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Oil spills on water surface and shoreline have caused significant water pollution, and one of the ways to deal with them is to use oil sorbents. An effective sorbent provides high oil uptake and retention values, high selectivity, super-fast uptake kinetics, and sufficient mechanical strength to ensure practical application under different conditions. In this regard, synthetic sorbents made up of graphene, carbon nanotubes, and polymers in the form of aerogels, thin films, pads, and non-woven fibers have been widely explored. However, none of them addresses all the attributes of an ideal oil sorbent. Aerogels provide extremely high uptake values, but they are so light that it is difficult for the end user to handle them. On the other hand, thin films and non-woven fibers can quickly absorb oil but suffer from low uptake capacity with low retention values. Similarly, commercial oil sorbent pads have sufficient mechanical strength, but low uptake capacity compared to aerogels. Herein, we present a super oil sorbent with a porous structure using a facile energy-efficient approach. The as-prepared sorbent comprises a porous thin film with micropores and macro-cavities, resulting in super-fast uptake kinetics and a high oil uptake value of 85 g/g. Moreover, tensile test results confirm sorbent's effectiveness in spill response. Lastly, our unique design does not involve expensive hydrophobic functionalization and thus utilizes lower embodied energy and generates lower carbon footprints. This publication was made possible by NPRP grant number NPRP12S-0325-190443 from the Qatar National Research Fund (a member of the Qatar Foundation).

Purpose: The complex geometry of many composites is in a loose multi-phase and the large difference in the mechanical and electrical properties of the different components makes it difficult to predict the effective properties of the composites. The mechanical properties of copper powder filled linear low-density polyethylene (LLDPE) were predicted using an artificial neural network (ANN) approach. Method: Artificial neural networks have been used to predict the mechanical properties of loose multi-phase material systems. ANN is a network motivated by biological neural networks. ANN is based on Feed Forward Back Propagation (FFBP) using three different training functions (TRAINGDA, TRAINGDM, and TRAINGDX). The ANN approach runs the threshold TANSIG-PURELIN function for 200 epochs with a back propagation algorithm. The input parameters manipulated for the prediction were elongation at break (δ), stress at break (ρ), Young’s modulus (Y), volume fraction of the filler (ϕ) and constants (KE1,KE2,KS1,KS2,KS3,KS4,KY1). Copper powder filled LLDPE has a complex structure which makes it difficult to accurately predict the mechanical properties. This prediction was done using the ANN approach. Results: The theoretical models were compared with the experimental data and there was a good agreement between some models and the data. Conclusion: In line with the experimental data, we found that as we increased the volume fraction of the copper powder, the elongation and stress at break of the composites decreased, while the Young’s modulus increased.

The paper aims to study the poly(lactic acid) (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) blend properties after their degradation under 2000 h of accelerated weathering conditions following the ASTM D4329 stan-dard. PLA/PHBV blends form a biphasic system shown by the presence of two distinct glass transition temperatures and melting temperatures in differential scanning calorimetry (DSC) analysis, attributed to the neat polymers regardless of the blend composition. Scanning electron microscopy (SEM) indicated that the addition of high PHBV content to the blend results in a very heterogeneous surface with cavities available for moisture and UV penetration resulting in easier bulk and in-depth degradation of the samples. Thus, the wettability properties (evaluated by contact angle measurements) of the blends changed significantly over the weathering time. On the other hand, the PLA content delays the degradation process of the blends because of the resultant crystallinity from weathering degradation which exhibits a physical barrier to protect the PHBV fraction. PHBV improves the toughness of the blend and acts as a nucleating agent for PLA, promoting its crystallinity during sample preparation. Fourier-transform infrared (FTIR) confirmed photodegradation of all the blends via a Norrish II mechanism. The authors would also like to thank the Qatar University Central Laboratories Unit (QUCLU) for their assistance with the SEM measurements of the samples. This research was funded through the Qatar University Collaborative Grant No. QUCG-CAM 19/20-3. The findings achieved herein are solely the responsibility of the authors. Scopus

The interactions and morphology of molecules in a polymer blend influence the physical properties of the blend. However, little is known about the influence of molecular interaction and morphology on the thermal and mechanical properties of LLDPE/wax blends. Although cooling rate can be used to investigate blends' thermal and mechanical properties, it is inadequate to determine interactions between the molecules in the LLDPE/wax blends. However, since the morphology is related to the thermal and mechanical properties of polymer blends and could be related to the cooling rate, LLDPE/wax samples prepared by melt mixing were cooled at different rates. The thermal and mechanical properties of the LLDPE/wax blends were modelled through molecular dynamic simulations. The modelled transitions were compared to experimentally determined mechanical relaxations of LLDPE/wax blends to investigate the effect of wax addition on the blend crystallinity. The crystallization behaviour of the blends was studied by differential scanning calorimetry, dynamic mechanical behaviour by dynamic mechanical analysis, and differences in crystallinity by X-ray diffraction. There were no significant differences between the results for the slow- and quench-cooled samples, confirming the rapid crystallization of both the LLDPE and the wax. Experiments and molecular dynamics simulations confirmed the cocrystallization of wax with LLDPE.Other Information Published in: Journal of Polymer Research License: https://creativecommons.org/licenses/by/4.0See article on publisher's website: http://dx.doi.org/10.1007/s10965-022-03136-w

Poly(lactic acid) (PLA) has been found to be important in various applications, such as in the medical, pharma-ceutical, and packaging industries. However, the long-term associated degradation process of PLA is a limiting factor for some applications. Therefore, in this research, the influence of corona and radio-frequency (RF) surface plasma treatment on the degradation of PLA in accelerated weathering tests was studied. The accelerated weathering test was applied using standard UV irradiation for up to 2000 h. The morphological/topographical, chemical, crystallization, mechanical, and thermal changes were analyzed after 500, 1000, and 2000 h of accelerated weathering time. The introduction of the polar functional groups caused by plasma treatment on the PLA surface improved its wettability, and therefore, hydrolytic degradation was promoted over the accelerated weathering time. It was revealed that the plasma treatment enhanced the hydrolytic and UV degradation of the PLA, as was confirmed by investigation of the physical, chemical, mechanical, and thermal properties. Moreover, the RF plasma was more pronounced than the corona plasma in the degradation of the PLA. Such an approach represents a pathway to promote and tailor PLA degradation. This publication was supported by the Qatar University Collaborative Grant No. QUCG-CAM 19/20-3 and QUCG-CAM-20/21-3. The findings achieved herein are solely the responsibility of the authors. The authors thank Prof. Sergei Naza-renko, University of Southern Mississippi, United States, and his group for their help in conducting the GPC analysis, with special thanks to Ms. Karina Reynolds for her efforts in running the samples. SEM analysis was accomplished in the Central Laboratories unit, Qatar University. Scopus

Metal–organic frameworks (MOFs) are a class of materials that are increasingly used for the detection and separation of gases. This article presents the influence of gamma radiation on the dielectric properties of a LDPE/ZIF-8 composite that can be used for the production of gas sensors and massive gas absorbers. A low-density polyethylene (LDPE)–microsized zeolitic imidazolate framework-8 (ZIF-8) composite, obtained by melt mixing (95/5 weight ratio), was gamma-irradiated at room temperature to different absorbed doses up to 300 kGy. Infrared spectroscopy and optical microscopy confirmed the degradation of the ZIF-8 due to the gamma irradiation. The AC conductivity (admittance) of the samples was studied in the frequency range of 24 Hz − 120 kHz and a temperature range 200–350 K. The composite showed larger admittance components relative to the admittance components of pure LDPE; the conductance of the samples increased almost linearly with increasing irradiation dose. On the other hand, the change in dielectric permittivity of the LDPE and the composite due to irradiation was weak and showed nonlinear behavior with increasing radiation dose.

Polymer composite films of tris-(8-hydroxy-quinoline) aluminum (Alq3) and polymethyl methacrylate (PMMA) at two different concentrations were investigated. Dielectric properties of the samples were measured in broad frequency range and results show an increase in specific conductance and susceptance by adding Alq3 in PMMA. Changes in dielectric spectra caused by irradiation of the samples with LED lamps at different wavelengths were also recorded. The samples were examined by UV-Vis and Fourier transform infrared spectroscopy. The interaction between Alq3 and the polymer matrix was observed in the photoluminescence spectroscopy spectra. The doping of the PMMA with different concentrations of the Alq3 leads to the unique photodielectric properties of the resulting composite, and that is the main result of this study. Due to its interesting optical and photodielectric properties, PMMA/Alq3 film may find application in solar cells and optoelectronics This project was supported in part by the Science Fund of the Republic of Serbia's Ministry of Education and Science (Contract No. 451-03-68/2020) and by the Ministry of Scientific and Technological Development, Higher Education and Information Society of the Republic of Srpska (contract grant number 19.032/961-112/19). Scopus

Accelerated (artificial) weathering and thermal aging tests were performed to investigate the effectiveness of different formulations in reducing the UV/heat degradation extent for two low-density polyethylene types (LDPE-A, LDPE-T). The two LDPEs differ in the type and extent of branching due to the applied polymerization process, with LDPE-A being produced in an autoclave and LDPE-T in a tubular reactor. Oligomeric or high molecular weight hindered amine light stabilizer (HALS), and two UV absorbers of benzophenone or hydroxyphenyl-triazine types were equally introduced to both the LDPE grades at a total content of 0.2 wt%. The surface morphology, as well as thermal and mechanical properties, were examined during aging showing a significant degradation extent for the neat samples. In particular, a mechanism of chain scission/branch-ing that resulted in crosslinking was assumed for the neat polyethylenes, after combining the decrease of molecular weight observed in the GPC analysis with the increase in Young's modulus after UV exposure. LDPE-T presented higher photo-ox-idation rates due to its comb-like branched structure and its higher possibility of intermolecular reactions between adjacent chains. Little or no degradation was observed for the stabilized grades, confirming the effectiveness of the selected UV/heat systems in improving the weathering resistance of the two LDPE grades and enhancing their useful lifetime. This publication was made possible by the NPRP award (NPRP 9-161-1-030) from the Qatar National Research Fund (a member of The Qatar Foundation). We are also grateful to BASF and Sabo for supplying the additives at no cost. The statements made herein are solely the responsibility of the author(s). Scopus

The effect of accelerated weathering on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and PHBV-based nanocomposites with rutile titanium (IV) dioxide (PHBV/TiO2) was investigated. The accelerated weathering test applied consecutive steps of UV irradiation (at 340 nm and 0.76 W m&minus, 2 irradiance) and moisture at 50 &deg, C following the ASTM D4329 standard for up to 2000 h of exposure time. The morphology, chemical structure, crystallization, as well as the mechanical and thermal properties were studied. Samples were characterized after 500, 1000, and 2000 h of exposure time. Different degradation mechanisms were proposed to occur during the weathering exposure and were confirmed based on the experimental data. The PHBV surface revealed cracks and increasing roughness with the increasing exposure time, whereas the PHBV/TiO2 nanocomposites showed surface changes only after 2000 h of accelerated weathering. The degradation of neat PHBV under moisture and UV exposure occurred preferentially in the amorphous phase. In contrast, the presence of TiO2 in the nanocomposites retarded this process, but the degradation would occur simultaneously in both the amorphous and crystalline segments of the polymer after long exposure times. The thermal stability, as well as the temperature and rate of crystallization, decreased in the absence of TiO2. TiO2 not only provided UV protection, but also restricted the physical mobility of the polymer chains, acting as a nucleating agent during the crystallization process. It also slowed down the decrease in mechanical properties. The mechanical properties were shown to gradually decrease for the PHBV/TiO2 nanocomposites, whereas a sharp drop was observed for the neat PHBV after an accelerated weathering exposure. Atomic force microscopy (AFM), using the amplitude modulation&ndash, frequency modulation (AM&ndash, FM) tool, also confirmed the mechanical changes in the surface area of the PHBV and PHBV/TiO2 samples after accelerated weathering exposure. The changes in the physical and chemical properties of PHBV/TiO2 confirm the barrier activity of TiO2 for weathering attack and its retardation of the degradation process.

The effect of accelerated weathering on poly(lactic acid) (PLA) and a PLA nanocomposite with rutile titanium (IV) dioxide (rutile&ndash, TiO2) was investigated. The accelerated weathering test applied consecutive steps of ultraviolet (UV) (at 340 nm and 0.76 W m&minus, 2 irradiance) and moisture at 50 &deg, C for 2000 h, following the ASTM D4329 standard. The morphology, chemical structure, molecular weight, crystallization, as well as mechanical and thermal properties were thoroughly studied. Samples were characterized after 500 h, 1000 h and 2000 h exposure. Different degradation mechanisms were proposed to happen during the weathering exposure and confirmed based on the experimental data. The PLA and PLA/TiO2 surfaces presented holes and increasing roughness over the exposure time. The molecular weight of the weathered samples decreased due to chain scission during the degradation processes. Thermal stability decreased in the presence of TiO2 and a double melting peak was observed for the PLA/TiO2 nanocomposite. A general improvement in the mechanical properties of the PLA/TiO2 nanocomposite was observed over time during the accelerated weathering analysis up to 1000 h of exposure time. After 2000 h of weathering exposure, the PLA and PLA/TiO2 became extremely brittle and lost their ductile properties. This was ascribed to a significant increase in the degree of crystallinity upon weathering, which was accelerated in the presence of TiO2. Atomic force microscopy (AFM) using amplitude modulation&ndash, frequency modulation (AM&ndash, FM) tool confirmed the mechanical changes in the surface area of the PLA samples after accelerated weathering exposure. The stiffness and Young&rsquo, s modulus achieved higher values than the unweathered ones up to 1000 h of exposure time. The changes in the physical and chemical properties of PLA/TiO2 over the ageing time confirm the photocatalytic activity of rutile&ndash, TiO2.

This study provides a new insight into the relationships between absorption and adsorption processes that occur during the treatment of iPP in aqueous solutions of metal-chloride salts, as well as the impact of these processes on the electrical conductivity of this nonpolar polymer. The polypropylene films (0.5 mm) were exposed to three-day treatments in aqueous solutions of chlorine salts of some alkali and transition metals at temperatures of 22 C and 80 C. The treatments induced an increase in the electrical conductivity of iPP, up to 800%. DC conductivity is not directly proportional to the concentrations of metals in the treated films due to the complex relationships between diffusion and adsorption processes. The experiment was set up to simulate the real-world conditions and the study provides practical knowledge on the stability of the electrical conductivity of iPP under exposure to aqueous solutions. The influence of electric aging on the electrical conductivity of the treated films was also examined. This work was supported in part by the Ministry of Education, Science and Technological Development of the Republic of Serbia, by the Ministry of Scientific and Technological Development, Higher Education and Information Society of the Republic of Srpska (project: 19.032/961-112/19) and by the National Research Foundation, South Africa. Scopus

Gas chromatography (GC) was used to study the kinetics of the 3-cyanopropyl triethoxysilane (CTES) polymerization. The reaction is a consecutive complex reaction that depends mainly on the kinetics of the first hydrolyzed leaving group. The activation energy of CTES hydrolysis is 20 and 58�kJ mol?1 in alkaline and acidic media, respectively. The activation energy of ethanol production ranged from 22 to 55�kJ mol?1 according to the catalyst type and concentration. Generally, the reaction is an endothermic reaction in an acidic medium, whereas it is exothermic in an alkaline medium, depending on the catalyst concentration. Moreover, the reaction is spontaneous at high temperatures in an acidic medium. The rate constant is related to the catalyst concentration with empirical formulas depending on the Arrhenius equation. The rate constant increases non-linearly (to the power 2) with the concentration of water in an acidic medium, whereas it behaves differently in an alkaline medium and depends on the initial concentrations of CTES and the catalyst. Scopus

Biodegradable polymers received considerable attention due to their contribution in the reduction of environmental concerns and the realization that global petroleum resources are finite. The development of double crystalline biobased blends such as poly(ε-caprolactone) (PCL) and poly(butylene succinate) (PBS) are particularly interesting because each component has an influence on the crystallization behaviour of the other component, and thus influences the strength and mechanical properties of a polymer blend. The lack of miscibility between PCL and PBS constitutes a bottleneck, and efforts have been made to improve the miscibility through the inclusion of copolymers. Having realized that incorporating conductive nanofillers such as carbon nanotubes (CNTs), (especially when the CNTs are functionalized or used as a masterbatch i.e., polycarbonate/MWCNTs masterbatch), into biopolymer matrices, can enhance the thermal and mechanical properties, as well as electrical and thermal conductivity, a lot of research was aimed at the production of bionanocomposites. This review paper discusses the properties of PCL, PBS, their blends, and their CNTs containing nanocomposites.

This work reports on the effect of commercial expandable graphite (EG) on the flammability and thermal decomposition properties of PLA-starch blend. The PLA-starch/EG composites were prepared by melt-mixing and their thermal stability, volatile pyrolysis products and flammability characteristics were investigated. The char residues of the composites, after combustion in a cone calorimeter, were analyzed with environmental scanning electron microscopy (ESEM). The thermal decomposition stability of the composites improved in the presence of EG. However, the char content was less than expected as per the combination of the wt% EG added into PLA-starch and the % residue of PLA-starch. The flammability performance of the PLA-starch/ EG composites improved, especially at 15 wt% EG content, due to a thick and strong worm-like char structure. The peak heat release rate (PHRR) improved by 74%, the total smoke production (TSP) by 40% and the specific extinction area (SEA) by 55%. The improvements are attributed to the ability of EG to exfoliate at increased temperatures during which time three effects occurred: i) cooling due to an endothermic exfoliation process, ii) dilution due to release of H2O, SO2 and CO2 gases, and iii) formation of a protective intumescent char layer. However, the CO and CO2 yields were found to be unfavorably high due to the presence of EG.

This work reports on the effect of expandable graphite (EG) on the morphology, thermal and dynamic mechanical properties of flame retardant poly(lactic acid) (PLA)/EG composites. The composites were prepared by melt-mixing and their structure, morphology, melting and crystallization behaviour, as well as their dynamic mechanical properties, were investigated. It was found that graphite layers still existed in an aggregate structure with poor filler dispersion resulting in a lack of interfacial adhesion between EG and the PLA matrix. The presence of EG did not favour the crystallization of PLA, increased the glass transition temperature and showed a reduction in the crystallinity of the composites. The composites with higher filler contents showed enhanced storage and loss moduli. The glass transition temperatures from the loss modulus and damping factor curves varied inconsistently with EG content. The use of commercial EG as filler in PLA can preserve the thermal properties of injection moulding grade Cereplast PLA. The financial assistance of the National Research Foundation towards this research is hereby acknowledged. Opinions expressed and conclusions arrived at are those of the authors and are not necessarily to be attributed to the NRF. Acknowledgements are also extended to colleagues and researchers for their undivided attention and support. The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors received the financial support from National Research Foundation for the research, authorship, and/or publication of this article. Scopus

This paper investigated the influence of TiO2 nanoparticles on the morphologies, as well as crystallization behaviour and kinetics, of neat PLA and PCL, and of these polymers in different PLA/PCL blends. We used transmission electron microscopy to evaluate the morphologies of the systems, while the crystallization behaviour and kinetics were investigated through differential scanning calorimetry (DSC). In addition to standard and modulated (StepScan) DSC analyses, the self-nucleation temperatures of neat PCL and PCL in the different nanocomposites were determined, followed by a self-nucleation and annealing thermal fractionation analysis of PCL crystallization and an Avrami isothermal kinetic analysis of PCL crystallization and PLA cold crystallization. We found that the nanoparticles were well dispersed, but only in the PLA phase of the blends, with only a few on the interface or in the PCL phase. They did nucleate and accelerate, and influence the mechanism of, the PCL crystallization in neat PCL, but had little influence on PCL crystallization in the blends. They strongly influenced the rate of cold crystallization of PLA, but had little influence on this parameter in the blends. The tensile properties were also determined, and changes in these properties could be related to the morphologies of the systems.

Silver nanoparticles are amongst the most valuable nanoparticles with interesting properties, such as a non-toxic nature and high antibacterial efficiency, making them applicable for tissue scaffold, protective clothing and wound dressing. In this study, silver nanoparticles (AgNPs) have been synthesized using chitosan as reducing and stabilizing agent. The formation of silver nanoparticles was confirmed by UV-vis, and the TEM showed that different shapes were obtained depending on the heating duration. The chitosan/AgNPs was coated onto an electrospun alginate membrane to produce stable polyelectrolyte complex (PEC) nanofibre composites with high antibacterial efficiency. These composites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). AgNPs were successfully impregnated into the PEC nanofibre composite, while there was complexation between the electrospun alginate and the chitosan/AgNPs composite. PEC demonstrated a good antibacterial activity against both gram negative and gram positive bacteria with acceptable water vapour transmission within the range required for the treatment of injuries or wounds.

This article reports on the morphology, interfacial interaction, thermal stability, and thermal degradation kinetics of polycarbonate (PC)/mesoporous silica (MCM-41) composites with various MCM-41 contents, prepared by melt compounding. The composites with low filler loadings (

This paper reports on the potential of electrospun alginate nanofibre membranes to be used for the bio-sorption of heavy metals from aqueous solutions. Poly(ethylene oxide) (PEO) and its blends were electrospun at an applied voltage of 1–1.3 kV/cm and a solution flow rate of 0.8 mL·hr–1. The electrospinnability of the nanofibre blends was enhanced by storing the blend solutions in a controlled environmental chamber. The electrospun nanofibre membranes were washed with calcium chloride to remove PEO. Beadless nanofibres with average diameters of 114 nm and a surface area of 18.03 m2·g–1 were obtained. Fourier transform infra-red (FTIR) spectroscopy and thermogravimetric analysis (TGA) confirmed the removal of PEO after washing with calcium chloride. The adsorption behaviour of the nanofibrous membranes was investigated using Cu(II) as model metalloid at different concentrations (0–1000 mg·L–1), temperatures (25, 40, and 60 °C) and pH values (2–6). The Langmuir isotherm better presented the equilibrium experimental data than the Freundlich model. The electrospun alginate membranes displayed a maximum monolayer sorption capacity (Q0) of 15.6 mg·g–1 at a pH of 4. In a competitive adsoption experiment the removal of metal ions in a mixture followed the order Cu > Ni > Cd > Co.

Alkoxysilanes and organoalkoxysilanes are primary materials in several industries, e.g. coating, anti-corrosion treatment, fabrication of stationary phase for chromatography, and coupling agents. The hydrolytic polycondensation reactions and final product can be controlled by adjusting the hydrolysis reaction, which was investigated under a variety of conditions, such as different alkoxysilanes, solvents, and catalysts by using gas chromatography. The hydrolysis rate of alkoxysilanes shows a dependence on the alkoxysilane structure (especially the organic attachments), solvent properties, and the catalyst dissociation constant and solubility. Some of the alkoxysilanes exhibit intramolecular catalysis. Hydrogen bonding plays an important role in the enhancement of the hydrolysis reaction, as well as the dipole moment of the alkoxysilanes, especially in acetonitrile. There is a relationship between the experimentally calculated polarity by the Taft equation and the reactivity, but it shows different responses depending on the solvent. It was found that negative and positive charges are respectively accumulated in the transition state in alkaline and acidic media. The reaction mechanisms are somewhat different from those previously suggested. Finally, it was found that enthalpy–entropy compensation (EEC) effect and isokinetic relationships (IKR) are exhibited during the hydrolysis of CTES in different solvents and catalysts; therefore, the reaction has a linear free energy relationship (LFER).

Scientists from various different fields use organo-trialkoxysilanes and tetraalkoxysilanes in a number of applications. The silica-based materials are sometimes synthesized without a good understanding of the underlying reaction kinetics. This literature review attempts to be a comprehensive and more technical article in which the kinetics of alkoxysilanes polymerization are discussed. The kinetics of polymerization are controlled by primary factors, such as catalysts, water/silane ratio, pH, and organo-functional groups, while secondary factors, such as temperature, solvent, ionic strength, leaving group, and silane concentration, also have an influence on the reaction rates. Experiments to find correlations between these factors and reaction rates are restricted to certain conditions and most of them disregard the properties of the solvent. In this review, polymerization kinetics are discussed in the first two sections, with the first section covering early stage reactions when the reaction medium is homogenous, and the second section covering when phase separation occurs and the reaction medium becomes heterogeneous. Nuclear magnetic resonance (NMR) spectroscopy and other techniques are discussed in the third section. The last section summarizes the study of reaction mechanisms by using ab initio and Density Functional Theory (DFT) methods alone, and in combination with molecular dynamics (MD) or Monte Carlo (MC) methods.

Dielectric characterization of materials in the RF domain is usually carried out on samples with applied electroconductive electrodes. A high-quality contact between a sample and the measuring electrodes provides a stable current flow through the sample and information on the exact value of the electric field in which the sample is located. It also enables a simple measuring instrument to determine the dielectric parameters of the material being tested. However, the presence of contact potentials and the exchange of charge between the test material and the applied electrodes can mask some electrical phenomena in the material or significantly affect how we perceive these phenomena. In order to detect weak electrical processes in the material, for example the photoelectric response of non-polar polymers, contactless dielectric measurements must be carried out. The literature on non-contact dielectric measurements in the RF domain is poor, and because of that, this paper presents the methodology for determining the dielectric parameters of film-shaped materials in conditions of contactless dielectric measurements.

Polymers are fast becoming a serious environmental hazard, and are normally disposed of through landfilling, recycling, and incineration. Landfill sites are becoming increasingly scarce, and incineration contributes to air pollution and global warming. Recycling is still not applied in most countries of the world. The uncontrolled disposal of plastic waste gives rise to a large amount of plastics ending up in the earth’s oceans, where they degrade very slowly into micro-plastics that are consumed and converted to toxic persistent organic pollutants by marine fauna. Biodegradable polymers, which can be petrochemical- or bio-based, may be a solution to these problems. They can be degraded by microorganisms to CO2, water, and biomass through a process of biodeterioration, bio-fragmentation, and assimilation. Although a large number of bacteria and enzymes have been identified to biodegrade these polymers, they cannot universally degrade all kinds of biodegradable polymers, and the effectiveness and/or rate of biodegradation depend on the polymers’ morphology and physical properties. In many cases the microbial degradation has to be preceded by UV- or hydrolytic degradation, or a specific composting environment has to be created. Even if biodegradable polymers with acceptable properties can be synthesized, and if most of the existing nonbiodegradable polymers can be replaced by biodegradable polymers, commercial composting sites still have to be established in all the countries of the world. As in recycling, the different biodegradable polymers will have to be separated, and the different kinds of polymers will have to be composted in environments that contain microorganisms that are effective for the biodegradation of the specific polymer(s).

The morphology, crystallization behavior and mechanical properties of PLA, PHBV and their blends and nanocomposites with TiO 2 as filler were investigated. An uncommon morphological change was observed with increasing PLA content in the blends, and this complicated the isothermal crystallization kinetics analyses of the different samples. It was, for example, observed that PLA, which do not normally crystallize during the cooling of the sample, showed isothermal crystallization for certain blend compositions. TiO 2 was found to be mainly present in the PLA phase, which was also confirmed through broadband dielectric analysis. The blend composition, as well as the presence of TiO 2 nanoparticles, had an influence on the cold crystallization of the PLA. The tensile properties changed with blend and nanocomposite composition, and these changes could to a certain extent be related to the respective morphologies. Very little could be said about differences between the melting behavior of the different samples, because the PLA and PHBV melted at almost exactly the same temperature. Scopus

A variety of poly(lactic acid) (PLA)-poly(ε-caprolactone) (PCL) samples with different PLA:PCL ratios, containing different contents of graphite nanoplatelets (GrP), were analysed in a thermogravimetric analyser (TG) under, respectively, nitrogen and oxygen atmospheres, and in a differential scanning calorimeter (DSC) in a nitrogen atmosphere. Their respective morphologies were determined through scanning electron microscopy. The TG analyses in nitrogen gave fairly predictable results, but the analyses in oxygen gave complex results that seemed to be dependent on the respective morphologies of the blend samples and on the presence and amount of GrP in the respective samples. It was observed that, depending on the blend or nanocomposite morphologies, the GrP could have played the role of catalysing the degradation process, or inhibiting the onset of degradation by immobilizing the polymer or free radical chains and by delaying the evolution of the degradation products from the respective samples. The DSC results clearly showed the influence of the respective components in the blends and composites on the crystallization behaviour and crystallinities of the two polymers. Acknowledgements This work was supported by Czech Science Foundation (Grant No: 16-03194S). Scopus

The current article deals with the development of different novel, tailor-made polyolefin formulations exhibiting both low flammability and high weathering resistance, so as to provide value-added polyethylene grades with extended service lifetime. Two low-density (LDPE) and one linear low-density (LLDPE) polyethylene grades were modified via melt compounding with an additive system comprising: (a) a nitrogen-phosphorous intumescent system for flame retardance and (b) a hindered amine light stabilizer and a benzophenone-type UV absorber for UV/heat stabilization, at a total loading of 30-35 wt%. The target was to reach V0 classification in UL94V flammability tests, while to a large extent maintaining the mechanical properties, such as, tensile and impact strength of the investigated polymers, thus ensuring that the additives do not interfere significantly with the material quality. Subsequently, the compounds were subjected to separate artificial UV and heat aging at 100 C for 1500 h; the formulations showed good flame retardance, even after prolonged artificial weathering, but there was an observable, although acceptable, decrease in the mechanical properties. Nevertheless, all the results show that the developed polyethylene compounds are very promising for outdoor applications, such as, irrigation piping and profiles, where long-term weathering stability is important, and where flame retardance is important for safety during storage. This publication was made possible by the NPRP award (NPRP 9-161-1-030) from the Qatar National Research Fund (a member of The Qatar Foundation). We are also grateful to BASF and Sabo for supplying the additives at no cost. We further express our gratitude to Dr. Mabrouk Ouederni from QAPCO for providing us with the three polyethylene grades. The statements made herein are solely the responsibility of the author(s). Scopus

The design of composite materials using environmentally compatible materials and adopting sustainable preparation techniques is very necessary for a better environment. The present study is a step towards developing an environmentally friendly alternative to foam-based composites. The aim of the study is to understand the effect of natural fibers from date palms on the property of foam biocomposites. We adopted an environmentally friendly method of compatibilization between the polymer and the fibers for better reinforcement. The compatibility was done by environmentally friendly physical modification using plasma treatment. Plasma treatment provides surface modification and is an economical solution for further processing. In fact, three types of interfaces have been created: (1) by the addition of maleic anhydride, (2) by the use of plasma-treated low-density polyethylene, (3) by the combination of maleic anhydride and plasma. The overall performance was best in the use of plasma treatment alone. The effect was carefully analyzed based on morphological, mechanical and thermal studies. Finally, a morphology-property correlation was established. This work was supported by the Centre for Advanced Materials, Qatar University, State of Qatar doing research work like preparation and experimentation.Part of the research was also supported by the Ministry of Science and Higher Education within the State assignment Federal Scientific Research Center Crystallography and Photonics of the Russian Academy of Sciences. Scopus

Poly(lactic acid)/ethylene vinyl acetate blends and poly(lactic acid)/ethylene vinyl acetate/sugarcane bagasse composites were prepared by melt mixing. The lower viscosity of poly(lactic acid), the lower interfacial tension between poly(lactic acid) and sugarcane bagasse, and the wetting coefficient of poly(lactic acid)/sugarcane bagasse being larger than one, all suggested that sugarcane bagasse would preferably be in contact with poly(lactic acid). A fairly good dispersion of sugarcane bagasse was observed in the composites. Exposed fibre ends were observed in the composite micrographs, which were believed to add to the efficiency of metal adsorption. The impact properties depended more on the poly(lactic acid):ethylene vinyl acetate ratio than on the presence of sugarcane bagasse. The poly(lactic acid)/ethylene vinyl acetate blends showed two melting peaks at approximately the same temperatures as those of the neat polymers, which confirms the complete immiscibility of poly(lactic acid) and ethylene vinyl acetate at all the investigated compositions. Sugarcane bagasse-related weight loss occurred at higher temperatures for sugarcane bagasse in the composites, which could have been the result of the sugarcane bagasse being protected by the polymers, or a delay in the diffusion of the sugarcane bagasse decomposition products out of the sample. Water absorption increased with an increase in sugarcane bagasse loading in the composites. More lead was adsorbed than one would expect if the partial coverage of the fibre by the polymer is taken into account, and therefore it may be assumed that some of the lead was trapped inside the cavities in the composites and that the polymers may also have played a role in the metal complexation process, since both polymers have functional groups that could interact with the lead ions. The metal impurities underwent monolayer adsorption.

This paper reports on an investigation of the influence of the presence of two different clays, Cloisite 15A and Cloisite 30B, and fibre drawing on the degradation behaviour and kinetics of PCL/PLA composites. It was found that the type of clay significantly influenced the mass loss behaviour of the composites because of physical interactions between the clay and the polymer chains and degradation volatiles. Melt drawing of the composite films, however, had little influence on the degradation behaviour of the investigated samples. This work was supported by Czech Science Foundation (Grant No 13-15255S).

Ce:YAG-polycarbonate composites were prepared with several amounts of Ce:YAG in the range 0.1-5 wt.% by using melt compounding. The structure and morphology of the composites were investigated by means of X-ray diffractometry and transmission electron microscopy. The optical properties of the composites were studied by using photoluminescence spectroscopy. The intermolecular interaction between the polymer and the filler surface was investigated using 13C cross-polarization magic-angle spinning NMR spectroscopy (13C {1H} CP-MAS NMR). The results showed that the dispersion of the particles in the polymer, and the optical properties, depend on the Ce:YAG amount. The composites were combined with a blue LED in order to test their performance in a white LED device. Results indicate that more suitable light is obtained using the Ce:YAG-PC composite loaded at 2 wt.%. 2016 Elsevier B.V. The authors acknowledge the University of Palermo, FFR 2012–2013 –ATE 0594 “Development of new methodologies for the synthesis and functionalization of nanoparticles with luminescence properties for advanced applications” and CORI2013 (Bando per la concessione di contributi per l'avvio e lo sviluppo di collaborazioni dell’Ateneo 2013- Azione D - prot. 32827 del 2/5/2013). NMR and TEM experimental data were provided by Centro Grandi Apparecchiature—UniNetLab—Universita' di Palermo funded by P.O.R. Sicilia 2000–2006, Misura 3.15 Azione C Quota Regionale. Student support was provided by the National Research ​Foundation in South Africa. Thanks to Dr. Camillo Sartorio for the registration of the excitation and of the emission spectra. Scopus