Xinliang Li,Guancheng Jiang,Xiulun Shen,Gongrang Li
The hydration and swelling of shale formations are serious problems for well drilling. The use of an efficient shale inhibitor is one of the most important methods for overcoming the wellbore instability issue. In this work, poly-l-arginine (PArg) was synthesized and used as an efficient and biodegradable shale inhibitor. This inhibitor was systematically evaluated through measuring the swelling degree of the bentonite (Bent) pellet, the rheological behavior of the Bent suspensions, and the recovery percentage of shale cuttings. The results demonstrated that 2.0 wt % PArg could reduce the swelling degree of Bent to 70.53%, improve the shale recovery percentage to 71.40% at 180 °C, and inhibit 12.0 wt % Bent mud-making. The PArg displayed a highly inhibitive performance and excellent high-temperature resistance property, better than common inorganic KCl and organic polyether diamine. The underlying inhibition mechanism was also proposed based on measuring the variation of the interlayer spacing of the Bent, observing the exterior morphologies of Bent particles, and assessing the particle size distribution and electrokinetic potential. The results indicated that the PArg displayed its inhibitive effect mainly by adsorbing onto the Bent, encapsulating the Bent particles efficiently, and decreasing the interlayer spacing in a certain degree with 0.9 Å. This study can contribute to designing highly inhibitive water-based drilling fluids containing PArg.
A novel P-N containing hyperbranched poly(phosphorodiamidate) (HBPPDA) was synthesized by the A 2 +B 3 polymerization, which had high thermal stability, with greater than 40 wt% of the char residue left at 750 °C. The benzene and triazine rings in HBPPDA contributed to a good char-forming capacity. Furthermore, a large number of terminal primary amines could release incombustible gases to dilute the concentration of oxygen. Thus, HBPPDA could act as blowing agent and carbonization agent simultaneously. Only 6.25 wt% of HBPPDA could greatly enhance the flame-retarding efficiency of ammonium polyphosphate (APP), showing a remarkable synergy to improve flame retardancy and dripping resistance of polypropylene (PP). When 25 wt% of flame retardant (APP:HBPPDA = 3:1) were added into PP matrix, the composite achieved V0 rating for UL-94 test, and its limiting oxygen index (LOI) value was increased to 30.6%. The reduction of 76.2% and 41.5% were available for the peak heat release rate (PHRR) and the total heat release (THR). Meanwhile, the composite showed strong smoke suppression.
Shizhen Jia,Hui Cao,Xiangchao Liang,Shuang Wu,Rong Zeng,Mei Tu
Medical sponges are widely used in wound management, however the adhesion of bacterial or wound tissue to them may cause infection or secondary damage to patients. In this work, anti-bioadhesive polyvinyl alcohol-formaldehyde sponges with zwitterionic coating were prepared by the dip-coating process using the reactive zwitterionic phosphorylcholineated polyvinylamine (PVAm-PC) and commercial silane coupling agent KH560 at different mass ratios, and their structure, physicochemical, biocompatible and anti-bioadhesive properties were investigated. As compared to pristine sponges, the PVAm-PC-KH560 (PPK) modified sponges with the interconnected pore structure had almost unchanged water vapor transmission rate but decreased swelling degree to a certain extent possibly due to the formation of rigid Si– O –Si networks in the sponges. In vitro biological evaluation confirmed that PVAm-PC-KH560 modified sponges were not cytotoxic and had good resistance to bacteria adhesion with only ∼16% and ∼11% relative bacterial adhesion rate for E. coli and S. aureus respectively. And the optimized PPK-2 sponge showed the best comprehensive bacterial adhesion inhibition properties. Further adhesion assay of L929 fibroblasts showed that PPK-2 sponge could significantly reduce the adhesion of L929 fibroblasts. The results strongly suggested that dip-coating with zwitterionic PVAm-PC and KH560 may provide a promising and facile method to construct an anti-bioadhesive surface for biomedical applications.
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