Optimization of the Production Process of Flash-Spinning UHMWPE Superfine Fiber by Response Surface Methodology

In this paper, statistical optimization method was used to optimize the flash-spinning process conditions. Ultra-high molecular weight polyethylene （UHMWPE） superfine fiber was fabricated by flash-spinning method using UHMWPE as the fiberforming polymer, 1, 2-dichloroethane as the main solvent. The important parameters of the flash-spinning were filtered by Plackett-Burman experimental design based on the single factor experiments. After determining the best regions of the fiber properties, the optimum level of the important parameters were determined by Box-Behnken design. The results of the design showed that the important parameters influencing on the properties of the flash.spinning fiber were spinning temperature, spinning pressure, and spinning solution concentration. The optimum technical parameters were： spinning temperature 186. 4 ~C, spinning pressure 6. 16 MPa, spinning solution concentration 3.06 %. The highest combination property of the flash-spinning fiber was 86.39 under this condition.

Properties and evaluation of amidoxime-based UHMWPE fibrous adsorbent for extraction of uranium from seawater

An amidoxime-based ultra-high molecular weight polyethylene （UHMWPE） fibrous adsorbent was successfully prepared by T-irradiation-induced graft copolymerization of acrylonitrile （AN） and acrylic acid （AA）, followed by amidoximation. The grafting of AN and AA on the UHMWPE fiber and the amidoximation of the grafted fiber were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The mechanical property of the original and modified UHMWPE fibers was compared by single-filament strength test. The adsorption property of the UHMWPE fibrous adsorbent was evaluated by adsorption test in uranyl nitrate solution and seawater. The surface of the modified UHMWPE fibers was covered by the grafting layer and became rough. The tensile strength of the amidoxime-based UHMWPE fibrous adsorbent was influenced by the absorbed dose and hydrochloric acid elution, but was independent of the grafting yield and amidoximation. The uranium adsorption amount of the amidoxime-based UHMWPE fibrous adsorbent after immersing in seawater for 42 days was 2.3 mg-U/g.

Tribological evaluation of thermoplastic polyurethane-based bearing materials under water lubrication:Effect of load,sliding speed,and temperature

Polymers are widely used in bearing applications.In the case of water-lubricated stern tube bearings,thermoplastic polyurethane(TPU)-based composites are used due to their excellent wear resistance,corrosion resistance,and tunable mechanical properties.Their tribological performance,however,depends on operating conditions.In this work,TPU was blended with carbon fiber,graphene platelet,and ultra-high molecular weight polyethylene(UHMWPE).Friction tests of TPU based-composites against copper countersurface were carried out in water to mimic the actual operating conditions of the bearing.Most of the resulting contacts were in the boundary lubrication regime,in which friction was attributed to both contact mechanics of asperities as well as water lubrication.Our results show that the viscoelasticity of TPU has a considerable impact on its tribological performance.Water lubrication at 50°C promotes the softening of polymer surface material during sliding,resulting in higher fluctuation in the coefficient of friction and wear loss.This is attributed to the reduced thermomechanical properties.In addition,Schallamach waviness is observed on worn surface.The tribological properties of TPU are significantly improved by the inclusion of carbon fiber,graphene platelet,and UHMWPE.The formation of graphene transfer-layers and UHMWPE transfer film reduces friction and wear loss,while the inclusion of carbon fiber enhances wear resistance due to improved mechanical properties and load bearing capacity.