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All issues / Volume 13 (2019) / Issue 4 (April)

The “reptation model” and the melts of condensation polymers
S. Fakirov
Vol. 13., No.4., Pages 302-302, 2019
DOI: 10.3144/expresspolymlett.2019.25
This is an editorial article. It has no abstract.
Epoxy resin coatings modified by ionic liquid. Study of abrasion resistance
M. D. Aviles, N. Saurin, F. J. Carrion, J. Arias-Pardilla, I. Martinez-Mateo, J. Sanes, M. D. Bermudez
Vol. 13., No.4., Pages 303-310, 2019
DOI: 10.3144/expresspolymlett.2019.26
In the present study, an epoxy resin coating containing a uniformly dispersed 9 wt% of the ionic liquid 1-octyl-3-methylimidazolium tetrafluoroborate (EP+9%[OMIM]BF4) has been applied by spin coating on a neat epoxy substrate, and its abrasion resistance under multiple scratch has been compared with that of neat epoxy coating. EP+9%[OMIM]BF4 presents the lowest surface damage after 15 successive scratches. The ionic liquid-modified coating reduces instantaneous penetration depth in a 13% and residual depth in a 22% with respect to EP, and increases viscoelastic recovery (after 30 seconds) in a 7.6%. The lubricating effect of the ionic liquid reduces the coefficient of friction up to the tenth scratch number. EP and EP+9%[OMIM]BF4 have also been obtained in the form of spin-coated films with similar visual transparency. Dynamic-mechanical characterization of the films under a tensile configuration confirms that the addition of the ionic liquid increases the ductility and reduces the glass transition temperature of the epoxy resin.
Fabrication of SA-SiO2 capsules with 3D microscopic re-entrant structures via one-step titration-gel method for the removal of methylene blue from water
D. C. Lin, M. Shi, Y. Cao, J. F. Cao, C. S. Peng
Vol. 13., No.4., Pages 311-326, 2019
DOI: 10.3144/expresspolymlett.2019.27
In this paper, the eco-friendly sodium alginate-silicon oxide capsule (SASC) with a brilliantly wide pH tolerance property was obtained via the one-step titration-gel method and in-situ sol-gel progress. The spherical droplets with SA and tetraethyl orthosilicate (TEOS) casting mixture were directly injected into the calcium chloride (CaCl2) solution. The effects of SiO2 nanoparticles (SiO2 NPs) on the morphology and adsorptive properties of the capsules were investigated. The interface of the SASC with micro-porous fracture aperture and microscopic re-entrant structures help to provide a stronger interaction between MB and surface channel thus increased its removed capacity during the courses of adsorption. The maximum absorption amount of the SASC against methylene blue (MB) was found to be 350.80 mg/g at 25 °C and the solution pH value of 8, which had a 12.82% enhancement compared with the neat capsule. The adsorptive performance of the prepared capsules was literally fitted the pseudo-second-order kinetic equation and Langmuir absorption isothermal model. Moreover, the pH of the MB solution was evidently declined after adsorption, indicating that the adsorption mechanism of the capsules against MB might be dominated by ion-exchange and electrostatic attraction. This facile method which was used to generate free-standing spherical support structures with specialized morphology might be more suitable for removing cationic pollutants from alkaline wastewater.
Influence of carbon nanotube and ionic liquid on properties of natural rubber nanocomposites
A. Krainoi, C. Kummerloewe, Y. Nakaramontri, S. Wisunthorn, N. Vennemann, S. Pichaiyut, S. Kiatkamjornwong, C. Nakason
Vol. 13., No.4., Pages 327-348, 2019
DOI: 10.3144/expresspolymlett.2019.28
Some properties of carbon nanotube (CNT) filled natural rubber (NR) composites were improved by adding an ionic liquid (IL), 1-butyl-3-methyl imidazolium bis (trifluoromethylsulphonyl)mide (BMI). In this work, the CNT and IL (CNT-IL) were mixed with NR by latex mixing method. Cure characteristics, thermo-mechanical properties, Payne effect, electrical conductivity and thermal stability were investigated. It was found that IL (BMI) accelerated vulcanization reactions and reduced scorch time. In addition, Fourier Transform Infrared (FTIR) results confirmed the role of IL in NR composites along with the reaction between CNT and NR molecules. The temperature scanning stress relaxation (TSSR) measurement was used to assess thermo-mechanical properties, and a relaxation peak of IL was found due to interactions of cations and anions in IL (BMI). Furthermore, the Payne effect was used to qualitatively analyze the roles of IL and CNT in three-dimensional CNT networks in the NR matrix. It was found that CNT dispersion was finer in the NR/CNT composites with IL. Furthermore, the NR/CNT-IL composite had higher electrical conductivity and lower percolation threshold concentration than the NR/CNT composite.
Semi-alicyclic polyimides as potential membrane oxygenators: Rheological implications on film processing, morphology and blood compatibility
R. M. Albu, C. Hulubei, I. Stoica, A. I. Barzic
Vol. 13., No.4., Pages 349-364, 2019
DOI: 10.3144/expresspolymlett.2019.29
Two polyimide structures were prepared from an alicyclic dianhydride and aromatic diamines, containing or lacking fluorine, and were tested as potential membrane oxygenators. First, the solution rheological properties were investigated to evaluate their effect on film processing by tape casting. Velocity and shear rates profiles were simulated to determine the shearing conditions during tape casting and transfer them in the flow curves. Proper films were obtained at a viscosity corresponding to a concentration in entangled regime, where pseudoplastic behavior is still noticed at shear rates beneath the blade. Theoretical predictions of gas permeability indicated a good oxygen (O2) exchange and carbon dioxide (CO2) removal through the studied polymers. Atomic force microscopy (AFM) scans revealed a morphology characterized by an intrinsic porosity. The pore size, uniformity and size distribution was affected by the structure of the diamine moiety. The interactions of blood with polyimide films indicated no prevalent adhesion of cells or plasma proteins. The results showed that the examined samples have adequate properties for potential membrane oxygenator applications.
Influence of the thermomechanical properties on the joining of adhesion incompatible polymers by form-fit using the vibration welding process
M. Wolf, S. Hertle, D. Drummer
Vol. 13., No.4., Pages 365-378, 2019
DOI: 10.3144/expresspolymlett.2019.30
In the product manufacturing cycle, the joining of polymers often takes a central position. Vibration welding is characterized by short cycle times, high process flexibility and stability as well as by the achievement of high bond strengths without using additives. However, the vibration welding process is clearly restricted by a necessary adhesion compatibility of the joining partners. By means of structuring one joining partner and subsequent filling of the structures by a second joining partner, the joining by form-fit using vibration welding enables the combination of adhesion incompatible polymers. Within these investigations, bonds between adhesion incompatible semi-crystalline thermoplastics were generated based on mechanical adhesion. Also semi-crystalline and amorphous polymers could be connected for the first time without any connecting elements, although they conventionally do not show mechanical resilience. The analysis of the thermomechanical material properties and the resulting multimaterial link enabled the determination of first influences on the resulting formfit connection caused by the occurring joining zone temperature.
Laser markability of PVC coated automotive electric cables
E. Bitay
Vol. 13., No.4., Pages 379-389, 2019
DOI: 10.3144/expresspolymlett.2019.31
This article describes the test results for laser markability of automotive electrical cables. The insulation is PVC, but the colour and construction of the insulations are different. Two types of laser workstations were used, one with a wavelength of 1064 nm and another with 532 nm. The penetration depth of the laser beam was determined by optical microscopy on cross sections. The 1064 nm laser beam can mark all investigated materials with good contrast, except the yellow insulation. The 532 nm laser beam with fast speed can hardly produce contrast with any of the materials. The laser markability of the yellow insulation was found to be the most problematic. On the two-layer insulation, despite the whitening of the inner material, dark marking is produced because the heat developing on the interface of the two layers will heat up and carbonize the transparent layer.
Effects of process parameters on core-back foam injection molding process
H. Wu, G. Zhao, J. Wang, G. Wang, W. Zhang
Vol. 13., No.4., Pages 390-405, 2019
DOI: 10.3144/expresspolymlett.2019.32
Experiments of a new core-back foam injection molding process are described in this paper wherein the blowing agent content [%], mold temperature [°C], shot size [mm], injection speed [mm/s], holding pressure [MPa], holding time [s] and core-back rate [mm/s] were taken as single variables, respectively. The effects and mechanisms of the above parameters on the molding process were studied. The relationships of the parameters with the mechanical properties and the weight reduction effect of the specimens were analyzed. The results show that the effect of blowing agent content, mold temperature, shot size, injection speed and core-back rate in the new method is similar to that of conventional core-back foam injection molding. However, the first stage holding pressure and holding time of the holding process in the secondary filling stage which the new method peculiarly possesses play the same role as shot size and injection speed in conventional foam injection molding, and the second stage holding pressure and holding time play the role of pressure holding in conventional foam injection molding. Compared with the conventional foam injection molding method, the specimens obtained by using the new method have higher weight loss rate, better mechanical properties, and higher specific strength.
Published by:

Budapest University of Technology and Economics,
Faculty of Mechanical Engineering, Department of Polymer Engineering