Adhesion of ethylene–octene copolymers to polypropylene: Interfacial structure and mechanical properties

Four separate ethylene-octene copolymers of differing molecular weight and co-monomer content have been moulded against polypropylene at various temperatures between 120 and 200°C. The adhesion, measured by a 90° peel test, varied with the particular copolymer, but for all of them it varied with moulding temperature, showing a maximum at about 160°C. It is argued that the temperature variation depends on the extent to which interpenetration of chains occurs in the interfacial region. This, in turn, depends on the recrystallization temperature of the polypropylene. The relative magnitudes of peel energy for the different copolymers can be understood in terms of the extent of plastic yielding necessary in order to transmit a critical stress to the interfacial regions during peeling.     

Blends of photovoltaic-grade ethylene–vinylacetate copolymers and low-density ethylene–octene copolymers,their morphology and their thermal,mechanical, and rheological properties

Blends of photovoltaic-grade ethylene–vinyl acetate copolymer (EVA), defined by high VA-content and low crystallinity, and low-density ethylene–octene copolymer (EO) have been investigated with regard to their processing, thermal and mechanical properties as well as their morphology. It was found that the amount of EO in the blend has a strong influence on the shear thinning behavior, melt viscosity and therefore the required extrusion temperature and resulting ability to incorporate temperature-sensitive additives like a peroxidic crosslinking agent. A phase separated morphology was found for all blend compositions, though partial miscibility leading to co-crystallization was observed for EVA rich blends. EO rich blends show lower glass transition and higher melting point compared to neat EVA and exhibit higher elastic modulus at elevated temperatures as well as greater elongation at break during tensile testing while the light transmission is diminished. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47714.     

Blends of ethylene–octene copolymers with different chain architectures – Morphology,thermal and mechanical behavior

Blends of two elastomeric ethylene–octene copolymers with similar octene contents having a random (ORC) and a blocky architecture (OBC) are prepared by melt mixing. The thermal and mechanical properties of ORC, OBC and their blends are investigated by DSC, dynamic mechanical analysis and tensile tests. The morphology of the semi-crystalline samples is studied by AFM and WAXS. Two types of crystals have been observed: (i) Orthorhombic crystals forming lamellae with an estimated thickness of about 13 nm composed mainly of long polyethylene-like sequences of OBC that melt a temperature of about 120 °C and (ii) fringed micellar crystals with a thickness of 2–4 nm formed basically by short polyethylene-like sequences of ORC that have melting temperatures between 30 and 80 °C. The amorphous phase contains a relatively homogeneous mixture of segments of both components indicated by the relatively uniform shape of the loss modulus peaks from dymamic-mechanical measurements for all investigated copolymers and blends. ORC crystallization is hindered in blends as indicated by lower melting enthalpies. This might be related to the high octene content of the amorphous phase at the relevant crystallization temperature as well as geometrical constraints since ORC crystallization occurs in an already semi-crystalline polymer. The results of tensile tests show that the mechanical behavior can be tailored via blend composition and morphology of the semi-crystalline material. The findings clearly indicate that blending is a powerful strategy to optimize the properties of polyolefin-based copolymers.     

Melt spinning of silane–water cross-linked polyethylene–octene through a reactive extrusion process

The aim of this study is to produce silane–water cross-linked polyethylene–octene (PEO) fibers through a reactive extrusion process. First, PEO is silane-grafted during an extrusion process followed by a spinning step. Then, grafted PEO monofilaments are introduced in water-based solution to perform cross-linking. The influence of process parameters on bulk PEO cross-linking degree was first investigated through a mixture design methodology which revealed that the most influent parameters are extrusion temperature and time. Using these results and the response surface methodology, silane–water cross-linked PEO monofilaments could be produced with desired gel contents after proceeding to some adjustments of processing parameters. The influence of cross-linking degree and draw ratio on macroscopic properties of PEO monofilaments was investigated. In particular, the cross-linked PEO fibers thermomechanical stability increases with cross-linking degree up to 170 °C for cross-linking degrees higher than 55%. Moreover, cross-linked PEO fibers exhibit higher elastic properties than neat PEO fibers.     

Synergistic toughening effects of nucleating agent and ethylene–octene copolymer on polypropylene

The synergistic toughening effect of nucleating agent (NA) and ethylene–octene copolymer (POE) on polypropylene was studied in the present work. Two different nucleating agents, such as α-form nucleating agent 1,3 : 2,4-bis (3,4-dimethylbenzylidene) sorbitol (DMDBS, Millad 3988) and β-form nucleating agent aryl amides compounds (TMB-5), were selected to blend with PP or PP/POE blends, respectively. The results show that PP containing 0.5–0.25 wt % DMDBS or 0.5–0.25 wt % TMB-5 has relatively low impact strength. For PP/POE blends, although the impact strength increases gradually with the increasing of POE content, high content of POE is needed to obtain the available PP toughness. However, once nucleating agent and POE are simultaneously added into PP, PP/POE/NA blends show great improvement of toughness even at low POE content. Furthermore, the synergistic toughening effect of POE/TMB-5 is more apparent than that of POE/DMDBS. SEM results show that whether DMDBS or TMB-5 has no apparent effect on the morphologies of POE in the PP/POE/NA blends. Further investigations using DSC and POM indicate that both DMDBS and TMB-5 induce the apparent enhancement of the crystallization temperature of PP and the sharp decrease of spherulites size of PP in the PP/POE/NA blends. The possible synergistic toughening mechanism is discussed in the work. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Properties influenced by addition of copoly (ethylene/octene) in BR–NBR blends

Abstract

The effects of copoly (ethylene/octene) (EOM) on rheological, mechanical, and cure properties and on carbon black distribution in each phase of butadiene rubber–nitrile/butadiene rubber (BR–NBR) blends have been investigated. It was found that EOM added to the blends is able to function as a plasticising agent for BR and NBR, and the plasticising efficiency of EOM is more significant in NBR than BR. With increasing EOM content, the deviation of Mooney viscosity from the additive line (interpolated values) reduces markedly. In pure components (i.e. 100 : 0 and 0 : 100), cure rate reduces and cure time increases with addition of EOM. In contrast in the blend systems, cure rate increases and cure time decreases when EOM is added. The distribution of carbon black in each phase of the blends is strongly controlled by the viscosity of each phase in the blend. The lower the phase viscosity, the greater the residual carbon black. Accordingly, dynamic mechanical thermal analysis reveals a slight shift in the glass transition temperature of the BR phase to higher temperature, compared with the NBR phase, as EOM is added. From the results obtained, it is proposed that EOM exists in the interfacial area between the two phases. However, at higher amounts of EOM, saturation of EOM at the interfacial area occurs and the excess EOM starts to migrate to the BR phase. Further increase in EOM concentration leads to saturation of EOM in the BR phase and EOM then migrates to the NBR phase.     

Synthesis of amphiphilic polycyclooctene-graft–poly(ethylene glycol) copolymers by ring-opening metathesis polymerization

In this paper, a novel monomer of 4-methyl-3-(carbamate)–carbanilic acid-4-cyclooctene ester (MCCCE) was synthesized and characterized by FTIR, NMR and ESI-MS. Polycyclooctene-graft-blocked isocyanate copolymers were prepared by the copolymerization of MCCCE and cyclooctene via ring-opening metathesis polymerization (ROMP). Amphiphilic polycyclooctene-graft–PEG copolymers were prepared by melt mixing the polycyclooctene-graft-blocked isocyanate copolymers with poly(ethylene glycol) (PEG) at 200 °C. The blocked isocyanate group on MCCCE can be dissociated to produce free isocyanate group, which will react with the end hydroxyl groups on PEG molecules. The effects of monomer-to-catalyst, monomer-to-chain transfer agent ratios on molecular weight of the copolymer were detailedly studied. The water contact angle of polycyclooctene-graft–PEG copolymer is much smaller than that of polycyclooctene.     

Quantitative study of photocatalyzed oxidation of ethylene–propylene rubber and atactic polypropylene

The effect of photoactive pigments such as ZnO, CdS, and TiO₂ on the photooxidation (with and without water vapor) of ethylene–propylene rubber and atactic polypropylene were examined. The effects of surface treatment (passivation) and low granulometry (nanopigments) were also studied for TiO₂. A drastic increase of ketone and an inhibition of carboxylic acid formation for ZnO filled polymers were revealed and quantitatively measured by using derivatization reactions. Such a phenomenon, as well as a small decrease of average molecular weight, were explained by a modification of the ZnO decomposition mechanism of tertiary hydroperoxides. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1681–1689, 1998     

Polystyrene–poly(ethylene oxide) diblock copolymers micelles in water

Micellization in water of polystyrene–poly(ethylene oxide) diblock copolymers is achieved by the stepwise dialysis technique in order to prepare micellar solutions for copolymers with a wide range of molecular parameters. Hydrodynamic radii, determined by quasielastic light scattering, are correlated with the molecular parameters, e.g. molecular weight and composition, and compared with the theory. Two couples of phenanthrene and anthracene labelled copolymers are used to prepare micellar solutions by mixing them before and after dialysis. The non radiative energy transfer is determined on these solutions to prove that polystyrene-poly(ethylene oxide) diblock copolymers micelles in water are "frozen" micelles even when heated near the Tg of polystyrene. Received: 3 November 1997/Revised version: 1 December 1997/Accepted: 2 December 1997     

The chemical structure of the amorphous phase of propylene–ethylene random copolymers in relation to their stress–strain properties

A better understanding of structure-property relations is necessary to design novel materials. In this study, we investigate the morphology and chemical structure of five commercial grades of propylene-based polymers in relation to the change in yield- stress as a function of strain-rate. Substantial emphasis has been laid on understanding the chain microstructure in the relation to chain dynamics in the amorphous phase. Heterogeneous Ziegler–Natta catalysis was used to prepare the samples with differing ratios of propylene and ethylene units. Various analytical techniques such as WAXS, SAXS, solution- and solid-state NMR were employed to characterize their structure. The results indicate a reduction in crystallinity, melting temperature, long-period and crystal thickness with increasing ethylene content. Solid-state NMR data reveal the presence of four components in these samples, which is an extension of the traditional three phase model found in most semi-crystalline polymers. The additional fourth phase is attributed to a rubber-like component that is primarily composed of chain segments rich in ethylene units and shows an increase in chain dynamics with increasing ethylene content in the samples. Mechanical experiments show that yield stress decreases with increase in the amount ethylene which can be correlated to the observed increase in chain dynamics in the amorphous phase.     

Synthesis,structure and behavior of new polycaprolactam copolymers based on poly (ethylene oxide)–poly (propylene oxide)–poly (ethylene oxide) macroactivators derived from Pluronic block copolymers

Novel series of poly (CL–co–Pluronic) polymers were successfully synthesized in situ by ring-opening polymerization (ROP) of ε-caprolactam (ε-CL). The copolymerization was activated by new type macroactivators (MAs) based on hydroxyl-terminated poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) [PEO-PPO-PEO] triblock copolymers, known under the trade name Pluronic^®. Toluene-2,4-diisocyanate (TDI) was used to obtain the isocyanate-terminated Pluronic prepolymers. The corresponding MAs were synthesized in situ with an N-carbamoyllactam structure. As an initiator of the copolymerization processes was used sodium lactamate (NaCL). To confirm the influence over the copolymerization process, microstructure, composition and molecular weight of the polymeric products two new types MAs based on Pluronic (P123 and F68) have been varied from 2 to 10 wt.% (vs. the monomer ε-CL). The structure of the both Pluronic based macroactivators (MAs) and accordingly obtained two series poly (CL-co-Pluronic) polymers were confirmed by ¹H NMR and FT-IR analyses. Additionally, the structure, molecular weight, physicomechanical behavior, thermal stability and morphology of the new synthesized poly (CL–co–Pluronic) polymers have been investigated by Differential Scanning Calorimetry (DSC), Wide-Angle X-ray Diffraction (WAXD), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM) analysis.     

Transport properties of cross-linked fullerenol–PVA membranes

Polyhydroxy fullerenes such as fullerenol C₆₀(OH)_22–24 have helped to bridge the gap between fullerenes and their innate solubility issues, where fullerenol solubility in water is 50 mg/ml whereas C₆₀ solubility is 1.3 × 10⁻¹¹ mg/ml. The improved solubility of these fullerene derivatives allows them to be better integrated into composite materials. Here we investigated the transport properties of cross-linked fullerenol–polyvinyl alcohol membranes with the addition of maleic acid for increased stability. High humidity causes the mechanical properties of polyvinyl alcohol to decrease. Using fullerenol as a cross-linker, we were able to decrease the sorption of water with these PVA membranes.     

Triple crystallization behavior of fractionated ethylene/α-olefin copolymers of different catalyst type

Non-isothermal crystallization processes in fractions of Ziegler-Natta (ZN) and single site (SS) based ethylene/1-butene and ethylene/1-hexene copolymers have been studied by differential scanning calorimetry (DSC). Fractionation of used copolymers was done according to molar mass (MM) and composition (comonomer content). It was observed in DSC scans that for fractions with high MM (larger than 10 kg/mol) in addition to the main high-temperature crystallization peak (HTCP), a very-low temperature crystallization peak (VLTCP) is present at temperatures in between 60–75 °C. Such peak is absent for the first fractions having very-low MM. The partial crystallinity and peak temperatures, obtained from VLTCP, increase with MM and level off at MM around 60–100 kg/mol. It was found that the crystallinity as related to the area of the VLTCP is catalyst type dependent, and is higher for the SS catalyst compared to the ZN. Peak temperature of VLTCP linearly decreases with increasing comonomer content at fixed MM while the partial crystallinity practically does not change with comonomer content.     

Self-assembly behavior of rod–coil–rod polypeptide block copolymers

Self-assembly behavior of rod–coil–rod poly(γ-benzyl-l-glutamate)-b-poly(ethylene glycol)-b-poly(γ-benzyl-l-glutamate) (PBLG-b-PEG-b-PBLG) triblock copolymers with various PBLG block lengths in aqueous solution was investigated. The PBLG-b-PEG-b-PBLG triblock copolymers are able to self-assemble into vesicles when PBLG block length is relatively short. Meanwhile, the initial polymer concentration was found to have influence on the self-assembly. Giant vesicles can be observed when the initial concentration is high. Dissipative particle dynamics (DPD) simulations about the vesicles revealed that the rigid rod blocks could be aligned parallelly with each other to form the monolayer vesicles wall. When the PBLG block length in the PBLG-b-PEG-b-PBLG triblock copolymers increases, the aggregate morphologies were observed to transform from vesicles to spherical micelles. Based on the experimental and simulation results, we proposed a possible mechanism of the morphological transitions of the rod–coil–rod triblock copolymer aggregates.     

Synthesis and characterization of a novel amphiphilic poly (ethylene glycol)–poly (ε-caprolactone) graft copolymers

A series of amphiphilic graft copolymers PEO-g-PCL with different poly (ε-caprolactone) (PCL) molecular weight were successfully synthesized by a combination of anionic ring-opening polymerization (AROP) and coordination-insertion ring-opening polymerization. The linear PEO was produced by AROP of ethylene oxide (EO) and ethoxyethyl glycidyl ether initiated by 2-(2-methoxyethoxy) ethoxide potassium, and the hydroxyl groups on the backbone were deprotected after hydrolysis. The ring-opening polymerization of CL was initiated using the linear poly (ethylene oxide) (PEO) with hydroxyl group on repeated monomer as macroinitiator and Sn(Oct)₂ as catalyst, then amphiphilic graft copolymers PEO-g-PCL were obtained. By changing the ratio of monomer and macroinitiator, a series of PEO-g-PCL with well-defined structure, molecular weight control, and narrow molecular weight distribution were prepared. The expected intermediates and final products were confirmed by ¹H NMR and GPC analyzes. In addition, these amphiphilic graft copolymers could form spherical aggregates in aqueous solution by self-assemble, which were characterized by transmission electron microscopy, and the critical micelle concentration values of graft copolymers PEO-g-PCL were also examined in this article.     

Electric-field-induced sphere–cylinder phase transitions of diblock copolymers

Using the real space self-consistent field theory, the transitions between the body-centered-cubic phases and the cylindrical phases were studied for the diblock copolymers in the external electrostatic fields along three different orientations [001], [110], and [111]. The different orientations of the external fields resulted in the cylinder structures with various symmetries through the intermediate ellipsoid structures, where the cylinder-to-cylinder transition was also observed in the electric field along the orientation [110]. Furthermore, the size of ellipsoid was investigated by varying the strength of electric field, and the factors that affect the critical values of electric field strengths were also considered for the sphere–cylinder transitions in the electric fields with orientation [001]. Our findings are compared with the available experimental and theoretical works, which is in a general agreement.     

Aging of Nanosized ZnO Modified Polyoxymethylene Blends with Ethylene–octene Copolymer

The influence of ethylene–octene copolymer and zinc oxide (ZnO) on structure and tensile stress–strain behavior of polyoxymethylene were investigated before and after ultraviolet weathering. Addition of ZnO considerably improved stress–strain characteristics of the ultraviolet-irradiation impaired composites. Crystallinities of ultraviolet-irradiated composites were affected by numerous competitive processes, including suppression of crystallization in the presence of multiple components in the system, nucleation induced by nanofiller, secondary crystallization and amorphization because of the chain scissions of the macromolecules. Addition of ZnO considerably improved stability of the composites, as testified by corresponding changes in the intensities of hydroxyl and carbonyl absorption peaks.     

Assessment of compatibilization role of nanoclay in immiscible polystyrene/ethylene–octene copolymer blends via wide-angle X-ray scattering,microstructure, rheological analyses,and mechanical properties

Polystyrene (PS)/ethylene–octene copolymer (EOC) blends with 80/20 wt % composition containing different amounts (0, 1.0, 2.5, 5.0 and 7.5 wt %) of an organically modified nanoclay were prepared by one-step melt-mixing method. Also, the EOC-rich blends with 80 wt % EOC content loaded with 0 and 5.0 wt % of the nanoclay were prepared under the similar processing conditions. Presence of both PS and EOC chains in between clay layers localized at the interface of the blends could be deduced by X-ray diffraction analysis, which suggested formation possibility of PS-EOC physical structures at the blend interface. Transmission electron microscopy results confirmed that clay nanoparticles were mainly localized at the interface of the blends and also partly in the PS and EOC components of the systems. The localization of the nanoclay was also described by the linear viscoelastic melt rheological studies. It is also revealed that nanoclay had stronger interactions with PS than EOC. This is reflected in the higher tensile properties in the PS-rich system. The analysis of morphology of the developed systems by emulsification curve revealed that the optimum amount of nanoclay to modify PS-rich blend is 2.5 wt %. At this clay loading, the blend exhibited the highest impact resistance. According to the overall results, suitability of nanoclay was confirmed for compatibilization of the PS/EOC blends. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48748.     

Swelling behaviours of styrene–isoprene–styrene triblock copolymers in supercritical methane

Styrene–isoprene–styrene triblock copolymers (SIS) are representative thermoplastic elastomers possessing both elastomeric and thermoplastic feature. SIS have been used in self-healing cement for natural gas wells, but the mechanism behind the application was not unravelled. We hypothesise such self-repairing function should be associated with the swelling of SIS in natural gas whose main component is methane. It was found that all the four SIS copolymers show similar swelling trend irrespective of their structure difference, and the swelling ratio increases as decreasing the polystyrene block content in SIS. These preliminary pioneering findings show the swelling behaviour of the rubbers displayed quite differently before and after supercritical point, and it is helpful for the further research about the swelling behaviour of rubber in natural gas wells.