Fragmentation of polypropylene into microplastics promoted by photo-aging; release of metals, toxicity and inhibition of biodegradability.

The widespread presence of microplastics (MP) in water represents an environmental problem, not only because of the harmful effects of their size and potential to vector other pollutants, but also because of the release of additives, degradation products and residues contained in the polymer matrix. The latter includes metallic catalysts, which are often overlooked. This study focuses on the photo-aging of polypropylene (PP) and the resulting structural changes that promote its fragmentation microplastics (PP-MPs) and release of metals, as well as the resulting toxicity of leachates and their potential to inhibit biodegradation of organics in water. The pristine, photo-aged and waste PP are ground under the same regime to assess susceptibility to fragmentation. Obtained PP-MPs are submitted to leaching tests; the release of organics and metals is monitored by Total Organic Carbon (TOC) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis, respectively. The leachates are assessed for their toxicity against Vibrio fischeri, Daphnia magna and Pseudokirchneriella subcapitata and their influence on the biodegradability of the glucose solution. Photo-aging induced changes in the crystallinity and morphology of the PP and manifested in the abundance of smaller MPs, as revealed by the particle size distribution. In the case of pristine PP, all particles were > 100 µm in size, while aged PP yielded significant mass fraction of MPs <100 µm. The toxicity of leachates from aged PP-MPs is higher than that of pristine and exhibits a positive correlation with portion of metals released. The biodegradability of glucose is strongly inhibited by PP-MPs leachates containing a mixture of metals in trace concentrations.

Influence of Ageing on Optical, Mechanical, and Thermal Properties of Agricultural Films.

Plastic films utilized as greenhouse coverings play a vital role in safeguarding plantations from diverse weather conditions like sunlight, rain, hail, and wind. It is essential for these films to preserve their properties even after extended exposure to sunlight and water, while also maintaining transparency to support the unhindered growth of plants. The purpose of the study was to compare the properties of three types of plastic films: low density polyethylene diffuse film, low density polyethylene clear film, and ethylene tetrafluoroethylene film, before and after their ageing in weather test chamber with xenon-arc light in the presence of moisture. Two distinct types of PE films were chosen based on their suitability for specific regions in Croatia, whereas ETFE film was chosen as a potential new material that is gaining popularity across various industries, including agriculture. The properties investigated were tensile properties, transmittance by spectral analysis, and viscoelastic properties by dynamic mechanical analysis. Also, untreated films and the ones exposed to artificial ageing were compared by means of Fourier-transform infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis. The administered tests revealed a certain level of property degradation due to ageing in all three films. However, none of the films showed a substantial level of deterioration, indicating their suitability as greenhouse coverings.

Effect of Aging on Physicochemical Properties and Size Distribution of PET Microplastic: Influence on Adsorption of Diclofenac and Toxicity Assessment.

Microplastics (MPs) are detected in the water, sediments, as well as biota, mainly as a consequence of the degradation of plastic products/waste under environmental conditions. Due to their potentially harmful effects on ecosystems and organisms, MPs are regarded as emerging pollutants. The highly problematic aspect of MPs is their interaction with organic and inorganic pollutants; MPs can act as vectors for their further transport in the environment. The objective of this study was to investigate the effects of ageing on the changes in physicochemical properties and size distribution of polyethylene terephthalate (PET), as well as to investigate the adsorption capacity of pristine and aged PET MPs, using pharmaceutical diclofenac (DCF) as a model organic pollutant. An ecotoxicity assessment of such samples was performed. Characterization of the PET samples (bottles and films) was carried out to detect the thermooxidative aging effects. The influence of the temperature and MP dosage on the extent of adsorption of DCF was elucidated by employing an empirical modeling approach using the response surface methodology (RSM). Aquatic toxicity was investigated by examining the green microalgae Pseudokirchneriella subcapitata. It was found that the thermooxidative ageing process resulted in mild surface changes in PET MPs, which were reflected in changes in hydrophobicity, the amount of amorphous phase, and the particle size distribution. The fractions of the particle size distribution in the range 100-500 µm for aged PET are higher due to the increase in amorphous phase. The proposed mechanisms of interactions between DCF and PET MPs are hydrophobic and π-π interactions as well as hydrogen bonding. RSM revealed that the adsorption favors low temperatures and low dosages of MP. The combination of MPs and DCF exhibited higher toxicity than the individual components.

Investigation of the Conditions for the Synthesis of Poly(3,4-ethylenedioxythiophene) ATRP Macroinitiator.

One of the most widely used conductive polymers in the growing conductive polymer industry is poly(3,4-ethylenedioxythiophene) (PEDOT), whose main advantages are good thermal and chemical stability, a conjugated backbone, and ease of functionalization. The main drawback of PEDOT for use as wearable electronics is the lack of stretchable and self-healing properties. This can be overcome by grafting PEDOT with flexible side branches. As pure PEDOT is highly stable and grafting would not be possible, a new bromine-functionalized thiophene derivative, 2-(tiophen-3-yl) ethyl 2-bromo-2-methylpropanoate (ThBr), was synthesized and copolymerized with EDOT for the synthesis of a poly(EDOT-co-ThBr) ATRP macroinitiator. After the synthesis of the macroinitiator, flexible polymers could be introduced as side branches by atom-transfer radical polymerization (ATRP) to modify mechanical properties. Before this last synthesis step, the conditions for the synthesis of the ATRP macroinitiator should be investigated, as only functionalized units can function as grafting sites. In this study, nine new copolymers with different monomer ratios were synthesized to investigate the reactivity of each monomer. The ratios used in the different syntheses were ThBr:EDOT = 1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1, 0.8:1, 0.6:1, 0.4:1, and 0.2:1. In order to determine the effect of reaction time on the final properties of the polymer, macroinitiator synthesis at a 1:1 ratio was carried out at different time periods: 8 h, 16 h, 24 h, and 48 h. The obtained products were characterized by different techniques, and it was found that polymerizations longer than 24 h yielded practically insoluble macroinitiators, thus limiting its further application. Reactivity ratios of both monomers were found to be similar and close to 1, making the copolymerization reaction symmetrical and the obtained macroinitiators almost random copolymers.

Amphiphilic Silver Nanoparticles for Inkjet-Printable Conductive Inks.

The large-scale manufacturing of flexible electronics is nowadays based on inkjet printing technology using specially formulated conductive inks, but achieving adequate wetting of different surfaces remains a challenge. In this work, the development of a silver nanoparticle-based functional ink for printing on flexible paper and plastic substrates is demonstrated. Amphiphilic silver nanoparticles with narrow particle size distribution and good dispersibility were prepared via a two-step wet chemical synthesis procedure. First, silver nanoparticles capped with poly(acrylic acid) were prepared, followed by an amidation reaction with 3-morpholynopropylamine (MPA) to increase their lipophilicity. Density functional theory (DFT) calculations were performed to study the interactions between the particles and the dispersion medium in detail. The amphiphilic nanoparticles were dispersed in solvents of different polarity and their physicochemical and rheological properties were determined. A stable ink containing 10 wt% amphiphilic silver nanoparticles was formulated and inkjet-printed on different surfaces, followed by intense pulsed light (IPL) sintering. Low sheet resistances of 3.85 Ω sq-1, 0.57 Ω sq-1 and 19.7 Ω sq-1 were obtained for the paper, coated poly(ethylene terephthalate) (PET) and uncoated polyimide (PI) flexible substrates, respectively. Application of the nanoparticle ink for printed electronics was demonstrated via a simple flexible LED circuit.

Intrinsically Stretchable Poly(3,4-ethylenedioxythiophene) Conducting Polymer Film for Flexible Electronics.

The aim of this study was to synthesize an intrinsically stretchable conductive polymer (CP) by atom transfer radical polymerization (ATRP). For this purpose, poly(3,4-ethyilenedioxythiophene) (PEDOT) was synthesized as a backbone, while poly(acrylate-urethane) (PAU) was grafted onto the PEDOT backbone to form graft polymers PEDOT-g-PAU. Different concentrations of acrylate-urethane (AU) were used to synthesize PAU side chains of different lengths. The successful synthesis of the obtained intermediates and products (PEDOT-g-PAU) was confirmed by infrared spectroscopy and nuclear magnetic resonance. Thermal properties were evaluated by differential scanning calorimetry and thermogravimetric analysis, while conductivity was determined by four-point probe measurement. A simple tensile test was performed to characterize the ductility of the samples. PEDOT-g-PAU has shown high stretchability of up to 500% and, therefore, could potentially be used in skin-worn flexible electronics, while additional subsequent doping is required to improve the deterioration of electrical properties after the addition of the insulating urethane layer.

Influence of Home Composting on Tensile Properties of Commercial Biodegradable Plastic Films.

In recent years biodegradable plastic films have been increasingly used for various purposes, most often as grocery bags and for collecting bio-waste. Typically, the biodegradation of these films should take place in industrial compost facilities where the biodegradation process occurs under controlled conditions. Nevertheless, many of these films are often disposed of in home composting bins, so the aim of this study was to examine the course of biodegradation of compostable plastic films under uncontrolled conditions in garden composting sites during a period of four months. Mechanical properties were tested on seven different commercially available biodegradable films and bags that were placed in a garden composting bin from February to May. Both tensile properties and tensile-impact strength showed some unexpected results in terms of increase of the properties after the first, second, and third month for some films and bags. The same unpredictability was seen in FTIR and TG analyses.

Catalytic pyrolysis of mechanically non-recyclable waste plastics mixture: Kinetics and pyrolysis in laboratory-scale reactor.

Post-consumer waste plastics that cannot be mechanically recycled represent a concerning environmental issue. According to the latest available data for Europe, as much as 25% of collected post-consumer waste plastics are landfilled, 43% is energy recovered, and 32% is recycled. One possible way of recovering non-recyclable plastics is pyrolysis, which is considered environmentally friendly technology for obtaining fuel or chemicals from plastic waste. To tackle the challenge of recovering non-recyclable plastics via pyrolysis, it is necessary to determine their actual composition. Visual separation of collected non-recyclable plastics was performed, and Fourier-transform infrared spectroscopy was used to confirm the accuracy of visual separation. A significant amount of plastics labelled as "other" was found. Since the composition of "other" waste plastics has not been sufficiently investigated, relatively few studies on their pyrolysis have been conducted. Therefore, they were characterised and added to the mixture with other found polymer types of non-recyclable plastics. Thermogravimetric analysis was conducted to determine thermochemical behaviour and kinetic parameters required for laboratory pyrolysis investigation. Kinetic analysis was conducted using the Friedman isoconversional model-free method and non-linear multivariate regression method. The goal of this paper was to analyse the kinetics, determine the product yield and characteristics of the pyrolysis process of non-recyclable plastics over zeolite catalysts. It was found how the decomposition of non-recyclable plastics occurs in two decomposition steps. The activation energy of non-recyclable plastics was 144 kJ/mol in the first stage of decomposition and 262 kJ/mol in the second stage of decomposition. It decreased by 34% and 6.5% after fresh fluid catalytic cracking catalyst was added and 41% and 18.3% with iron-modified Zeolite Socony Mobil-5 catalyst. The yield of condensate was 55% (wax) for the original sample, and it decreased to 50% (wax and oil) and 27% (mostly oil) with fresh fluid catalytic cracking and iron modified Zeolite Socony Mobil-5 catalysts. Processes with catalysts promoted the formation of olefins and aromatic compounds in pyrolytic oil. All pyrolysis products had a high value of higher heating value ranging from 39 MJ/kg to 43 MJ/kg showing good potential for further energy use.

Development of PE/PCL Bilayer Films Modified with Casein and Aluminum Oxide.

The studied samples were prepared from polyethylene (PE) polymer which was coated with modified polycaprolactone (PCL) film in order to obtain bilayer films. Thin PCL film was modified with casein/aluminum oxide compound to enhance vapor permeability as well as mechanical and thermal properties of PE/PCL films. Casein/aluminum oxide modifiers were used in order to achieve some functional properties of polymer film that can be used in various applications, e.g., reduction of water vapor permeability (WVTR) and good mechanical and thermal properties. Significant improvement was observed in mechanical properties, especially in tensile strength as well as in water vapor values. Samples prepared with aluminum oxide particles indicated significantly lower values up to 60%, and samples that were prepared with casein and 5% Al2O3 showed the lowest WVTR value.