Ethylene-propylene Copolymer Research Articles

Functionalisation of ethylene–propylene copolymer by melt grafting of maleic anhydride using a high shear internal mixer

This study focused on synthesising a peroxide-initiated maleic anhydride-g-ethylene–propylene copolymer via melt grafting using a Haake internal mixer at high shear rate. The effect of maleic anhydride and dicumyl peroxide percentage on the grafting efficiency of maleic anhydride onto ethylene–propylene copolymer chains was carried out through a two-level factorial experimental design using Design Expert 6.0.5 software. The maleic anhydride and dicumyl peroxide content were varied, in the range of 1–5 and 0·1–0·3 phr, respectively. The grafting parameters were fixed at a temperature of 180°C and rotor speed of 60 rev min−1 for 5 minutes. The grafting efficiency was determined by Fourier transform infrared spectroscopy analysis based on cumulative absorbance of anhydrides’ characteristic peaks and supported by differential scanning calorimetry and field emission scanning electron microscopy analyses. The grafting was highly influenced by maleic anhydride and dicumyl peroxide content. The optimum functionalisation was achieved at 5 phr maleic anhydride and 0·3 phr peroxide addition.

Methyl branching in polyethylene from homopolymerization of ethylene with N‐arylcyano‐β‐diketiminate methallyl nickel‐B(C6F5)3

ABSTRACTN‐Arylcyano‐β‐diketiminate methallyl nickel complexes activated with B(C6F5)3 were used in the polymerization of ethylene. The microstructure analysis of obtained polyethylene (PE) was done by differential scanning calorimetry and 13C nuclear magnetic resonance (NMR). The branched polymer structures produced by these catalysts were attributed to one step isomerization mechanism of the catalyst along the polymer chain. The ortho or para position of the cyano group with co‐ordinated B(C6F5)3 in both methallyl nickel catalysts influenced the polymer molecular weight, branching, and consequently melting and crystallization temperatures. NMR spectroscopic studies showed predominantly the formation of methyl branches in the obtained PE. Catalysts under study gave linear low‐density PEs with good crystallinities at temperatures of reaction between 50 °C and 70 °C at moderate pressures (12.3 atm). A propylene–ethylene copolymer produced by the metallocene catalyst had the same concentration of branches as the PE synthesized from methallyl nickel/B(C6F5)3. Comparing the two polyolefins with the same degree of branching, it was observed that the polymer obtained with the nickel catalyst proved to be twice more crystalline and had greater Tm. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 452–458

Synthesis of Ethylene-Propylene Copolymer and their Structures

This work reports copolymerization of ethylene-propylene (EP) using a novel phenoxy–ester ligated titanium catalyst. Copolymerization reactions were conducted in toluene at 70 °C with varied E/P flow ratios. Fourier transform infrared spectroscopy, X-ray diffractometer, nuclear magnetic resonance spectroscopy and differential scanning calorimetry analysis were performed to characterize the structures, compositions and glass transition temperatures of the copolymers. The results show that ethylene-propylene copolymers are random polymers and the link ratios of ethylene to propylene are between 0.89 and 1.26. The glass transition temperature of ethylene-propylene copolymer is-43.3 °C.

Synthesis of N-Allyloxycarbonyl 3,5-Dihydroxyphenylglycine via Photochemical Wolff Rearrangement—Nucleophilic Addition Sequence in a Micro-Flow Reactor

In this study, two practical and scalable procedures were developed for the synthesis of N-arylacetyl oxazolidinone, which is an intermediate for the preparation of N-allyloxylcarbonyl 3,5-dihydroxyphenylglycine. The key sequence in the developed procedures was a photochemical Wolff rearrangement–nucleophilic addition in a micro-flow reactor. A power-saving, inexpensive, and readily available light source (4-W portable ultraviolet [UV] lamp) along with a fluorinated ethylene propylene copolymer (FEP) tube was employed in the developed procedures. The first-generation procedure afforded the desired N-arylacetyl oxazolidinone in the highest yield. The yield was lower in the second-generation procedure, but it afforded pure N-arylacetyl oxazolidinone without column chromatographic purification. The use of the two parallel channel tube reactors enabled the gram-scale preparation of N-arylacetyl oxazolidinone. N-Allyloxylcarbonyl 3,5-dihydroxyphenylglycine was successfully prepared via the second-generation pr...

Defining the distribution of ethylene-propylene copolymer phases in heterophasic ethylene-propylene copolymers by a sequential xylene extraction method: Chemical and morphological analysis

Sequential xylene extraction (SXE) in combination with scanning electron microscopy (SEM) and high temperature solvent gradient interaction chromatography (HT-SGIC) were employed for the detailed visualisation and understanding of the evolution of phase morphology in heterophasic ethylene-propylene copolymer (HEPC) particles. The study focused on sequentially extracting the soluble EP rubber phase and EP block or segmented copolymers by SXE at various temperatures. Major changes in the particle morphology (significant increase in both size and number of voids in the particles) after SXE were revealed using SEM imaging. These void structures are believed to result from the amorphous phase (EPR) being removed during the xylene extraction which was further confirmed by differential scanning calorimetry (DSC), high temperature 13C NMR spectroscopy and HT-SGIC. The extractables obtained at 100 °C were found to be a mixture of EP random copolymers, semi-crystalline EP (block or segmented) copolymers, as well as iPP and PE homopolymers. Upon complete dissolution of the particles by SXE at 100 °C, significant amounts of the EP rubber fractions were obtained. Our results show a very heterogeneous distribution of EPR components with varying chemical compositions in HEPC particles produced by dual-reactor processes. For the layered structure observed from this study, truly amorphous EP rubber was found in the outer most regions followed by continuous regions of EP random copolymers having increasing ethylene contents. Propylene-rich EPR, extracted at temperatures of 100 and 130 °C, was observed as the inner EPR phase. Semi-crystalline EP (segmented or block copolymer) and PE homopolymer were detected as intermediate structures between these two EPR regions, inside and outside the pores of the iPP particles. Based on these findings a modified multi-layered core–shell structure was proposed. The results obtained by the proposed SXE fractionation method and its combination with various analytical approaches are found to be very effective for the investigation of the phase composition present in HEPC particles. The present approach is general and can also be used for other multiphase semi-crystalline polyolefins.

Single ethylene molecular insertion as a probe into the nature of the active species in MgCl2-supported Ziegler–Natta catalysts

The propylene-ethylene copolymers with a very small amount of ethylene (from 0.01 to 1.8mol%) obtained with different catalyst systems at 100°C or 120°C were characterized by 13C NMR. The chain end group n-propyl formed through the chain transfer reaction of species to alkylaluminum following “one” ethylene molecule insertion was detected in these copolymers of low molecular weight. 13C NMR chain end group analysis of these copolymers implied that most of syndiotactic species in the MgCl2-supported Ziegler–Natta catalysts would be “dormant” for propylene insertion while highly isotactic species would remain highly active for propylene insertion when these two species were inserted by “one” ethylene molecule. For isotactoid species occasional “one” ethylene molecule insertions remarkably slowed down propagation of propylene. The active species could be divided into three classes according to their behavior following “one” ethylene molecule insertion, which fit Busico [1] three-state model of active species to a great degree. The chain end group ethyl (Et′) formed by chain transfer reactions by alkylaluminum at “one” ethylene molecule insertion followed by a 2-1-last-insertion was also detected by 13C NMR. Thus, the fraction of “dormant” polypropylene chains with a 2,1-last inserted unit was estimated to be in the 3–6mol% range for a TiCl4/MgCl2/diester-silane catalyst while for a TiCl4/MgCl2/diether catalyst the content of such the fraction was ca. 7–9mol%. 13C NMR analysis indicated that a large part of the “dormant” 2-1-inserted sites revived by “one” ethylene insertion were still “dormant” for propylene insertion at high polymerization temperature.

Modified and Unmodified Zinc Oxide as Coagent in Elastomer Compounds

Abstract The aim of this work was to study the activity of unmodified and modified ZnO in the peroxide crosslinking of hydrogenated acrylonitrile-butadiene elastomer (HNBR) and ethylene-propylene copolymer (EPM). In the first step, zinc oxide was obtained by emulsion precipitation. Maleic acid was introduced onto the surface of ZnO using an in situ method. The unmodified and modified zinc oxide was characterized using dispersive and morphological analysis, BET surface area analysis, and elemental, spectroscopic and thermal analysis. In the second stage of the research, the ZnO/MA systems were incorporated into the structure of elastomer compounds improving the kinetic and mechanical properties of vulcanizates. The proposed modification method had a favorable effect on the physicochemical properties of the zinc oxide and on the kinetic and mechanical properties of the vulcanizates. This study demonstrated that modification of zinc oxide by maleic acid is a promising technique.

Toward Absolute Chemical Composition Distribution Measurement of Polyolefins by High-Temperature Liquid Chromatography Hyphenated with Infrared Absorbance and Light Scattering Detectors

Chemical composition distribution (CCD) is a fundamental metric for representing molecular structures of copolymers in addition to molecular weight distribution (MWD). Solvent gradient interaction chromatography (SGIC) is commonly used to separate copolymers by chemical composition in order to obtain CCD. The separation of polymer in SGIC is, however, not only affected by chemical composition but also by molecular weight and architecture. The ability to measure composition and MW simultaneously after separation would be beneficial for understanding the impact of different factors and deriving true CCD. In this study, comprehensive two-dimensional chromatography (2D) was coupled with infrared absorbance (IR5) and light scattering (LS) detectors for characterization of ethylene-propylene copolymers. Polymers were first separated by SGIC as the first dimension chromatography (D1). The separated fractions were then characterized by the second dimension (D2) size exclusion chromatography (SEC) with IR5 and LS detectors. The concentrations and compositions of the separated fractions were measured online using the IR5 detector. The MWs of the fractions were measured by the ratio of LS to IR5 signals. A metric was derived from online concentration and composition data to represent CCD breadth. The metric was shown to be independent of separation gradients for an "absolute" measurement of CCD breadth. By combining online composition and MW data, the relationship of MW as a function of chemical composition was obtained. This relationship was qualitatively consistent with the results by SEC coupled to IR5, which measures chemical composition as a function of logMW. The simultaneous measurements of composition and MW give the opportunity to study the SGIC separation mechanism and derive chain architectural characteristics of polymer chains.

Synthesis and Characterization of Low Molecular Weight Ethylene–Propylene Copolymers Prepared Using Metallocene Catalysts

AbstractThe synthesis in a liquid propene phase of ethylene–propylene copolymers of low molecular weights (3 000–20 000 g mol−1) is accomplished using three different metallocenes containing bridged bis(indenyl) moieties: (A) rac‐dimethylsilylbis(4,5,6,7‐tetrahydro‐1‐indenyl)zirconium dichloride, (B) rac‐ethylenebis(4,5,6,7‐tetrahydro‐1‐indenyl)zirconium dichloride, and (C) rac‐ethylenebis(indenyl)zirconium dichloride. Hydrogen pressures higher than 1 bar were required to drop the molecular weight below 25 000 g mol−1. Metallocene B gives rise to the copolymers with lower molecular weights (<5 000 g mol−1), irrespective of the ethylene content, due to the presence of a hydrogenated six membered ring in the indenyl moiety as well as a CH2 bridge. DSC experiments indicate that for low ethylene contents (below 4 wt%), metallocene A gives rise to copolymers with the highest melting temperatures and the lowest melting enthalpies, suggesting the existence of longer isotactic propylene sequences into the copolymer backbone.

Solution and solid-state NMR characterization of heterophasic propylene–ethylene copolymers (HEPC) with increasing ethylene content

Solid-state and solution 13C NMR were used as complementary techniques to investigate changes in the molecular dynamics and chemical composition of different semi-crystalline fractions obtained using temperature rising elution fractionation (TREF) from heterophasic ethylene/propylene copolymers (HEPCs). The HEPCs were selected during a transition from homopolymer to copolymer and represent a range of total ethylene contents between 2 and 12mol%. It was found that these techniques yielded complimentary information, further breaking down the complexity of these polymers and providing observations that have not yet been obtained for these polymers by other experimental techniques. Ethylene dependent changes in the methylene region of solid-state spectra obtained for the bulk HEPCs was observed. Solid-state analysis of the semi crystalline fractions of these polymers provided more insight on this observation as well as on the distribution of these components between fractions with different crystallinities. From the solution NMR results, the distribution of different ethylene sequences between the fractions was evaluated and a statistical model proposed for this evolution. Furthermore the development of longer ethylene sequences observed by solution NMR was found to correspond with an increase of ethylene within rigid areas in the higher temperature semi-crystalline fractions. Thus a clearer understanding was obtained of how the different semi-crystalline copolymers, responsible for phase interactions and ultimately final product properties, develop with increasing ethylene incorporation.

Practical approach in surface modification of biaxially oriented polypropylene films for gravure printability

Abstract Biaxially oriented polypropylene (BOPP) film is one of the most popularly used materials for the gravure printing process in flexible packaging industry. The skin layers of BOPP film were associated with 3–6 weight % of propylene–ethylene copolymer. These films were completely biaxial-oriented by sequential stretching process after which the film surfaces were subjected to corona treatment integrated in the production line. The FT-IR results exhibited that polar functional groups as carbonyl molecules were established on the corona-treated BOPP film. The contact angles of these BOPP films were measured; the surface free energies (SFE) were then calculated. AFM topographical images also agreed well with the SFE which increased as the contents of propylene–ethylene copolymer increased. An approximated 20% increased SFE was obtained for the BOPP film that was associated with 6% propylene–ethylene copolymer. The printing quality on BOPP films was tested by light microscope which confirmed that the chromatic resolution of the printed images improved down to even more smaller groove sizes, 10 or 5 dot%. This improvement was also examined and found to correspond well with the interfacial tensions and work of adhesion between the inks and the modified BOPP films.

Separation of Polypropylene Polymers by Crystallization and Adsorption Techniques

The fractionation of industrial polypropylene resins by crystallization or adsorption is a challenging task due to the existence of stereoregularity and the fact that homopolymer and propylene‐rich copolymers are semicrystalline, as is the case with polyethylene homopolymer, which is usually present in complex polypropylene resins. The separation mechanisms involved in crystallization and adsorption techniques are investigated. Crystallization techniques and adsorption chromatography on graphitized carbon using a temperature gradient separate the full range of propylene ethylene copolymers following a U‐shaped curve and cannot provide unequivocal compositional results. The addition of an infrared detector to measure the level of branches at each elution temperature provides a new dimension that better defines the separated components. A step further in separation is using cross‐fractionation chromatography (composition followed by molar‐mass separation), which makes use of all the mechanisms investigated to provide the most‐extended separation of complex high‐impact polypropylene resins. image

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.

내열성 향상을 위한 폴리케톤/탄성체 블렌드 제조 및 특성

폴리케톤은 일산화탄소, 에틸렌, 프로필렌을 단량체로 중합되는 삼중공중합체 (terpolymer)로서 폴리아미드, 플리에스테르, 폴리카보네이트 등의 일반 엔지니어링 플라스틱 소재에 비해 원료 및 중합 공정비가 저렴한 소재이다. 또한 기계적 특성과 내열성, 내화학성, 연료투과성, 내마모성 등이 우수하여 기존 엔지니어링 플라스틱 소재를 대체할 수 있는 환경 친화적인 소재로 주목을 받고 있다. 본 연구에서는 폴리케톤의 내열성을 향상시키기 위해 탄성체(Ethylene propylene copolymer, Nitrile butadiene rubber, Ethylene acrylic rubber)를 배합하여 블렌드물을 제조하였고, 각 소재에 대하여 내열성, 내유성에 평가에 따른 특성을 분석하였다. Terpolymer polymerized carbon monoxide, ethylene and propylene as monomer, Polyketone is low-cost material compared with general engineering plastics such as polyamide, polyester, polycarbonate. Moreover, it is excellent in mechanical properties, chemical resistance, fuel permeability and abrasion resistance. So, it is attracted attention as the environmental friendly material to replace conventional engineering plastics. In this study, has been prepared Polyketone/Rubber (Ethylene propylene copolymer, Acrylonitrile butadiene rubber, Ethylene acrylic rubber) blends to improve heat resistance and investigated characteristic behavior after heat/oil aging.

Preparative solution crystallization fractionation: a simple and rapid fractionation method for the chemical composition separation of complex ethylene-propylene copolymers

The molecular structure elucidation of complex ethylene-propylene copolymers (EPCs) has benefited tremendously from the ability to combine preparative temperature rising elution fractionation (prep TREF) with various conventional analytical techniques. Recently reported, prep TREF-high-temperature solvent gradient interaction chromatography (HT-SGIC) (Cheruthazhekatt et. al, Macromolecules 45:2025-2034, 2012) is one of the most effective and highly useful coupled methods that allow for the exact measurement of the chemical composition distribution (CCD) present in various components of EPCs. The major drawback of prep TREF involving slow crystallization and elution steps is the long time per experiment. Here, we present a new and by far the simplest and fastest preparative fractionation method for complex polyolefins-preparative solution crystallization fractionation (prep SCF). The scope of the present study was to achieve a fast fractionation of complex bulk samples into an amorphous, semicrystalline and highly crystalline fraction, in sufficient amounts for the subsequent detailed compositional analysis. The effects of two different solvents, xylene and trichlorobenzene (TCB), and their influence on the solution crystallization of chemically different components of EPC were systematically investigated by combining prep SCF with crystallization analysis fractionation (CRYSTAF), FTIR, differential scanning calorimetry (DSC) and HT-SGIC analyses. Significant differences in the chemical composition of similar SCF fractions obtained from xylene and TCB were observed indicating the strong influence of the solvent on solution crystallization. Prep SCF-HT-SGIC results showed that, under similar experimental conditions, TCB as the fractionation solvent provides superior separation of complex semicrystalline ethylene-propylene (EP) components. Very interestingly, for the first time, separation of soluble fractions (30°C) of iPP, EPC and PE homopolymer components in complex EPC was achieved by prep SCF in TCB. On the other hand, SCF fractionation in xylene provides a soluble fraction that is perfectly amorphous as has been shown by DSC and CRYSTAF. Based on these results, the present SCF approach and an updated method of the combination of prep SCF-HT-SGIC hold significant promise for the fractionation and characterization of similar complex EPCs in a simple way within a short analysis time, by using significantly smaller amounts of solvent compared to the previously reported, rather time-consuming, prep TREF-HT-SGIC combination. No similarly selective solution crystallization fractionations in preparative scale have been reported before.

Evaluation of the fracture behaviors of multilayered propylene–ethylene copolymer/polypropylene homopolymer composites with the essential work of fracture

ABSTRACTAs one of the most appropriate techniques for evaluating the fracture behavior, the essential work of fracture (EWF) was introduced to investigate the fracture toughness of multilayered composites. Propylene–ethylene copolymer (CPP)/polypropylene homopolymer (HPP) alternating multilayered composites with 2–128 layers were prepared though multilayered coextrusion. Polarized optical microscopy photographs revealed that the CPP and HPP layers aligned alternately vertical to the interfaces and continuously parallel to the extrusion direction. The dichroic Fourier transform infrared spectroscopy results showed that the coextrusion sheet had a preferential orientation parallel to the melt flow direction (MD); this caused crack propagation along the blunted MD and the necking ligament section. After heat treatment, the orientation parallel to the MD could been largely eliminated, and the crack propagated in a stable manner. The specific essential work of fracture (we) of the multilayered composite was higher than that of the blend; this indicated a higher resistance of crack propagation. The number of layers had little effect on the toughness of the multilayered composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40574.

Preparation of synthetic hydrocarbon oil by high-pressure hydrocracking of ethylene-propylene copolymers

Degradation reactions of ethylene-propylene copolymers at a high temperature (380–430°C) and a high pressure (180–220 atm) in the presence of a nickel catalyst and hydrogen have been studied. In contrast to the previously known processes, the degradation reactions have been conducted simultaneously with hydrogenation reactions. The effects of temperature, pressure, and time on the yield of each fraction have been examined. As a result, optimal process conditions have been found for each fraction. The physicochemical properties of the lube oil fraction (C18–C25) used as a base oil have been studied. It has been found that as in the case of oils derived from ethylene-propylene copolymers by other methods, these oils have a high viscosity index (VI > 95), a high flash point (Tf > 210°C), and a low pour point (Tp < −50°C).

Quantification of highly oriented nucleating agent in PP-R by IR-microscopy, polarised light microscopy, differential scanning calorimetry and nuclear magnetic resonance spectroscopy

To relate a morphological structure of polymeric specimens to the applied conditions of the production process requires to be able to analyse the morphology and composition of the specimen with high spatial resolution, ideally with a single technique. Infrared microscopy (μFTIR) is a highly attractive technique to map the crystallinity and additive content of polymer samples due to its simplicity and spatial resolution. However, no methods exist yet which allow to exploit these advantages for oriented minority phases with high aspect ratio, and to study the degree of crystallinity in oriented polymer samples. Based on a theoretically derived approach we show for the first time that the spatial distribution of the β-nucleating agent N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide (NU-100) in random ethylene propylene copolymer (PP-R) can be determined by μFTIR from the sum of the absorption intensities in three directions of inspection. Using the same approach the degree of crystallinity of the polymer can be profiled, thus eliminating the problem arising from dichroism inferred by chain orientation. The newly developed method was applied to specimen of PP-R prepared by extrusion, injection and compression moulding. The results regarding the NU-100 content are in good agreement with results from nuclear magnetic resonance (NMR) and the results regarding morphology confirm those from polarised light microscopy (PLM) and differential scanning calorimetry (DSC). This method development opens the perspective to establish process → structure relationships for samples having an arbitrary degree of orientation with regard to the main phase as well as the minority phase.

A quantitative analysis of the effect of interface delamination on the fracture behavior and toughness of multilayered propylene–ethylene copolymer/low density polyethylene films by the essential work of fracture (EWF)

The multilayered propylene–ethylene copolymer (CPP)/low density polyethylene (LDPE) composite sheets were prepared by the microlayered coextrusion system. The essential work of fracture (EWF) method was firstly used to quantitatively evaluate the fracture behavior of layered materials. The experimental results indicated that the two-dimensional layered interfaces in the multilayered materials could play an important role in the fracture behavior. The specific essential work of fracture, we, increased with the layers due to interfacial delamination. Additionally, the different testing speeds had a dual effect on the increscent trend of the specific essential work of fracture, we, with increasing layers.

Unique microstructure analysis of ethylene-propylene copolymer synthesized using catalytic system based on α-diimine nickel complexes: a comparative study by 13C NMR technique

The microstructure of rubber-like ethylene-propylene copolymer (MN4) produced by a mixed nickel-based system (MN) containing catalysts of dibromo[N,N′-bis(2,6-diisopropylphenyl)-2,3-butanediimine]nickel(II) n1 and dibromo[N,N′-(phenanthrene-9,10-diylidene)bis(2,6-diisopropylaniline)]nickel(II) n2 was determined by 13C NMR technique. Sequences distribution of ethylene (E), propylene (P), EP, inverted propylene and uninterrupted methylene and also methylene number-average sequence lengths for the copolymer (MN4) were estimated. The results obtained from the MN4 EP copolymer were compared with reported copolymers which had been synthesized using constrained geometry catalyst (CGC) and vanadium-based Ziegler-Natta catalyst. The results demonstrated that the MN4 EP copolymer had fewer alternating comonomer sequences than ethylene-propylene elastomers obtained by CGC and vanadium-based (V) catalysts. A large number of the inversion structures (66 %) and high mole percent of sequences containing a long branch (3.2 mol%) were also observed in unique microstructure of the copolymer (MN4).