Ethylene-propylene Block Copolymer Research Articles

Reactive Extrusion of Multifunctional Conducting Nanocomposites Based on Polypropylene Random Copolymer and Ethylene–Propylene Block Copolymer

Reactive Extrusion of Multifunctional Conducting Nanocomposites Based on Polypropylene Random Copolymer and Ethylene–Propylene Block Copolymer

Physical–mechanical properties of multifunctional thermoplastic elastomers based on polyolefins and styrene-butadiene elastomer

The article presents the results of a study of the effect of the content of styrene-butadiene elastomer on the change in ultimate tensile stress, tensile yield strength, elongation at break, flexural strength, enthalpy and melting temperature, Vicat softening temperature, and melt flow rate of polymer blends based on a wide range of thermoplastic polyolefins: high-density polyethylene, low-density polyethylene, polypropylene, ethylene-hexene-1 copolymer, polypropylene random copolymer, and block copolymer of ethylene with propylene. Nanoparticles of technical carbon (TC), aluminum, and calcium stearate were used as fillers. It has been shown that, depending on the type of polyolefin used and the specific concentration of elastomer, the polymer mixture can acquire the properties of a thermoplastic elastomer (TPE). In high-density polyethylene and an ethylene-hexene-1 copolymer, the properties of TPE appear at an elastomer concentration of 30 wt %; in low-density polyethylene, this effect occurs at its 20 wt % content. In polypropylene, polypropylene random copolymer, and ethylene-propylene block copolymer, TPE properties appear at 40 wt % concentration of the elastomeric component. This was confirmed by the results of scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, as well as the “stress–strain” dependence of polymer mixtures. To achieve technological compatibility and miscibility of non-polar polyolefins with polar elastomer, compatibilizers based on high-density polyethylene and polypropylene modified with maleic anhydride were used. It is shown that the equality of the values of the ultimate tensile stress and the tensile yield strength is a consequence of the occurrence of phase inversion in the polymer mixture, that is, change of the dispersed medium to the dispersed phase and vice versa.

Modelling of Propylene Polymerization in a Loop Reactor on the Titanium–Magnesium Catalyst Taking into Account the Transformation of Active Centers

The volume of consumed and produced polymers is increasing in the market every day. This is due to the indispensability and convenience of polymers in all industries. The article presents the distinctive features of the use of titanium–magnesium catalysts in the process of propylene polymerization. A mathematical model of the polypropylene polymerization is presented. This model is the basis of creating an expert control complex of the propylene–ethylene block copolymer (PEBC) synthesis process and allowing a quantitative connection to be made between technological parameters of reactors, which allows control of the technological mode with the acceptable accuracy. The experiment catalytic system is microspheric titanium trichloride (MS-TiCl3) and co-catalyst-diethylaluminum chloride. Dependences of different parameters on others are illustrated. The result of the research is as follows: according to the calculations, when increasing the number of blocks in the chain, the average values of molecular weights increase and the polydispersity index decreases; changing the values of the transformation rate coefficients of active centers by the donor k 12 and k 21 allows research into the effect of the donor type.

Crystallization behavior of impact copolymer polypropylene revealed by fast scanning chip calorimetry analysis

The crystallization behaviors of two impact copolymer polypropylenes (ICP) were investigated by using fast scanning chip calorimetry (FSC) and micro-focus wide-angle X-ray diffraction (WAXD) techniques. Different crystallization peaks of these two samples during cooling were observed at cooling rates from 50 to 4000 K/s. For ICP-A, the crystallization of polypropylene (PP) matrix into α crystallites, polyethylene (PE) sequences in ethylene-propylene segmented copolymer (EsP), PP segments in ethylene-propylene block copolymer (EbP), and PP matrix into mesophase successively occurred from high to low temperatures. As the cooling rate increased, the crystallization of PP matrix into α crystallites, PP segments, and mesophase were suppressed one by one. Nevertheless, the crystallization of PE segments was hardly suppressed. For ICP-B, it showed almost the same crystallization behavior as ICP-A, except for the absence of independent crystallization peak of PP segments. The different crystallization performance in these two samples could be ascribed to their different chain microstructures.

Enhanced multiphase interfacial interaction of impact polypropylene copolymer by in-situ introducing polyethylene

Impact polypropylene copolymer (IPC) is utilized in various commercial products worldwide due to its excellent physical properties and low production costs. Introducing polyethylene (PE) into IPC is known to improve the impact properties with little rigidity loss, but little is known about the influence of the multiphase interfacial interaction on these properties. In this work, we investigate this matter through fabricating a series of in-reactor alloys with multi-stage polymerization. Morphology observations revealed that introducing PE into IPC in-situ can promote the phase structure without the external force. Dynamic mechanical analysis results revealed that the introduction of well-dispersed PE in-situ could strengthen the interface interaction between PP matrix and EPR dispersed phase, which is conducive to the dissipation of impact energy. Atomic force microscopy-infrared results suggested that the in-situ introduction of PE promotes the enrichment of the ethylene-propylene block copolymers (EbP) to the multiphase interface. This work offered a new insight into the rational design of the next generation IPC with improved properties.

Analysis of Defects in Biaxially Oriented Polypropylene Films by Micro-Fourier Transform Infrared and Raman Spectroscopies

Abstract A practical method for identification of defects that occur occasionally during the production of biaxial oriented polypropylene (BOPP) films is developed. The size and morphology of the defects in the BOPP film were observed with optical microscopy, and micro Fourier transform infrared (Micro-FTIR) and Raman spectroscopies were employed to identify the chemical composition of the defects. Significant amounts of ethylene and propylene units were found in the defects, and characteristic vibrational bands for crystalline PP were observed by both IR and Raman. However, one defect exhibited IR characteristics for ordered PE whereas the other showed amorphous PE structure. These results indicate that the defects are composed of either ethylene-propylene block copolymers with long sequences of both propylene and ethylene that can form ordered structures, or ethylene-propylene segmented copolymers with long propylene sequences that can crystallize and shorter ethylene sequences that are amorphous. Possible sources of these foreign materials and corresponding mitigation measures were discussed.

The fracture testing of ductile polymer films: Effect of the specimen notching

The fracture of a ductile polymer film, a heterophase ethylene-propylene block copolymer, has been studied, combining a range of characterisation methods in an attempt to provide a better understanding of the intricate details that play an important role in the repeatability and reproducibility of the essential work of fracture test. The experimental factors that have a strong influence on the resulting parameters are clearly explained, with particular attention to the effect of the quality of the notches, the non-collinearity of the two edge notches in double edge notched tension specimens, and the lack of alignment of the specimen with the load axis once it is mounted on the load train. Furthermore, the influence of these experimental factors on the registered stress-displacement curves is also studied, and a criterion and the method for separating non-valid specimens are established.

Highly Active ansa-(Fluorenyl)(amido)titanium-Based Catalysts with Low Load of Methylaluminoxane for Syndiotactic-Specific Living Polymerization of Propylene

ansa-Dimethylsilylene(fluorenyl)(amido)titanium complexes bearing various electron-donating substituents are synthesized and applied to propylene polymerization by the use of MMAO/2,6-di-tert-butyl-4-methylphenol as a cocatalyst. The complexes containing adamantylamido ligands (1a,b) show unexpectedly high activity (31150 kg of polymer (mol of Ti)−1 h–1) with a low Al:Ti ratio of 20. The catalysts also promote syndiotactic-specific living polymerization to produce propylene-ethylene block copolymers.

Effect of specimen notch quality on the essential work of fracture of ductile polymer films

The essential work of fracture approach has been employed to analyse the effect of notch sharpening on the fracture toughness of a semicrystalline multiphase ethylene-propylene block copolymer. Double edge notched tension specimens were sharpened using different techniques: femtolaser ablation, razor blade sliding at room and liquid nitrogen temperatures, saw cutting, plastically deformed saw cutting, and scalpel sliding. The notch sharpening techniques provide notches of different quality in relation to both the notch tip radius and the plastic deformation in front of the crack tip. The best quality notches were produced by the femtolaser ablation technique, which provides very sharp notches without plastic deformation ahead of the crack tip. The effects of the non-collinearity of the notches and tilted specimens on the testing machine grips were also analysed. The shape of the registered stress–displacement curves shows differences, but only in the range comprised between the displacements corresponding to the maximum stress and the onset of crack initiation. A larger crack tip radius and/or larger extent of plastic deformation in front of the notch root leads to larger values of the displacement at the onset of crack initiation, resulting in higher values for the specific essential work of fracture. Yet on the other hand, the values of the slope of the essential work of fracture plot remain unchanged. A lower value for the specific essential work of fracture was obtained for the specimens sharpened using the femtolaser ablation technique.

Polypropylene based thermoplastic polymers for potential recyclable HVDC cable insulation applications

Thermoplastic materials are highly desirable for power cable insulation application because of their recyclability and ease of processing. They are particularly suitable for high voltage direct current (HVDC) cable insulation because of the absence of byproducts during cable production, which may result in the reduction of undesirable space charge accumulation and the degassing cost. Polypropylene based polymers may have the potential for recyclable thermoplastic cable insulation application because of their high melting temperatures and adjustable mechanical and electrical properties. This work aimed at evaluating the potential of isotactic polypropylenes, propylene-ethylene block copolymers and random copolymers for thermoplastic cable insulation application. We investigated the melting and crystallization behavior, crystal structure, supramolecular structure, mechanical properties, space charge distribution and DC breakdown strength of six different polymers (two isotactic polypropylenes, two block copolymers and two random copolymers). A comprehensive analysis of these parameters indicates that the propylene-ethylene binary random copolymers are more potentially suitable for thermoplastic cable insulation application.

Controlled properties of high-impact polypropylene in-reactor alloys by tailoring chemical structure and morphology

The compositional heterogeneity, morphology and melting behavior of two commercial high-impact polypropylene (HiPP) in-reactor alloys were systematically investigated by the combined use of thermal fractionation, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Correlations between the mechanical properties and the molecular architectures and phase morphologies were discussed. The results show that the mechanical properties of the alloys are strongly influenced by the contents of ethylene-propylene rubber (EPR) and ethylene-propylene block copolymer (EPC), intrinsic viscosity ratios of EPR and the matrix, and the morphology in polypropylene in-reactor alloys. The EPC component acts as a bridge connecting the dispersed amorphous phase and crystalline polypropylene matrix. The advanced impact toughness of the HiPP samples can be interpreted as a consequence of their high EPR content and the good compatibility between the different components in the multiphase system. When the xylene soluble (XS) component was 20 wt% and an intrinsic viscosity ratios (λ) of xylene soluble component and xylene insoluble (XIS) component was1.6, the impact strength and flexural modulus of the HiPP samples were higher than 50 kJ/m2 and 900 MPa, respectively.

Correlation between impact properties and phase structure in impact polypropylene copolymer

The influence of the dispersed phase on impact properties of impact polypropylene copolymer (IPC) was systematically investigated by preparing a series of samples with different self-structure and size of dispersed particles. The impact test results at room temperature revealed that in case of rubber size below the critical value, the core–shell structure was dominant in the excellent impact strength though the impact strength was also affected by the size. For the impact strength at lower temperature, it seemed to be independent of the core–shell structure of dispersed particle and only dropped with the increase of rubber size. Compared with common polypropylene/ethylene–propylene rubber (PP/EPR) binary blend, IPC samples presented larger rubber sizes but higher impact strength at lower temperature, which was ascribed to the presence of ethylene propylene block copolymers (EbP) component. For describing the toughening mechanism of IPC at room temperature determined by size and self-structure of dispersed phase, a quantity linear relationship between toughness and rubber size was proposed.

Destruction mechanism of core–shell particles in impact polypropylene copolymer during short molten-state annealing

Morphology evolution of the dispersed phase with a multilayered core–shell structure in impact polypropylene copolymer (IPC) during molten-state annealing was systematically studied through scanning electron microscopy (SEM), phase contrast microscopy (PCM) and dynamic rheological test. To demonstrate the evolution path of the dispersed phase comprised of ethylene-propylene random copolymer (EPR) and ethylene–propylene block copolymer (EbP) during annealing, different binary blends comprised of different fractions were prepared and their diffusion behavior during liquid–liquid phase separation was investigated. Compared with EPR, EbP presented a higher diffusion rate in propylene homopolymer (hPP) matrix, owing to its lower molecular weight and lower entanglement density. The statistical results of EbP and EPR domain sizes reveal that the coalescence of EbP is faster than that of EPR. In addition, the interaction parameters of EbP/hPP and EbP/EPR estimated using the Nishi–Wang equation show that EbP has a stronger affinity for hPP than EPR. Based on the diffusion rates, entanglement densities of components and great disparity in viscosity between EPR and hPP, a potential mechanism was proposed for the morphology evolution of core–shell dispersed particles in IPC during molten-state annealing.

Determination of fracture toughness of propylene polymers at different operating temperatures

The influence of the temperature on the fracture parameters of three types of polypropylenes under static loading conditions has been analyzed. Single-phase polypropylene homopolymer and random ethylene–propylene copolymer were tested slightly above their glass transition temperatures (within the ductile-to-brittle transition region), and well below and above them; heterophasic ethylene–propylene block copolymers were tested on the range of temperatures from above the glass transition temperature of propylene matrix to below the glass transition temperature of the elastomer phase. Attending to the mechanical response, suitable Fracture Mechanics approaches were used. Fracture toughness increased with temperature for single-phase polymers but block copolymers were not temperature sensitive for the range of temperatures above the glass transition temperature of the elastomeric phase despite their variation on the mechanical properties.

Influence of the notch sharpening on the impact fracture toughness of ethylene-propylene block copolymers

The impact fracture toughness of several ethylene-propylene block copolymers has been evaluated using the traditional contact notch sharpening technique of tapping and a new non-contact technique based on femtolaser ablation. The fracture toughness values obtained with the specimens notched by the femtolaser ablation technique were always lower than the tapped specimens. The impact fracture toughness values of these block copolymers does not depend only on the ethylene content, but also the molecular weight has a remarkable influence.

Strain rate and loading modes in DMTA experiments on ethylene/propylene block copolymers

A broad experimental programme using Dynamical–Mechanical Thermal Analysis (DMTA) was carried out on ethylene/propylene block copolymers (EPBC). The samples were subjected to frequency scans to evaluate the dependence of stored modulus on frequency. Tests were conducted on similar samples using different loading modes such as single cantilever, dual cantilever and tension configurations. If the stored modulus is plotted versus the test frequency, a different trend corresponding to each loading mode is obtained. Similar conclusions can be drawn regarding the glass transition temperature. In this work, strain rate, instead of frequency, is used to compare results provided by different loading modes. If the strain rate is used as the reference variable, a unique trend is observed despite the loading modes used to perform the experiment.

Influence of the Injection‐Molding Parameters on the Cellular Structure and Thermo‐Mechanical Properties of Ethylene‐Propylene Block Copolymer Foams

AbstractMicrocellular injection‐molding technology is capable of producing lightweight polymeric products. The foam morphology is determined by the injection‐molding parameters, and it has been observed that depending on the parameter variations, the cell structure may exhibit substantial morphological differences through the entire section along the melt flow direction of the injected part. The effects of varying injection‐molding parameters on foam morphology and thermal mechanical properties of a multiphase ethylene‐propylene block copolymer (EPBC) were tested on 5‐mm plaque specimens using a constant temperature profile. It has been found that injection speed does not have a significant effect on the thermal‐mechanical properties of the foam, whereas shot volume and mold temperature do have a significant influence. Low shot volume produces uniform density cellular structures and larger cores, whereas lower mold temperatures help maintain small cell sizes. Furthermore, the effect of the copolymer's crystalline phase on foam morphology has been observed. This study identifies the achievable foam morphologies and the thermal‐mechanical performance of cellular molded EPBC parts. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E692–E704, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21311

The role of notch sharpening on the J-fracture toughness of thermoplastic polymers

The effect of the notch sharpening on the fracture toughness obtained under Elastic–Plastic Fracture Mechanics (EPFMs) approach has been analyzed in two different types of thermoplastic polymers, a semicrystalline multi-phase ethylene–propylene block copolymer and an amorphous polycarbonate. The samples for fracture characterization were sharpened using a steel razor blade and the femtosecond laser ablation technique. Both notching techniques gave rise to the very same size of crack tip radii, 1–2μm. For all the materials under study, the fracture toughness values of the specimens sharpened through femtosecond laser ablation were lower than those measured on samples sharpened using a steel razor blade. The largest differences were achieved for the amorphous polycarbonate. The damage produced ahead of the crack tip through plastic deformation in the steel razor blade sharpened samples over against the lack of damage in the femtolaser sharpened specimens explains the disparity in the fracture values. Besides, the stress state ahead of the crack tip is closely related to the plastic deformation zone to specimen thickness ratio. The fracture toughness values determined from the femtolaser sharpened samples were all in plane strain conditions while the values of the fracture toughness obtained from the steel razor blade sharpened specimens were not.

Effect of strain rate and temperature on tensile properties of ethylene–propylene block copolymers

Tensile tests were conducted on several ethylene–propylene block copolymers with different ethylene content, over a range of temperatures (−120 to 23°C) and strain rates, 10−4–10−2s−1. The effect of temperature and strain rate on elastic modulus, Poisson’s ratio and yield stress has been analyzed. To determine the elastic properties, a video-extensometer was used to determine the deformation field. The experimental results about yielding are interpreted in terms of the well known principle of temperature–time equivalence. Several models have been considered to explain the significant increase in the yield stress at low temperatures or high strain rates.

Effect of ethylene–propylene copolymers on the phase morphologies and properties of ultrahigh molecular weight polyethylene: Dissipative particle dynamics simulations and experimental studies

Abstract This work aims to experimentally and theoretically study the effects of ethylene–propylene copolymers as compatibilizer on the phase morphologies, interfacial properties, rheological behaviors and mechanical properties of ultrahigh molecular weight polyethylene/homopolymerized polypropylene (UHMWPE/HPP) blends. The results indicate that the addition of ethylene–propylene block copolymer EPS30R or random copolymer DP3000 ranging within 1–3 parts per hundred parts (phr) of UHMWPE/HPP blends can remarkably reduce the sizes of the UHMWPE particles and significantly improve the mechanical property such as tensile strength and elongation at break. Moreover, the ternary blends still show two-phase morphologies, and the favorable melt flowability of the UHMWPE/HPP blends can be basically maintained. Besides, dissipative particle dynamics simulations on the ternary UHMWPE/HPP/ethylene–propylene copolymer blends indicate that with fixed mole number of the block copolymer, longer block chains have higher efficiency on reducing the interfacial tension than the shorter ones. But for the block copolymers with fixed volume fraction, interfacial tensions firstly decrease and then increase with increasing the chain length of block copolymer.