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All issues / Volume 14 (2020) / Issue 6 (June)

The coronavirus and plastics
T. Czigany, F. Ronkay
Vol. 14., No.6., Pages 510-511, 2020
DOI: 10.3144/expresspolymlett.2020.41
This is an editorial article. It has no abstract.
Bio-based epoxy thermosets with rosin derived imidoamine curing agents and their structure-property relationships
T. Thakur, S. Jaswal, S. Parihar, B. Gaur, A. S. Singha
Vol. 14., No.6., Pages 512-529, 2020
DOI: 10.3144/expresspolymlett.2020.42
Multifunctional bio-based epoxy resin (PEMPAE) was synthesized by reacting Diels-Alder adduct of gum rosin and maleic anhydride (MPA) with pentaerythritol to get the esterified product (PEMPA) which was further epoxidized using epichlorohydrin and potassium hydroxide. This paper includes the synthesis of bio-based imidoamine curing agent (IAEDK) by reacting diamino diphenyl ether (DDE) with dimaleopimaryl ketone (DMPK), a dehydrodecarboxylated derivative of MPA. The synthesized products were characterized by Fourier transform infrared Spectroscopy (FTIR), proton and 13C nuclear magnetic resonance spectroscopy (1H-NMR and 13C-NMR). Curing dynamics of rosin-based epoxy cured with rosinbased imidoamine crosslinker were evaluated using differential scanning calorimetry (DSC) and were compared with resin cured with synthesized DMPK and commercial DDE curing agents. The mechanical properties and thermal stability of the cured epoxy samples were evaluated using a universal testing machine (UTM) and thermogravimetric analyzer (TGA), respectively. The chemical resistance of the samples was determined in terms of % weight loss when immersed in NaOH, HCl and NaCl solutions. The morphological changes were also evaluated via scanning electron microscopy (SEM). Results revealed that rosin-based epoxy cured with imidoamine curing agent gave preeminent properties over the commercial one. The studies suggested that curing properties were greatly affected by the molecular topology and kind of curing agent used.
α-methylstyrene-assisted maleic anhydride grafted poly(lactic acid) as an effective compatibilizer affecting properties of microcrystalline cellulose/poly(lactic acid) composites
F. Y. Wang, L. Dai, T. T. Ge, C. B. Yue, Y. M. Song
Vol. 14., No.6., Pages 530-541, 2020
DOI: 10.3144/expresspolymlett.2020.43
A new compatibilizer, maleic anhydride-grafted poly(lactic acid) (PLA-g-AMS/MAH), was synthesized for microcrystalline cellulose (MCC)/poly(lactic acid) (PLA) composites. PLA-g-AMS/MAH copolymer was prepared by freeradical melt grafting using α-Methylstyrene as a co-monomer and dicumyl peroxide (DCP) as a free-radical initiator. The molecular structure of the prepared PLA-g-AMS/MAH was characterized by Fourier transform infrared spectroscopy (FTIR), and the grafting degree (Dg) of PLA-g-AMS/MAH was studied by acid-alkali titration. The effects of the Dg of PLA-g-AMS/MAH on the rheological and mechanical properties of MCC/PLA composites were investigated. The results showed that MAH was successfully grafted onto PLA molecular chains and the Dg of PLA-g-AMS/MAH was dramatically higher than the Dg of PLA-g-MAH. At an AMS/MAH ratio of 2:1, the Dg value of the graft copolymer reached maximum. Additionally, the storage modulus, complex viscosity, equilibrium torque, and shear heat of the MCC/PLA composite melts increased with increased Dg of PLA-g-AMS/MAH. The mechanical properties of the MCC/PLA composites also were significantly improved after the addition of PLA-g-AMS/MAH copolymer.
Multifaceted bioinspired hyperbranched polyurethane nanocomposite as a non-contact triggered self-healing material
R. Duarah, A. Deka, N. Karak
Vol. 14., No.6., Pages 542-555, 2020
DOI: 10.3144/expresspolymlett.2020.44
The current investigation reports in situ fabrication of hyperbranched polyurethane (HPU) nanocomposites with different weight percentages of functionalized silica nanoparticle as nano-reinforcing material. Silica nanoparticles were functionalized with sodium dodecyl sulfate and polyethylene glycol using a facile, simple one-pot method. The nanomaterial and the HPU nanocomposites were assessed by Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet (UV)-visible, X-ray Diffraction (XRD), Transmission Electron Microscope (TEM), mechanical and thermal studies. The fabricated nanocomposites demonstrated notable tensile strength (25.8 MPa), excellent elongation at break (1495%), outstanding toughness (340.88 MJ・m–3), good scratch hardness (7.5 kg), significant impact strength (19.02 kJ・m–1) and sufficient improvement in hydrophobicity (105.2° from 76.7°). They also demonstrated remarkable non-contact triggered thermo-responsive shaperecovery (97.6–-99.4%). Moreover they displayed efficient self-healing behavior within just 20 s under microwave (360 W). The nanocomposites also exhibited biodegradation by bacterial strains, Pseudomonas aeruginosa, and Bacillus subtilis. Thus, the present work promotes this biodegradable nanocomposite as a potential high performing self-healing and selfcleaning material.
EPR studies on the interaction between additives and polyethylene matrix initiated by gamma radiation
G. Przybytniak, J. Sadlo, M. Walo
Vol. 14., No.6., Pages 556-565, 2020
DOI: 10.3144/expresspolymlett.2020.45
Silane cross-linked polyethylene (PE) modified with two antioxidants (Irganox 1076 and Irganox PS802) and aluminum hydroxide (ATH) as a flame retardant, was irradiated with gamma rays at 77 K. The radical processes initiated by radiation were investigated by Electron Paramagnetic Resonance (EPR) spectroscopy from 100 K to the temperatures at which the spectra disappeared. Interpretation of the experimental signals was proposed. The mechanism of the two-stage action of phenolic antioxidant on PE was suggested on the basis of EPR spectra of individual components. It was found that paramagnetic defects generated by radiation in ATH decayed in parallel and independently of radical processes in PE matrix due to phase separation. Thus, in contrast to antioxidants, they did not affect the degradation of the PE matrix. The decrease in concentration of ATH defects in the range of 100–190 K was more efficient in the dispersed phase of the polymer composite than in the microcrystalline ATH powder.
Bending control of liquid-crystal elastomers based on doped azo derivatives synthesized via controlled gradient polymerization
S. Fitriyani, C. Y. Liu, Y. H. Hung, Y. S. Zhang, J. H. Liu
Vol. 14., No.6., Pages 566-575, 2020
DOI: 10.3144/expresspolymlett.2020.46
The intelligence, complexity, and diversification of nature is a continuous source of inspiration for humankind. Imitating natural intelligence to devise bionic microrobots with self-regulated features remains an enormous challenge. Herein, we demonstrate a biomimetic soft material that uses light to trigger mechanical motion. This light-sensitive mimosa mimetic film was designed based on liquid crystal elastomers (LCEs) and photoisomerizable azo compounds. To control the bending direction, a predesigned UV-induced gradient polymerization was used. The energy-controlled polymerized film comprises one high-density and one low-density liquid crystal mesogen face. Similar to mimosas, the fabricated films achieved stimuli-responsive actuation, exhibiting shape deformation upon light illumination. The elastic network undergoes reversible shape changes via photochemical trans-cis isomerization of an azo compound in response to a stimulus. In this study, only a small amount of photoisomerizable 1-Hydroxy-n-(4-nitro-azobenzene-4′-oxy)hexane (AZO) was used; however, the domino effect caused a significant reversible actuation. The mesogen density of the top and bottom faces was found to be an important factor for the bending control. This study explores a new way to fabricate films that can bend in controlled directions during light irradiation. This phototunable film is expected to be used for applications in microrobotics and micromachinery.
3D printing of polybutadiene rubber cured by photo-induced thiol-ene chemistry: A proof of concept
M. Bragaglia, F. R. Lamastra, V. Cherubini, F. Nanni
Vol. 14., No.6., Pages 576-582, 2020
DOI: 10.3144/expresspolymlett.2020.47
Mechanical performance of 3D printed ‘Rubber-like’ commercial resins are not comparable to typical vulcanized diene rubbers since they show lower strain at break. In the present work, samples made of liquid butadiene rubber have been photocured by thiol-ene chemistry and 3D printed. Morphological features and mechanical properties have been investigated by means of scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and tensile tests. The 3D printed samples show the characteristic mechanical properties of unfilled diene rubbers reaching a strain at break up to 400%.
A comparative study on the reactive compatibilization of melt-processed polyamide 1010/polylactide blends by multi-functionalized additives derived from linseed oil and petroleum
L. Quiles-Carrillo, O. Fenollar, R. Balart, S. Torres-Giner, M. Rallini, F. Dominici, L. Torre
Vol. 14., No.6., Pages 583-604, 2020
DOI: 10.3144/expresspolymlett.2020.48
This research work describes the manufacturing and characterization of novel engineering materials consisted of fully bio-based blends of polyamide 1010 (PA1010) with 20 wt% of polylactide (PLA). Four different compatibilizers were used to enhance the miscibility and the performance of the biopolymer blends. Two multi-functionalized vegetable oils (maleinized linseed oil (MLO) and epoxidized linseed oil (ELO)) and two petroleum-derived glycidyl-based additives (epoxy styrene-acrylic oligomer (ESAO) and styrene-glycidyl methacrylate copolymer (PS-GMA)) were tested during melt compounding. The resultant biopolymer blends were processed by either cast film extrusion or injection molding to obtain films and pieces, respectively. Thin films with an average thickness of 50–60 µm and thick pieces of 4 mm were obtained, and their mechanical, morphological, thermal, thermomechanical, barrier and, optical properties were characterized. Although all four compatibilizers successfully provided compatibilization to the blends, the chemically modified vegetable oils, that is, MLO and ELO yielded the injection-molded pieces with the most balanced mechanical properties in terms of strength and toughness. Besides, the resultant films showed very low oxygen transmission rate values, thus broadening the potential of these biopolymer blends for the food packaging industry.
Published by:

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