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All issues / Volume 12 (2018) / Issue 10 (October)

Plastics – the good, the bad and the ugly?
J. Seppala
Vol. 12., No.10., Pages 855-855, 2018
DOI: 10.3144/expresspolymlett.2018.73
This is an editorial article. It has no abstract.
Morphology and improved impact strength of cellulose acetate butyrate blended with polyethylene copolymer
A. Podshivalov, F. Besson, T. Budtova, S. Bronnikov
Vol. 12., No.10., Pages 856-866, 2018
DOI: 10.3144/expresspolymlett.2018.74
Incompatible blends of cellulose acetate butyrate (CAB) and copolymer of ethylene, acrylic ester, and maleic anhydride (PE-Acr-MA) with a component ratio 70/30 vol% were prepared by melt extrusion at the rates of 150 and 500 rpm. The goal was to modify weak impact properties of CAB. We showed that at a speed of 500 rpm, both small individual (0.9 µm in diameter) and large coalesced (2.3 µm in diameter) particles of the PE-Acr-MA phase were formed; the impact strength of the blend increased in 6.5 times as compared with that of pure CAB. However, at a melt mixing rate of 150 rpm, the size of the individual PE-Acr-MA particles decreased in 3.8 times, whereas that of the coalesced particles diminished by 6.6 times; the impact strength of the blend increased in about 40 times as compared with that of pure CAB and reached the values around and higher than 70 kJ/m2. The effect of the screw rotating speed on viscoelastic properties of each component and their viscosity ratio was analyzed and shown to control blend morphology and mechanical properties.
Effect of bis(triethoxysilylpropyl) tetrasulfide (TESPT) on properties of carbon nanotubes and conductive carbon black hybrid filler filled natural rubber nanocomposites
Y. Nakaramontri, C. Kummerloewe, N. Vennemann, S. Wisunthorn, S. Pichaiyut, C. Nakason
Vol. 12., No.10., Pages 867-884, 2018
DOI: 10.3144/expresspolymlett.2018.75
Natural rubber (NR) and epoxidized natural rubber (ENR) vulcanizates reinforced by carbon nanotubes (CNT), conductive carbon black (CCB) and CNT/CCB hybrid filler without and with bis(triethoxysilylpropyl)tetrasulfide (TESPT) silane coupling agent were prepared using an internal mixer and a two-roll mill. Attenuated total reflection infrared spectroscopy (ATR-FTIR) was used to determine chemical interactions among rubber molecules, filler surfaces and silane molecules. In addition, the filler-filler interaction in NR and ENR matrices were assessed from wetting ability and Payne effect. Furthermore, the coupling by TESPT of filler surfaces and rubber molecules was clarified by temperature stress scanning relaxation (TSSR) technique. It was found that the rubber bound by physical absorption decreased with addition of TESPT, while the chemically bound amount significantly increased. This correlates well with estimates of physically and chemically bound rubber from swelling method and morphological properties. It was also found that the optimal electrical conductivity, percolation threshold concentration and dielectric constant of the composites were effectively improved by addition of TESPT. The improvement was confirmed by ANOVA. This indicates a great opportunity to manufacture smart materials with superior conductivity and dielectric constant, together with optimal scorch time, cure time and crosslinking properties.
A study on the effects of graphene nano-platelets (GnPs) sheet sizes from a few to hundred microns on the thermal, mechanical, and electrical properties of polypropylene (PP)/GnPs composites
Y-S. Jun, J. G. Um, G. Jiang, A. Yu
Vol. 12., No.10., Pages 885-897, 2018
DOI: 10.3144/expresspolymlett.2018.76
Polypropylene (PP) is incorporated with four different grades (H100, M25, M5, and C300) of graphene nanoplatelets (GnPs) via twin screw extrusion followed by injection moulding. The composites’ thermal stability, crystallization behaviour, tensile strength, and electrical property are carefully examined. The thermal stability is significantly enhanced with the incorporation of small-sized GnPs as shown by the 11.2% improvement in T5% (the temperature at which 5 wt% of the mass loss occurs) and 5.1% improvement in Tmax (the temperature at which the maximum loss rate occurs). The thermal stabilizing effect of fillers can be significantly enhanced when they are well distributed with less aggregation as is the case for small-sized GnPs. The GnPs show a considerable nucleating effect on PP by increasing the crystallization temperature (Tc). The greatest improvement in tensile property is achieved with the use of small-sized GnPs. A 33.0% enhancement in tensile strength and 59.1% improvement of tensile modulus are obtained with the use of C300 and M5, respectively. The significantly increased thermal stability and mechanical property with small-sized GnPs are due to the fact that these smallsized fillers achieve a high degree of dispersion with less agglomeration as shown in the scanning electron microscope (SEM) images. However, the fillers with a large sheet size are still beneficial for purposes concerning electrical conductivity since the lowest percolation is obtained with H100. The greater the size of the GnPs, the smaller the percolation threshold of composites is exhibited.
Application of ionic liquids in thermosetting polymers: Epoxy and cyanate ester resins
A. Vashchuk, A. M. Fainleib, O. Starostenko, D. Grande
Vol. 12., No.10., Pages 898-917, 2018
DOI: 10.3144/expresspolymlett.2018.77
Thermosetting polymers are widely used as industrial materials due to good heat resistance, dimensional stability and chemical resistance. There is a longstanding and widespread interest in designing novel polymer networks, and utilization of ionic liquids (ILs) opens up new frontiers to meet this challenge by creating new materials. For thermosetting polymers, ILs offer many advantages, either as catalytic agents, plasticizers, conducting additives, or porogens. Furthermore, ILs show rich structural diversity and can be incorporated into a polymer matrix to achieve better final properties. This review emphasizes the urgent need for understanding the role, efficiency and perspectives of an innovative class of components, namely ILs with the potential to impact across many areas of thermosetting polymers. To avoid ambiguity and make the review selfreading, basic ideas about the application of ILs in thermosetting polymers are first outlined.
UV-light-induced curing of branched epoxy novolac resin for coatings
S. Gaidukovs, A. Medvids, P. Onufrijevs, L. Grase
Vol. 12., No.10., Pages 918-929, 2018
DOI: 10.3144/expresspolymlett.2018.78
UV-light induced curing of the branched epoxy novolac resin (ENR) is reported. Cross-linked ENR coatings with a thickness of 150 µm were produced by the cationic photopolymerization of poly((phenyl glycidyl ether)-co-formaldehyde), which was photoinitiated by bis(4-dodecylphenyl)-iodonium hexaflurorantimonate. ENR crosslinking efficiency of UVlight polymerization accomplished by Hg-lamp with a power of 1 kW continuous irradiation was investigated as a function of the photoinitiator content and UV curing time. Optimal cross-linking properties were observed for photoinitiator concentration of 1.5%, and curing time 5 min. It was found that higher Vickers hardness of the polymer resulted in an increased cross-linking density of the developed chain network. UV irradiation time longer than 6 min results in the photodegradation of the polymer. This was confirmed by scanning electron microscopy investigations of polymer surface microstructure, as well as complemented by Fourier transform infrared (FTIR), ultraviolet-visible (UV-VIS) and Raman spectroscopy measurements that evidence the oxygen containing groups. Furthermore, the developed ENR photopolymerization technology can be used to obtain protective coatings for applications in power generation and maritime industries where thermal curing processes and two-component resin hardening are unacceptable.
Novel improvement in processing of polymer nanocomposite based on 2D materials as fillers
P. A. R. Munoz, C. F. P. de Oliveira, L. G. Amurin, C. L. C. Rodriguez, D. A. Nagaoka, M. I. B. Tavares, S. H. Domingues, R. J. E. Andrade, G. J. M. Fechine
Vol. 12., No.10., Pages 930-945, 2018
DOI: 10.3144/expresspolymlett.2018.79
Here, for the first time, novel improvement in processing of polymer nanocomposite based on 2D materials as fillers leading to manufacturing by melt mixing is described. Two new strategies were used to insert pre-exfoliated 2D material into the polymer matrix, liquid-phase feeding (LPF), and solid-solid deposition (SSD). Initially, graphene oxide (GO) and polystyrene (PS) were used as templates for the 2D material and polymer, respectively. Traditional characterizations (tensile mechanical test, molecular weight, rheological measurements and transmission electron microscopy) were carried out, therefore, two unique characterization techniques beyond micro and nanoscale were also used allowing the evaluation of the nanocomposite morphology for millimeter samples size (X-ray Microtomography and Low-Field Nuclear Magnetic Resonance). The results show that both methods could be suitable as large-scale manufacturing, and the process parameters must be optimized to obtain a low level of agglomerates. SSD and LPF methods were also applied to other different polymer/2D materials systems (poly(butylene adipate-co-terephthalate) – PBAT/GO and PS/Molybdenum disulfide – MoS2), and the results are also presented here. The methodologies described here show indications that can be extended to all thermoplastic polymers and 2D materials providing nanocomposites with suitable morphology to obtain singular properties and to trigger the start of the manufacturing process on a large scale.
Preparation and structural characterization of lignin micro/nano-particles with ionic liquid treatment by self-assembly
C. Liu, Y. M. Li, Y. Hou
Vol. 12., No.10., Pages 946-956, 2018
DOI: 10.3144/expresspolymlett.2018.80
In the present research, 1,3-dimethyl-imidazolium dimethyl phosphate ([Mmim][DMP]) ionic liquid was applied to dissolve alkali lignin from wheat grass to prepare for lignin micro/nano-particles. The alkali lignin can be dissolved completely at 80 °C in 30 min under microwave condition with [Mmim][DMP] (solid-liquid ratio of 1:10) which is easy to be recycled. The dissolved lignin can be precipitated by diluting the ionic liquid-lignin solution with water to get lignin micro/nano-particles with diameter ranged from 200 nm to 1.5 µm. Structural analyses with Gel permeation chromatography (GPC), 2D heteronuclear single quantum coherence nuclear magnetic resonance (2D-NMR), Thermogravimetric Analysis (TGA), etc., indicate that a large number of dehydration reactions occurred during dissolution process to result in the generation of unsaturated bonds with higher degree of unsaturation (ω) (from 197–334), lower polydispersity (from 1.49 to 1.12) and lower average molecular weight (from 8634 to 5406 Da). Compared with original alkali lignin, the regenerated alkali lignin as micro/nano-particles showed higher thermal stability. It was also found from the 2D NMR spectra that the cleavages of aryl-ether bonds dramatically happened during the dissolution process, [Mmim][DMP] ionic liquid is more likely to destroy lignin units linked by β–O–4′ bonds to G-type lignin with less steric hindrance, resulting in the least amount of β–O–4′ linkages. In addition, dehydration and demethylation of lignin occurred during the dissolution of ionic liquid.
Published by:

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