Band 44, Heft 7

The hydrophobicity of polyolefin separators causes poor compatibility with the internal environment of lithium-ion batteries and thus elevates lithium-ion migration barriers. In this research, hydroxy-terminated hyperbranched polymer (HTHP) coated separators are fabricated successfully based on the simple and easy-on impregnation method. Abundant hydroxyl groups in HTHP reinforce separator electrolyte affinity, generating the much lower contact angle and higher electrolyte uptake. Accordingly, HTHP-coated separators show broader electrochemical window and superior ionic conductivity and Li + transport number, which facilitate the Li + migration within porous pathways and hence maximally weaken counteranions-induced polarizations. The lower interfacial resistances also guarantee the Li + accelerated diffusion via the separator–electrodes interfaces. Therefore, batteries containing modified separators exhibit optimized C -rate capacity and cycling stability. However, immoderate HTHP coating blocks partial pores and thus restricts Li + transference, which deteriorates C -rate capacity and cycling durability in turn. This separator modification scheme possesses advantages of simple preparation, environment-friendly, and low manufacturing cost, providing practical guidance for low-cost and high-performance separator manufacture.

Nanofibrous proton exchange membranes (PEMs) play an important role in improving the performance of the fuel cells. In this paper, two kinds of Nafion nanofibrous PEMs, Nafion-E/W and Nafion-DMF, were fabricated respectively by using ethanol/water (E/W) and N, N -dimethylformamide (DMF) as the solvent and their properties, such as the morphologies, water uptake, area swelling, ion exchange capabilities, conductivities, and mechanical properties were examined. Nafion-E/W nanofibers showed a thick diameter of 6,089 nm and Nafion-DMF nanofibers a thin diameter of 410 nm. Then the two Nafion nanofibers were annealed to provide the PEMs. Compared with Nafion 117 membranes and Nafion-DMF PEMs, Nafion-E/W PEMs showed the greatest water uptake and area swelling of respectively 59.75 % and 30.31 % and the conductivity increased to 0.1405 S/cm, more than twice as much as Nafion 117 membranes, but the broken stress decreased to 5.49 MPa, nearly half of Nafion 117 membranes. Nafion-DMF PEMs showed the lowest water uptake, area swelling, and conductivity of 22.67 %, 10.75 %, and 0.0410 S/cm, and the broken stress reached 14.20 MPa, greater than 11.0 MPa of Nafion 117 membranes. The obtained experimental results are instructive to improve the properties of Nafion PEMs.

Polyurethane composites synthesized by interaction of fly ash filler with polyether polyol, cross-linking agent, and curing agent in a certain ratio. The study’s findings show that the mechanical properties of polyurethane composite are lowered by the hydroxyl moieties of surface-functionalized fly ash that are chemically or physically linked. The study also reveals that prior subjecting the samples of surface-functionalized fly ash–reinforced polyurethane composite material for destructive analysis by UTM for evaluating mechanical properties. The in-depth study of the IR spectroscopy data of the composites is done focusing onto the stretching frequency of carbonyl group of carbamate links the trend in mechanical behavior of the samples, the number of fly ash–carbamate links, and proximity of HS–SS (hard segment–soft segment) of fly ash–reinforced polyurethane composites can be foretold. By a detailed analysis of the patterns of carbonyl stretching frequencies of carbamate links, one can gain insight into the microphasic level of the separation and proximity of hard and soft segments in composites, which govern their mechanical properties. The relationships between carbamate carbonyl stretching frequencies and mechanical characteristics of composites have been found to be inversely correlated. In order to offset the excess hydroxyl group contribution due to OH-loaded fly ash, as indicated by the isocyanate (NCO) peak intensity (2,240–2,280 cm −1 ) in the composite’s infrared spectra, the studies were conducted at a higher index ratio (1.64).

In this work, poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV) was modified by cellulose derivatives, and the effects of different kinds of cellulose derivatives on the crystallization and mechanical properties of PHBV were investigated. The crystallization and mechanical properties of PHBV/cellulose derivatives composites were measured by means of differential scanning calorimeter, polarizing microscope, and mechanical properties testing instruments. Studies show that cellulose acetate (CA) can promote the crystallization of PHBV, a small amount of CA can significantly increase the crystallization temperature of PHBV. The crystallization rate of PHBV was also accelerated by CA. However, the addition of cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) decreased the crystallization temperature of PHBV and inhibited the nucleation of PHBV. And the degree of inhibition increased with the increase of CAB and CAP content. CAB and CAP have good compatibility with PHBV, CAB, and CAP can be uniformly dispersed in PHBV. Cellulose derivatives with specific component content can enhance the tensile properties of PHBV without losing the impact strength.

A transparent poly(methyl methacrylate-butyl acrylate-hexafluorobutyl methacrylate) stone relics protective material was synthesized using one-pot method. The synthesized polymer was coated on the surface of the stone samples or glass plates. SEM was used to observe the micromorphology of pristine stone and stone covered polymer coating samples. Physical properties of polymer coatings were characterized by FTIR, XRD and TGA-DSC. The conservation properties of polymer coatings were investigated by testing adhesion, transparency, hydrophobicity, mass loss rate and appearance of the simulated stone relics after freeze–thaw, UV irradiation and acid aging processes. Results show that poly (MMA-BA-20.04 %HFMA) outperformed the others with water contact angle remained 108.23°, 109.34° and 106.96° as well as the change of chromaticity difference values of 0.79, 0.02 and 0.08, after freeze-thaw, UV-aging and acid-aging processes, respectively. All these data indicate that the as-synthesized polymer could potentially use in conservating the stone relics due to its superior hydrophobicity, transparency, anti-acid and anti-UV aging properties as well as durability for freeze–thaw.

An optimal portable microfluidic device should ensure least number of accessories for versatile field application. Typically, in such a device fabricated with polydimethylsiloxane (PDMS), the transport of fluid is enabled through a nonconventional pumping mechanism. This pumping system has been demonstrated to utilize the relatively high air permeability of polydimethyl siloxane (PDMS) to transport small volume fluid. In the recent past, microporous PDMS has replaced PDMS in this capacity. Microporous PDMS is typically fabricated through a series of steps where a sacrificial template is used to infiltrate the polymer. This template is removed after the polymer undergoes curing. This method has consistently produced a spongy structure that is nonrigid, sticky, and moist rendering it unwieldy. In this work, we present a novel concept of using camphor ( Cinnamomum camphora ) as a template to fabricate a dry polymeric sponge. The proposed sponge is molded on a sublimable material, camphor to avoid the additional step of template dissolution. The sponge is demonstrated to be stiff yet flexible rendering it convenient to be compacted into a confined space. Additionally, the sponge is dry and nonsticky as compared to structures that have been generated through sugar leaching.

The kneading elements play a crucial role in the distributive and dispersive mixing in the conventional co-rotating twin screw extruders. A novel kind of asymmetrical dual-speed co-rotating non-twin kneading elements (NTKE) with a zero staggered angle was designed to introduce symmetry break to improve mixing. Finite element method was applied to solve the time-dependent flow field where mesh superposition technique was used to impose the boundary conditions of moving parts and further to avoid the remeshing at every time steps. The flow and mixing of several fluids obeying the Carreau constitutive model with the different power law exponents were investigated numerically and compared with the conventional co-rotating twin kneading elements (TKE). Distributive mixing was evaluated through evolution of tracer droplets and decaying of variance index with time. Moreover, the dispersive mixing was examined in terms of the statistical distributions of mixing index. An integral function with regard to the mixing index was proposed to evaluate the proportion of tracer particles subjected to the elongation.

To promote theoretical understanding for optimizing the entire process parameters (temperature, pressure, flow rate, etc.) and quality indicators (molar fraction, end-group concentration, and number-average molecular weight) in the industrial production of polyethylene terephthalate (PET), a dataset construction for production parameters and product quality indicators was accomplished in conjunction with industrial process simulation software. A complete deep learning workflow including data collection, dataset construction, model training, and evaluation was established. A prediction method for process-product quality of PET production based on the residual neural network (ResNet) network was proposed to reduce the complexity of quality control in polyester production. The results show that compared to traditional convolutional neural network (CNN), ResNet has higher accuracy ( R 2  ≥ 0.9998) in predicting the PET production process and product quality. It can accurately establish the mapping relationship between production parameters and product quality indicators, providing theoretical guidance for intelligent production.