Ethylene-propylene Copolymer Research Articles

Polyethylene/crystalline ethylene-propylene copolymer/amorphous ethylene-propylene copolymer in-reactor alloys synthesized by periodic switching polymerization process: An excellent toughener for polypropylene

In order to obtain softer polyolefins applicable as toughener for polypropylene (PP), a series of in-reactor alloys composed of polyethylene, crystalline ethylene-propylene copolymer (cEP) and amorphous ethylene-propylene copolymer (aEP) were synthesized by sequential ethylene polymerization followed by ethylene-propylene copolymerization in periodic switching polymerization process (PSPP) using a spherical MgCl2-supported Ziegler-Natta catalyst. In the PSPP step, ethylene-propylene copolymerization was repeatedly switched between two different monomer feed ratios: one with high propylene/ethylene ratio to form aEP component, and the other with low propylene/ethylene ratio to form cEP component. In the synthesized PE/cEP/aEP in-reactor alloys, aEP accounted for 40~56 wt%, and cEP accounted for 18~30 wt% of the alloy. With aEP content rising above 48 wt%, the alloys showed rather low modulus, and no yielding appeared in their stress–strain curve, implying that they were a sort of elastomeric material. By blending the PE/cEP/aEP alloys with isotactic PP, their PP-toughening performances were evaluated and compared with a commercial EPDM. Impact strength of PP toughened by the alloy was significantly higher than that toughened by EPDM at the same blend ratio. Cryo-fractured surface of PP/alloy blends showed that the alloy particles were uniformly dispersed in PP matrix, and showed a core–shell type morphology, in which the core domain was composed of polyethylene, and aEP constituted the shell domain in between the core and the PP matrix. Segmented EP copolymer chains (s-EP) located inside the aEP domains formed thin filaments bridging the core and the PP matrix, which are believed to act as compatibilizer that significantly enhanced interfacial adhesion between the PP matrix and the dispersed phase.

A direct proof for Maxwell–Wagner effect of heterogeneous interface

In this paper, the Maxwell–Wagner effect and the charge characteristics of the heterogeneous interface at the action of higher electric field and elevated temperature are investigated by means of electret technology. A composite membrane with a double-layer structure of a polypropylene (PP) film and a fluorinated ethylene propylene copolymer (FEP) film was made. After being polarized under electric field and elevated temperature, the component PP and FEP films of the composite membranes were separated. The charge density of the PP and FEP films was measured to analyze the characteristics of interfacial charge in the composite membrane. Experimental results directly prove that the charge characteristics at the interface of the composite membranes are consistent with the result calculated by the Maxwell–Wagner effect. The polarity of the interfacial charge can be switched by changing the polarity of the polarizing voltage. The characteristics of the accumulated interfacial charge are strongly dependent on the conductivity, which is affected by the temperature and the polarizing electric field. A new phenomenon, that is, the measured charge density is much higher than that calculated by the Maxwell–Wagner effect, is found. The reason is ascribed to the electret effect from the FEP and PP films. This research provides a new insight into the charge characteristics at the heterogeneous interface.

Kinetic and thermal study of ethylene-propylene copolymerization catalyzed by ansa-zirconocene activated with Alkylaluminium/borate: Effects of linear and branched alkylaluminium compounds as cocatalyst

Ethylene-propylene (EP) copolymerizations was carried out with two ansa-metallocene: rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (Mt-I) and rac-Et(Ind)2ZrCl2 (Mt-II) combined with borates activators like ([Me2NPh][B(C6F5)4] (Borate-I), [Ph3C][B(C6F5)4] (Borate-II). Different structures of alkylaluminum( triethylaluminium (TEA), triisobutylaluminium (TIBA) and TEA/TIBA mixture of 25/75, 50/50, 75/25 mol ratios were used as cocatalysts. The choice of ligand structure and, more importantly, the nature of the cocatalyst significantly impact these systems' activity and the polymeric materials' properties. Borate-II has been shown as giving higher activities than Borate-I with both ansa-metallocene, attending 5.6 × 106 g/mol Zr*h. Mt-I gives higher activities and molecular weight but produced copolymers with low ethylene content, melting points, and crystallinity than Mt-II. The activities were very close to each other with 100% TIBA. Still, Mt-I became more active than Mt-II when TEA was more than 25% in the cocatalyst system. The effects of alkylaluminiums catalysts cocatalyst on EP copolymer molecular weight (Mw) and molecular weight distribution (MWD) were much more complicated. The MWD curve changed from broad to narrow with Mt-I when TIBA was replaced by a different mole ratio of TEA/TIBA ratio. The technique used for the assessment of active centers [C*]/[Zr] fraction in the ansa-metallocene catalyst was quenched label by using 2-thiophenecarbonyl chloride (TPCC) to determine the effects of alkylaluminiums catalysts structure on the propagation rate constants (kP) of EP copolymers. The [C*]/[Zr] value of Mt-I/Borate-I/TIBA is lower than those of the Mt-I/Borate-I/TEA and Mt-I/Borate-I/TEA/TIBA system. The main differences appear between catalysts containing pure TIBA and those containing TEA, possibly due to the faster rate of chain transfer with Al—Et than with bulky Al—iBu. Adding TEA in metallocene/borate/alkylaluminiums catalysts catalysts can be applied as an effective method to regulate the molecular weight of EP copolymer with a high degree of activity

PP/PP-HI/silica nanocomposites for HVDC cable insulation: Are silica clusters beneficial for space charge accumulation?

New potential High Voltage Direct Current (HVDC) cable insulation materials based on nanocomposites are developed in this study. The nanocomposites are produced by blending of polypropylene (PP), propylene-ethylene copolymer (PP–HI) and a modified fumed silica (A-silica) in a concentration of 1 and 2 wt %. The A-silica is successfully modified with (3-aminopropyl)triethoxysilane (APTES) via a solvent-free method, as proven by infrared spectroscopy, thermogravimetry and transmission electron microscope mapping.A-silica in the polymer matrix acts as a nucleating agent resulting in an increase of the crystallization temperature of the polymers and a smaller crystal size. Moreover, the silica addition modified the crystals morphology of the unfilled PP/PP-HI blend. The composite containing A-silica with 2 wt% contains bigger-size silica clusters than the composite filled with 1 wt%. The composite with the higher A-silica concentration shows lower space charge accumulation and a lower charge current value. Besides, much deeper traps and lower trap density are observed in the composite with 2 wt% A-silica addition compared to the one with a lower concentration. Surprisingly, the presence of silica clusters with dimensions of more than 200 nm exhibit a positive effect on reducing the space charge accumulation. However, the real cause of this improvement might be due to change of the electron distribution stemming from the amine-amine hydrogen bond formation, or the change of the chain mobility due to the presence of occluded polymer macromolecules constrained inside the high structure silica clusters. Both phenomena may lead to a higher energetic barrier of charge de-trapping, thus increasing the depth of the charge traps.

Progress in vanadium complex catalysts and their catalytic behavior toward copolymerization of ethylene with α-olefins

<p indent=0mm>Ethylene-propylene rubber, linear low density polyethylene and polyolefin elastomer, which are prepared by copolymerization of ethylene with α-olefins, have an important market share of the industry due to their excellent properties. Catalyst plays important roles in the copolymerization of ethylene with α-olefins. Many vanadium complexes in the oxidation states of +3, +4 and +5 have been developed as precatalyst for the copolymerization. The progress of vanadium complex catalysts and their use in copolymerization of ethylene with α-olefins were reviewed. The effects of chelated ligands on the catalytic activity of catalysts, composition, molecular weight, molecular weight distribution and sequence of the resulting copolymers were discussed. Vanadium(III) complexes are widely used since vanadium(III) species are usually considered as active species in olefin coordination polymerization. Vanadium(III) complexes bearing monodentate <italic>N</italic>-heterocyclic carbene (NHC) ligand or bidentate β-diketonate ligands have been used as prcatalyst in copolymerization of ethylene with propylene, affording ethylene-propylene copolymers with high propylene content. Ethylene-propylene copolymers with ultra-high molecular weight were prepared by using vanadium(III) complexes containing NHC ligand. Vanadium(III) complexes bearing chelated bidentate N^N or N^O, etc. ligands show high catalytic activity up to <sc>8820 kg mol^–1 h^–1</sc> toward copolymerization of ethylene with 1-hexene. The introduction of bulky substitutes on the ligand results in an increase in the reactive ratio of ethylene and a decrease in the reactive ratio of 1-hexene, and thus a change in the sequence of monomer in the resulting copolymer. Vanadium(III) complexes containing tridentate and tetradentate ligands display relatively lower catalytic activity than their analogues containing similar bidentate ligand. Most vanadium(IV) complexes display lower catalytic activity than vanadium(III) complexes bearing similar ligands. Ethylene-propylene copolymer with high propylene content could be prepared by copolymerization of ethylene and propylene catalyzed by vanadium(IV) complexes containing monodentate amide ligands. Vanadium(V) complexes bearing chelating aryloxides have been shown to be highly active (up to <sc>144400 kg mol^–1 h^–1)</sc> in copolymerization of ethylene with propylene, affording ethylene-propylene copolymers with low propylene content (less than 15%(mol)). Ethylene-propylene copolymers with high propylene content (more than 30%(mol)) could be prepared by vanadium complexes containing monodentate or bedentate ligands. It is interesting to note that quasi-living copolymerization of ethylene with propylene was realized by using vanadium(V) complexes containing NHC ligand and ethylene-propylene copolymers with ultrahigh molecular weight and narrow molecular weight distribution were obtained. In conclusion, the vanadium complex catalysts have displayed good catalytic behavior towards the copolymerization of ethylene with α-olefins. The vanadium complexes discussed here may be an inspiration for future work in the development of vanadium complex catalyst with high catalytic activity and high comonomer incorporation for copolymerization of ethylene with α-olefins.

Influence of Cellulose Fiber Content on Morphology and Properties of Poly(Lactic Acid)/Propylene-Ethylene Copolymer/Cellulose Composites

This work studied the effects of medium-length fibrous cellulose (MFC) on the morphology, mechanical and thermal properties of poly(lactic acid) (PLA)/propylene-ethylene copolymer (PEC) (90/10) blends. The morphological analysis of PLA/MFC composites observed MFC fibers inserted in the PLA matrix and MFC appeared agglomeration when added high MFC loading. The phase morphology showed the two-phase separation of PLA/PEC blends. The presence of PEC reduced the agglomeration of MFC fibers in polymer matrix. The tensile stress and strain curves found that the ultimate stress of PLA was the highest value and the addition of MFC increased Young’s modulus of PLA/MFC and PLA/PEC/MFC composites. The PEC presence improved the strain at breaking point of PLA/PEC blends. The thermal properties found that the incorporation of MFC did not improve the thermal stability of PLA/MFC and PLA/PEC/MFC composites due to the PLA had degradation temperature higher than MFC.

Structural evolution in propylene-based elastomer with γ form during stress relaxation

The stress relaxation and the structural evolution of a random propylene-ethylene copolymer of about 12 mol% of ethylene co-units with pure γ form (iPPcoE12-γ), which was pre-stretched to various strains at 30 °C, were investigated by means of in situ wide angle X-ray diffraction techniques. The two-dimensional X-ray diffraction patterns were decomposed into oriented and unoriented parts. It turned out that the unoriented fraction of the iPPcoE12-γ sample became oriented in the process of the relaxation. Due to the unique “cross-β” arrangement in the γ form, the fraction of elastic stress of iPPcoE12-γ was higher than that of iPPcoE12-α with pure α form at a small pre-stretched strain (εH = 0.27) and the increased fraction of oriented parts was much less than that of iPPcoE12-α at medium strains (εH = 0.71 and 1.27). A comparative analysis of the relaxation behavior of iPPcoE12-γ and iPPcoE12-α revealed that the elasticity and stability of iPPcoE12-γ were more attractive at smaller strains (smaller than critical strain C—the strain of the starting of the fragmentation of crystalline blocks), while at larger strains (larger than 1.27) iPPcoE12-α had its advantages in elasticity. In addition, it was found that the γ to α transition occurred during the relaxation, and the unoriented crystallites with γ form were more difficult to transform than the oriented one.

The Analysis of Light Intensity Transmission Coefficient Through Plastic Fibers for the Design of Closed Room Lighting without Electricity

The phenomenon of total internal reflection can be used to guide the light to be transmitted from one place to another, it is applied to the guiding principle of light in fiber optics. A fiber rope made of clear plastic material with a uniform refractive index, when one end fired a beam of light then the light will be forwarded along the strap so that out at the other end. This principle can be applied as a lighting source in a closed room by passing light from the outdoors by using plastic fiber, so it doesn’t need the electricity. In this study, theoretical analysis of the percentage of the intensity of light transmitted by the fiber plastic succeed as a function of the refractive index and determine the transmission coefficient for some plastic seeds are eligible to be used as a plastic fiber light successor. From the results of deriving the equation, the light transmission coefficient of plastic is and the terms of plastic seeds that can be used as a plastic fiber are having a refractive index . Based on refractive index data from profesionalplastics, the maximum transmission coefficient value for Ethylene Tetrafluoro Ethylene Copolymer is 82.23% and the minimum transmission value of Fluorinated Ethylene Propylene Copolymer is 55.99%.

Distribution characteristics of microplastics in agricultural soils from the largest vegetable production base in China

The study area is situated in Shouguang City, Shandong Province, as the largest greenhouse vegetable production base in Northern China. Samples of facility agricultural soil, open-field agricultural soil, and agricultural plastic mulch film were collected to investigate the distribution characteristics, influencing factors, and discharging sources of microplastics (MPs). Microplastic abundance of three soil layers at all sampling sites ranged from 310 to 5698 items/kg, with an average value of 1444 ± 986 items/kg. The main size category of MPs was less than 0.5 mm, and the contribution of MPs with sizes <0.5 mm in the 10–25 cm layer of facility agricultural soils was significantly higher (p < 0.05) than that in the 0–5 cm soil layer, which indicated that small MPs tended to migrate to deeper soil layers. The prevailing shapes of MPs were fragment and film, while polypropylene, ethylene-propylene copolymer, and polyethylene dominated among chemical compositions. The fractions of silty and sandy particles were correlated with the abundance of MPs, and the microplastic abundance in sandy loam was significantly higher (p < 0.05) than that in silty loam or loam based on the international classification standard. Thus, the soil texture may affect the distribution of MPs in local agricultural soils. In addition, the planting age of facility agricultural soil was related to microplastic abundance, while there was no significant difference in the microplastic abundances of facility agricultural soils under different irrigation methods. CapsuleThe microplastic abundance in sandy loam surpassed that in silty loam or loam, small size (<0.5 mm) MPs tended to migrate to deeper soil layers, and planting age affected microplastic abundance in facility agricultural soils.

Foaming behavior of the fluorinated ethylene propylene copolymer assisted with supercritical carbon dioxide

Foaming behavior of the fluorinated ethylene propylene copolymer (FEP) and its composites assisted with supercritical carbon dioxide (scCO2) as the blowing agent were investigated. The batch foaming process was applied at temperature ranging from 250°C to 265°C and pressure ranging between 12 MPa and 24 MPa. The optimal foaming temperature and saturation pressure were obtained for both pure FEP and FEP composites with 1 wt% different-sized BaTiO3 as nucleating agent. The cell diameter of pure FEP foam ranging from 80–140 µm was observed while the cell diameter decreased to 20–40 µm after adding BaTiO3 particles. The cell density of foamed FEP with BaTiO3 increased significantly from 106 to 108 cells/cm3 and the expansion ratio ranged between 4.0 and 5.5. Moreover, a decrease in an abnormal phenomenon that expansion ratio for the pure FEP foam was observed as the saturation pressure increased. This unexpected phenomenon can be explained by the relationship between foaming and crystallization coupling processes.

Fiber Orientation and Concentration in an Injection-Molded Ethylene-Propylene Copolymer Reinforced by Hemp.

This paper characterizes and analyzes the microstructures of injection-molded polypropylene parts reinforced with 20 wt% of hemp fibers in order to understand the process induced variations in thermomechanical properties. In-thickness fiber orientation and fiber content were determined by X-ray tomography along the flow. The fiber content along the flow path was also determined by direct fiber content measurements after matrix dissolution, showing an increase of 2%/100 mm for a 2.2 mm-thick plate due to fiber migration during the filling stage. A typical shell/core structure for fiber orientation in injection molding was observed, but with a very clear transition between the layer solidified under high shear rates and the core in which the fiber content was reduced by more than 50%. The orientation of hemp fibers is lower than the one of glass fibers, especially in thickness direction. However, the overall fiber orientation in the injection direction induces significant anisotropic thermomechanical properties, which cannot be explained by simple micromechanical models that consider isotropic mechanical properties for hemp fibers. These phenomena must be taken into account in process simulation codes for injection molding to better predict thermomechanical properties as well as part shrinkage and warpage to design molds.

Preparation of Resin Added Graphite Sheet As Current Collector of Lead Acid Batteries

Introduction Lead Acid Batteries(LAB) have been widely used for more than 100 years. Conventionally, LAB cannot be recharged after over-discharged, and its performance is greatly declined. We found that the deterioration after deep-discharge is caused by local cell reaction between lead current collector and cathode active material.[1] We also revealed that the decline of the battery performance can be prevented by using gold or graphite material current collector.[2-3] In that case, the LAB can be recharged even after over-discharge. Graphite sheet is practical as current collector, however, it was revealed that raw graphite sheet absorbs sulfuric acid electrolyte, and the properties deteriorates. In this study, to prevent the property degradation, we tried to mix resin materials into raw graphite sheet and investigated the characteristics improvement as a function of type and amount of additive resins. Experimental We used four kinds of resin material(polyethylene(PE), polypropylene(PP), ethylene-propylene copolymer(EPM) and polyvinylidene fluoride(PVDF)) and dispersed it by 5, 10, and 15wt% into expanded graphite. Then we made graphite sheet from expanded graphite mixed with resin by a rolling mill. Next, in the heat treatment process, we carried out preheating at 100°C for 10 minutes, and raised the temperature to various appropriate high temperature for each resin, then hold for 10 minutes.For characterization of resin added graphite sheet, we measured the tensile strength of longitudinal direction and contact angle of pure water. The test piece size was 100×20×0.5mm for tensile strength measurement. We also conducted charge/discharge experiments by using 5%PP or 5%PE added graphite sheet as current collector. The cathode paste was prepared by mixing β-PbO2 powder as active material, acetylene black as conductive additive, and PTFE as binder at the ratio of 80:15:5 in weight. We constructed the cathode by pressing the cathode paste on each current collector. We used 35% H2SO4 as electrolyte and lead plate as the anode. Results and discussion We conducted characterization for PP or PE resin dispersed graphite sheet, because it was found that resin was not dispersed uniformly into graphite even after heat treatment at 200℃ for EPM or PVDF. The tensile strength of raw graphite sheet was 4.8 MPa, and graphite sheet with PP was 7.5, 9.7, and 10.8 MPa for the 5, 10, and 15% additive amount, respectively. The Tensile strength of graphite sheet with PE was 6.2, 4.1, and 4.4 MPa for the 5, 10, and 15% respectively. It was confirmed that addition of PP gives higher tensile strength than raw graphite sheet. Graphite sheets with PE showed the highest value at 5%PE addition, but when 10 or 15% was added, the tensile strength was reduced due to inhomogeneous force concentration.The contact angle of pure water was about 40° for raw graphite sheet, and over 80° for each resin dispersed graphite sheet regardless of kind or amount of resin. This means that dispersion of resin makes water repellency increase for graphite sheet.Figure 1 shows the weight increase of graphite sheet with resin when immersed in 47% sulfuric acid at around 70°C. It is indicated that graphite sheets containing 5%PP and 15%PE showed no mass increase due to sulfuric acid absorption even after 14 d.Figure 2 shows the charge-discharge results of LAB using graphite sheet with 5%PP or 5%PE or raw graphite sheet for reference, as the current collector. It is shown that the charge/discharge cycle was restarted after complete discharge to 0 V and 48 h open circuit rest, for all three cases. This result is very much consistent with our previous study that graphite material current collector prevents degradation of cathode active material by local cell reaction control.[4] In the case of raw graphite sheet, cell voltage was fluctuating. For PP or PE cases, the voltage fluctuation is well suppressed. It is thought that this is due to graphite sheet degradation by absorption of sulfuric acid and addition of PP or PE is effective to prevent the degradation.From these results, especially in the improvement of tensile strength and discharge potential, it is concluded that 5% polypropylene addition to raw graphite sheet is most suitable for use as a cathode current collector of LAB.

Optimising the chemical demulsification of water-in-crude oil emulsion using the Taguchi method

This study examines the effect of important factors such as the temperature, pH, freshwater, concentration, and type of demulsifier on chemical demulsification (CD) using the bottle test method. Three Iraqi heavy crude oils, each with different properties, were tested. Each of these samples contained different concentrations of salt solution, which need to be removed to improve the properties of the crude oil. Five different types of commercial chemical demulsifiers, namely oxyalkylated copolyether (D1), Polyethylene glycol octaadacyl ether (D2), polyether butoxy ethanol (D3), Ethylene-propylene copolymer (D4), and Cumene 1,2,4-trimethylbenzen (D5), were tested. The Taguchi method was used to design the experiments to obtain optimum separation. The data analysis was carried out using signal-to-noise (S/N) ratio and analysis of variance (ANOVA). The results of the best combination test show that the maximum removal efficiency of CD for the three samples are 94.2%, 95%, and 92%, respectively. In addition, there was a noticeable improvement in the original values of the API from 23.2 to 28.4, 14 to 20.9, and 4.6 to 24.1, respectively. The work plan and the results of this work could be used to improve crude oil processing in the Iraqi oil industry.

Natural Antioxidants as Multifunctional Additives for Polymeric Materials

The additional substances commonly used for polymeric materials mostly have a negative impact either on the natural environment or human health. Therefore, there is a need for replacing these compounds by more pro-ecological ones. In this paper, some natural antioxidants of plant origin, including xanthone, rutin hydrate, quercetin and a mixture of various polyphenols derived from green tea, were proposed as multifunctional as well as eco-friendly additional compounds for polymers. These substances were implemented by means of the impregnation process into ethylene-propylene copolymer (EPM) matrix. Some significant results of the research work are presented, including the mechanical properties and oxidation induction time (OIT) of the material tested. Moreover, ethylene-propylene copolymer (EPM) with antioxidants was investigated in terms of thermooxidative and UV ageing resistance. The impact of ageing processes on the material tested was analysed mainly by means of Fourier transform infrared spectroscopy (FT-IR) absorbance spectra and colour change assessment.

Superstrate-type flexible and bifacial Cu(In,Ga)Se2 thin-film solar cells with In2O3:SnO2 back contact

Bifacial and flexible Cu(In,Ga)Se2 (CIGS) thin-film solar cells with superstrate-type structure were fabricated. For this fabrication, the substrate-type solar cells were first transferred from Mo/Glass substrates to 50-µm-thick flexible fluorinated ethylene propylene (FEP) copolymer films as superstrates using a lift-off process. The 300-nm-thick In2O3:SnO2 (ITO) thin-films were subsequently deposited on the rear sides of the CIGS absorber layers as back contacts (BC) of the finished bifacial devices with the structure of FEP/Epoxy/Al/Ni/Zn0.9Mg0.1O:Al/Zn0.8Mg0.2O/CdS/CIGS/ITO/Ni/Al. Particular attention was paid to maintain the high optical and electrical transport properties of ITO-BC as well as to improve the Ohmic-like contact behavior at the CIGS/ITO interface to improve cell performances. Under the optimized ITO preparation, the resulting ITO thin film possesses the average optical transparency of ITO (>77%) in the wavelength range of 400–1100 nm, and the resistivity of 6.1 × 10−4 Ωcm with corresponding high carrier mobility of 42.8 cm2/Vs, as well as Ohmic-like characteristics at the CIGS/ITO interface can be realized with shunt resistance as low as 5.5 Ωcm2. Consequently, the flexible and bifacial CIGS thin-film solar cell was fabricated with efficiencies of 9.1% and 2.4% for frontside and backside illuminations, respectively. In this study, highly transparent and conductive ITO thin films have been successfully used as BC in flexible and bifacial CIGS solar cells.

The Role of Interfacial Interactions on the Functional Properties of Ethylene-Propylene Copolymer Containing SiO2 Nanoparticles.

In this paper, the mechanical properties, thermal stability, and transparency of ethylene–propylene copolymer (EPC) elastomer modified with various weight percentages (1, 3, and 5 wt.%) of SiO2 nanofillers have been studied. The nanocomposites were prepared via a simple melt mixing method. The morphological results revealed that the nanofillers were uniformly dispersed in the elastomer, where a low concentration of SiO2 (1 wt.%) had been added into the elastomer. The FTIR showed that there are interfacial interactions between EPC matrix and silanol groups of SiO2 nanoparticles. Moreover, by the addition of 1 wt.% of SiO2 in the EPC, the tensile strength and elongation at break of EPC increased by about 38% and 27%, respectively. Finally, all samples were optically transparent, and the transparency of the nanocomposites reduced by increasing the content of SiO2 nanoparticles.

Rapid characterization of high-impact ethylene–propylene copolymer composition by crystallization extraction separation: comparability to standard separation methods

High-impact copolymers of propylene and ethylene are complex materials with several components and at least two different phases, a crystalline polypropylene (PP) matrix and a predominantly amorphous ethylene–propylene copolymer (EPC) normally present as disperse particles. Next to overall composition analysis and morphology studies, fractionation into crystalline and amorphous components followed by further analysis of those components is the most important characterization technique for this technically very relevant class of copolymers. This process, involving separation into xylene cold-soluble (XCS) and insoluble fractions and follow-up determination of intrinsic viscosities (IV) as well as ethylene (C2) content is, however, tedious and time-consuming. A far more rapid approach is presented here through the separation of the amorphous and crystalline fractions of PP in 1,2,4-trichlorobenzene (TCB) using the crystallization extraction technique and the Crystex QC instrument. As the standard methods and Crystex technique are using different solvents (xylene and decalin versus TCB), correlations need to be established in order to be able to compare the results. Based on nine structurally very different polymers, respective correlation curves were developed and predictions for 95% confidence intervals were calculated statistically. In addition, these correlation curves were validated by testing over 100 different PP samples covering a broad range of all tested characteristics. The results show agreement and comparability between the traditional test methods techniques and the Crystex technique inside statistically calculated prediction intervals at 95% over a broad range of all tested characteristics (XCS, C2 and IV).

Living Chain-Walking (Co)Polymerization of Propylene and 1-Decene by Nickel α-Diimine Catalysts.

Homo- and copolymers of propylene and 1-decene were synthesized by controlled chain-walking (co)polymerization using phenyl substituted α-diimine nickel complexes activated with modified methylaluminoxane (MMAO). This catalytic system was found to polymerize propylene in a living fashion to furnish high molecular weight ethylene-propylene (EP) copolymers. The copolymerizations proceeded to give high molecular weight P/1-decene copolymers with narrow molecular weight distribution (Mw/Mn ≈ 1.2), which indicated a living nature of copolymerization at room temperature. The random copolymerization results indicated the possibility of precise branched structure control, depending on the polymerization temperature and time.

Preparation of Antimicrobial Fibres from the EVOH/EPC Blend Containing Silver Nanoparticles.

The article presents a new fabrication method for bioactive fibres with a microporous structure of ethylene–vinyl alcohol copolymers (EVOH)/ethylene−propylene copolymer (EPC) blends. The experimental work carried out resulted in obtaining EVOH/EPC polymer blends fibres with the addition of glycerol and sodium stearate. Different concentrations of glycerol (38%, 32%) and sodium stearate (2%, 8%) were used to prepare the fibres. The purpose of using different concentrations of stearate and glycerol was to evaluate the effect of additives on the structure and properties of the fibres. A significant influence of the additives used on the morphological structure of the fibres was found. The resulting fibres were modified with an AgNO3 solution and reduced to silver nanoparticles (AgNPs), to give the fibres bioactive properties. The fibres obtained with the addition of 8% stearate have a more developed surface, which may influence the amount of adsorbed silver particles inside the fibre. However, the durability of depositing silver particles after multiple washes has not been tested. Three types of microorganisms were selected to assess the microbiological activity of the obtained fibres, i.e., Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa and Escherichia coli. The fibres have antibacterial activity against gram positive and negative bacteria. The largest inhibition zones were obtained for gram-positive bacteria Staphylococcus aureus, ranging from 3 to 10 mm depending on the concentration of AgNPs. The morphology of the blends fibres was characterized by scanning electron microscopy (SEM) and optical microscopy (OM). The occurrence of elemental silver was analysed by energy dispersive spectroscopy (EDS) analysis. The changes of the polymer structure chemistry are studied by Fourier transform infrared spectroscopy (FTIR).

Structure-property correlation of an impact- modified random polypropylene copolymer

The combination of rheological and interfacial properties is utilized in this work to explain the thermal and mechanical properties of a random polypropylene copolymer (RPP) toughened with an ethylene-propylene copolymer (EPR). RPP/EPR blends are directly prepared by injection molding. The EPR exhibits higher viscosity in comparison with the RPP over the evaluated shear rate, while the RPP/EPR blends show similar viscosities at high shear rates. The interfacial properties indicate a strong interaction between the RPP and EPR domains. Differential scanning calorimetry analyses indicate that the EPR does not act as a nucleating agent for the RPP, with the RPP crystallinity only decreasing at high EPR contents, suggesting that the EPR can modify the RPP crystallite size. Scanning electron micrographs of the blends demonstrate a ductile fracture surface, indicating that EPR can increase the RPP tenacity. The RPP impact strength is improved by up to 102% in the RPP/EPR 90/10 wt.% blend, while the RPP deformation at break is increased from 183% to 246% after the incorporation of 10% EPR. The tensile strengths of the RPP and RPP/EPR blends are very similar, indicating that the RPP achieves a good balance between stiffness and toughness after being blended with the EPR.