Ethylene-propylene Copolymer Research Articles

Robust propylene-ethylene copolymer/polypropylene films: Extensional stress-induced orientation realized at low temperature processing

From the viewpoint of energy conservation, exploring low temperature processing of robust polypropylene-based films is meaningful. By blending polypropylene (PP) and propylene-ethylene copolymer (coPP), the processing temperature of oriented films is significantly reduced to 80 °C, compared to that of PP which is normally close to its melting point. Besides, the addition of PP remarkably enhances mechanical properties of the films after stretching. When PP content is 60 wt%, the increasing draw ratio leads to increase in tensile strength of up to 250 MPa, showing enhancement of 600% attributed to extensional stress-induced orientation structure. Intriguingly, it is found with significance that coPP/PP blends exhibit the PP spherulites formed in the range of tens of micrometers, while phase separates in the range of sub-micrometers within the spherulites. Additionally, the evolution of phase and crystalline structures of coPP/PP system during the deformation is studied for the first time, demonstrating that the structural evolution of PP phase always lags behind that of coPP phase. These results give a new insight into the relationship between structure and properties of PP multiphase system during stretching, offering helpful guidance to economically fabricate robust films based on polypropylene related polymers widely used in industry.

New Insights into Crystallization of Heterophasic Isotactic Polypropylene by Fast Scanning Chip Calorimetry.

The crystallization kinetics of metallocene-catalyzed heterophasic isotactic polypropylene composed of a matrix of isotactic polypropylene (iPP) and rubbery particles made of random ethylene–propylene copolymers (EPC), often denoted as heterophasic iPP copolymers, was analyzed as a function of the cooling rate and supercooling in nonisothermal and isothermal crystallization experiments, respectively. Fast scanning chip calorimetry (FSC) allowed assessing crystallization at processing-relevant conditions, and variation of the content (0–39 wt %) and composition (0–35 wt % propylene counits) of the EPC particles revealed qualitatively new insight about mechanisms of heterogeneous crystal nucleation. For neat iPP homopolymer, the characteristic bimodal temperature dependence of the crystallization rate due to predominance of heterogeneous and homogeneous crystal nucleation at high and low temperatures, respectively, is reconfirmed. At high temperatures, in heterophasic iPP, the here studied ethylene-(C2)-rich EPC particles accelerate crystallization of the iPP-matrix, with the acceleration or nucleation efficacy correlating with the EPC-particle content. The crystallization time reduces by more than half in presence of 39 wt % EPC particles. An additional nucleating effect of the EPC particles on iPP-matrix crystallization is detected after their crystallization, suggesting that liquid/rubbery particles are less effective than solid/semicrystalline particles in affecting crystallization of the surrounding iPP-matrix. At low temperature, homogeneous crystal nucleation in the iPP-matrix outpaces all heterogeneous nucleation effects, and the matrix-crystallization rate is independent of the sample composition. The obtained results lead to the conclusion that the crystallization kinetics of iPP can be affected significantly by the content and composition of EPC particles, even towards superfast crystallizing iPP grades.

Ionic Liquids and Calcium Oxide Grafted with Allylmalonic Acid Applied to Support the Peroxide Crosslinking of an Ethylene-Propylene Copolymer.

Nanosized calcium oxide (CaO) featuring a surface grafted with allylmalonic acid (ALA) was used to increase the efficiency of the peroxide crosslinking of an ethylene–propylene copolymer (EPM) filled with silica nanoparticles. In this study, 1-butyl-3-methylimidazolium ionic liquids (ILs) with different anions were applied to improve the dispersion of CaO/ALA and silica nanoparticles in the EPM copolymer, as well as to catalyze the interfacial crosslinking reactions. In this article, we discuss the effects of CaO/ALA and ILs on the curing characteristics, vulcanization temperature, crosslink density, mechanical properties, and thermal stability of EPM, as well as the resistance of EPM to weather aging. The CaO/ALA with ILs reduced the vulcanization time of the rubber compounds without a significant effect on the vulcanization temperature. Their application resulted in an increased vulcanizate crosslink density, as well as improved tensile strength compared to the pure peroxide system. The influence of 1-butyl-3-methylimidazolium ILs on EPM vulcanization and performance depends on the anion present in the molecules of the ionic liquid. The most active IL seems to be that with the tetrafluoroborate anion.

Copolymer Structure and Performance Consequences of High‐Impact Ethylene–Propylene Copolymers Based on a Ziegler–Natta Catalyst with Novel Internal Donor

AbstractCatalyst development for advanced isotactic polypropylene copolymer grades cannot be considered without parallel work on the polymerization process, especially when multi‐phase high‐impact ethylene‐propylene copolymers (also called heterophasic copolymers, HECOs) of complex composition are considered. Using a Ziegler–Natta type catalyst produced in an emulsion process and using citraconate ester as internal donor, a series of such high‐impact copolymers is first produced in a bench‐scale reactor. At this stage, the content of ethylene‐propylene copolymer (EPC) phase is varied in a wide range for understanding the catalyst performance as well as the resulting structure‐property relations, using three‐stage polymerization to emulate multiple reactors. Selected compositions are subsequently scaled up to a multi‐reactor pilot plant, demonstrating composition effects on mechanical performance. Both stages are accompanied by structural investigations using 13C‐NMR spectroscopy and atomic force microscopy. The novel catalyst is found to be capable of synthesizing HECOs in a wide range of elastomer (EPC) content, achieving free‐flowing polymer powders up to an elastomer content as expressed by the xylene cold soluble fraction of 37 wt%.

Effects of process parameters on silane grafting of liquid ethylene-propylene copolymer by reactive extrusion as quantified by response surface methodology

Here, we report the continuous peroxide-initiated grafting of vinyltrimethoxysilane (VTMS) onto a standard polyolefin by means of reactive extrusion to produce a functionalized liquid ethylene propylene copolymer (EPM). The effects of the process parameters governing the grafting reaction and their synergistic interactions are identified, quantified and used in a mathematical model of the extrusion process. As process variables the VTMS and peroxide concentrations and the extruder temperature setting were systematically studied for their influence on the grafting and the relative grafting degree using a face-centered central composite design (FCD). The grafting degree was quantified by 1H NMR spectroscopy. Response surface methodology (RSM) was used to calculate the most efficient grafting process in terms of chemical usage and graft yield. With the defined processing window, it was possible to make precise predictions about the grafting degree with at the same time highest possible relative degree of grafting.

Deep-Discharge Performance of Lead Acid Battery Using Graphite Based Composite As Cathode Current Collector

Introduction Lead Acid Batteries (“LAB”) have been widely used for more than 100 years. LAB cannot be recharged after over-discharged, and its performance is greatly declined. Iwai et al. have found that the above deterioration is caused by the formation of α-PbO2 on the surface of cathode active material β-PbO2 due to the reduction by local cell reaction. They also have revealed that the formation of α-PbO2 can be prevented by using gold or platinum as cathode current collector. At that case, the LAB can be recharged even after over-discharge.[1,2] We revealed, furthermore, that LAB using graphite sheet as cathode current collector also has high resistance to over-discharge.[3] This LAB can charge/discharge without performance degradation even after full discharge followed by 48 h rest period. In order to improve sulfuric acid resistance, we tried to mix four kinds of resin (polyethylene, polypropylene, ethylene propylene copolymer and fluororesin) to the graphite sheet. It is revealed that the weight of graphite sheet did not increase by immersion test into sulfuric acid for more than or equal to 5 wt% polypropylene mix, and that surface electrical resistance of the sheet did not increase for less than or equal to 5 wt% polypropylene mix.[4] We decided to use graphite sheet with 5 wt% polypropylene as cathode current collector. For this LAB, we have investigated long term charge deep-discharge cycle performance including various kinds of rest-period. We also investigated the rechargeablity after 0V discharge followed by various long rest period. Experiment We made the resin-dispersed graphite sheet in order to improve electrolyte repellency compared to normal graphite sheet. We used polypropylene for resin material and dispersed it by 5 wt% into expanded graphite, then we made it into sheet by rolling mill. The heat treatment was preheating at 100℃ for 10 min and then at 180℃ for 10 min to disperse resin evenly.We used two-electrode glass cell for charge/discharge experiments. The cathode active material was prepared by mixing β-PbO2 powder, acetylene black and PTFE at the ratio of 80:15:5 in weight. We added acetylene black as a conductive additive and PTFE as a binder. The cathode was made by pressing the paste on a current collector. We used 35% H2SO4 as electrolyte and lead plate as anode.First experiment is the long term deep-discharge durability test. The cycle was consisted of 4 times of discharge down to 0V and full charge, and then 48 h rest period. Charge/discharge rate was 180 mAg-1 for charge and 9 mAg-1 for discharge. The stabilization cycle prior to deep-discharge was consisted of 20 cycles of discharge at 9 mAg-1 for 30 min and charge at 180 mAg-1 for 20 min. We determined charge and discharge rates by weight of cathode active material.The second experiment is to evaluate durability against over-discharge followed by various rest period. After the stabilization cycle, we discharged the cell down to 0V and kept it in open-circuit for various period, and then rechargeablity was examined by charging the cell. Results and discussion Fig.1 shows the result of the first experiment. The LAB using 5 wt% polypropylene-dispersed graphite sheet current collector continued the cycle of 4 times charge/deep-discharge and 48 h rest for more than 5 months. The cause of the breakage of the cell after 5 months was due to fall of active material off the current collector. It is thought that this cell could charge/discharge for longer term by improving the filling method of active material. This result shows that this type of battery has high durability to deep-discharge for long term.Fig.2 shows the result of the second experiment. The rest period was 2 d or 1 week. It was found that the cell was rechargeable for either rest period. It was confirmed that The LAB using 5 wt% polypropylene-dispersed graphite sheet current collector has high durability to both over-discharged and long term rest.

Thermooxidative stability of hot melt adhesives based on metallocene polyolefins grafted with polar acrylic acid moieties

The present paper describes the thermal oxidation of a mixture applied as hot melt adhesive and particularly of its essential polymeric component ethylene-propylene copolymer Licocene 2602 either virgin or grafted by acrylic acid. Chemiluminescence in oxygen under both nonisothermal and isothermal conditions was used as the tool for evaluation of oxidation stability of samples. The effect of various concentrations of stabiliser Naugard XL1 acting as a metal deactivator and phenolic antioxidant was also determined and the antioxidant selected was found to be an efficient thermooxidative stabiliser. The results appear to be of importance for practical multiple application of hot melt adhesives to be used for binding books.

Polymerization of heterophasic propylene copolymer with Me2Si(2-Me-4-PhInd)2ZrCl2 supported on SiO2 and SiO2-MgCl2 carriers

Me2Si(2-Me-4-pbind)2ZrCl2 supported on SiO2/MgCl2 binary support was prepared for the preparation of heterophasic copolymer of polypropylene. The bi-support underwent surface treatment with various alkyl aluminum compounds such as trimethylaluminum (TMA), triethylaluminum (TEAL), and triisobutylaluminum (TIBA) before supporting the metallocene catalyst for 3 or 24 hours and were used for homopolymerization. It was notable that the generated SiO2/MgCl2 bi-support had lower surface area, pore volume and size as compared to the conventional SiO2. Impact polypropylene copolymers (IPCs) were obtained using two-step polymerization in one reactor with the presence of metallocene catalyst supported on SiO2. Propylene was polymerized in the reactor to produce the iPP matrix followed by polymerization of ethylene resulting to heterophasic material. It is apparent that the molecular weight of the polymer increased with longer PE polymerization time and as the polymerization time was more than 40 min, PP peak appeared near 147.9–149.2 °C, and a new peak emerged at 116.9–119.9 °C which could be attributed to the melting temperature of iPP crystallites and a less intense peak to either chains of ethylene-propylene copolymers. SEM images also confirmed that spherical PE particles were deeply embedded in the crystalline PP matrix and a large amount was produced as the polymerization time of the second stage ethylene polymerization was increased.

Heterophasic ethylene-propylene copolymers: New insights on complex microstructure by combined molar mass fractionation and high temperature liquid chromatography

The present study investigates the changes in the microstructure of heterophasic ethylene propylene copolymers (HEPCs) with increasing ethylene content, before and after visbreaking. Three samples obtained from commercial gas process reactors at Sasol Polymers at varying times after the addition of the ethylene comonomer are further visbroken to produce three more samples. Bulk sample analyses indicate that the ethylene-rich rubber phase which is essential in aiding peroxide mobility during visbreaking as observed in narrower dispersities and lower peak molar masses with increasing ethylene content. Further investigations of the microstructure via offline coupling of preparative molar mass fractionation (pMMF) to advanced analytical techniques such as solvent gradient interaction chromatography (SGIC) reveal that ethylene-rich copolymer chains are not significantly affected by the peroxide as the polypropylene homopolymer. Consequently, the polypropylene (PP) homopolymer and polypropylene-rich fractions with high molar mass diminish after visbreaking. Furthermore, the increase in ethylene content was observed to reduce the impact of the peroxide on the fraction quantities before and after visbreaking implying that visbreaking affects more the polyolefin chains with more PP segments and less those with more ethylene comonomer.

Novel strategy to improve the tribological property of polymer: In-situ growing amorphous carbon coating on the surface

Surface of ethylene-propylene copolymer (EPC) plastic was continuously treated by carbon plasma in a direct-current magnetron sputtering deposition (DC-MSD) system. Microstructure evolution of the polymer surface with different treating time was analyzed by Diffusive Reflectance infrared Fourier Transform (DRIFT) spectroscopy, Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Focus Ion Beam Scanning Electron Microscopy (FIB-SEM), respectively. The adhesion strength and tribological performance were measured by scratch tester and reciprocating ball-on-disc tribometer. Results showed that the bombardment of energetic plasma was capable of activating the surface polymer substrate, which could induce an in-situ transformation from organic carbon to inorganic carbon of the surface layer, following with an epitaxial growth of amorphous carbon upon the in-situ transition layer with the continuous treatment of carbon plasma. This kind of in-situ growing a-C coating on polymer including the in-situ transformation of top layer and the epitaxial growth on in-situ transition layer endow the weak substrate an excellent protective surface with strong adhesion, which exhibited much lower friction and wear. The possible wear mechanism of a-C coatings on polymer substrates was also presented.

Morphology, Mechanical and Thermal Properties of Poly(Lactic Acid)/Propylene-Ethylene Copolymer/Cellulose Composites

This work studied the effects of various types of cellulose fibers on the morphology, mechanical and thermal properties of poly(lactic acid) (PLA)/propylene-ethylene copolymer (PEC) (90/10 w/w) blends. The PLA/PEC blends before and after adding cellulose fibers were prepared by melt blending method in the internal mixer and molded by compression method. The morphological analysis observed that the presence of cellulose in PLA did not change the phase morphology of PLA, and PLA/cellulose composite surfaces were observed the cellulose fibers inserted in PLA matrix and fiber pull-out. The phase morphology of PLA/PEC blends was changed from brittle fracture to ductile fracture behavior and showed the phase separation between PLA and PEC phases. The presence of celluloses did not improve the compatibility between PLA and PEC phases. The tensile stress and strain curves found that the tensile stress of PLA was the highest value. The addition of all celluloses increased Young’s modulus of PLA. The PEC presence increased the tensile strain of PLA over two times when compared with neat PLA and PLA was toughened by PEC. The incorporation of cellulose fibers in PLA/PEC blends could improve Young’s modulus, tensile strength, and stress at break of the blends. The thermal stability showed that the degradation temperatures of all types of cellulose were less than the degradation temperatures of PLA. Thus, the incorporation of cellulose in PLA could not enhance the thermal stability of PLA composites and PLA/PEC composites. The degradation temperature of PEC was the highest value, but it could not improve the thermal stability of PLA. The incorporation of cellulose fibers had no effect on the melting temperature of the PLA blend and composites.

A conceptual approach to the formation of paramagnetic nanospecies of noble metals

Abstract The general concepts are analyzed regarding the approach for the formation of paramagnetic species of noble metals, with a non-rigid (labile) molecule being used as a supporting matrix. The formation of the metal nanospecies follows three stages: (i) the metal ions are captured by the matrix, (ii) the reducing agent causes formation of individual atoms separated by the matrix fragments, (iii) the individual atoms agglomerate due to conformational transformations of the labile molecule-matrix. This algorithm is realized in two distinct systems: Ag-containing nanospecies embedded within the system of polyacrylic acid (PAA) chains grafted to the film of fluorinated ethylene propylene copolymer (FEP) and Au-containing nanospecies in the free matrix of tannin-citrate- oxo-hydroxo aluminate. The evolution of the electron paramagnetic resonance (EPR) spectra while cooling down demonstrates the appearance of the exchange interaction which is suppressed at higher temperatures by the vibrational modes of the molecule-matrix. The role of the oxo-hydroxo aluminate form is one of a molecular motor sorting the individual nanospecies by their size and charge state.

Thermally and electrically conducting polycarbonate/elastomer blends combined with multiwalled carbon nanotubes

In this article, we have studied thermal and dielectric conductivity and morphology of polycarbonate (PC)/ethylene–propylene copolymer (EPC)/multiwalled carbon nanotubes (MWCNTs) nanocomposites. Transmission electron microscopy has been used to investigate the localization and migration of MWCNTs within the matrix. The MWCNTs were located in the PC phase and at the interface of PC and EPC. The results showed that the thermal conductivity of the PC decreased with the increasing content of EPC elastomeric particles. However, at the same time, one could observe an increase of the thermal conductivity in the polymer blends along with an addition of MWCNT. The electrical conductivity of the PC/EPC blends containing 10 wt% of EPC increased with the incorporation of MWCNTs, and the conducting paths were formed at additive content less than 0.5 wt% of MWCNT.

A novel efficient catalyst for water-crosslinking reaction of silane-grafted polyolefin system: Specific influence of axially coordinated n-alkylamine ligand on catalytic abilities of metal acetylacetonate complex

Catalytic activities of the novel acid-base hybrid catalyst on the water-crosslinking reaction (hydrolysis and condensation) of 3-methacryloxypropyltrimehoxysilane-grafted ethylene-propylene copolymer (EPR-g-MTMS) were investigated by means of attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and gel fraction measurements. We have synthesized RNH2-M(acac)2 complex as an acid-base hybrid catalyst which shows the high catalytic activities for water-crosslinking reaction in EPR-g-MTMS system. It is noted that the catalytic activity of RNH2-M(acac)2 complex clearly shows dependence on axially coordinated n-alkylamine compounds in hydrolysis reaction, meanwhile, the center metal ion in RNH2-M(acac)2 complex affects on the catalytic activities for overall water-crosslinking reaction in this study. The design concept of an acid-base hybrid catalyst showed bifunctional catalytic activity for the water-crosslinking reaction in the alkoxysilane-grafted polyolefin system.

Heatfireprotection Polymer Coatings on the Basis of EPDM-40 with Additives

Triple ethylene-propylene copolymers (EPDM) are used for the making of structural elements exposed to mechanical loads and are heat-resistant [1, 2], but their widespread use in aviation and shipbuilding equipment and other industries is limited due to Flammability. Double ethylene-propylene rubbers are practically limiting, and triple (EPDM), Dicyclopentadiene is used as the third component, due to the small content of double bonds in the side chains, have high heat resistance compared to diene rubbers [2], and therefore the issues of fire resistance of rubber-technical products based on them remain more and more urgent [3-7]. In [7] it is shown that if the values of the oxygen index (OI) and PP and EPDM are equal 17 % and 18.5 %, respectively, the coke numbers (CN) - 0 % and 0.5 %, and the copolymer is a PP/EPDM = 37,5/62,5 OI increases to 19.5% and CN up to 1.5 %. For copolymer PP / EPDM = 61.5 / 38.5 OI and CN are 21% and 3.4%, respectively, i.e. fire resistance in copolymers does not increase, which is an urgent problem. Polyolefins as it is shown in [7] and other works, at pyrolysis in soft conditions decompose practically without the rest, at thermal blows the mechanism of destruction changes and the carbonized rest is formed. The presence of cross-linked structures in the macromolecules of polyolefins also leads to the appearance of a carbonized residue. In work [8] the formulations of rubber mixtures resistant to wet chlorine, aqueous solutions of sodium hydroxide and sodium chloride, hydrogen, for the production of gaskets for electrolyzers and in [9] the effect of dithiophosphate accelerators on the complex properties of rubbers based on rubber grade EPDM-40. In [10] investigated the effect of a modified alumino-silicate intumescent microfiber filler kaolin microfiber (KMF) on the fire and heat protective properties (FHP) of vulcanizates based on ethylene-propylene-diene rubber EPDM-40. The compositions contained from 3 to 15 Weight Part (W.P.) KMV with a fractional composition of 25-110 microns and a fiber diameter of about 10 microns. As modifiers used a phosphorus boron containing oligomer (FBO), contributing to the increase of fireheat protective properties and multifunctional additive - hexachlor-p-xylene. It has been established that the modification of the kaolin microfiber leads to an improvement in the fire and heat protective properties at high temperature exposure: the rate of linear combustion decreases by 14%, the formation of the coke layer (CL) increases. It is shown that in conditions of erosion ablation, the fire-protective material has a 10 to 15% increase in tearing strength of CL, the time of onset of fire increases by 20-40% and the time of CL separation by 30%. In [ 11 ], the effect of HYPERLINK "https://translate.google.com/translate?hl=ru&prev=_t&sl=ru&tl=en&u=https://elibrary.ru/keyword_items.asp%3Fid%3D12826492" microcarbon fiber, a solution of FBO, HYPERLINK "https://translate.google.com/translate?hl=ru&prev=_t&sl=ru&tl=en&u=https://elibrary.ru/keyword_items.asp%3Fid%3D2483721" elastomers and HYPERLINK "https://translate.google.com/translate?hl=ru&prev=_t&sl=ru&tl=en&u=https://elibrary.ru/keyword_items.asp%3Fid%3D4285142" elastomeric materials on the fire-protective properties of EPDM-40 was investigated. The aim of the study was to investigate the processes of pyrolysis in the condensed phase, improving the properties of incombustibility and the creation of flame retardant rubber based on EPDM-40 for metal constructures.

Разработка многослойного упаковочного материала на основе полиолефиновых смесей, модифицированных сополимером этилена с пропиленом, для хранения пищевых продуктов

The research features a comprehensive study aimed at increasing the technological compatibility of multilayer packaging materials. The paper describes a recycling technology with the prospect of returning the resulting secondary raw materials to the production cycle. The research included the following tasks: to conduct a comprehensive study of polyolefin mixtures modified by ethylene propylene copolymer; to study the effect of the copolymer on the rheological and physicomechanical properties of polymer compositions; to propose a technology for the recycling of secondary polyolefin mixtures. The research involved the following methods: the capillary viscometry method was used to determine the rheological properties of polymer compositions; the tensile test method was employed to define the physicomechanical properties of the compositions; the pycnometric method was used to assess the density of the mixtures. The study featured such polymers as polyethylene, polypropylene, and ethylene-propylene copolymer, which was chosen as a link between the polymers. The authors obtained polymer compositions in various ratios of polyethylene, polypropylene, and ethylene-propylene copolymer: 70:30:0; 68.5:28.5:3; 65:25:10; 30:70:0; 28.5: 68.5: 3; 25:65:10. The article describes the process of modifying polyolefin compositions based on polyethylene and polypropylene by ethylene-propylene copolymer on a single-screw extruder. The authors defined the rheological properties and the deformation-strength characteristics of the polymer mixtures. Repeated processing proved to lead to a decrease in the physicomechanical properties of polyolefin mixtures, with the exception of compositions based on polyethylene and polypropylene in the ratio of 30:70, where the breaking stress increased. The number of processing cycles increased the melt flow rate of the mixtures. The proposed technology is meant for producing multilayer packaging materials using packaging waste in the middle layer for contact with food.

Occurrence and Species-Specific Distribution of Plastic Debris in Wild Freshwater Fish from the Pearl River Catchment, China.

Freshwater systems are an important source and vector of plastic debris found in oceans. However, plastic debris in freshwater organisms has not been well studied. The occurrence, characterization, polymer composition, and seasonal and spatial distribution of plastic debris were investigated in 9 species of wild freshwater fish from the Pearl River catchment, south China. Approximately 50% of the total fish (n = 279) belonging to 9 species were found to ingest plastic debris with an average abundance of 7.0 ± 23.8 items/individual, indicating wide plastic contamination in the Pearl River catchment. Plastic debris were predominantly transparent or white in color, fibers or fragments in shape, and polyethylene, polypropylene, ethylene-propylene copolymer (PE-PP), and polyethylene terephthalate (PET) in polymer composition. A species-specific distribution of the plastic debris was observed in terms of abundance, shape, and polymer composition. Redbelly tilapia had the highest (27.4 ± 54.0 items/individual), whereas common carp had the lowest (0.2 ± 0.4 items/individual) abundance of the plastic debris in their gastrointestinal tracts. Fibers of PET were predominant in the freshwater species except in barbel chubs, which had mostly PE-PP fragments. Omnivores and bottom-dwellers were more likely to ingest plastic debris. Seasonal variation was observed, with generally higher abundance of plastic debris in fish collected in the dry season than in the wet season. Environ Toxicol Chem 2019;38:1504-1513. © 2019 SETAC.

Distribution, sedimentary record, and persistence of microplastics in the Pearl River catchment, China

Microplastics (MPs) in the environment have become an issue worldwide. However, data about MPs in freshwater systems are still limited so far. This study investigated sources, fate, and seasonal and spatial distribution of MPs in the main stream Pearl River and its tributaries, as well as in the Pearl River Estuary (PRE), China. MPs were widely detected in the river water, river bed sediment, and estuarine sediment, with abundances of 0.57 ± 0.71 items L−1, 685 ± 342 items kg−1 dry weight (dw), and 258 ± 133 items kg−1 dw, respectively. Sheet, fragmental, and fibrous polyethylene, polypropylene, and ethylene-propylene copolymers were predominant, suggesting that MPs in the Pearl River catchment be mainly derived from fragmentation of discarded plastic wastes. In addition, municipal wastewater was also an important MPs source, especially for polyethylene terephthalate (PET) fibers. Polymers of higher density, such as PET and polyvinyl alcohol were relatively more abundant in the sediment than in the river water, especially in the estuarine sediment. Upward increase of the MP abundance was observed in the sedimentary core, probably indicating increasing release of plastic wastes due to growing production and uses of plastic products. On the other hand, percentage of finer MPs increased with increasing depth. The results revealed persistence and potential downward dispersion of the fine MPs. The MPs abundance was positively related with population density and gross domestic product, demonstrating impacts of human activities and economic development on the MPs contamination. Higher MPs abundance was detected in dry season than in wet season in the river water, suggesting dilution effect of precipitation. It's estimated that 15963 tons of MPs could be released annually into the PRE from the main stream Pearl River and its tributaries.

ExxonMobil moves on expansions

ExxonMobil Chemical is moving forward with $2 billion in expansions at its Baytown, Texas, complex. The company is building a plant that will have 400,000 metric tons (t) of capacity per year for its Vistamaxx propylene-ethylene copolymers, which are known for their elasticity and softness. The company is also entering the linear α-olefins market with a new 350,000 t plant. The company is a consumer of linear α-olefins for its polymer and poly-α-olefin business. The expansions are expected to come on line in 2022. Separately, ExxonMobil pledged to invest $100 million in a collaboration with the US Department of Energy’s National Renewable Energy Laboratory and the National Energy Technology Laboratory. The partners will research new biofuels and carbon-capture technologies.

Performance of Lead Acid Battery Using Graphite Based Composite As Cathode Current Collector

Introduction Lead acid batteries have been widely used for more than 100 years. They are used for vehicles and backup power supplies. However, when overdischarged, lead acid battery cannot be recharged and its performance is greatly declined. Recently, Iwai et al. had revealed that the cause of not being able to be recharged is the nucleation of α-PbO2 on cathode material, β-PbO2, and that, when gold or platinum is used as the current collector, formation of α-PbO2 is prevented due to local cell reaction, then that lead acid battery can be recharged even after overdischarge [1,2]. In this study, we investigated the possibility of realizing the lead acid battery with high resistance to overdischarge using graphite materials, such as natural expanded graphite sheet as a current collector. We think that graphite materials will be advantageous for cost reduction, weight reduction and improvement of processability for lead acid batteries. Experiment We developed graphite based composite material as a current collector which was prepared by the following procedure, in order to improve water repellency. Resin materials such as polyethylene, polypropylene (PP), ethylene propylene copolymer and fluororesin were dispersed with graphite sheet, preheated in air at 100 degrees for 10 minutes, and then heated at 160 degrees to 200 degrees for 10 minutes. Then, the graphite-based composite material was immersed in sulfuric acid (H2SO4) and the weight variation was measured. Also, the surface electric resistance of the graphite composite material was measured by four-terminal method. We decided to use PP as resin for graphite based composite materials, because graphite based composite material using PP have a low electric resistance and PP is easily dispersed in graphite sheet. Then, we chose PP contents of 5% from the viewpoint of water resistance. We used two-electrode glass cell for charge-discharge experiments. The cathode paste was prepared by mixing purchased β-PbO2 powder as an active material, acetylene black as a conducting additive and PTFE as a binder at the ratio of 80:15:5 in weight. The cathode was fabricated by pressing the paste on a current collector. In this study, we tested three kinds of current collectors, Pb plate, graphite sheet and graphite-based composite material. Each current collectors were used in 35 wt% H2SO4. Lead plate and 35 wt% H2SO4 were employed as anode and electrolyte, respectively. Firstly, we discharged the cell at 9 mAg-1 for 30 min and charged at 180 mAg-1 for 20 min. We repeated this cycle 20 times in order to stabilize the charge-discharge reaction. Secondly, we deeply discharged the cell down to 0 V at 9 mAg-1 and opened the circuit for 48 h. Finally, we once again charged the cell at 180 mAg-1 for 60 min, then we discharged the cell at 9 mAg-1 for 30 min and charged at 180 mAg-1 for 20 min and repeated the cycle to study the cell performance. Results and discussion Figure 1 (A) and (B) show the charge-discharge curves for the lead acid battery using Pb plate and graphite sheet as a current collector, respectively. In the case of Pb plate, the lead acid battery cannot be recharged after the open circuit. On the other hand, in the case of graphite sheet, it can be recharged even after the open circuit. Electrode potential does not come out for carbon, so it is thought that carbon has a role of stopping the local cell reaction. From this reason, it can be explained that the formation of α-PbO2 is prevented on cathode β-PbO2 then that the similar performance was shown when using gold or platinum as a current collector. In figure 2, performance of lead acid battery using graphite based composite as cathode current collector is shown. We discharged the cell at 9 mAg-1 to 0 volt and charged at 180 mAg-1 for 60 min and repeated the cycle between 0 volt and 2 volt. Between 1.9 V and 1.3 V, potential flat area is clearly observed. Just only inserting a thin graphite based composite, lead acid battery repeating charge / discharge cycles between 0 volt and 2 volt so many times without decay was realized. This result may be caused by improvement of water repellency of current collector by impregnate with PP into graphite sheet.