Due to high viscosity of the ultra-high molecular weight polyethylene (UHMWPE), it is difficult for the melt UHMWPE to flow through the small aperture spinneret orifice in the melt spinning forming process. The geometrical parameters of the spinneret orifice become critical to the melt spinning process. Based on the theory of polymer rheology, the finite element model of UHMWPE melt spinning had been developed by using POLYFLOW, and the length-to-diameter ratio and taper angle of the spinneret orifice effects on the UHMWPE melt flow characters were discussed. The results show that suitable length-to-diameter ratio and taper angle are helpful for the compactness and flow stability of the melt.
Abstract The extremely low melt flowability of ultra‐high molecular weight polyethylene (UHMWPE) is the primary obstacle to its melt processing. Particularly in melt spinning processes, the extremely high molecular weight of UHMWPE and the density of entangled molecular chains severely limit its production efficiency and monofilament performance. This study investigates the effect of flow modifiers on the melt spinning process of UHMWPE/HDPE blends, focusing on CaSt 2 , PEG, and CaSt 2 /silicone powder composite additives, and their impact on the standard tensile samples and monofilament tensile properties of UHMWPE/HDPE. The mechanism of additive influence on the tensile properties of UHMWPE/HDPE blends is analyzed through tensile strength testing, thermal analysis, and microscopic morphology observation. The results show that in standard tensile samples, CaSt 2 or CaSt 2 /silicone powder composite additives can enhance the crystallinity of the blend, thereby improving its tensile strength. Conversely, adding PEG significantly reduces the crystallinity and tensile strength of the blend. The maximum tensile strength of CaSt 2 ‐modified UHMWPE/HDPE monofilament is 1236.61 MPa. This enhancement is attributed to the lubricating effect of CaSt 2 , which simultaneously assists the molecular chains in the amorphous region, and the reorientation of the stress‐induced molten lamellar structure under tension, greatly promoting the formation of straight‐chain crystals in the monofilament. During hot drawing, PEG inhibits the formation of straight‐chain crystals in the monofilament, resulting in a 3.06% decrease in maximum crystallinity compared with standard tensile samples. When CaSt 2 is combined with silicone powder, the additives tend to aggregate during hot drawing, and these larger aggregate particles hinder the orientation of molecular chains along the drawing direction, resulting in a 30.75% decrease in maximum tensile strength of the monofilament compared with the standard tensile samples. Highlights The tensile property of UHMWPE/HDPE blends modified with additives was discussed. Analytical techniques including DSC, SEM, and tensile strength tests were used. The maximum tensile strength of the monofilament can reach up to 1236.61 MPa. UHMWPE/HDPE/CaSt 2 = 60/40/0.5 exhibits the best tensile property.
Nitrogen doped ordered mesoporous carbons with a 3-D body-centered cubic pore structure have been synthesized by means of a low-temperature autoclaving route under basic conditions, showing excellent performances for supercapacitors and CO2capture.
The thermal deformation behavior of a novel CrFeNiSi0.15 medium entropy alloy (MEA) was studied in detail by means of isothermal compression experiments deformed under 900-1200ºC and 0.001-0.1s-1. According to experimental data, the modified Arrhenius-type constitutive equation was obtained, which could precisely predict the flow stress of CrFeNiSi0.15 MEA during thermal deformation. The hot activation energy (Q) of CrFeNiSi0.15 MEA was calculated to be about 417.270 kJ/mol. At the same time, the processing map of CrFeNiSi0.15 MEA were also carried out on the basis of dynamic material model (DMM) theory. In the thermal processing map of CrFeNiSi0.15 MEA, the peak efficiency of the CrFeNiSi0.15 MEA was about 39%, which occurred at the deformation parameter of 1200ºC/1s-1. Meanwhile, full dynamic recrystallization (DRX) occurred at such parameter. The flow instability of CrFeNiSi0.15 MEA was estimated to occur at 900-985°C/ 0.12-1s-1, which was shown as grain boundaries cracking. Furthermore, microstructure analysis suggested that the nucleation mechanism of continuous DRX (CDRX) as well as discontinuous DRX (DDRX) occurred simultaneously in thermal deformation, and CDRX was the dominant nucleation mechanism of DRX in high deformation temperature.
Tidal variation is one of the fundamental elements of the ocean. To address the problem of low accuracy in ocean exploration, this article introduces a tide gauge measurement system design based on STM32. The system uses the STM32 microcontroller as the control core, collects pressure and temperature data through high-precision ADC chips, and employs the Kalman filter algorithm to store the data in Flash memory. The results of the water experiment demonstrate that the system exhibits high accuracy and minimal error when compared to actual tidal data. At the same time, the phenomenon of "jumping point" in actual measurement is solved by fitting the mathematical model of tidal level data, which provides a more scientific theoretical basis for the field of tidal level observation.
In this study, we investigated the effects of different concentrations of Cr (VI) on various physiological and biochemical indexes of C. vulgaris, and to explore the biological response mechanism of C. vulgaris to Cr (VI) stress. Added different concentrations of carbon (Na2CO3), nitrogen (NH4Cl) and phosphorus (NaH2PO4·2H2O) to promote the growth of C. vulgaris. Using the optical density (OD680) of C. vulgaris as the evaluation standard, the effects of carbon, nitrogen and phosphorus on OD680 of C. vulgaris were studied. According to the results of single factor test, the addition amount of carbon, nitrogen and phosphorus was optimized by response surface method and neural network. The results showed that the optimal supplemental amounts of carbon, nitrogen and phosphorus were 160 mg/L, 30 mg/L and 54 mg/L. With this concentration, exploring the promoting effect of nutrient factors on the growth and the Cr (VI) stress tolerance of C. vulgaris.In summary, C. vulgaris has a certain tolerance to low concentration Cr (VI), such as 2、10、20 mg/L and the tolerance mechanism of C. vulgaris is mainly the stress regulation of antioxidant enzymes to external stress. Nutrient conditions such as C, N and P can promote the growth of C. vulgaris and improve its tolerance to Cr (VI). The OD680 of C. vulgaris could reach 0.966, which was twice that of the control group (L1 medium, OD680: 0.477).
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