring the change of viscosity with time. The ratio of the shell material with the best performance was explored, and the enhancement mechanism of the SA shell by TOCNFs was discussed. The experiments showed that the release time of PAM from the microcapsules was significantly prolonged with the addition of TOCNFs. The longest release time was observed when the ratio of SA and TOCNFs was 5: 1, with the release time of the microcapsules from the original 8 h to 16 h. The enhanced shear resistance of the microcapsules was attributed to the semi-interpenetrating network structure of SA and TOCNFs via Ca2+ cross-linking as well as hydrogen bonding. The prepared microcapsules have promising applications in enhancing oil recovery.

Tough chitosan/poly(acrylamide-acrylic acid)/cellulose nanofibrils/ethylene glycol nanocomposite organohydrogel with tolerance to hot and cold environments.

Simultaneously achieving good mechanical properties and high tolerance to hot and cold environments in hydrogel materials remains a challenge. In this work, ethylene glycol (EG) and cellulose nanofibrils (CNFs) were introduced into chitosan/poly(acrylamide-acrylic acid) double-network hydrogels to improve their toughness and tolerance to hot and cold environments. The effect of EG and CNFs on the properties of the hydrogels was studied respectively. EG increases the tolerance of the hydrogel to hot and cold environments. However, EG had a negative effect on the mechanical properties of hydrogels. In addition, CNFs substantially enhanced the strength and toughness of the chitosan/poly(acrylamide-acrylic acid)/EG organohydrogels. Finally, with the cooperative action of EG and CNFs, high-strength and tough organohydrogels (tensile strength = 0.71 MPa, elongation at break = 787.2%) with a high tolerance to hot and cold environments (-23 °C to 60 °C) were obtained. Further, EG enabled the organohydrogel to revert to its original state after drying at 60 °C. This paper provides a new route to prepare high-strength and tough organohydrogels with a high tolerance to hot and cold environments.

Evaluation of early macrophage activation and NF-kappaB activity in pulmonary injury caused by deep hypothermia circulatory arrest: an experimental study.

This study aimed to analyze changes in nuclear factor-kappa B (NF-kappaB), inflammation factors, and macrophages in pulmonary tissue under deep hypothermia circulatory arrest (DHCA) at different time points, which can be used to infer the role of early macrophage activation and NF-kappaB activity in pulmonary injury. The possible pathogenic mechanisms of DHCA-induced pulmonary injury were investigated in this study to provide an experimental basis for clinical lung protective strategies. Piglets (n = 12) were randomly divided into 2 groups, with 6 piglets in each group. The control group had ambient temperature cardiopulmonary bypass (CPB), and the experimental group had DHCA. Both groups had conventional CPB with 30 min of parallel circulation. Changes in NF-kappaB and inflammatory factors were examined in each group at 6 different time points. At 0.5 h after ischemia-reperfusion, NF-kappaB expression in the nucleus of pulmonary tissue reached its peak, and brown-stained nuclei were mainly polymorphonuclear antibodies. At 1 h after ischemia-reperfusion, plasma tumor-necrosis factor (TNF)-alpha in the experimental group was significantly increased compared with that before reperfusion (P < 0.05). The plasma levels of interleukin (IL)-8 and IL-6 in the experimental group were significantly increased at 1.5 h after ischemia-reperfusion compared with the levels before reperfusion (P < 0.05). Early activation of NF-kappaB under DHCA might play an important role in DHCA-induced pulmonary injury.

Stability, seepage and displacement characteristics of heterogeneous branched-preformed particle gels for enhanced oil recovery.

Inspired by the viscoelastic displacement theory and the advantages of preformed particle gels, we develop an innovative product called branched-preformed particle gel (B-PPG) for enhanced oil recovery. Due to its excellent viscoelastic properties, B-PPG can be used both in profile control and to improve sweep efficiency in heterogeneous reservoirs. Laboratory experiments indicate that B-PPG shows improved stability and long-term aging resistance under high temperature and salinity when compared with HPAM. The migration and displacement behaviors of B-PPG are studied by a series of sandpack core flow experiments. The results show that the B-PPG particles can migrate through the porous media, and the migration is a dynamic process of plugging and flooding. Besides, B-PPG can significantly create fluid diversion and increase the swept volume in low permeability zones. Moreover, micro visualization and oil displacement experiments are also carried out and prove that B-PPG can displace residual oil in small channels, leading to a high swept volume and enhanced displacement efficiency.

[Tissue-engineered graft constructed by bone marrow mononuclear cells and heterogeneous acellularized tissue matrix: an animal experiment].

OBJECTIVE: To construct a tissue-engineered graft by using bone marrow cells as seeding cells and heterogeneous acellularized matrix as scaffold. METHODS: Mononuclear cells were isolated from the bone marrow from piglets and cultured in different mediums including either vessel endothelial growth factor (VEGF) or platelet derived growth factor BB (PDGF-BB) to observe the differentiation of cells. Immunoassay was used to detect the expression of specific markers of endothelial cells or specific markers of smooth muscle cells. Adult dogs were killed and their thoracic or abdominal aortas were taken out and processed by multi-step decellularizing technique to remove the original cells while the elastic and collagen fibers were preserved. The undifferentiated bone marrow mononuclear cells were seeded onto the acellularized matrix and incubated in vitro. The cell-seeded grafts were then transplanted to the bone marrow donating piglets to substitute part of the native pulmonary artery. Three weeks later right ventriculography was performed. 100 days later the piglets were sacrificed. The transplanted vessels and the nearby tissues of native pulmonary vessels were excised for inspection. RESULTS: The mononuclear cells cultured in the medium including VEGF showed the morphological features of endothelial cells and were positive of the specific markers of endothelial cells: platelet-endothelial cell adhesion molecule-l, vascular endothelial growth factor receptor Flk-1, VE-cadherin, and plasma factor VIII. The cells cultured in the medium including PDGF-BB showed morphological feature of smooth muscle cells and were positive of he specific marks of smooth muscle cells: alpha-SMA and calponin. One hundred days after transplantation, the inner surfaces of the grafts were smooth without thrombosis, calcification, and aneurysm. The maximal load was 2.76 N and the maximal elongation was 20.31 mm. Under the microscopy a great number of growing endothelial cells and smooth muscle cells could be seen and elastic and collagen fibers were abundant. CONCLUSION: The mononuclear cells from bone marrow and acellularized matrix may be used to construct tissue-engineered graft.

[Simulation research of extracorporeal circulation reflux control method].

Using engineering fluid dynamics (EFD) softwares,we conducted a study on the simulation of flow field in vessel which was partially blocked by a clamp. The flow field of the partial block vessel was studied once more in real vessel when methylene blue as a marker was injected into the vessel. The change in the characteristics of blood flow was observed by way of computer imitation and methylene blue show. It was found that some defect might appear in the conventional method which partially blocked the vein.

[Research on the feasibility of a magnetic-coupling-driven axial flow blood pump].

A new-designed axial flow blood pump, dived by magnetic coupling and using internal hollow brushless DC motor and inlet and outlet in line with impeller, was tested in mimic circuit. The results showed good performance of the new pump and indicated that its hydrodynamic characteristic can meet the demands of clinical extracorporeal circulation and auxiliary circulation.