Complex Dynamics of a Fluorinated Vinylidene Cyanide Copolymer Highlighted by Dielectric Relaxation Spectroscopy

The complex dynamics of a nearly alternating copolymer of vinylidene cyanide (1,1-dicyanoethylene, VCN) with 2,2,2-trifluoroethyl methacrylate (TFEMA), including two alpha-relaxations with diverging time scale in the glass transition temperature range, was thoroughly characterized by dielectric spectroscopy over wide temperature and frequency ranges and analyzed in the frame of the Ngai’s coupling model. The dielectric relaxation strength as well as the glass transition temperature, the temperature dependence of the α-relaxation time, and the corresponding distribution of relaxation times were all larger than those of a reference TFEMA homopolymer, as expected from the introduction of the stiffening VCN units all along the macromolecular chain. The effect of casting solvent and applied poling electric field on the copolymer dielectric strength suggests the onset of local orientational order involving the strong dipoles in the VCN units, a requirement for piezo- and pyroelectricity in amorphous polymer

Functionalized carbon nanotubes as a filler for dielectric elastomer composites with improved actuation performance

Among the broad class of electro-active polymers, dielectric elastomer actuators represent a rapidly growing technology for electromechanical transduction. In order to further develop this applied science, the high driving voltages currently needed must be reduced. For this purpose, one of the most widely considered approaches is based on making elastomeric composites with highly polarizable fillers in order to increase the dielectric constant while maintaining both low dielectric losses and high-mechanical compliance. In this work, multi-wall carbon nanotubes were first functionalized by grafting either acrylonitrile or diurethane monoacrylate oligomers, and then dispersed into a polyurethane matrix to make dielectric elastomer composites. The procedures for the chemical functionalization of carbon nanotubes and proper characterizations of the obtained products are provided in detail. The consequences of the use of chemically modified carbon nanotubes as a filler, in comparison to using unmodified ones, were studied in terms of dielectric, mechanical and electromechanical response. In particular, an increment of the dielectric constant was observed for all composites throughout the investigated frequency spectrum, but only in the cases of modified carbon nanotubes did the loss factor remain almost unchanged with respect to the simple matrix, indicating that conductive percolation paths did not arise in such systems. An effective improvement in the actuation strain was observed for samples loaded with functionalized carbon nanotubes

Nylon 6 and nylon 6,6 micro- and nanoplastics: a first example of their accurate quantification, along with polyester (PET), in wastewater treatment plant sludges

A novel procedure for nylon 6 and nylon 6,6 polyamide (PAs) microplastics (MPs) quantification is described for the first time. The overall procedure, including quantification of poly(ethylene terephthalate) (PET), was tested on wastewater treatment plant (WWTP) sludges. The three polymers account for the largest global share of synthetic textile microfibers, being possibly the most common MPs released upon laundering in urban wastewaters. Therefore, measuring their content in WWTP sludges may provide an accurate picture of the potential risks associated with both the inflow of these MPs in natural water bodies and the practice of using WWTP sludges as agricultural soil amendment. The novel procedure involves PAs depolymerization by acid hydrolysis followed by derivatization of the monomers 6-aminohexanoic acid (AHA) and hexamethylene diamine (HMDA) with a fluorophore. Reversed-phase HPLC analysis with fluorescence detection results in high sensitivities for both AHA (LOD = 8.85·10–4 mg/L, LOQ = 3.73·10–3 mg/L) and HMDA (LOD = 2.12·10–4, LOQ = 7.04·10–4 mg/L). PET quantification involves depolymerization, in this case by alkaline hydrolysis, followed by HPLC analysis of its comonomer terephthalic acid. Eight sludge samples from four WWTPs in Italy showed contamination in the 29.3–215.3 ppm and 10.6–134.6 ppm range for nylon 6 and nylon 6,6, respectively, and in the 520–1470 ppm range for PET

Aqueous Dispersions of Nanostructured Particles Hybridized with Mono- and Multifunctional POSS Methacrylates: Heterophase Polymerization and Material Properties of the Resulting Latex Films

The synthesis of aqueous dispersions of hybrid acrylic copolymer particles containing either a monofunctional or a multifunctional oligomeric silsesquioxane as a comonomer has been performed by heterophase free radical polymerization. The miniemulsion process allowed to produce stable latexes, as opposed to the less controlled emulsion route. The thermal, mechanical and surface properties of the nanocomposite latex films have been investigated

A Systematic Study on the Degradation Products Generated from Artificially Aged Microplastics

Most of the analytical studies focused on microplastics (MPs) are based on the detection and identification of the polymers constituting the particles. On the other hand, plastic debris in the environment undergoes chemical and physical degradation processes leading not only to mechanical but also to molecular fragmentation quickly resulting in the formation of leachable, soluble and/or volatile degradation products that are released in the environment. We performed the analysis of reference MPs–polymer micropowders obtained by grinding a set of five polymer types down to final size in the 857–509 μm range, namely high‐ and low‐density polyethylene, polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET). The reference MPs were artificially aged in a solar‐box to investigate their degradation processes by characterizing the aged (photo‐oxidized) MPs and their low molecular weight and/or highly oxidized fraction. For this purpose, the artificially aged MPs were subjected to extraction in polar organic solvents, targeting selective recovery of the low molecular weight fractions generated during the artificial aging. Analysis of the extractable fractions and of the residues was carried out by a multi‐technique approach combining evolved gas analysis–mass spectrometry (EGA–MS), pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS), and size exclusion chromatography (SEC). The results provided information on the degradation products formed during accelerated aging. Up to 18 wt% of extractable, low molecular weight fraction was recovered from the photo‐aged MPs, depending on the polymer type. The photo‐degradation products of polyolefins (PE and PP) included a wide range of long chain alcohols, aldehydes, ketones, carboxylic acids, and hydroxy acids, as detected in the soluble fractions of aged samples. SEC analyses also showed a marked decrease in the average molecular weight of PP polymer chains, whereas cross‐linking was observed in the case of PS. The most abundant low molecular weight photo‐degradation products of PS were benzoic acid and 1,4‐benzenedicarboxylic acid, while PET had the highest stability towards aging, as indicated by the modest generation of low molecular weight species

Rapid Solvent-Free Microcrystalline Cellulose Melt Functionalization with L-Lactide for the Fabrication of Green Poly-Lactic Acid Biocomposites

A green approach is proposed to achieve a rapid surface functionalization of microcrystalline cellulose (MCC) in 30 min by a solvent-free grafting by the reaction of L-lactide through compression molding without the need for an inert atmosphere. A sufficient hydrophobization of the MCC surface is achieved with an amount of grafted poly(L-lactic acid) (PLLA) oligomers of 7 wt % with respect to MCC. The obtained PLLA-g-MCC is subsequently melt-compounded with poly(lactic acid) (PLA) through extrusion and injection molding. As a result of higher compatibility and interfacial adhesion of the functionalized filler with PLA, PLA/ MCC-g-PLLA biocomposites with a cellulose content ranging from 4 to 20 wt % exhibit an enhancement in important physicochemical properties (i.e., water vapor barrier, crystallinity, stiffness) compared to both pure PLA and formulations containing an equal or higher amount of nonfunctionalized MCC. At the same time, the materials retain the mechanical strength and resistance to thermal degradation of PLA. The physicochemical characteristics, excellent biocompatibility, and biodegradability of PLA and cellulose and the simplicity, rapidity, and cost-effectiveness of the grafting process render these biocomposites suitable for several applications within the plastics domain including packaging, agriculture, automotive, consumer goods, and household appliances