Effect of octene content on peroxide crosslinking of ethylene–octene copolymers

Various ethylene–octene copolymers were crosslinked by dicumyl peroxide. Octene content was 16, 20, 30, 35 and 38 wt% and melt flow index was 1 or 3 g/10 min. The concentration of dicumyl peroxide was 0.3, 0.5 and 0.7 wt%. Crosslinking was analyzed by a rubber process analyzer in the temperature range 150–200 °C. Cross‐linkability was evaluated from the real part modulus s'_max versus peroxide level plots as the slope of the line. With decreasing octene content and increasing melt flow index the crosslinkability increased. This was confirmed also by tan δ analysis. The network density was measured by the gel content. A higher gel content was found for melt flow index 3 and low octene content. The melting points T_m and the crystallinities were evaluated by DSC. © 2012 Society of Chemical Industry     

Effect of strain on the properties of an ethylene–octene elastomer with conductive carbon fillers

Composites that incorporate a conductive filler into an ethylene–octene (EO) elastomer matrix were evaluated for DC electrical and mechanical properties. Comparing three types of fillers (carbon fiber, low structure carbon black, and high structure carbon black), it was found that the composite with high structure carbon black exhibited a combination of properties not generally achievable with this type of filler in an elastomeric matrix. A decrease in resistivity at low strains is unusual and has only been reported previously in a few instances. Reversibility in the resistivity upon cyclic deformation is a particularly unusual feature of EO with high structure carbon black. The mechanical and electrical performance of the high structure carbon black composites at high strains was also impressive. Mechanical reinforcement in accordance with the Guth model attested to good particle–matrix adhesion. The EO matrix also produced composites that retained the inherent high elongation of the unfilled elastomer even with the maximum amount of filler (30% by volume). The EO matrix with other conducting fillers did not exhibit the exceptional properties of EO with high structure carbon black. Composites with carbon fiber and low structure carbon black did not maintain good mechanical properties, generally exhibited an increase in resistivity with strain, and exhibited irreversible changes in both mechanical and electrical properties after extension to even low strains. An explanation of the unusual properties of EO with high structure carbon black required unique features of both filler and the matrix. The proposed model incorporates the multifunctional physical crosslinks of the EO matrix and dynamic filler–matrix bonds. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 894–905, 2000     

Preparation of polyethylene–octene elastomer foams by compression molding

To produce polyethylene–octene elastomer foams with compression molding, the influences of various activators on the thermal decomposition temperature of the chemical blowing agent azodicarbonamide were investigated with thermogravimetric analysis, which showed that the decomposition temperature of azodicarbonamide could be effectively reduced by the addition of zinc oxide/zinc stearate. The results of a moving die rheometer suggested that the vulcanization and blowing curves were influenced by the content of azodicarbonamide and temperature, and the optimum temperature was about 170°C. The morphology and physical properties of the microcellular polyethylene–octene elastomer were studied. The results indicated that the amount of azodicarbonamide and the processing temperature played important roles in the cell morphology and physical properties of polyethylene–octene elastomer foams. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Melt grafting of maleic anhydride onto elastomeric ethylene‐octene copolymer by reactive extrusion

Melt grafting of maleic anhydride onto elastomeric ethylene‐octene copolymer was carried out in a twin‐screw extruder, in the presence of dicumyl peroxide as an initiator. Dimethyl formamide was used as an inhibitor to reduce crosslinking and as a solvent for peroxide initiator. The aim of the work is to produce the copolymer with reactive functionality without the expense of elastomeric characteristics. Particular consideration was, therefore, given to the effects of initiator and monomer concentrations, and of screw speed on the degree of grafting, percentage of conversion, amount of crosslinked products, and on the stress‐strain behaviors of the grafted products. The degree of grafting was found to be dependent mainly on the initiator and monomer concentrations. Increasing the initiator concentration increased the degree of grafting, and at the same time, increased the amount of gel (crosslinking). An increase in gel content of the grafted products resulted in a change of tensile behaviors from uniform deformation followed by strain‐hardening at high strains to low extensibility and fracture at low strains.     

A study on electrical and thermal conductivities of ethylene–octene copolymer/expandable graphite composites

A series of ethylene–octene copolymer (EOC) composites have been prepared by melt‐mixing with different weight ratios of expandable graphite filler (0–50% by weight). Electrical conductivity [both alternating current (AC) and direct current (DC)] and thermal conductivity studies were carried out. Effect of filler loading and frequency on electrical conductivity was studied. DC conductivity has increased from 1.51 × 10^?13 S cm^?1 to 1.17 × 10^?1 S cm^?1. Percolation threshold by DC and also AC methods was observed at about 16 vol% of the filler. Real part of permittivity was found to be decreasing with increase in frequency while conductivity was increasing. Thermal conductivity was also found to be increasing gradually from 0.196 to 0.676 Wm^?1 K^?1 which is about 245% increase. Graphite not only increases the electrical and thermal conductivities but at and above 40 wt%, also acts as a halogen‐free, environmental friendly flame retardant. Shore‐A hardness of EOC/graphite composites shows that even with high graphite loading, the hardness is increased from about 50–68 only so that the rubbery nature of the composite is not affected very much. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Property transitions in high‐density polyethylene/maleated poly(ethylene–octene)/calcium carbonate ternary composites

Ternary composites of high‐density polyethylene (HDPE)/maleated poly(ethylene–octene) (POE‐g)/calcium carbonate (CaCO₃) were prepared by the melt extrusion process. Crystallization behavior investigation and mechanical properties study showed that there existed a transition in both crystallization temperature (T_c) and impact strength of ternary composites. These transitions were attributed to the development of morphology, with variation of concentration of POE‐g in ternary composites. The strength of interfacial adhesion also influenced the property transitions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3361–3366, 2006     

Modification of polyethylene–octene elastomer by silica through a sol–gel process

In this study, tetraethoxysilane (TEOS) and a metallocene polyethylene–octene elastomer (POE) were chosen as the ceramic precursor and the continuous phase, respectively, for the preparation of new hybrids by an in situ sol–gel process. To obtain a better hybrid, a maleic anhydride‐grafted polyethylene–octene elastomer (POE‐g‐MAH), used as the continuous phase, was also investigated. Characterizations of POE‐g‐MAH/SiO₂ and POE/SiO₂ hybrids were performed by Fourier transform infrared (FTIR) and ²⁹Si solid‐state nuclear magnetic resonance (NMR) spectrometers, a differential scanning calorimeter (DSC), a thermogravimetry analyzer, and an Instron mechanical tester. The results showed that the POE‐g‐MAH/SiO₂ hybrid could improve the properties of the POE/SiO₂ hybrid because the interfacial force between the polymer matrix and the silica network was changed from hydrogen bonds into covalent Si? O? C bonds through dehydration of hydroxy groups in POE‐g‐MAH with residual silanol groups in the silica network. The existence of covalent Si? O? C bonds was proved by FTIR spectra. For the POE/SiO₂ and POE‐g‐MAH/SiO₂ hybrids, maximum values of the tensile strength and the glass transition temperature were found at 9 wt % SiO₂ since a limited content of silica might be linked with the polymer chains through the covalent bond. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 966–972, 2003     

Supertoughness in Polysulfone/Poly(ethylene‐octene) Blends

Summary: Poly(sulfone of Bisphenol A) (PSU) based blends were obtained by melt blending PSU with up to 15 wt.‐% poly(ethylene‐octene) either modified with maleic anhydride (mPEO) or not (PEO). The dispersed particle size was small and similar in blends with PEO or mPEO. These facts indicated respectively that the interfacial tension was low and the lack of compatibilizing effect of mPEO. Some preferential presence of PEO in the outer surface of the specimens was observed, and was attributed to the large viscosity difference between the two components of the blends. This had no effect on the modulus of elasticity, but speeded up both the yield stress and ductility decreases at rubber contents above 3.25 wt.‐%. However, despite the immiscibility of the components, and thanks to the small particle size of the blends, super‐toughness was attained in the unmodified PSU/PEO blends. This was at PEO contents (3.25 wt.‐%) at which the modulus, yield stress and ductility of the blends were almost as good as those of pure PSU. It appeared that a change of the chemical nature of the rubber did not influence by itself super‐toughness, unless it was accompanied by either a morphological or adhesion change.

Impact strength of PSU‐based blends vs. PEO (○) or mPEO (?) content.     

Rheological and morphological properties of high‐density polyethylene and poly(ethylene–octene) blends

The rheological and morphological properties of blends based on high‐density polyethylene (HDPE) and a commercial ethylene–octene copolymer (EOC) produced by metallocene technology were investigated. The rheological properties were evaluated in steady and dynamic shear experiments at 190°C in shear rates ranging from 90 s^?1 to 1500 s^?1 and frequency range between 10^?1 rad/s and 10² rad/s, respectively. These blends presented a high level of homogeneity in the molten state and rheological behavior was generally intermediate to those of the pure components. Scanning electron microscopy (SEM) showed that the blends exhibit dispersed morphologies with EOC domains distributed homogeneously and with particle size inferior to 2 μm. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2240–2246, 2002     

Comparing elastomeric behavior of block and random ethylene–octene copolymers

This work compared the elastomeric properties of two low‐crystallinity ethylene–octene copolymers. One was a block copolymer with lamellar crystals and the other was a random copolymer with fringed micellar crystals. The comparison of the stress–strain behavior at 23°C revealed that the initial elastic modulus and the yield stress depended only on the crystallinity of the copolymer. When the temperature was raised above 23°C, melting of the fringed micellar crystals of the random copolymer caused a rapid decrease in the modulus. Some decrease in the modulus of the block copolymer over the same temperature range was attributed to the crystalline α‐relaxation. Both polymers exhibited strain‐hardening, ultimate fracture at high strains, and high recovery after fracture. However, in the block copolymer, the onset of strain‐hardening and the ultimate fracture occurred at higher strains. The block copolymer also showed higher recovery from high strains. The initial stretching resulted in a permanent change in the stress–strain curve. It was suggested that following the onset of crystal slippage at the yield, the crystals underwent permanent structural changes through the course of the strain‐hardening region. The transformation of the fringed micellar crystals occurred at lower strains than the transformation of the lamellar crystals. The extent of the structural transformation was described by the crosslink density and the strain‐hardening coefficient extracted from elasticity theory. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Evaluation of toughening mechanisms of polypropylene/ethylene–octene copolymer/maleic anhydride‐grafted poly(ethylene‐co‐octene)/clay nanocomposite

The toughness of a polypropylene (PP)/ethylene‐octene copolymer (EOC)/maleic anhydride‐grafted poly(ethylene‐co‐octene) (EOC‐g‐MA)/clay nanocomposite and blends of PP/EOC and PP/EOC/EOC‐g‐MA was investigated using Charpy impact and single‐edge‐notch tensile (SENT) tests. In order to understand the toughening mechanisms, impact fracture surfaces and damage zones of single‐edge‐notch samples were studied with scanning electron microscopy and transmission optical microscopy, respectively. It was observed that the addition of EOC‐g‐MA to PP/EOC blend led to improvements in both impact strength and fracture energy of SENT tests because of the enhanced compatibility of the blend, which resulted from reduced EOC particle size and improved interfacial adhesion, and the decreased crystallinity of PP. The incorporation of clay to PP/EOC/EOC‐g‐MA blend caused a further increase of the toughness, owing to the greater decrease in the size of elastomer particles, to the presence of clay tactoids inside the elastomer phase and presumably to debonding of clay layers during the low‐speed SENT tests. The results of microscopic observations showed that the main toughening mechanism in PP/EOC/EOC‐g‐MA blend and PP/EOC/EOC‐g‐MA/clay nanocomposite is crazing. Copyright © 2012 Society of Chemical Industry     

Study on composition and characteristics of maleated ethylene‐octene copolymer prepared by reactive extrusion on the morphology and properties of polyamide 6/ethylene‐octene copolymer blends

Blends of polyamide 6 (PA6) and elastomeric ethylene‐octene copolymer (EOR), with and without maleated EOR (EOR‐MA) were studied. EOR‐MA with various amounts of grafted MA and gel content were prepared by reactive extrusion. The effects of EOR‐MA characteristics and composition on the morphology, thermal and mechanical properties of the blends were investigated. EOR‐MA was found to promote the toughness efficiency of PA6 remarkably. High impact resistance was achieved by the use of EOR‐MA containing less than 2% gel. The content of MA grafted on EOR‐MA in the range of 0.5%–1.0% gave a similar effect on the blend properties. The blend containing 20% of EOR grafted with 1% MA exhibited twenty times higher impact strength (1000 J/m) than pure PA6 (55 J/m). The presence of EOR‐MA in the blends led not only to a drastic reduction in the dispersed particle size, but also to some changes in fracture mechanisms, thus enhancing the impact resistance of the blends.     

Cross‐linking of ethylene‐octene copolymer (EOC) by dicumyl peroxide (DCP)

Ethylene‐octene copolymer (EOC) was crosslinked by dicumyl peroxide (DCP) at various temperatures (150–200°C). Six concentrations of DCP in range 0.2–0.7 wt % were investigated. cross‐linking was studied by rubber process analyzer (RPA) and by differential scanning calorimetry (DSC). From RPA data analysis real part modulus s', tan δ, and reaction rate were investigated as a function of peroxide content and temperature. The highest s'_max and the lowest tan δ were found for 0.7% of DCP at 150°C. Chain scission was analyzed by slope analysis of conversion ratio, X in times after reaching the maximum. Less susceptible to chain scission are temperatures in range 150–170°C and peroxide levels 0.2–0.5%. Heat of reaction was analyzed by DSC at various heating rates (5–40°C min⁻¹). It was found to be exothermic. By projection to zero heating rate, the reaction was found to start at 128°C with the maximum at 168°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of octene content in poly(ethylene‐co‐1‐octene) on the properties of poly(propylene)/poly(ethylene‐co‐1‐octene) blends

Ethylene‐octene random copolymer (EOC) is one of the most commonly employed elastomers for PP, and as such its rubber toughening efficiency has been extensively studied. However, most existing studies employ EOC containing an octene comonomer of about 8 mol %. Therefore, in this study, we investigated the effect of EOC octene comonomer content on the morphology and thermal and mechanical properties of PP‐ethylene random copolymer (PP‐CP)/EOC (80/20 wt %/wt %) blends. It was clearly shown that the properties of the blends are significantly affected by the octene content. The rubber particle size of the blends decreased as the octene content in the EOC was increased, which was a consequence of the reduced interfacial tension between PP‐CP and EOC. Impact strength of the blends as a function of octene content displayed a brittle‐ductile transition. The tensile yield strength and modulus of the PP‐CP/EOC blends were decreased by addition of EOC, owing to incorporation of the soft EOC into the hard PP‐CP. The tensile yield strength and modulus of PP‐CP/EOC blends decreased monotonically with the octene content in the EOC. The melting temperature as well as the crystallinity of the PP‐CP phase were not affected significantly by the addition of EOC whereas a notable shift in melting and crystallization temperatures was observed for the EOC phase. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1133–1139, 2007     

Preparation and characterization of blends of high density polyethylene and poly(ethylene‐co‐1‐octene) elastomer

Mechanical, thermal, and morphological properties of blends of high density polyethylene and poly(ethylene‐co‐1‐octene) (PEO) were evaluated. The blends were prepared in a single screw extruder at 230°C and 50 rpm with volume fraction of elastomer varying in the range from 0.05 to 0.8. Factors such as chemical similarity and melt viscosity favor the interdiffusion process of phases, resulting in better interfacial adhesion. A synergistic effect on the strength at break and elongation at break for a particular range of blend composition was observed. Blends with a volume fraction of PEO higher than 5% presented a super tough behavior at room temperature. Thermal analysis showed that there is a certain degree of interaction between high density polyethylene and PEO. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1991–1995, 2001     

Self‐reinforcing elastomer composites based on ethylene–propylene–diene monomer rubber and liquid‐crystalline polymer

In this study, the prime factor determining the size, shape, and distribution of liquid‐crystalline polymer (LCP) was the viscosity ratio at the processing conditions. The fiber‐forming capacity of the LCP depended on the viscosity of the ethylene–propylene–diene monomer rubber (EPDM). With increasing LCP content, the tensile and tear strengths did not increase, perhaps because of incompatibility between the EPDM and LCP. The hardness increased because of the hard mesogenic groups in the LCP. The percentage swelling decreased as the LCP content increased. With increasing LCP content, processability became easier because of a lower melt viscosity. The scorch time increased at higher LCP levels. A higher percentage crystallinity was observed with increasing LCP content. Scanning electron microscopy clearly showed the fiber phase formation, which was two‐dimensionally isotropic in nature, confirming fiber formation even in a shear field. The addition of LCP improved the thermal stability. The onset degradation temperatures shifted to higher values with increasing LCP content. Dynamic mechanical thermal analysis revealed that with the addition of LCP, the mechanical damping increased at its lower level. High‐temperature processing increased the effective amorphous zone. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 711–718, 2004     

Ionically bonded filler–elastomer composites

Tertiary amine-modified corn starches were converted to their basic or hydroxide form and combined with carboxylated butadiene–acrylonitrile copolymer and butadiene–styrene–sulfonic acid polymer to produce ionically bonded filler–elastomer composites. An increasing percentage of the elastomer fraction in the starch–elastomer composite is insolubilized as the starch-to-elastomer ratio increases. In addition to ionic bonding, a significant amount of elastomer is believed to be physically adsorbed onto the filler. The resulting composites are reprocessible, and some have sufficient tensile properties at room temperature for making rubber goods.     

Microwave‐absorbing properties of linear low‐density polyethylene/ethylene–octene copolymer/carbonyl iron powder composites

Using linear low‐density polyethylene (LLDPE)/ethylene–octene copolymer (POE) as a polymer matrix and carbonyl iron powders (CIPs) as filler, we prepared polymer matrix composites with microwave‐absorbing properties by means of melt blending. Scanning electron microscopy and transmission electron microscopy were used to characterize the samples. The absorbing properties of the composites were measured with the arch method in the range of frequency 2.0–18.0 GHz. The results indicate that the absorbing peaks moved to low frequency as the CIP content in composites increased and that there was an appropriate CIP content in LLDPE/POE/CIP composites to achieve the best absorbing effectiveness. The electromagnetic parameters of the composites were determined with the transmission/reflection method in the range 2.6–17.8 GHz. The experimental results show that there were both dielectric loss and magnetic loss in the LLDPE/POE/CIP composites. Therefore, the microwave absorption of the LLDPE/POE/CIP composites was attributed to the combining contributions of the dielectric loss and magnetic loss. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structure development and viscoelastic properties in silane‐crosslinked ethylene–octene copolymer

The development of structure and viscoelastic properties during silane crosslink reaction in metallocene ethylene–octene copolymer has been investigated. Using attenuated and transmission infrared spectroscopy, the concentrations of certain functional groups and change in sample thickness were monitored, giving the information on the progress of crosslink reaction. The evolution of crosslink content and viscoelastic properties was analyzed using a parallel‐plate rheometer. The results showed that crosslinking process started with the hydrolyzation of methoxy groups in the near‐surface layer, proceeding in a diffusion manner. At this stage no silanol groups could be detected, revealing that the condensation occurred promptly after hydrolyzation. The internal crosslink could not begin until there are sufficient water molecules in the surrounding. A water by‐product from the condensation reaction played an essential part in the center region. The rheological data showed a reduction in magnitude of creep compliance. As the reaction proceeded, more networks took place within an existing gel. The materials, then, acted more like elastic and exhibited an improvement in ability for recovery process. The immobilization of chain segments, due to the presence of tight network, disallowed conformations necessary for crosslink reaction and a certain amount of hydrolyzable groups and silanol groups remained after a long crosslinking process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Dynamic‐mechanical and thermal characterization of polypropylene/ethylene–octene copolymer blend

Polypropylene/Ethylene–Octene copolymer (PP/EOC) blends were prepared by melt blending technique followed by compression molding. The effect of addition of EOC on the mechanical behavior of the PP matrix was investigated. Tensile and flexural strengths decreased with the incorporation of EOC. However, the impact strength of the matrix polymer increased in all the blend systems. The blends prepared at 30% EOC content showed an increase in the impact strength to the tune of 380% as compared with polypropylene (PP) matrix. The morphology of the fractured surfaces was investigated employing Scanning Electron Microscopy. SEM micrographs depicted the formation of biphase structure, wherein the EOC phases were homogeneously dispersed as small droplets within the PP matrix. WAXD patterns revealed that the α monoclinic form of isotactic PP does not show any significant change with the incorporation of EOC up to 70 wt %. DSC thermograms revealed a decrease in the melting temperature of the virgin matrix with the addition of EOC. The blend system at 50% EOC exhibited a broad crystallization exotherm at 75°C thus indicating multiple crystallization behavior primarily attributed to the difference in the nucleation process. Further DMA analysis showed presence of two different relaxation peaks corresponding to the T_g of EOC and PP matrix respectively, confirming the formation of a biphase structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007