Preparation of ultra‐high‐molecular‐weight polyacrylamide by vertical solution polymerization technique

Fabrication of flexible accelerated-wound-healing chitosan/dopamine-based bilayer hydrogels for strain sensors

Flexible conductive hydrogels have great potential for healthcare and human motion sensing. However, it is difficult to simultaneously achieve conductive hydrogel epidermal sensors with reliable adhesion capabilities and excellent sensing properties, as well as accelerated wound healing performance in wearable hydrogels. Here, an epidermal sensor with excellent adhesion (0.6 kPa) and tensile strain (218.0 %) properties was assembled from an easy-to-prepare bilayer antimicrobial hydrogel, which effectively accelerates wound healing, as well as for human motion sensing. The upper hydrogel layer was composed of PVA, which could effectively enhance the mechanical properties of the bilayer hydrogel. The lower hydrogel layer consisted of polyacrylamide (PAm) and chitosan-dopamine (CC-DA). PAm with good adhesion properties adhered effectively to the skin surface. CC-DA not only had adhesion properties, but also has good antibacterial effects. It inhibited the growth of bacteria, which assisted in wound healing and infection prevention. Therefore, the design of the bilayer hydrogel combined the mechanical enhancement of PVA with the adhesion properties and antimicrobial effect of PAm and CC-DA to provide better wound repair. In addition, the double-layer hydrogel with good electrical conductivity (1.65 S·m-1) could sensitively monitor the tiny electrophysiological signals emitted by the human body during exercise rehabilitation training.

Hydrophobically Associating Polymers Dissolved in Seawater for Enhanced Oil Recovery of Bohai Offshore Oilfields

As compared to China’s overall oil reserves, the reserve share of offshore oilfields is rather significant. However, offshore oilfield circumstances for enhanced oil recovery (EOR) include not just severe temperatures and salinity, but also restricted space on offshore platforms. This harsh oil production environment requires polymers with relatively strong salt resistance, solubility, thickening ability, rapid, superior injection capabilities, and anti-shearing ability. As a result, research into polymers with high viscosity and quick solubility is recognized as critical to meeting the criteria of polymer flooding in offshore oil reservoirs. For the above purposes, a novel hydrophobically associating polymer (HAP) was prepared to be used for polymer flooding of Bohai offshore oilfields. The synthetic procedure was free radical polymerization in aqueous solutions starting at 0 °C, using acrylamide (AM), acrylic acid (AA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and poly(ethylene glycol) octadecyl methacrylate (POM) as comonomers. It was discovered that under ideal conditions, the molecular weight of HAP exceeds 2.1 × 10⁷ g⋅mol⁻¹. In a simulated reservoir environment, HAP has substantially greater solubility, thickening property, and salt resistance than conventional polyacrylamide (HPAM), with equivalent molecular weight. Finally, the injectivity and propagation of the two polymers in porous media were investigated. Compared with HPAM, which has a similar molecular weight, HAP solution with the concentration of 0.175% had a much better oil displacement effect in the porous medium, which can enhance oil recovery by 8.8%. These discoveries have the potential to pave the way for chemical EOR in offshore oilfields.

A pH-sensitive W/O emulsion for the preparation and rapid dissolution of polyacrylamide-based friction reducer

The pH-sensitive modified-polyacrylamide emulsion shows a fast dissolution rate with a dissolution time of about 1 min and long storage stability.

Dynamic floc characteristics of flocculated coal slime water under different agent conditions using particle vision and measurement

To determine the effect of different agents on the dynamic characteristics of floc structures, ferric chloride (FC) and anionic polyacrylamide (APAM) were dosed as coagulant and flocculant, respectively, to flocculate the coal slime water. Particle vision and measurement (PVM) was employed to monitor the flocculation process in situ. The results showed that the floc could grow to a size of approximately 1 mm only under conditions of 100 mg/L FC and 50 mg/L APAM. The coagulant dosage influenced either the aggregation of the slime particles or the conformation of the flocculant. If the coagulants were insufficient or excessive, the flocculant conformations were stretch chains and resembled unable to bridging the slime particles as shown in the captured images. The variation of the relative backscatter index (RBI) during the process indicated that the required residence time for flocculation was proportional to the ratio of particle size at the end of flocculation to that at the beginning of the process. It can be concluded that PVM is an effective instrument that can obtain useful dynamic information of the flocculation process by combining real-time images and the RBI. PRACTITIONER POINTS: The coagulant concentration affects the conformation of the flocculant. The required retention time is depended on the max size that flocs can reach. PVM is a powerful instrument for studying dynamic flocculation process in situ.