Ethylene-propylene Copolymer Research Articles

Effect of monomer sequence on structural and dynamic properties of ethylene-propylene copolymer melts

Effect of monomer sequence on structural and dynamic properties of ethylene-propylene copolymer melts

Impact polypropylene copolymers containing multifold H-shape long-chain-branching structures: Synthesis and properties

ω -Alkenylmethyldichlorosilane as a proven in-situ long-chain-branching agent particularly effective with olefin polymerization by Ziegler-Natta catalysts was seamlessly fit into fully implemented impact copolymerization of propylene exercised by polymerization, steam-treatment of afforded polymer granules, and twin-screw extrusion in a row to deliver, for the first time, long-chain-branched impact polypropylene copolymers (LCB-IPCs). Multifold H-type LCB structures were revealed with the LCB-IPCs, including two homologous structures based on polypropylene (PP- H -PP) and ethylene-propylene copolymer (EPC- H -EPC) individually, and a heterologous structure mixed of PP and ethylene-propylene copolymer (PP– H -EPC). Though all in minute amount, the LCB structures induced significant improvement in IPCs on many fronts. On melt properties, LCB-IPCs gained the unprecedented strain hardening property in extensional flow. On phase morphology, the LCB structures helped reduce the dispersion dimension of ethylene-propylene copolymer and the tendency of grain coarsening in post-preparation processing. On melt crystallization, the LCB structures enhanced the crystallization in an all-round way by prompting self-nucleation. On mechanical properties, by reinforcing the PP matrix and strengthening the interface to facilitate stress transfer between PP and EP copolymer, the LCB structures enabled an all-out promotion of mechanical properties with simultaneous reinforcement on stiffness and toughness. Fully implemented impact copolymerization of propylene preparing impact polypropylene copolymers was engaged with LCB agent 5-hexenylmethyldichlorosilane, which prompted formation of multifold H-shape LCB structures in the copolymers. The multifold LCB structures in turn induced profound improvement on multiple fronts of the copolymer properties. • ω -Alkenylmethyldichlorosilane is used as a LCB agent in impact copolymerization of propylene. • The new IPC polymers contain multifold H-type LCB structures. • The LCB structures induced significant improvement in properties of IPC on many fronts.

Effect of carbon nanotube location and dispersed phase on the dielectric properties of polypropylene/high‐density polyethylene/carbon nanotube nanodielectrics

AbstractThe effect of carbon nanotube location and dispersed phase on the dielectric properties of nanocomposites with carbon nanotubes (CNTs) and polypropylene/high‐density polyethylene (PP/HDPE) blends was investigated. Different compatibilizers styrene‐ethylene‐buthylene‐styrene copolymer (SEBS), ethylene‐propylene‐diene‐methylene rubber (EPDM), and ethylene‐propylene copolymer (EP) were used. In order to obtain a smaller HDPE phase, 0.1%(w/w) of CNT was added to a PP/HDPE (90/10) blend with 3%(w/w) of compatibilizer. Samples were processed in a twin‐screw extruder with a controlled sequential mixing based on thermodynamic (using the wetting parameter, ) and kinetic parameters (such as melting temperature and melting flow indices). FESEM images show the formation of nanoblends for all compositions, with a dispersed morphology with HDPE droplets with a diameter of about 100 nm (measured with ImageJ© software) inside the PP matrix, and TEM images show the CNTs present in both phases. However, compatibilizers seemed to expel the nanoparticles from the dispersed phase, which may have contributed to a reduction of the dielectric constant of the CNT nanocomposites. Dielectric properties were evaluated through Impedance Spectroscopy, showing that CNTs contribute to the interfacial polarization and constant dielectric rise from 3.15@1 Hz (without CNTs) to 16.91@1 Hz (with CNTs, but no compatibilizer).

Wear resistance effects of alumina and carbon nanoscale fillers in PFA, FEP, and HDPE polymers

Following numerous studies demonstrating the ability of nanostructured alpha-alumina filler to reduce the prohibitively high wear rate of polytetrafluoroethylene (PTFE) down to extremely small values (∼10−7 mm3/Nm) well below those of conventional PTFE micro-composites, alpha-alumina filler was also shown capable, in a couple recent studies, of imparting similar performance to another fluoropolymer, perfluoroalkoxy (PFA) copolymer, which otherwise was similarly lacking wear resistance in the unfilled state. In addition to duplicating such alpha-alumina performance in PFA, in this study such an extreme wear-reducing capability has also been demonstrated using nanocarbon powder, as an example representative of several other forms of nanoscale carbon filler that like alpha-alumina had been shown capable of providing extreme resistance to PTFE. Fluorinated ethylene propylene (FEP) copolymer, whose nanocomposites have not been tribologically explored previously, was thus more fully investigated here with not only alpha-alumina and nanocarbon, but also other nanotube (CNT) and mesoporous forms of nanoscale carbon fillers. In preliminary testing, only the alpha-alumina filler indicated an ability to impart its wear-reducing capability to FEP; a wear rate of ∼0.8 × 10−6 mm3/Nm was observed at 2 wt% alpha-alumina concentration. While this is an impressive reduction in wear rate, it is not quite as extreme a reduction as that observed in PTFE or PFA. The transport of the extreme wear resistance of nanocarbon powder in PTFE and PFA was even more partial and incomplete in FEP, with the ∼0.3 × 10−3 mm3/Nm unfilled FEP wear rate only reduced to ∼10−5 mm3/Nm, while the CNT and mesoporous carbon fillers were even less effective. Correspondingly, ATR-FTIR spectra from FEP wear surfaces displayed sizable peaks evident of the chelation of chemical interactions known to be associated with wear resistance for PTFE and PFA matrices only in the most wear-resistant alpha-alumina case and to a lesser extent for the nanocarbon. Finally, it is demonstrated that such fillers demonstrate such strongly beneficial effects only in polymers that otherwise lack wear resistance, and may actually be deleterious for polymers such as high density polyethylene (HDPE) already having some inherent wear resistance in their unfilled state.

Structure Property Relationships in PA 6 and PP Copolymers Blended by Single and Twin Screw Extrusion

AbstractPolyamides such as polycaprolactam (PA 6) and poly(hexamethylene adipamide) (PA 6.6), are generally classified as pseudo-ductile materials. Fracture behaviour of PA can be changed by melt compounding with modified olefinic elastomers such as Ethylene-propylene copolymers (EPM and EPDMs) and nitrile rubbers (NBRs). Often, small amounts of a compatibilizer are added to the polymer blend in order to assure good dispersion, morphology stability and consistent end-use properties. Maleated polypropylene (PP-MAH) has been used as compatibilizer in blends of polyamides with polyolefins as they tend to react with amine end groups in the polyamide molecules and also interact by molecular entanglement with non-funcionalized polypropylene chains. This work was intended to optimise stiffness-toughness balance in polyamide/ polypropylene blends by reactive processing of PA 6 with polypropylene heterophase copolymers using the PP-MAH as a compatibilizer. Effects of processing conditions on the blend morphology and mechanical properties were investigated by comparing compatibilized and non-compatibilized blends prepared by single and twin screw extrusion. Such approach was intended to investigate whether blend morphology and its response to processing steps can be controlled by blend composition, changes in rheology and interfacial tension during reactive processing. Viscosity measurements by torque rheometry and particle coalescence in-situ observations were performed in order to provide additional evidence of mechanisms relating to phase morphology definition in such systems.

Rheological properties and UV photo-oxidation of montmorillonite-filled random propylene–ethylene copolymers

Rheological properties and UV photo-oxidation of montmorillonite-filled random propylene–ethylene copolymers

Self-powering vibration sensor based on a cantilever system with a single-electrode mode triboelectric nanogenerator

Here, we report a vibration sensor based on a single-electrode mode triboelectric nanogenerator (TENG). The main objective of this study is to develop a vibration sensor (architecture) that can be employed in any application with minor design changes to meet individual objectives. Hence, a cantilever-based vibration system is selected, which offers optimum design control in fine-tuning the sensor to operate in the desired frequency spectrum. The cantilever’s proof mass is suspended by isotropic linear elastic material constituting a scalable and tunable cantilever–mass system. The oscillations create contact separation between the triboelectric-active layers (i.e. fluorinated ethylene–propylene copolymer and screen-printed zinc oxide), which develop triboelectric waveforms. This voltage waveform is used for both sensing and powering mechanisms. At resonance, the device produces peak-to-peak voltage, short-circuit current, and power density of 25 V, 10 µA, and 1.38 W m−2, respectively. To measure the influence of change in cantilever properties, we varied the number of cantilevers and evaluated the sensor performance. The sensor is reliable with >99% accuracy in a broad frequency range of 0–400 Hz. The sensor exhibits a maximum sensitivity of 14 V g−1 and can charge a 1 µF capacitor to 2.75 V in <150 s. The sensor is further tested on a lab-scale vacuum pump with known (induced) faults to estimate the sensor’s competence in detecting the machinery faults. Considering the market acceptability, the sensor is developed with established manufacturing techniques such as screen-printing, and laser cutting. This study hopes to bridge the lab-to-market gap for TENG-based (vibration) sensors.

Probing the interactions between pour point depressants (PPDs), viscosity index improvers (VIIs), and wax in octane using fluorescently labeled PPDs

A poly(octadecyl methacrylate) sample fluorescently labeled with 6.7 mol% of pyrene (Py(6.7)-PC18MA) was used as a mimic of a pour point depressant (PPD) to investigate how Py(6.7)-PC18MA interacts with wax found in engine oils and ethylene-propylene (EP) copolymers used as mimics of viscosity index improvers (VIIs). The fluorescence spectra of Py(6.7)-PC18MA solutions in octane were acquired in octane at low and high concentrations of Py(6.7)-PC18MA and analysed to obtain the molar fraction ( finter) of pyrene labels, which formed excimer intermolecularly, a measure of the level of intermolecular interactions between Py(6.7)-PC18MA molecules in the solution. The finter-versus- T profile obtained for Py(6.7)-PC18MA alone in octane confirmed that Py(6.7)-PC18MA formed microcrystals at solution temperatures below 0 °C. The effect induced by the addition of wax and an amorphous (EP(AM)) and semicrystalline (EP(SM)) EP copolymer on the interactions experienced by Py(6.7)-PC18MA were characterized by monitoring finter as a function of temperature and comparing the different finter-versus- T plots obtained after the addition of the different components with the finter-versus- T plot obtained for Py(6.7)-PC18MA alone. These studies demonstrated that wax and EP(AM) increased the level of intermolecular interactions between the Py(6.7)-PC18MA molecules at all temperatures in octane. EP(SM) increased the interactions between Py(6.7)-PC18MA molecules at high temperature, where it was soluble in octane, but finter reverted to its value in the absence of EP(SM) at low temperatures, where EP(SM) had crystallized. These experiments illustrate how pyrene excimer fluorescence can be applied to probe the complex interactions taking place between the different components found in engine oils.

Investigation of the Properties of Compositions Based on Modified Polymer Mixtures

The properties of vulcanized compositions based on mechanical mixtures of Ethylene propylene rubber (EPR)and Ethylene propylene terpolymer (EPTR)with PVC deteriorate compared to the properties of EPR and EPTRperoxide vulcanizers, which is explained by the poor mixing of PVC with these copolymers. In the extruder of the specified polymer mixtures -145 ° C, 36 MPa, n = 200 qra. The thermal and mechanical effects (MIC) under these conditions cause a significant improvement in the properties of the compositions based on these mixtures. The formation of EPR –PVC, and EPTR -PVX copolymers as a result of IMT in these polymer mixtures was confirmed by the construction of these copolymers with peroxide-free, PVC clusters with methemtal oxides - MgO, ZnO, and PbO (mass fraction 8-18). Modification of ethylene-propylene copolymers with PVC was carried out at a temperature higher than the flow temperature of PVC, which ensures its good dispersion in the mixture and chemical bonding with the elastomer phase, the effect of strengthening the elastic phase with the dispersed PVC phase occurs

Selective branch formation in ethylene polymerization to access precise ethylene-propylene copolymers

Polyolefins with branches produced by ethylene alone via chain walking are highly desired in industry. Selective branch formation from uncontrolled chain walking is a long-standing challenge to generate exclusively branched polyolefins, however. Here we report such desirable microstructures in ethylene polymerization by using sterically constrained α-diimine nickel(II)/palladium(II) catalysts at 30 °C–90 °C that fall into industrial conditions. Branched polyethylenes with exclusive branch pattern of methyl branches (99%) and notably selective branch distribution of 1,4-Me2 unit (86%) can be generated. The ultrahigh degree of branching (>200 Me/1000 C) enables the well-defined product to mimic ethylene-propylene copolymers. More interestingly, branch distribution is predictable and computable by using a simple statistical model of p(1-p)n (p: the probability of branch formation). Mechanistic insights into the branch formation including branch pattern and branch distribution by an in-depth density functional theory (DFT) calculation are elucidated.

Thermal Degradation Kinetics Analysis of Ethylene-Propylene Copolymer and EP-1-Hexene Terpolymer.

LLDPE is a less crystalline polymer with vast industrial and domestic applications. It is imperative to understand the synthesis, processing conditions, and thermal degradation mechanism of the co- as well as terpolymers. This paper reports the in-situ synthesis and thermal degradation studies of the ethylene-propylene copolymer and ethylene-propylene-1-hexene terpolymer and its nanocomposite with ZnAL LDH sheets. The 1-hexene dosing during the in-situ process influenced the product yield and immensely affected the thermal stability of the resultant polymer. One milliliter 1-hexene in-situ addition increased the product yield by 170 percent, while the temperature at 10 percent weight loss in TGA was dropped by about 60 °C. While only 0.3 weight percent ZnAL LDH addition in the terpolymer improved the thermal stability by 10 °C. A master plot technique and combined kinetics analysis (CKA) were deployed to access the thermal degradation mechanism of the synthesized polymers.

Self-powered multifunctional monitoring and analysis system based on dual-triboelectric nanogenerator and chitosan/activated carbon film humidity sensor

A humidity sensor driven by a dual-TENG has been developed for humidity detection at room temperature. In this work, we report a polymer humidity sensor with high response linearity. The sensitive material is made of chitosan (CS) and activated carbon (AC). The sensor is driven by a triboelectric nanogenerator based on fluorinated ethylene propylene copolymer (FEP). The CS/AC humidity sensitive film is coated on a PET substrate with a nickel-chromium alloy interdigitated electrode by spray technique. The peak-to-peak voltage of TENG can be close to 700 V, and the maximum output power is 12.208 mW. The output voltage of TENG is rectified to 48 V to power the humidity sensor, and then we realize that the voltage change range of the humidity sensor is between full voltage of 0–48 V through adjusting the resistance ratio and designing operational amplifier circuit. The sensor has a wide detection range (0%~97% RH) and good stability. Its response/recovery time under 33% RH and 97% RH conditions are 12 s/20 s and 22 s/21 s, respectively. The sensor can realize obvious identification of breathing characteristics in practical application tests. Meanwhile, the sensor can also be used to monitor the distance of the finger from the sensor surface and the response when the water column passes over the sensor surface. In addition, we also sent the signal of the humidity sensor to the smart terminal via WIFI module to monitor the signal changes caused by breathing and finger movement, and matlab was used to analyze the breathing data.

Enhanced melt-recrystallization process of propylene-ethylene copolymer during the uniaxial stretching with the aid of isotactic polypropylene

The structural evolution of propylene-ethylene copolymer (coPP) and propylene-ethylene copolymer/polypropylene (coPP/iPP) films has been studied by in-situ WAXD/SAXS in a tensile process. Both coPP and coPP/iPP films show obvious melt-recrystallization during the deformation process. In the initial stage of stretching, the crystallinities of films decrease due to the stress-induced crystal fragmentation. After that, a large number of oriented crystals form in the late stage of the tensile process. Compared with that of coPP, the initial strain of recrystallization for coPP/iPP is smaller, and recrystallization-induced crystallinity (from 4.9% for coPP sample to 10.2% for coPP/iPP sample) and crystal orientation (from 0.75 for coPP to 0.93 for coPP/iPP) are improved. Structural evolution occurs in close relation to tensile rates. At low strain rate, molecular chains are easier to pull from the lattice, resulting in a significant decrease in crystallinity. At low strain rate, samples display stronger recrystallization in the late stage of stretching. Interestingly, there is a difference in the growth process for lamellae between coPP and coPP/iPP samples. For coPP samples, crystals grow on existing lamellae, leading to an increase in the average thickness of crystals. In contrast, recrystallization between lamellae tends to occur in coPP/iPP samples, leading to a decrease in average lamellar thickness and long period.

Degradation kinetics and thermomechanical properties of in‐situ polymerized layered double hydroxides‐ethylene‐propylene copolymer

AbstractThis paper reports the study of in‐situ incorporation of NiFe‐(Anion) layered double hydroxides (LDH) in the ethylene‐propylene (EP) (95:05 molar ratio) copolymerization. NiFe LDHs were synthesized with different intercalated anions using the coprecipitation method. The EP/LDH nanocomposites showed improved thermal stability, nevertheless, the various types of intercalated anions in the LDH showed a remarkable effect on the thermal stability and the degradation mechanism of the resultant polymer nanocomposites. EP/LDH constituted with NiFe‐CO3/A (A = acetone washed) showed maximum improvement in the thermal stability concerning neat EP. The LDH incorporation in the composite influenced the polymer microstructure which was evident from the DSC and CRYSTAF analysis. The degradation kinetics of neat EP and EP/LDH nanocomposites were studied by employing the isoconversional method. The degradation kinetics models of different polymer samples were predicted by applying a generalized master plot. Moreover, EP nanocomposites exhibited higher storage modulus and elasticity as compared to neat EP copolymer.

Dynamic light scattering studies on ethylene-propylene copolymers in a hydrocarbon based oil

Viscosity modifiers are inherent to many lubricating multigrade oils as they reduce the temperature dependence on the viscosity of the oil, thus increasing the viscosity index. However, direct evidence of physical mechanisms to which viscosity modifiers increase viscosity index is still lacking due to the lack of appropriate analysis tools. Here, we report a method using dynamic light scattering (DLS) to study the solution behavior and coil size change of ethylene-propylene copolymers as well as polyoctadecylmethacrylate at 1.0 wt. % in a polyalphaolefin oil. The usefulness and limitations of the DLS for monitoring polymer coil size and dynamic solution behavior in oil are discussed.

Time-Resolved SAXS/WAXD under Tensile Deformation: Role of Segmental Ethylene–Propylene Copolymers in Impact-Resistant Polypropylene Copolymers

Structural evolution of impact-resistant polypropylene copolymers (IPCs), having different compositions of segmental ethylene–propylene (sEP) copolymers, under tensile deformation was investigated ...

Revisiting the Mechanism of the Meso-to-α Transition of Isotactic Polypropylene and Ethylene–Propylene Random Copolymers

In this work, we have conducted in situ simultaneous small- and wide-angle X-ray scattering and Raman spectroscopy experiments to investigate the fundamental differences in the mechanism of the mesomorphic to α phase transition of the isotactic polypropylene homopolymer and the random ethylene–propylene copolymer. Via quantitative analysis of the results coming from the three techniques, we found that in the homopolymer, chain interlock and chain extension occur during the transition. However, these processes are not necessary for the transition to occur. Indeed, the presence of randomly distributed ethylene co-units hinders the chain interlock process in the early stages of the phase transition (T > 60 °C) and suppresses the chain elongation process at the later stages (T > 90 °C). Consequently, the mesomorphic to α-phase transition in the random copolymer occurs with inclusion of the ethylene co-units inside the crystal lattice, causing increased lateral interchain distance and larger crystalline sizes. Our results show how differences exist in the way solid phase transitions occur at the molecular scale when co-monomers are included into the macromolecular chains, leading to a better understanding of the thermal behavior of semi-crystalline polymers.

EFFECT OF TALC ON THE PROPERTIES OF A COMPOUND BASED ON ETHYLENE-PROPYLENE COPOLYMER

The aim of the research is to study the possibility of replacing Korean-made talc with inexpensive talc from an Afghan deposit, processed in Uzbekistan and used for the production of polypropylene compounds. In the future, these compounds are used for the manufacture of plastic car parts. A block copolymer produced by Uz Kor Gaz Chemical was chosen as a binder. For this, the influence of the content and type of talc on the properties of a compound based on an ethylene-propylene copolymer was studied. The properties of the obtained compounds checked using ISO standards. The fractional composition of the studied types of talc, strength, thermophysical, gravimetric properties of compounds with different concentrations of talc were studied. The results of studies of these properties of compounds based on ethylene-polypropylene copolymers modified with various types of talc filler revealed the possibility of obtaining materials with specified properties based on Afghan talc,

Engineered PP impact copolymers in a single reactor as efficient method for determining their structure and properties

Impact polypropylene (PP) copolymers (IPCs) are important materials for many commercial applications. These materials are usually synthetized through different methods involving two consecutive reactions in the same phase or in different phases. Here, a laboratory-scale synthesis method based on a sequential liquid- and gas-phase two-step process in a single reactor is developed. Propylene homopolymers and IPCs were synthesized with varying amounts of comonomers and hydrogen. The IPC materials obtained were fully characterized via analytical temperature rising elution fractionation (TREF), differential scanning calorimetry (DSC), 13C nuclear magnetic resonance (13C NMR), gel permeation chromatography with an infrared detector (GPC-IR5), Charpy impact, scanning electron microscopy (SEM), and cross-fractionation chromatography (CFC). The addition of only ethylene to the second step in the absence of hydrogen led to the creation of an ethylene-propylene (EP) copolymer with similar impact strength to that of a propylene homopolymer. The addition of hydrogen to the first step dramatically shortened the length of the PP chains and inhibited catalytic active centers that led to EP copolymer synthesis. This material exhibited very low molecular weight, low ethylene incorporation, and rubbery phases irregularly distributed along the isotactic polypropylene (iPP) matrix, resulting in the formation of an EP copolymer material with poor impact properties. IPCs synthesized without hydrogen and with a 50/50 (v/v) mixture of propylene/ethylene monomers in the second step enhance ethylene incorporation, facilitating adequate homogeneous and heterogeneous ethylene distribution and resulting in a high increment of amorphous ethylene-propylene-rubber (EPR) domains, which remarkably improves impact properties. Additionally, a criterion based on the ratio between EEE and EPE + PEP triads ranging between 1 and 2 was also established to predict the impact resistance of any heterophasic PP. Fractionation of the optimal sample provided a detailed understanding about the microstructure of this copolymer through the study of the molecular weight and composition of the fractions via GPC-IR, analytical TREF, and DSC measurements. Finally, the liquid–gas-phase two-step IPC material was compared, by means of SEM and CFC measurements, with synthesized IPC using liquid–liquid-phase two-step polymerization, and the results showed that the range of EP composition as well as ethylene distribution in the molar mass molecules of the IPCs was correlated to their mechanical behavior. This proves that crystalline families composed of high-molecular-weight EP copolymers in the liquid–gas-phase process can act as a compatibilizing agent between the iPP matrix and the elastomeric rubbery phase, allowing one to improve the impact resistance of the IPC, more so than that of IPCs obtained in the gas–gas and liquid–liquid phases. The results indicate that the synthesis of IPC resins in a single reactor is an efficient experimental method for fundamental research on IPCs.

Physicomechanical Properties of Organic-Inorganic Hybrid Gels Based on Various Thermoplastic Ethylene-Propylene Copolymers and Natural Minerals

Physicomechanical Properties of Organic-Inorganic Hybrid Gels Based on Various Thermoplastic Ethylene-Propylene Copolymers and Natural Minerals