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All issues / Volume 13 (2019) / Issue 7 (July)

Polymers and polymer composites as ideal systems for testing and understanding 'dissipative structures'?
Gy. Banhegyi
Vol. 13., No.7., Pages 589-589, 2019
DOI: 10.3144/expresspolymlett.2019.49
This is an editorial article. It has no abstract.
Electrospinning scale-up and formulation development of PVA nanofibers aiming oral delivery of biopharmaceuticals
E. Hirsch, P. Vass, B. Demuth, Zs. Petho, E. Bitay, S. K. Andersen, T. Vigh, G. Verreck, K. Molnar, Zs. K. Nagy, Gy. Marosi
Vol. 13., No.7., Pages 590-603, 2019
DOI: 10.3144/expresspolymlett.2019.50
Electrospinning is a promising drying technology providing a rapid and gentle drying at ambient temperature, thus electrospinning of polyvinyl alcohol aqueous solutions was investigated for the solid formulation of biopharmaceuticals. The commonly used single-needle electrospinning does not have adequate productivity to satisfy the industrial requirements, therefore our aim was to study the scale-up of the technology by using high-speed electrospinning. High molecular weight polyethylene oxide as a secondary polymer was applied to enhance the fiber formation of polyvinyl alcohol. While polyvinyl alcohol-polyethylene oxide formulations resulted in adequate fiber formation it was not possible to process them further as the friability of the fibers was too low. In order to increase the friability, the effect of adding various sugars (mannitol, glucose, lactose, saccharose, and trehalose) was investigated. The results showed that mannitol was the best friability enhancing excipient because of its crystallinity and low moisture content in the fibrous sample. In contrast, glucose, lactose, saccharose, and trehalose were amorphous with higher moisture content and fibers containing these were grindable only after post-drying.
Comparative corrosion protection studies of electroactive/non-electroactive epoxy thermoset composites containing conductive rGO/non-conductive GO platelets
W. F. Ji, K. Y. Chen, C. J. Ke, Y. J. Liao, W. J. Liu, M. H. Tsai, J. M. Yeh
Vol. 13., No.7., Pages 604-617, 2019
DOI: 10.3144/expresspolymlett.2019.51
In this study, comparative corrosion protection studies of cold-rolled steel (CRS) electrodes coated with electroactive/non-electroactive epoxy thermoset (denoted as EET/NEET) composites containing dispersed reduced graphene oxide (rGO) and graphene oxide (GO) platelets are presented. All composites were obtained through the thermal ring-opening reaction of bisphenol A diglycidyl ether (DGEBA) with amino-capped aniline trimer (ACAT) or trimethylolpropane tris[poly(propylene glycol), amine terminated] ether (T-403) at a specific mixing ratio in the presence of dispersed rGO/GO were characterized Fourier Transform Infrared (FTIR) spectroscopy and Transmission Electron Microscopy (TEM). In gas permeability measurements, the GO was found to display a slightly better dispersion capability in both EET and NEET membrane than in rGO. Conductive rGO platelets were found to promote the redox behavior of EET and non-conductive GO platelets was found to depress the redox behavior of EET, as measured by electrochemical cyclic voltammetry (CV) studies. Corrosion protection of composite coatings was investigated by electrochemical corrosion measurements in saline solution. It should be noted, in the EET system, that rGO was found to exhibit better anticorrosion performance as compared to that of GO. However, in NEET system, GO was found to have better anticorrosion performance than rGO. Better anticorrosion of rGO in EET may be attributed to better synergistic effect of electro-catalytic and the oxygen barrier properties of rGO in EET. On the contrary, better anticorrosion of GO in NEET may be associated with better oxygen barrier property of GO alone in NEET than that of rGO. The passive metal oxide layer formed on the cold rolled steel (CRS) electrode induced by EET was further confirmed by Raman and Electron Spectroscopy for Chemical Analysis (ESCA).
Synthesis and characterization of isophorondiamine based epoxy hardeners from aminolysis of PET
L. Karpati, M. Fejer, D. Kalocsai, J. Molnar, V. Vargha
Vol. 13., No.7., Pages 618-631, 2019
DOI: 10.3144/expresspolymlett.2019.52
The solvolysis of poly(ethylene-terephthalate) (PET) is one of the most researched areas in chemical recycling. In this study PET aminolysis with isophorondiamine has been done - in opposition to recent trends - without excess reagent and the raw reaction product was further used without purification. The aminolysis product was thoroughly characterized with nuclear magnetic resonance (NMR) spectroscopy. Isophoronediamine was used as a solvent to prepare amine cross-linker solutions for epoxy resins. The effect of the concentration on the cross-linking reaction and thermomechanical prop¬erties were investigated. The curing reaction was found to be significantly accelerated by the presence of the aminolysis product. Both the ethylene-glycol and the terephthal-amide-diamines have a catalytic effect on the reaction. The glass transition temperature decreased with increasing concentrations of the cross-linker solutions due to the decreasing cross-link density. Thus, raw aminolysis products can be utilized for epoxy curing and are advantageous in modifying slower curing cycloaliphatic cross linker systems.
3D scanning probe nanotomography of tissue spheroid fibroblasts interacting with electrospun polyurethane scaffold
A. E. Efimov, O. I. Agapova, L. A. Safonova, M. M. Bobrova, V. A. Parfenov, E. V. Koudan, F. D. A. S. Pereira, E. A. Bulanova, V. A. Mironov, I. I. Agapov
Vol. 13., No.7., Pages 632-641, 2019
DOI: 10.3144/expresspolymlett.2019.53
We present a 3D study of nanostructural features of a bioprinted tissue spheroid interacting with polyurethane dual-scale biocompatible scaffold manufactured by three-dimensional printing and electrospinning. Three-dimensional analysis of fibroblasts interacting with electrospun polyurethane fibers was conducted using scanning probe nanotomography with an experimental setup combining ultramicrotome and a scanning probe microscope. Three-dimensional reconstruction demonstrates direct visualization of cell membrane protrusions and coherent cell-fiber interfaces, the formation of which is a prerequisite for an efficient tissue engineered implant. Analysis of obtained 3D data allows for quantitative calculation of the important morphological parameters of adhered cells, scaffolds, and cell-scaffold interfaces. The proposed method may be successfully applied to investigate 3D cell-scaffold constructs at nanoscale.
Blocked isocyanates as alternative curing agents for epoxy-polyurethane resins based on modified vegetable oils
A. Sienkiewicz, P. Czub
Vol. 13., No.7., Pages 642-655, 2019
DOI: 10.3144/expresspolymlett.2019.54
Presented research shows the results of a study on the synthesis and mechanical properties of materials obtained by crosslinking polyaddition bio-products with blocked isocyanate based on toluene diisocyanate (TDI) as curing agent. Bio-resins, polyaddition product of epoxidized soybean oil and bisphenol A or hydroxylated soybean oil and low molecular weight epoxy resin, were synthesized via modern and pro-ecological modification of the synthesis of epoxies, namely, the epoxy fusion process. The obtained polyaddition product contains free epoxy and hydroxyl groups, which are suitable for the curing purposes. Material cured with Desmodur BL 1265/MPA/X in the presence of organometallic or amine catalyst (respectively: Dabco T9 and Dabco 33-LV) is characterized by mechanical properties better than the composition crosslinked without the catalyst. Additionally, there is a possibility of the synthesis of two-layer materials by chemical bonding of two different compositions via the previously unused oxirane groups of the cured ESBO_BPA or SMEG_EPR products.
High-temperature hybrid phthalonitrile/amino-MMT nanocomposites: Synthesis, structure, properties
V. A. Bershtein, A. M. Fainleib, P. N. Yakushev, D. A. Kirilenko, K. G. Gusakova, D. A. Markina, O. G. Melnychuk, V. A. Ryzhov
Vol. 13., No.7., Pages 656-672, 2019
DOI: 10.3144/expresspolymlett.2019.55
Hybrid nanocomposites based on heterocyclic network, obtained from bisphenol A based phthalonitrile (BAPhN) with different (0.03–5.0 wt%) contents of reactive amino-montmorillonite (MMT) nanolayers, were synthesized and studied for the first time. Their structure, dynamics, thermal, relaxation and elastic properties were characterized using transmission electron microscopy (TEM), mid-infrared (mid-IR), far-infrared (far-IR) and energy dispersive X-ray (EDX) spectroscopies, differential scanning calorimetry (DSC), and by dynamic mechanical analysis (DMA) and thermogravimetry (TGA) measurements performed in both air and nitrogen mediums at temperatures from 20 to 600–900 °C. Depending on nanofiller content, different extents of MMT stacks exfoliation, from single nanolayers to MMT stacks with tens nanolayers-thickness, are observed in the nanocomposites. The pronounced dynamic heterogeneity in the glass transition and the ‘constrained dynamics’ effects are shown. For the pristine matrix, Tg (DMA) = 446 °С varying from 460 to 570 °С for the nanocomposites. After high-temperature treatment in N2 medium, the relaxation spectrum and glass transition disappear, and constant dynamic modulus E′ ≈ 3 GPa at 20–600 °С is registered. A satisfactory thermal stability of the nanocomposites, with retaining the sample integrity is observed at temperatures up to ~500 °C in air and up to 900 °C in N2 medium.
Preparation and properties of polylactic acid-based composite fluorescent membrane based on layer-by-layer assembly
M. M. Wang, H. L. Li, M. R. Liu
Vol. 13., No.7., Pages 673-684, 2019
DOI: 10.3144/expresspolymlett.2019.56
In this paper, a kind of multi-functional polylactic acid-based membrane with adjustable aggregate thickness and properties was prepared. When the number of assembled layers was 20 bilayers, the mean thickness of every bilayer was found to be 10.75±0.25 nm, and the tensile strength was increased by 20% compared with the polylactic acid (PLA) films. The assembled layered double hydroxides (LDHs) could serve as a type of promising organic-inorganic luminescent material, and endow PLA with photoluminescent properties. Besides, the photoluminescence of the composite films was discovered to be highly tunable by simply adjusting the structural constituents of LDHs, and the fluorescence intensity was uniformly enhanced as the number of assembled layers increases, which was not eliminated by the isolation due to cellulose nanocrystals (CNCs). Moreover, the composite films exhibited excellent fluorescence stability in comparison with the literature. After being repeatedly bleached 1000 times by confocal laser scanning fluorescence microscope, the fluorescence intensity of the PLA/(CNCs/Mg-Al-Eu LDHs)10 film remained 96%. It could be concluded that the immobilization of CNCs and LDHs realized the microscopic controllability of the optical functional molecular spacing. With satisfactory fluorescence, the resulting PLA-based membranes exhibited considerable application potential in optoelectronic devices and anti-counterfeiting packaging.
Published by:

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