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1.
J Chem Phys ; 151(12): 124706, 2019 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-31575160

RESUMO

Most theories of the binding of molecules to surfaces or for the association between molecules treat the binding species as structureless entities and neglect their rigidity and the changes in their stiffness induced by the binding process. The binding species are also taken to be "ideal," meaning that the existence of van der Waals interactions and changes in these interactions upon molecular binding are also neglected. An understanding of the thermodynamics of these multifunctional molecular binding processes has recently come into focus in the context of the molecular binding of complex molecules, such as dendrimers and DNA grafted nanoparticles, to surfaces where the degree of binding cooperativity and selectivity, as well as the location of the binding transition, are found to be sensitive to the number of binding units constrained to a larger scale polymeric scaffold. We address the fundamental problem of molecular binding by extending classical Langmuir theory to describe the particular example of the reversible binding of semiflexible polymer chains to a solid substrate under melt conditions. The polymer chains are assumed to have a variable number N of binding units (segments) and to exhibit variable bending energies and van der Waals interactions in the bulk and on the surface, in addition to strong directional interactions with the surface. The resulting generalized Langmuir theory is applied to the examination of the influence of the chain connectivity of ideal polymers on the surface coverage Θ, transition binding temperature T1/2 at which Θ = 1/2, and on the derivative |dΘ/dT|T=T1/2 and the constant volume specific heat of binding, Cv bind, measures of the cooperativity and "sharpness" of the binding transition, respectively. Paper II is devoted to the impact of the van der Waals attractive interactions and chain stiffness on the reversible binding of nonideal polymer chains to a solid surface, including the enthalpy-entropy compensation phenomenon observed experimentally in many molecular and particle binding processes.


Assuntos
Modelos Químicos , Polímeros/química , Adsorção , Congelamento , Termodinâmica
2.
J Environ Sci (China) ; 85: 147-155, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31471021

RESUMO

Polymer hydrogel-based materials have been shown to act as novel Fenton catalysts for water treatment, but the rational design of hydrogel-based catalysts with good stability has been a great challenge. To increase the stability and activity of polymer-based Fenton catalysts, uniform urchin-like α-Fe2O3 was grown in situ in a PVA carrier matrix here. PVA molecules promoted the growth of urchin-like α-Fe2O3, and then the PVA hydrogel acted as a barrier and carrier to reduce agglomeration. Through coordination by hydroxyl groups, PVA had good combination with Fe ions and α-Fe2O3. The formation of Fe-O-C bonds between iron oxides and polymers was reported for the first time, enhancing the material stability during catalysis. Under higher PVA concentrations, the resulting composite hydrogel could generate more ˙OH due to the increase in the number of active sites because of the hairy urchin-like structure. In tetracycline degradation through a heterogeneous Fenton reaction, the resulting material had good catalytic activity from pH 2 to pH 10 with low iron leaching, good reusability and remained at a level of nearly 90% after five consecutive cycles. Density functional theory calculations were used to further prove the mechanism of structural change of the iron oxides. The HOMO and LUMO energies of the iron oxides changed from 5.428 and 4.899 eV to 5.926 and 5.310 eV, indicating that the presence of PVA could influence the charge of the iron atom. The results provide new insights into the preparation of polymer hydrogel-based heterogeneous Fenton catalysts with enhanced stability for water treatment.


Assuntos
Hidrogéis/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Compostos Férricos , Peróxido de Hidrogênio/química , Polímeros
3.
Bioresour Technol ; 293: 122056, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31514117

RESUMO

Aiming at optimizing the adsorption process of Chlorella vulgaris and cationic starch, the adsorption thermodynamic characteristics were evaluated. Different from inorganic calcium salt adsorbent, the adsorption nature of organic polymer cationic starch is exothermic (ΔH°â€¯< 0) and spontaneous (ΔG°â€¯< 0). Besides, the adsorption capacity and rate can be well described by Langmiur isotherm and pseudo second kinetic models. As results of exothermic nature and great driving force of lower temperature, the adsorption capacity and rate declined with the rising temperature. The maximal values of them were obtained at 278.15 K, which were 9148.14 mg microalgae (g cationic starch)-1 and 8.74 × 10-6 mg g-1 min-1. Additionally, with insufficient adsorbent, the highest adsorption efficiency (96.37%) was achieved at 278.15 K for stirring 150 min. For 288.15, 298.15, 308.15 and 318.15 K, the adsorption efficiency decreased to 93.77%, 86.75%, 83.32% and 81.57% and the time consumed were at least 40 min longer.


Assuntos
Chlorella vulgaris , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Polímeros , Amido , Temperatura Ambiente , Termodinâmica
4.
Adv Exp Med Biol ; 1148: 151-172, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31482499

RESUMO

Oral application of therapeutic enzymes is a promising and non-invasive administration that improves patient compliance. However, the gastrointestinal tract poses several challenges to the oral delivery of proteins, including harsh pH conditions and digestive proteases. A promising way to stabilise enzymes during their gastrointestinal route is by modification with polymers that can provide both steric shielding and selective interaction in different digestive compartments. We give an overview of modification technologies for oral enzymes ranging from functionalisation of native proteins, to site-specific mutation and protein-polymer engineering. We specifically focus on enzymes that are active directly in the gastrointestinal lumen and not systemically absorbed. In addition, we discuss examples of microparticle and nanoparticle encapsulated enzymes for improved oral delivery. The modification of orally administered enzymes offers a broad chemical variability and may be a promising tool for enhancing their gastrointestinal stability.


Assuntos
Sistemas de Liberação de Medicamentos , Enzimas/farmacologia , Trato Gastrointestinal , Nanopartículas , Engenharia de Proteínas , Administração Oral , Estabilidade Enzimática , Humanos , Peptídeo Hidrolases , Polímeros
5.
Phys Chem Chem Phys ; 21(37): 20999-21006, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31528872

RESUMO

A substantial number of diseases leading to loss of neurologic functions such as Morbus Alzheimer, Morbus Parkinson, or Chorea Huntington are related to the fibrillation of particular amyloidogenic peptides. In vitro amyloid fibrillation strongly depends on admixture with other proteins and peptides, lipids, nanoparticles, surfactants and polymers. We investigated amyloid-beta 1-40 peptide (Aß1-40) fibrillation in mixture with thermoresponsive poly(oligo(ethylene glycol)macrylates), in which the polymer's hydrophobicity is tuned by variation of the number of ethylene glycol-units in the side chain (m = 1-9), the end groups (B = butoxy; C = carboxy; D = dodecyl; P = pyridyldisulfide) and the degree of polymerization (n) of the polymers. The polymers were prepared via RAFT-polymerization, obtaining a broad range of molecular masses (Mn = 700 to 14 600 g mol-1 kDa-1, polydispersity indices PDI = 1.10 to 1.25) and tunable cloud point temperatures (Tcp), ranging from 42.4 °C to 80 °C, respectively. Proper combination of hydrophobic end groups with hydrophilic side chains of the polymer allowed to alter the hydrophilicity/hydrophobicity of these polymers, which is shown to enhance Aß1-40 aggregation significantly in case of the endgroup D (with n = 16, 23, 56). We observed that the less hydrophilic polymers (m = 1-2) were able to both decrease and elongate the lag (tlag) and characteristic times (tchar) of Aß1-40 fibril formation in dependence of their end groups, molecular mass and hydrophilicity. On the other hand, highly hydrophilic polymers (m = 3, 5, 9) either decreased, or only marginally influenced the lag and characteristic times of Aß1-40 fibrillation, in all cases forming ß-sheet rich fibrils as observed by TEM and CD-spectroscopy. Our results support that balanced hydrophobic and hydrophilic interactions of a polymer with Aß1-40 is important for inhibiting amyloid-formation pathways.


Assuntos
Peptídeos beta-Amiloides/química , Fragmentos de Peptídeos/química , Polímeros/química , Amiloide/química , Amiloide/ultraestrutura , Peptídeos beta-Amiloides/ultraestrutura , Interações Hidrofóbicas e Hidrofílicas , Fragmentos de Peptídeos/ultraestrutura
6.
Chem Commun (Camb) ; 55(66): 9829-9832, 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31363730

RESUMO

Polyethylene glycol grafted pyrrole-based conjugated polymers are synthesized through a one-pot multicomponent methodology, the self-assemblies of which enable nanoparticle size-selective encapsulation of drug molecules and their sustained release. Efficient loading of curcumin through drug-nanoparticle core interactions is probed using FRET, and the inherently fluorescent nature of polypyrrole could be used to detect these nanocarriers intracellularly.


Assuntos
Portadores de Fármacos , Nanopartículas/química , Polietilenoglicóis/química , Polímeros/química , Pirróis/química , Linhagem Celular Tumoral , Curcumina/administração & dosagem , Transferência Ressonante de Energia de Fluorescência , Humanos , Interações Hidrofóbicas e Hidrofílicas , Concentração Inibidora 50 , Microscopia Eletrônica de Transmissão , Espectrofotometria Ultravioleta
7.
J Biomed Nanotechnol ; 15(10): 2045-2058, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31462370

RESUMO

Combining photodynamic therapy (PDT) and chemotherapy can improve anti-cancer efficacy. In this study, a novel copolymer PTPP combining thioketal and protoporphyrin was synthesized and tested for antitumor activity. Self-assembled PTPP micelles loaded with doxorubicin (DOX) showed uniform size, narrow particle size distribution and greater antitumor activity in vivo and in vivo than DOX-loaded micelles made from the commonly used material mPEG-PCL. Under laser irradiation, the photosensitizing protoporphyrin of DOX/PTPP produces abundant reactive oxygen species (ROS) that directly kill tumor cells as well as destroy the micelles themselves, leading to drug release. The ROS and DOX then act synergistically against the tumors. These ROS-responsive, laser-sensitive polymeric micelles may be useful for combining PDT and chemotherapy.


Assuntos
Espécies Reativas de Oxigênio/química , Doxorrubicina , Liberação Controlada de Fármacos , Micelas , Fotoquimioterapia , Polímeros
8.
J Biomed Nanotechnol ; 15(10): 2090-2099, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31462373

RESUMO

Chemodynamic therapy based on Fenton or Fenton-like reactions is an emerging cancer therapy that has attracted considerable attention due to its high selectivity for tumors. However, the low catalytic efficiency of the Fenton or Fenton-like agent limits its therapeutic effect. Combination therapies based on chemodynamic therapy using "all-in-one" agents show great potential for cancer treatment. In this study, W18O49 nanorods with strong near-infrared absorption and excellent Fenton-like reaction performance were prepared, and their application in photoacoustic imaging-guided photothermal-chemodynamic combination cancer therapy was explored. First, hydrophobic W18O49 nanorods were synthesized via a one-step pyrolysis method. Hydrophilic W18O49 nanorods were then prepared via hydrophobic self-assembly between oleyl amine-coated W18O49 nanorods and an amphiphilic polymer. The W18O49 nanorods exhibited good photoacoustic, photothermal, and chemodynamic performance in vitro along with good photoacoustic imaging contrast and excellent therapeutic effect in photothermal-chemodynamic combination cancer therapy in vivo. This study provides a low-cost and easy-to-prepare agent for photothermal-chemodynamic combination therapy and promotes the application of photothermal-chemodynamic combination therapy in cancer treatment.


Assuntos
Nanotubos , Neoplasias , Técnicas Fotoacústicas , Terapia Combinada , Humanos , Polímeros
9.
Bioresour Technol ; 291: 121873, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31377506

RESUMO

Cholinium-glycinate ([Ch][Gly]) and cholinium-alanate ([Ch][Ala]) were investigated on the pretreatment of mulberry stem (MS). It resulted in an increase of glucose from 14% to more than 74% compared to the untreated sample. Pretreatment by reused [Ch][Gly] showed good performance for delignification of >60%, and improved structural polysaccharide digestion. Each fractional component has high potential for lignin purification, and succinic acid fermentation. The extracted lignin with [Ch][Gly] showed >90% purity with good qualities of aromatic unit as confirmed by FT-IR and 1H NMR spectra. The carbohydrate rich material was employed for succinic acid fermentation with the highest yield of succinic acid more than 0.89 gsuccinic acid/gglucose. After purification, poly(butylene) succinate (PBS) was synthesized, and was characterized in comparison to commercial PBS.


Assuntos
Butileno Glicóis/metabolismo , Fermentação , Morus/metabolismo , Polímeros/metabolismo , Ácido Succínico/metabolismo , Aminoácidos/metabolismo , Glucose/metabolismo , Líquidos Iônicos/química , Lignina/química
10.
J Biomed Nanotechnol ; 15(9): 1897-1908, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31387677

RESUMO

With the advance in nanomedicine, diagnostic and therapeutic nanoscale prodrugs have been rapidly developed in the field of cancer treatment. In this study, we constructed an enzyme-responsive polymer-paclitaxel (PTX) prodrug with a biocompatible saccharide-containing polymer backbone through the reversible addition-fragmentation chain transfer (RAFT) polymerization. A near-infrared fluorescent molecule (pheophorbide a) and magnetic resonance imaging (MRI) contrast agent (gadolinium-tetraazacyclododecanetetraacetic acid) were further conjugated onto the copolymer backbone to impart the ability of multimode imaging and tracing, forming the final diagnosis and treatment polymeric prodrug. This prodrug was amphiphilic and was able to self-assemble into uniform-size nanoparticles (80.1 nm). With the specific catalysis of enzymes, the anti-cancer drug, PTX, in the nanoparticles could be effectively released to kill cancer cells. The results of near-infrared fluorescence imaging and MRI showed that the diagnostic prodrug was preferentially concentrated at the tumor site compared with the free imaging reagents, suggesting improved and durable tumor imaging effects, which are beneficial for precise cancer diagnosis. The tumor growth in the mice could be effectively retarded after the administration of the prodrug. The tumor almost completely disappeared till the final treatment, and the tumor inhibition rate was as high as 96.4%. Immunohistochemical analysis indicated that the high anti-tumor effects might be attributed to the result that the prodrug not only induced the apoptosis of tumor cells, but also inhibited the formation of new blood vessels in the tumor environment. Therefore, this theranostic prodrug, which is based on the saccharide-containing polymer, holds potency for the development of a robust nanoscale platform for the diagnosis and treatment of cancer.


Assuntos
Neoplasias/tratamento farmacológico , Animais , Linhagem Celular Tumoral , Sistemas de Liberação de Medicamentos , Camundongos , Polímeros , Pró-Fármacos , Nanomedicina Teranóstica
11.
J Agric Food Chem ; 67(37): 10481-10488, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31433940

RESUMO

Here, we report two methods that chemically modify alginate to achieve neutral-basic pH sensitivity of the resultant hydrogel. The first method involves direct amide bond formation between alginate and 4-(2-aminoethyl)benzoic acid. The second method that arose out of the desire to achieve better control of the degradation rate of the alginate hydrogel involves reductive amination of oxidized alginate. The products of both methods result in a hydrogel vehicle for targeted delivery of encapsulated payload under physiological conditions in the gastrointestinal tract. Two-dimensional diffusion-ordered spectroscopy and internal and coaxial external nuclear magnetic resonance standards were used to establish chemical bonding and percent incorporation of the modifying groups into the alginate polymer. The hydrogel made with alginate modified by each method was found to be completely stable under acidic pH conditions while disintegrating within minutes to hours in neutral-basic pH conditions. We found that, while alginate oxidation did not affect the ß-d-mannuronate/α-l-guluronate ratio of alginate, the rate of disintegration of the hydrogel made with oxidized alginate was dependent upon the degree of oxidation.


Assuntos
Alginatos/química , Portadores de Fármacos/química , Sistemas de Liberação de Medicamentos/instrumentação , Administração Oral , Difusão , Hidrogéis/química , Concentração de Íons de Hidrogênio , Oxirredução , Polímeros/química
12.
Polim Med ; 49(1): 5-18, 2019.
Artigo em Polonês | MEDLINE | ID: mdl-31464108

RESUMO

BACKGROUND: Hydrophilic matrices used as oral forms of sustained release drugs are a suitable application medium for short-acting nonsteroidal anti-inflammatory drugs (NSAID) - ketoprofen. A properly selected hydrophilic matrix in oral preparations may significantly increase efficacy and application safety of ketoprofen. OBJECTIVES: The aim of the research was to analyze the usefulness of polymers (synthetic Kollidon K25 and K90, semi-synthetic hydroxyethylcellulose) and calcium hydrogen phosphate dihydrate (as an inorganic filler) in manufacturing solid oral matrix forms of ketoprofen and to study of the effect of non-ionic surfactants (Tween 80, Rofam 70) on release kinetics. MATERIAL AND METHODS: Ketoprofen, HEC, Kollidon K25, and K90, calcium hydrogen phosphate, magnesium stearate. Incorporation. Studies on the tablet mass. Direct tableting. Studies on the pharmacopoeial parameters and pharmaceutical availability. Approximation of the results. RESULTS: The results of the granulometric studies on tablet mass were in accordance with pharmacopoeial standards. The results of morphological and biopharmaceutical studies of the obtained matrices (tablets) were consistent with the pharmacopoeial standards for formulations with HEC, K25 and K90. The release results most closely related to row 0 kinetics were obtained for the matrix containing HEC and K25. Tween 80 added to 0.1N HCl accelerated the release of ketoprofen, while Rofam 70 decelerated it. Tween 80 and Rofam 70 added to the pH 7.4 buffer accelerated the release of ketoprofen. CONCLUSIONS: The presented model system of preformulation studies showed the usefulness of HEC and Kolidon K25 in the technology of hydrophilic matrices with ketoprofen. Surfactants added to the medium do not affect the release rate of ketoprofen.


Assuntos
Anti-Inflamatórios não Esteroides , Portadores de Fármacos , Cetoprofeno , Polímeros , Anti-Inflamatórios não Esteroides/administração & dosagem , Preparações de Ação Retardada , Cetoprofeno/administração & dosagem , Cinética , Polissorbatos , Povidona , Solubilidade , Tensoativos , Comprimidos
13.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 36(4): 604-612, 2019 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-31441261

RESUMO

In vitro experimental test for mechanical properties of a vascular stent is a main method to evaluate its effectiveness and safety, which is of great significance to the clinical applications. In this study, a comparative study of planar, V-groove and radial compression methods for the radial support property test were performed, and the effects of compression rate and circumferential position on the test results were conducted. Based on the three-point bending method, the influences of compression rate and circumferential position on flexibility were also explored. And then a best test proposal was selected to evaluate the radial support property and flexibility of the three self-designed stents and the comparative biodegradable vascular stent (BVS) (BVS1.1, Abbott Vascular, USA) with different outside diameters of 1.4 mm, 1.7 mm and 2.4 mm. The results show that the developing trends of the compression load with the compression displacement measured by the three radial support property test methods are the same, but normalized radial force values are quite different. The planar compression method is more suitable for comparing the radial support properties of stents with different diameters and structures. Compression rate has no obvious effect on the testing results of both the radial support property and flexibility. Compression circumferential position has a great impact on testing radial support property with the planar or V-groove compression methods and testing flexibility with three-point bending method. The radial support properties of all the three self-designed stents are improved at a certain degree compared to that of the BVS stent. The study has better guide significance and reference value for testing mechanical properties of vascular stents.


Assuntos
Implantes Absorvíveis , Fenômenos Mecânicos , Stents , Polímeros , Desenho de Prótese , Estresse Mecânico
14.
Eur J Prosthodont Restor Dent ; 27(3): 113-121, 2019 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-31433133

RESUMO

Various materials have been used over time in prosthetic dentistry. However, due to the evolution of science and knowledge, new materials are being brought to the forefront. Polyether ether ketone (PEEK) is a polymer with many potential applications in dentistry. The use of PEEK has become increasingly more common in dental practice; its favorable properties have made it a compelling alternative biomaterial in restorative dentistry. The current trend is moving towards the use of metal-free restorations and biomaterials which exhibit advanced properties in the complex oral environment. This review paper presents and summarizes clinical applications of PEEK in contemporary dentistry.


Assuntos
Éter , Polímeros , Prostodontia , Odontologia , Éteres , Cetonas , Polietilenoglicóis
15.
Am J Dent ; 32(4): 187-190, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31436939

RESUMO

PURPOSE: To evaluate the shear bond strength between denture base and artificial teeth subjected to five different modifications on the ridge surface. METHODS: 30 acrylic central anterior teeth were randomly divided into five groups (n= 6). The ridge surface of these teeth were treated with different methods: (1) No treatment applied; (2) Monomer wetting; (3) Grinding; (4) Grinding followed by sandblasting; (5) Grinding followed by monomer wetting. After the ridge surface of the teeth were treated, they were packed with denture base resin. The shear bond strength between acrylic teeth and denture base resin was performed using a universal testing machine. The data was statistically analyzed using one-way ANOVA (P< 0.05). RESULTS: The monomer wetting group showed the highest shear bond strength values, and the grinding followed by sandblasting group was the lowest, both were statistically significant compared to each other. There were no statistical differences between the other groups. CLINICAL SIGNIFICANCE: Treating the surface of the denture ridge with a monomer provided the highest shear bond strength values, and the grinding followed by sandblasting group was the lowest, statistically significant compared to each other.


Assuntos
Resinas Acrílicas , Colagem Dentária , Polímeros , Análise do Estresse Dentário , Bases de Dentadura , Teste de Materiais , Distribuição Aleatória , Resistência ao Cisalhamento , Propriedades de Superfície
16.
Inorg Chem ; 58(17): 11294-11299, 2019 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-31411862

RESUMO

The first two examples of polyoxopalladates(II) (POPs) containing tetravalent metal ion guests, [MO8Pd12(PO4)8]12- (M = SnIV, PbIV), have been prepared and structurally characterized in the solid state, solution, and gas phase. The interactions of the metal ion guests and the palladium-oxo shell were studied by theoretical calculations. The POPs were shown to possess anticancer activity by causing oxidative stress inducing caspase activation and consecutive apoptosis of leukemic cells.


Assuntos
Antineoplásicos/farmacologia , Metais Pesados/química , Compostos Organometálicos/farmacologia , Polímeros/química , Antineoplásicos/síntese química , Antineoplásicos/química , Morte Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Cristalografia por Raios X , Ensaios de Seleção de Medicamentos Antitumorais , Células HL-60 , Humanos , Íons/química , Modelos Moleculares , Compostos Organometálicos/síntese química , Compostos Organometálicos/química
17.
Bioresour Technol ; 292: 121970, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31421590

RESUMO

Co-pyrolysis of tobacco stalk (TS) with different types of polymer wastes such as scrap tire (ST), polypropylene (PP) and polyvinyl chloride (PVC) was investigated. Thermogravimetric analyzer coupled with Fourier transform infrared spectrometer was carried out to examine the thermochemical properties, kinetics, and gas generation. The results of the co-pyrolysis showed a synergistic effect compared to the pyrolysis of the individual components. When using TS/ST co-pyrolysis, the reduction in char residue was about 6% (dry wt. basis) and the increase in organic gases exceeded 20%. It indicates that the addition of ST can increase both carbon conversion efficiency and volatiles yield. HCl from PVC underwent a complex physicochemical reaction with TS, increasing coke yield by 11-12% and inhibiting the gas release. In the main pyrolysis temperature range of ST, the activation energy is reduced by 40-80% by blending with TS; for PP this value is reduced by about 22%.


Assuntos
Polímeros , Tabaco , Gases , Cinética , Pirólise , Termogravimetria
18.
Waste Manag ; 99: 22-30, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31470263

RESUMO

In this paper a full recognition of the different materials and valuable metals constituting mobile phones was performed. To this aim, a sample of 20 end-of-life devices has been dismantled and quantitative and qualitative chemical composition of the individual components was determined. From dismantling operations, it was found that plastics, metals, electronic components, batteries and displays account for 33%, 11%, 23%, 24% and 9% respectively, as a weighted average. Plastic parts of each item were analyzed by spectroscopy and then classified according to the plastic polymer type; it was found that polymeric components of mobile phones were made of five polymers: acrylonitrile-butadienestyrene, polycarbonate, polyurethane, polymethylmethacrylate and silicone. Electronic parts were leached by a twofold aqua regia treatment and the metal composition was determined: 15 elements were identified with concentration >0.2%. On the basis of these results, some considerations about the recycling context of end-of-life mobile phones were performed.


Assuntos
Telefone Celular , Resíduo Eletrônico , Plásticos , Polímeros , Reciclagem
19.
Waste Manag ; 96: 75-85, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31376972

RESUMO

Recycling of plastic is an important step towards circular economy. However, plastic from household waste (HHW) is a heterogeneous and contaminated resource, leading to recycled plastic with reduced quality, limiting the potential for closed-loop recycling. In addition to regulatory requirements for the chemical composition of recycled plastic, reduced physical and mechanical properties may limit the potential for closed-loop recycling. Consequently, this study analyses the thermal degradation, processability and mechanical properties of a range of reprocessed PET, PE and PP samples from source-separated plastic in HHW. On this basis, the potential for closed-loop recycling is evaluated. The study demonstrated that PET, PE and PP recycling represent different challenges. Potential degradation of the PET polymer can be reversed in a decontamination process, making PET waste well-suited for closed-loop, multiple times recycling, even when the degree of heterogeneity in the waste is high. The processability of different kinds of PE and PP packaging types varied considerably, especially for PP. Consequently, current recycling of mixed PP waste and even separate recycling of individual PP waste packaging types, will not technically facilitate recycling into new packaging products. This highlights the importance of PE and PP waste homogeneity when sent to reprocessing. Such homogeneity may be achieved through additional plastic sorting and regulatory harmonisation of product design, accounting for polymer properties and recyclability. Degradation of PP during recycling was shown to be substantial, representing another important limitation for PP recycling, necessary to address in the future.


Assuntos
Plásticos , Reciclagem , Polietilenotereftalatos , Polímeros , Embalagem de Produtos
20.
Waste Manag ; 97: 105-114, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31447017

RESUMO

Plastics are an indispensable material but also a major environmental pollutant. In contrast, biodegradable polymers have the potential to be compostable. The biodegradation of four polymers as discs, polycaprolactone (PCL), polyhydroxybutyrate (PHB), polylactic acid (PLA) and poly(1,4 butylene) succinate (PBS) was compared in soil and compost over a period of more than 10 months at 25 °C, 37 °C and 50 °C. Degradation rates varied between the polymers and incubation temperatures but PCL showed the fastest degradation rate under all conditions and was completely degraded when buried in compost and incubated at 50 °C after 91 days. Furthermore, PCL strips showed a significant reduction in tensile strength in just 2 weeks when incubated in compost >45 °C. Various fungal strains growing on the polymer surfaces were identified by sequence analysis. Aspergillus fumigatus was most commonly found at 25 °C and 37 °C, while Thermomyces lanuginosus, which was abundant at 50 °C, was associated with PCL degradation.


Assuntos
Plásticos Biodegradáveis , Compostagem , Biodegradação Ambiental , Poliésteres , Polímeros , Solo , Microbiologia do Solo
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