Compostability of polymers

In recent years, biobased polymers have gained attention from industries, consumers and governments as a way to reduce municipal solid waste. Much attention has been given to their production and implementation. However, these materials only reach their potential environmental benefits when they are recovered through recycling or composting and/or their energy is recovered by incineration. These end‐of‐life scenarios allow closing the carbon cycle loop. A lot of confusion and misunderstanding about these new materials and their end‐of‐life scenarios, particularly composting, have been generated. This paper addresses definitions and environmental performance of these materials and their compostability. Current methods for measuring biobased content and biodegradability of polymers and factors affecting it, such as exposure conditions and polymer characteristics, are discussed, and the use of life cycle assessment as a tool to evaluate the environmental performance of biopolymers is presented. Although there are some obstacles for the growth and implementation of biobased polymers, such as consumer adoption and available composting facilities accepting these materials, new opportunities are growing due to government regulation and business initiatives in the past five years. However, consumers' understanding of when the use of these materials provides environmental benefits and when not is still missing. Therefore, to adopt and to implement these new biopolymers cooperative work among industry, consumers and government is needed. Copyright © 2008 Society of Chemical Industry     

Chemical recycling of PET flakes into yarn

Polyesters such as polyethylene terephthalate are widely used in textile fibers, films, and packaging of food and beverages. Originally driven by environmental reasons, recycling of postconsumer polyester bottles into textile fibers is now becoming commercially attractive. We studied the chemical recycling wherein part of the virgin raw‐materials during preparation of polyester was replaced by washed post consumer polyester. During the process, the postconsumer polyester undergoes partial depolymerization before repolymerization. Role of reactor‐agitator configuration in achieving the solid‐slurry and solid‐melt mixing, and in depolymerization, was studied. Finally, suitability of the polymer for melt spinning and drawing of polymer into yarn was examined. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Solid‐state recycling of polyimide film waste

Possibility of the polyimide (PI) films waste recycling by solid‐state mechanochemistry was investigated in this study. Obtained PI powder was used for development of thermostable blends and multicomponent tribocompositions, which include additions of carbon black, ultradispersive diamond powder, and quasicrystalls. PI films waste treatment was provided in high‐energy planetary ball mill. Powder compositions were mixed by low‐energy planetary ball mill. Bulk samples were obtained by compression molding. Structural and thermal properties of initial polymers and composite materials were determined from scanning electron microscope, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis and fourier transform infrared spectroscopy. Tribological tests of composite materials were provided in dry sliding regime on “pin‐on‐disk” tribometer. Finally, optimal regimes of polymer composite materials producing were obtained. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Up‐cycling end‐of‐use materials: Highly filled thermoplastic composites obtained by loading waste carbon fiber composite into fluidified recycled polystyrene

Carbon fibers reinforced epoxy resins are used in a wide range of applications, such as automotive and aerospace industry. Because of their thermosetting nature, recycling at the end of the life cycle is a difficult issue. However, lack of recyclability poses environmental concerns to the use of these composite materials. In this article, a sustainable, cost‐effective technological approach aiming at recycling postconsumer carbon fibers reinforced thermosets (CFRT) is proposed. Composites containing 50 and 70 wt% of CFRT particles were prepared by incorporating the filler fraction into a fluidified postconsumer expanded polystyrene matrix. A cold mixing approach consisting in the use of a low boiling solvent as a binder to guarantee the dispersion homogeneity on micro‐ and macroscopic level was set up. For comparison, analog composites were also prepared through melt mixing process. Morphological, mechanical, and thermal analyses allowed to prove the effectiveness of the cold mixing approach and to evaluate the influence of particle size on the performance of new recycled composites. Thermogravimetric analysis and thermal conductivity tests of samples highlighted further peculiarities of the cold mixing process. The approach proposed is an effective recycling technology for CFRT and could be extended to other postconsumer materials. POLYM. COMPOS., 35:1621–1628, 2014. © 2013 Society of Plastics Engineers     

Trends in Conducting Polymer and Hybrids of Conducting Polymer/Carbon Nanotube: A Review

Several conducting polymers, including polyaniline, polypyrrole, polythiophene, polyvinylpyrrolidone, poly(3,4-ethylenedioxythiophene), poly(m-phenylenediamine), polynaphthylamine, poly(p-phenylene sulfide), and their carbon nanotube reinforced nanocomposites are discussed in this review. The physical, electrical, structural and thermal properties of polymers along with synthesis methods are discussed. A concise note on carbon nanotubes regarding their purification, functionalization, properties and production are reported. Moreover, the article focuses upon synthesis methods, properties and applications of conducting polymer/carbon nanotube nanocomposites are focused. Nanotube dispersion, loading concentration and alignment within conducting polymer/carbon nanotube nanocomposite affect their performance and morphology. The conducting polymer/carbon nanotube nanocomposites are substantially used in sensors, energy storage devices, supercapacitors, solar cells, EMI materials, diodes, and coatings.     

Recycling of polymers from plastic packaging materials using the dissolution–reprecipitation technique

In this work, results are presented on the application of the dissolution/reprecipitation technique in the recycling of polymers from waste plastic packaging materials used in food, pharmaceuticals and detergents. Initially, the type of polymer in each packaging was identified using FT-IR. Furthermore, experimental conditions of the recycling process (including type of solvent/non-solvent, initial polymer concentration and dissolution temperature) were optimized using model polymers. The dissolution/reprecipitation technique was applied in the recycling of a number of plastic materials based on polyethylene (LDPE and HDPE), polypropylene, polystyrene, poly(ethylene terephthalate) and poly(vinyl chloride). The recovery of the polymer was measured and possible structural changes during the recycling procedure were assessed by FT-IR spectroscopy. Potential recycling-based degradation of the polymer was further investigated by measuring the thermal properties (melting point, crystallinity and glass transition temperature), of the polymer before and after recycling, using DSC, their molecular properties (average molecular weight) using viscosimetry, as well as their mechanical tensile properties. High recoveries were recorded in most samples with the properties of the recycled grades not substantially different from the original materials. However, a slight degradation was observed in a few samples. It seems that this method could be beneficial in waste packaging recycling program.     

Recent developments in polymers derived from industrial lignin

Lignin is an aromatic polymer that makes up 15–30% of the cell walls of terrestrial plants. While lignin's role in facilitating water transport through the vasculature, providing rigidity and acting as a defense against pests and pathogens is important for the plant's survival, industries that process plant biomass for the production of biofuels and bio‐based chemicals have historically primarily been interested in the cell wall polysaccharides, especially cellulose. Consequently, lignin is generated in large quantities as a by‐product that is often burned to generate heat and electricity, or that is used in low‐value applications. It is becoming clear that, rather than treating it as waste, lignin is very suitable for the production of enhanced composites, carbon fibers, and nanomaterials, which offers both economic and environmental benefits. This review highlights recent uses of these polymers as adsorbents, flocculants, adhesives, anti‐oxidants, energy storing films, and vehicles for drug delivery and gene therapy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42069.     

Poly(vinylpyrrolidone) as a tool: aqueous dispersion of nanodiamonds by wrapping in the solid state

Among carbon‐based nanomaterials such as fullerenes, carbon nanotubes and nanodiamonds, the latter are good candidates as prospective materials in the future due to their potential physical, chemical and biological properties. Thus, nanodiamonds were wrapped with biocompatible polymers in the solid state. The dispersibility of the polymer‐wrapped nanodiamonds in water was investigated with respect to reaction time and mass ratio of the polymers during the wrapping process. The dispersibility of the materials was monitored using UV spectroscopy, and the size distribution of the polymer‐wrapped nanodiamonds was analyzed using high‐resolution transmission electron microscopy and dynamic light scattering measurements. In addition, molecular modeling calculations were performed. Finally, the best dispersion for the polymer‐wrapped nanodiamonds in water was found for a reaction time of 120 min. Copyright © 2012 Society of Chemical Industry     

The fire performance of electrical insulating materials used in fluorescent lighting fixtures

Analysis of a major fire incident at a home furnishings warehouse led to the conclusion that extended exposure of electrical insulating materials composing a lampholder in a fluorescent lamp were the initial items ignited. It was thought that these items, composed of thermoset polymers, were ignition‐resistant materials. However, analysis showed that thermally induced degradation caused the material to degrade into an easily ignited, char‐like residue. The parent polymer, highly cross‐linked urea formaldehyde, had been initially cast into the lampholder configuration to prevent high voltage conditions and arcing. Thermal and elemental analyses as well as the investigation conducted at the fire site, helped to determine that the original polymer had pyrolysed into a residue differing in both chemical composition — reduced hydrogen and oxygen content — and physical characteristics when compared with the parent material. The changes in the chemical and physical properties of the original polymer explain the observed thermal inertia of the residue and its tendency to smolder (as opposed to the ‘parent polymer’). They are characterized by (1) an increased accessibility to oxygen, (2) reduced thermal conductivity and (3) increased proportion of carbon. Copyright © 2002 John Wiley & Sons, Ltd.     

Natural Polymers from Biomass Resources as Feedstocks for Thermoplastic Materials

With the objective of a more sustainable circular economy, one long‐term goal is the utilization of renewable resources as feedstock for the production of polymer‐based materials. In order to successfully process such materials using existing industrial‐scale technologies or even recycling processes, the natural polymers must have thermoplastic properties. With only a few exceptions, natural polymers are not thermoplastic. However, chemical and physical modification techniques are able to induce thermoplasticity in natural polymers from biomass resources such as cellulose, lignin, and chitin. Modification techniques focus on masking the hydroxyl groups to disrupt dense hydrogen bonding and so enable polymer chain mobility upon heating. The introduction of long alkyl chains into the polymer backbone effectively improves the thermoplastic processing of natural polymers. With regard to polymer blending, chemical grafting and graft copolymerization are powerful tools for enhancing compatibility. For both chemical and physical modification, solvents such as ionic liquids and deep eutectic solvents are currently being explored for biomass and fiber processing and show promise for the future development of thermoplastic biopolymers. This review describes possible modifications, potential processing difficulties, and gives a summary of relevant studies described in the scientific literature.     

Current approaches to waste polymer utilization and minimization: a review

The mass production of polymer products, in particular plastics, and their widespread use depending on the inherent advantages they have, make these materials ironically a threat to life on Earth. Polymer recycling is being considered as one of the most widely accepted remedies to the threat of growing amounts of plastic waste by both the public and scientists. In practice, recycling is associated with many difficulties, such as problems related to separation, sorting and cleaning operations, lack of fiscal subsidies, instability of selective garbage separation programs, high transport and electricity costs, etc. Still, a large section of society and the authorities agree on the necessity and importance of recycling to protect the environment, and natural habitats and resources for future generations in a balanced manner to conserve raw materials, and to reduce energy consumption, municipal solid waste production and greenhouse gas emission. The recycling effort is almost endless in itself and includes a variety of approaches such as refurbishing, mechanically reshaping, chemically treating, thermally utilizing, etc. Some novel approaches such as application in carbon capture or synthesis of carbon nanostructures from the plastic waste are among the new process technologies of recycling. From traditional and promising polymer waste utilization approaches, this review will highlight sustainable methods to reduce impacts of plastic waste on the environment. © 2018 Society of Chemical Industry     

Poly(2‐alkyloyloxyethylacrylate) and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) comblike polymers as novel phase‐change materials for thermal energy storage

A series of poly(2‐alkyloyloxyethylacrylate) and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) polymers as novel polymeric phase‐change materials (PCMs) were synthesized starting from 2‐hydroxyethylacrylate and fatty acids. The chemical structure and crystalline morphology of the synthesized copolymers were characterized with Fourier transform infrared and ¹H‐NMR spectroscopy and polarized optical microscopy, respectively, and their thermal energy storage properties and thermal stability were investigated with differential scanning calorimetry and thermogravimetric analysis, respectively. The thermal conductivities of the PCMs were also measured with a thermal property analyzer. Moreover, thermal cycling testing showed that the copolymers had good thermal reliability and chemical stability after they were subjected to 1000 heating/cooling cycles. The synthesized poly(2‐alkyloyloxyethylacrylate) polymers and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) copolymers as novel PCMs have considerable potential for thermal energy storage and temperature‐control applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Hybrid organosiloxane coatings containing epoxide precursors for protecting mild steel against corrosion in a saline medium

Hybrid organic–inorganic materials made from sol–gel precursors can be used as anticorrosion barriers on metal substrates. The modification of epoxy resins with silicones is an interesting approach toward the synthesis of hybrid materials that combine the advantages offered by epoxy resins with those of silicones. In this study, novel hybrid epoxy‐silicon materials were synthesized using sol–gel chemistry and subsequently functionalized with 4,4′‐methylenebis(phenyl isocyanate), incorporating urethane functionality into the final polymer. The study screened five different epoxide precursors for use in the synthesis of the new hybrid materials and optimizing their anticorrosion properties. Spectral characterization confirms the proposed chemical structures of the newly synthesized polymers. The newly developed polymers were painted on mild steel panels, thermally cured, and their thermal, surface morphological, adhesion, and anticorrosion properties were fully characterized. The new coatings were found to have excellent thermal stability and adherence properties to steel surface. The results of corrosion testing on coated steel panels following long‐term immersion in a 3.5 wt % aqueous NaCl medium revealed that the polymer prepared using the epoxide precursor bisphenol A diglycidyl ether provided the best anticorrosion protection property among the synthesized polymers. This could be attributed to the excellent integrity and crosslink density properties in addition to the lack of microdefects in the surface of this coated sample as confirmed by scanning electron microscopy analyses. The newly prepared hybrid coatings reported in this study are very promising as an alternative to toxic chromate‐based coatings. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43947.     

Rohstoff-Recycling und Energie-Gewinnung von Kunststoffabfällen

Feedstock Recycling and Energy Recovery from Plastics Waste. The disposal concept of the plastics industry comprises the following four steps: prevention/reduction, recycling of material (mechanical recycling, feedstock recycling), energy recovery and dumping. Feedstock recycling or chemical recycling stands for the chemical conversion of polymer materials with reduction of macromolecular structure to low-molecular raw materials. The combustion of plastics waste uses the high calorific value of plastics for energy recovery. This paper describes some of the processes for feedstock recycling and for energy recovery from plastics waste.     

Recycling Tetrafluoroethylene–Perfluoroalkyl Vinylether Copolymer (PFA) Using Extrusion Process

Tetrafluoroethylene–perfluoroalkyl vinylether copolymer (PFA) has a broad application ranging from biomedical and aerospace to corroding environments in the chemical industry. Despite a low share in end-of-life products, PFA processing can produce up to 30% of waste. Thus, understanding how recycled fluorinated polymers affect product performance is crucial to ensure primary recycling, besides economic and environmental reasons. In this paper, the utilization feasibility of PFA waste materials is investigated, i.e., recycled PFA (PFAr) in closed-loop recycling. The effect of PFAr loading (5–100 wt.%) on the thermal, mechanical, rheological, and color properties and chemical resistance are studied. Thermal properties and chemical resistance showed no significant changes in all ranges of PFAr content tested. The addition of higher loads of PFAr (≥50 wt.%) leads to a reduction in mechanical properties, particularly stress-strength analysis and elongation at break. However, elastic modulus and hardness have improved concurrently with an increase in the degree of crystallinity. The decrease in complex viscosity and yellowing of the samples occurred probably induced by a polymer chain degradation. Despite that, the addition of up to 10 wt.% of PFAr proved to be an effective alternative to reusing PFA residues based on mechanical recycling.     

Synthesis of ethylene terephthalate and ethylene naphthalate (PET‐PEN) block‐co‐polyesters with defined surface qualities by tailoring segment composition

Ethylene terephthalate and ethylene naphthalate oligomers of defined degree of polymerization were synthesized via chemical recycling of the parent polymers. The oligomers were used as defined building blocks for the preparation of novel block‐co‐polyesters having tailored sequence compositions. The sequence lengths were systematically varied using Design of Experiments. The dispersive surface energy and the specific desorption energy of the co‐polymers were determined by inverse gas chromatography. The study shows that polyethylene terephthalate‐polyethylene naphthalate (PET‐PEN) block‐co‐polyesters of defined sequence lengths can be prepared. Furthermore, the specific and dispersive surface energies of the obtained block‐co‐polyesters showed a linear dependence on the oligomer molecular weight and it was possible to regulate and control their interfacial properties. In contrast, with the corresponding random‐block‐co‐polyesters no such dependence was found. The synthesized block‐co‐polyesters could be used as polymeric modifying agents for stabilizing PET‐PEN polymer blends. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40731.     

Thermodynamic Stability of Low‐k Amorphous SiOCH Dielectric Films

Si–O–C‐based amorphous or nanostructured materials are now relatively common and of interest for numerous electronic, optical, thermal, mechanical, nuclear, and biomedical applications. Using plasma‐enhanced chemical vapor deposition (PECVD), hydrogen atoms are incorporated into the system to form SiOCH dielectric films with very low dielectric constants (k). While these low‐k dielectrics exhibit chemical stability as deposited, they tend to lose hydrogen and carbon (as labile organic groups) and convert to SiO₂ during thermal annealing and other fabrication processes. Therefore, knowledge of their thermodynamic properties is essential for understanding the conditions under which they can be stable. High‐temperature oxidative drop solution calorimetry measurement in molten sodium molybdate solvent at 800°C showed that these materials possess negative formation enthalpies from their crystalline constituents (SiC, SiO₂, C, Si) and H₂. The formation enthalpies at room temperature become less exothermic with increasing carbon content and more exothermic with increasing hydrogen content. Fourier transform infrared spectroscopy (FTIR) spectroscopy examined the structure from a microscopic perspective. Different from polymer‐derived ceramics with similar composition, these low‐k dielectrics are mainly comprised of Si–O(C)–Si networks, and the primary configuration of carbon is methyl groups. The thermodynamic data, together with the structural analysis suggest that the conversion of sp² carbon in the matrix to surface organic functional groups by incorporating hydrogen increases thermodynamic stability. However, the energetic stabilization by hydrogen incorporation is not enough to offset the large entropy gain upon hydrogen release, so hydrogen loss during processing at higher temperatures must be managed by kinetic rather than thermodynamic strategies.     

Preparation of a functional reduced graphene oxide and carbon nanotube hybrid and its reinforcement effects on the properties of polyimide composites

The homogeneous dispersion and strong interfacial interactions of carbon nanomaterials are vital factors on enhancing the properties of polymer composites. Two‐dimensional reduced graphene oxide (rGO) and one‐dimensional carbon nanotubes (CNTs) were first grafted by 4,4′‐oxydianiline (ODA). The successful grafting of ODA onto the rGO and CNTs were confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and X‐ray photoelectron spectroscopy. The hybrid carbon nanomaterials of the functionalized CNTs and rGO with different ratios were prepared via a solution‐mixing method, and their dispersion state was investigated. The hybrid carbon nanomaterials with good stability were introduced to polyimide (PI) via in situ polymerization. The morphology and properties of the polymer composites were studied. The results show that much better mechanical and electrical properties of the composites could be achieved in comparison with those of the neat PI. An improvement of 100.7% on the tensile strength and eight orders for the electrical conductivity were achieved at only a 1.0 wt % hybrid content. A significant enhancement effect was attributed to the homogeneous dispersion of the filler, filler–matrix strong interfacial interactions, and unique structure of the hybrid carbon nanomaterials in the composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44575.     

Benign enzymatic synthesis of multiwalled carbon nanotube composites uniformly coated with polypyrrole for supercapacitors

BACKGROUND: Recently, various composites of carbon nanomaterials and conducting polymers have been actively investigated as potential electrode materials for supercapacitors which can store and deliver large amounts of electrical energy promptly. Harsh chemical or complex electrodeposition methods have been studied to prepare such composites. In this report, the mild and simple enzymatic catalysis of horseradish peroxidase (EC 1.11.1.7) in aqueous solutions (pH 4.0) was utilized for the first time to prepare composites of multiwalled carbon nanotubes and polypyrrole. RESULTS: Electron micrographs show that in situ enzymatic reaction by horseradish peroxidase enables the uniform coating of multiwalled carbon nanotubes with polypyrrole without containing the polymer aggregates. The specific capacitance of the composites (46.2 F g^?1) measured with a two‐electrode cell containing an electrolyte of 1 mol L^?1 NaNO₃ increased more than four‐fold compared with that obtained with bare multiwalled carbon nanotubes (10.8 F g^?1). CONCLUSIONS: Horseradish peroxidase‐catalyzed in situ synthesis of the composites of multiwalled carbon nanotubes and polypyrrole requires neither the derivatization of multiwalled carbon nanotubes and/or pyrrole monomers nor the post‐doping of the synthesized composites to enhance the capacitance of the composites. © 2012 Society of Chemical Industry     

Thermoplastic elastomers derived from bio‐based monomers

Series of copolyesters based on poly(propylene succinate) (PPS) and poly(butylene succinate) (PBS), which can be produced from biological feedstock, and postconsumer poly(ethylene terephthalate) (PET) were synthesized with the aim of developing sustainable materials, which combine the mechanical properties of high performance elastomers with those of flexible plastics. The aliphatic polyesters were synthesized by the catalyzed two‐step transesterification reaction of dimethyl succinate, 1,3‐propanediol, and 1,4‐butanediol followed by melt reaction with PET in bulk. The content of PET segments in the polymer chains was varied from about 10 to 100 wt % per 100 wt % PPS or PBS. The effect of the introduction of the PET segments on the structure, thermal, physical, and mechanical properties was investigated. The composition and structure of these aliphatic/aromatic copolyesters were determined by NMR spectroscopy. The thermal properties were investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The level of crystallinity was studied by means of DSC and wide‐angle X‐ray scattering. A depression of melting temperature and a reduction of crystallinity of copolyesters with increasing content of PET segments were observed. Consequently, the tensile modulus and strength of copolyesters decreased, and the elongation at break increased with PET content in the range of 10?50 wt %. Thus, depending on PET content, the properties of copolyesters can be tuned ranging from semicrystalline polymers possessing good tensile modulus (380 MPa) and strength (24 MPa) to nearly amorphous polymer of high elongation (～800%), and therefore they may find applications in thermoplastics as well as elastomers or impact modifiers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39815.