Radiation effect on properties of carbon black filled NBR/EPDM rubber blends

Rubber blend of acrylonitrile butadiene rubber (NBR) and ethylene-propylene diene monomer (EPDM) rubber (50/50) has been loaded with increasing contents, up to 100 phr, of reinforcing filler, namely, high abrasion furnace (HAF) carbon black. Prepared composites have been subjected to gamma radiation doses up to 250 kGy to induce radiation vulcanization under atmospheric conditions. Mechanical properties, namely, tensile strength (TS), tensile modulus at 100% elongation (M₁₀₀), and hardness have been followed up as a function of irradiation dose and degree of loading with filler. On the other hand, variation of the swelling number as a physical property, as a function of same parameters, however, in car oil as well as brake oil has been undertaken. In addition, the electrical properties of prepared composites, namely, their electrical conductivity, were also evaluated. The thermal behavior of the prepared composites was also investigated. The results obtained indicate that improvement has been attained in different properties of loaded NBR/EPDM composites with respect to unloaded ones.     

Stability of electrical and mechanical properties of polyethylene/carbon black composites

The stability of electrical and mechanical properties of two kinds of polymer composites ‐ polyethylene/carbon black and polyethylene/carbon black modified by polypyrrole ‐ was investigated during slow cycle heating and cooling. Conductivity in composites was measured in heating/cooling cycles in the temperature range from 16°C to 125°C. It was found that the thermal treatment resulted in the conductivity changes and the mechanical properties of treated composites have also been influenced. The effect was explained by increased crystallinity in the polymer matrix of thermally treated composites.     

Effects of functionalized multiwalled carbon nanotubes on the morphologies and mechanical properties of PP/EVA blend

The maleic anhydride‐grafted multiwalled carbon nanotubes (MWCNTs‐g‐MA) have been introduced into polypropylene/ethylene‐co‐vinyl acetate (PP/EVA) blend. To clearly describe the effects of MWCNTs‐g‐MA on the morphology and mechanical properties of PP/EVA blends, the selective distribution of MWCNTs‐g‐MA in the blends is realized through different sample preparation methods, namely, MWCNTs‐g‐MA disperse in EVA phase and MWCNTs‐g‐MA disperse in PP matrix. The results show that the distribution of MWCNTs‐g‐MA has an important effect on the final morphology of EVA and the crystallization structure of PP matrix. Compared with PP/EVA binary blend, distribution of MWCNTs‐g‐MA in PP matrix induces the aggregation of EVA phase at high EVA content and the decrease of spherulite diameters of PP matrix simultaneously. However, when MWCNTs‐g‐MA are dispersed in the EVA phase, they induce more homogeneous distribution of EVA, and the crystallization behavior of PP is slightly affected by MWCNTs‐g‐MA. The corresponding mechanical properties including impact strength and tensile strength are tested and analyzed in the work. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1481–1491, 2009     

Rheology, morphology and mechanical properties of polyethylene/ethylene vinyl acetate copolymer (PE/EVA) blends

Rheology, morphology and mechanical properties of binary PE and EVA blends together with their thermal behavior were studied. The results of rheological studies showed that, for given PE and EVA, the interfacial interaction in PE-rich blends is higher than EVA-rich blends, which in turn led to finer and well-distributed morphology in PE-rich blends. Using two different models, the phase inversion composition was predicted to be in 45 and 47 wt% of the PE phase. This was justified by morphological studies, where a clear co-continuous morphology for 50/50 blend was observed. The tensile strength for PE-rich blends showed positive deviation from mixing rule, whereas the 50/50 blend and EVA-rich blends displayed negative deviation. These results were in a good agreement with the results of viscoelastic behavior of the blends. The elongation at break was found to follow the same trend as tensile strength except for 90/10 PE/EVA blend. The latter was explained in terms of the effect of higher co-crystallization in 90/10 composition, which increased the tensile strength and decreased the elongation at break in this composition. The results of thermal behavior of the blends indicated that the melting temperatures of PE and EVA decrease and increase, respectively, due to the dilution effect of EVA on PE and nucleation effect of PE on EVA.     

Nanosized carbon black as synergist in PP/POE-MA/IFR system for simultaneously improving thermal,electrical and mechanical properties

Nanosized carbon black (CB) was introduced into polypropylene/maleic anhydride-grafted polyolefin elastomer/intumescent flame retardant (PP/POE-MA/IFR) system to investigate the effect of nanofiller as synergist on thermal, electrical and mechanical properties of polymer composites. With 5 mass% CB into PP/POE-MA/IFR system (POFC5), the T_max (corresponded to the temperature at the maximum mass loss rate) under air was increased by 122.4 °C; its limited oxygen index was as high as 31.4%; its vertical burning rating (UL-94) reached V0, and the peak value of heat release rate was decreased to only 19% of neat PP in cone calorimeter testing. Moreover, PP composites exhibited good electrical conductivity with more than 1.6 mass% CB, which is a low loading level to reach the critical percolation concentration. In addition, a good balance on stiffness and toughness of PP composites was achieved; especially, Young’s moduli and impact strength of POFC5 were increased to 1.26 and 2.5 times in comparison with that of neat PP, respectively. These results indicated that CB was an effective synergist in multi-component PP composites to simultaneously improve thermal, electrical and mechanical properties.

     

Physical blends of PLA with high vinyl acetate containing EVA and their rheological,thermo-mechanical and morphological responses

Rheological, morphological and thermo-mechanical responses of poly(lactic acid) (PLA)/ethylene-co-vinyl-acetate copolymer (EVA) blends at EVA volume fractions varying in the range of 0–0.35 were evaluated. The micro-structural analysis demonstrated dispersive mixing at low content and co-continuous morphology at 30 wt % of EVA in PLA. Dynamic rheology demonstrated enhanced storage modulus and complex viscosity (η*) with increase in frequency of the blends indicated strong phase interaction. Cole-Cole and Han plots indicated partial miscibility and incompatibility between the polymer matrix and the dispersed phase. Dynamic mechanical analysis (DMA) revealed slight increase in damping parameters which indicated interaction or reinforcement in the blends. Additionally, the thermogravimetric analysis (TGA) of the blends showed two step degradation and enhanced thermal stability.     

The effect of hot air exposure on the mechanical properties and carbon dioxide permeability of hydrogenated nitrile butadiene rubber (HNBR) with varying carbon black content

The effect of hot air exposure at 150 °C for up to 12 weeks (ca. 2000 h) on the properties of hydrogenated nitrile butadiene rubber (HNBR) compounds with varying degrees of carbon black content was investigated and reported in this paper. The composition of the HNBR was varied with 0, 10, 30 or 50 PHR carbon black. The tensile properties, hardness, density, solvent saturation swelling and carbon dioxide permeability of these specimens was investigated before and after exposure in a hot air oven. Correlations between these results are reported for the compounds considered in this work. These correlations illustrate how the changes in performance which would require test samples of specific geometries (such as tensile modulus or gas permeation) might in some cases be predicted by tests which do not require exact geometries (such as density or surface hardness), for the materials investigated in this paper.     

聚喹啉/十八胺/稀土杂多阴离子杂化LB膜的制备、结构及电性质

将聚喹啉(PQ)、十八胺(OA)和含稀土元素的1;11钨系双系列杂多阴离子RE(PW₁₁O₃₉)₂^11-(RE=Ce^Ⅲ,Eu^Ⅲ,Gd^Ⅲ)通过LB技术掺杂,成功地制备了三种PQ/OA/稀土杂多阴离子杂化LB膜,通过π-A曲线、荧光、吸收光谱和原子力显微镜等手段对PQ/OA/稀土杂多阴离子杂化LB膜的成膜方式、性能、结构及形貌进行了表征;扫描隧道显微镜研究表明,将稀土杂多化合物掺杂到聚喹啉中可使聚喹啉的导电性明显增强.     

Cure kinetics, dynamic mechanical and morphological properties of epoxy resin-Im6NiBr2 system

The aim of this study was to examine effects of a catalyst of Nickel-imidazole, i.e. Im₆NiBr₂ on the cure reaction and network properties of diglycidyl ether of bisphenol A. DSC and FT-IR measurements are carried out on the epoxy resin loaded with 5, 15, and 30 phr of nickel salt to get some insights into the storage stability. It has been concluded that the storage stability has mainly depended on the epoxy composition and was the lowest for the highest level of curing agent. Kinetics of the cure has been described by applying iso-conversional method of Ozawa to scanning DSC data demonstrating that the studied cure reaction is autocatalytic in nature. The Kamal phenomenological approach has been utilized to fit the experimental isothermal DSC data. The model showed a satisfactory fitting of the experimental results at either early stages or at the final steps of the studied cure reaction. Further, the model did not provide a reasonable fitting in the propagation step of polymerization, 0.3 < α < 0.5, possibly due to existence of the additional reaction/s which did not consider in the used model. DMTA is used to find the optimum cure schedule. It has been shown that the sample with a postcure treatment offers the highest value of glass transition temperature (T_g) in the tan δ peak. SEM and X-ray analyses are employed to investigate the fracture surface morphology and to understand the distribution of nickel in the cured samples exhibiting that the nickel is scattered in the continuous phase homogenously. Flexural properties of the sample cured at optimum conditions are also determined.     

Toughening of poly(2,6-dimethyl-1,4-phenylene oxide)/nylon 6 alloys with functionalized elastomers via reactive compatibilization: morphology, mechanical properties, and rheology

Blends of poly(2,6-dimethyl-1,4-phenylene oxide)/nylon 6 alloys based on ethylene-propylene-diene elastomer (EPDM) grafted with maleic anhydride (MA) (EPDM-g-MA), EPDM grafted with glycidyl methacrylate (EPDM-g-GMA), and styrene-ethylene-butadiene-styrene block copolymer grafted with MA (SEBS-g-MA) were prepared via melt extruction, and morphology, mechanical properties, and rheology were studied. The compatibilizing effects of functionalized elastomers on the PPO/nylon 6 alloys were proved by DSC analysis and confirmed by the significant improvement in the notched Izod impact strength. Toughening was resulted from the smaller particle size and finer dispersion of EPDM in the PPO/nylon 6 matrix as well as a novel network structure of SEBS-g-MA domain in matrix. The notched Izod impact strength of the blends exhibited an optimum value when the extent of MA or GMA graft ratio of EPDM varied, which was an order of magnitude higher than the non-toughened alloys. The morphology revealed that the size of EPDM particles decreased with an increase in graft ratio of MA or GMA onto EPDM. Rheology investigation indicated that the MA or GMA moieties on EPDM reacted with the amine groups of nylon 6, which increased the molecular weight and the degree of branching, and thus resulted in an increase in the viscosity of the blends. This proved the reactive compatibilization between functionalized EPDM and PPO/nylon 6 matrix.     

Effect of carbon black content on electrical and microwave absorbing properties of polyaniline/carbon black nanocomposites

Carbon black coated with polyaniline, forming a core-shell structure, was synthesized by in situ polymerization at different carbon black contents (5-30 wt.%) and introduced into epoxy resin to be a microwave absorber. The spectroscopic characterizations of the formation processes of polyaniline/carbon black composites were studied using Fourier transform infrared, ultraviolet-visible spectrophotometer, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and electron spin resonance. Microwave absorbing properties were investigated by measuring reflection loss in the 2-18 and 18-40 GHz microwave frequencies range using the free space method. The results showed that a wider absorption frequency range could be obtained by adding different carbon black contents in polyaniline.     

Crystallization,rheological, and mechanical properties of PLLA/PEG blend with multiwalled carbon nanotubes

Functionalized multiwalled carbon nanotubes (FMWCNTs) were introduced into poly(L‐lactide)/polyethylene glycol (PLLA/PEG) blend and the effects of FMWCNTs on crystallization behaviors, rheological, and mechanical properties of PLLA/PEG/FMWCNTs were investigated. The results show that FMWCNTs exhibit good distribution in the nanocomposites and absorb some PEG to agglomerate around them. The crystallization behavior of PLLA in the nanocomposites is greatly dependent on the content of FMWCNTs. At low content of FMWCNTs, the addition of FMWCNTs improves the crystallization behavior of PLLA by enhancing the crystallization temperature and accelerating the crystallization rate, whereas at high content of FMWCNTs, the crystallization of PLLA is restricted to a certain degree. Rheological properties show the formation of the network structure of FMWCNTs at high content, which is the main reason for the retarded crystallization behavior of PLLA due to the network structure providing restriction to mobility and diffusion of PLLA chains to crystal growth fronts. The mechanical properties show that FMWCNTs exhibit reinforcement effect for plasticized PLLA. Copyright © 2010 John Wiley & Sons, Ltd.     

Influence of thermoplastic spacer on the mechanical,electrical, and thermal properties of carbon black filled epoxy adhesives

A new approach of mimicking the selective localization mechanism of conductive filler into one phase of immiscible polymer blend system is proposed here, where a moderate fine of polymethylmethacrylate (PMMA) powder is prepared and used as the spacer in the carbon black (CB) filled epoxy adhesives system that can be applied at room temperature. The main purpose of PMMA‐spacer is to promote the formation of conductive networks via aiding the 3D self‐assembly of CB filler, selectively in the continuous phase of epoxy. PMMA‐spacer content ranged from 10, 20, 30, 40, and 50 vol.% were investigated under electrical, mechanical, and thermal properties for both unfilled and 15 vol.% CB filled system. With the incorporation of 10 vol.% PMMA‐spacer, the filled system shows promising improvement in electrical conductivity, with three order of magnitude increment at 15 vol.% CB loading. Toughening mechanism of epoxy was observed, where crack deflection upon the PMMA‐spacer is observed under scanning electron microscopy characterization and agreed by fracture toughness calculation. Thermal stability and coefficient of thermal expansion were improved at the minimum addition of PMMA‐spacer content, at 10 vol.%, while a small reduction in flexural strength is observed because of the poor interface interaction between the PMMA‐spacer and epoxy matrix. Interestingly, a limited interaction between the PMMA‐spacer with epoxy at the curing temperature of 100°C is observed, indicating the solubility of PMMA‐spacer in epoxy before crosslinking process occurred. Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of coupling agents on mechanical and morphological behavior of the PP/HDPE blend with two different CaCO3

The main purpose of incorporating fillers, such as calcium carbonate, into blends of polyolefins is to decrease costs and change tensile and impact properties. Structural differences between both components give rise to the formation of large filler agglomerates in the polymer matrix, which influence the mechanical response of the material. Therefore, the coupling agents of the Lica 12 type at various concentrations was used to facilitate the link between filler and matrix (the latter consisting of PP/HDPE 80/20 wt). Filler was added to the PP/HDPE blend at a 30 wt.% concentration. Two types of calcium carbonate (CaCO₃) were used. These have different average sizes (3.0 and 1.8 μm) which were determined by means of laser diffraction techniques. In addition other coupling agents of the titanate type, such as Lica 09, Lica 01, zirconates ZN 12, and a 1:1 mixture of Lica 12 and Lica 01, were used. This study clearly demonstrated that the addition of the coupling agent to CaCO₃ modifies the mechanical properties of the PP/HDPE/CaCO₃ composites. Values of the mechanical properties indicate that due to its characteristics, each coupling agent gives rise to increases in a particular mechanical property. In the case of Lica 01 an increase was verified in Young’s modulus at 0.7 wt.% and in elongation at break at both concentrations (0.3 and 0.7 wt.%), whereas ZN 12 brought about an increase in elongation at break. The 1:1 mixture of Lica 12 and Lica 01 caused impact resistance of the blend of PP/HDPE with CaCO₃ to increase considerably.     

Morphology, morphology development and mechanical properties of polystyrene/polybutadiene blends

Polystyrene/polybutadiene (PS/PB) blends with different plastic/rubber ratios were prepared by melt mixing. A detailed investigation on phase morphology development of 30/70 wt.% PS/PB blends as a function of processing conditions was quantitatively analyzed. Morphology is developed at the initial stages of mixing. Suitable blending conditions resulting in optimum phase morphology were obtained at 180 °C, 60 rpm and at 8 min mixing time. Phase morphologies of the blends were also studied as a function of composition. Mechanical properties of the blends were measured. Attempts were made to correlate the morphologies with the properties. Parallel-Voids model has been applied to characterize phase morphology of these blends.     

Compatibilization of polypropylene/poly(glycolic acid) blend with maleated poe/attapulgite hybrid compatibilizer: Evaluation of mechanical,thermal, rheological,and morphological characteristics

In this work, the compatibilization effects of hybrid maleated POE/attapulgite hybrid compatibilizer (M-POE/ATP) on the immiscible polypropylene/poly(glycolic acid) (PP/PGA) blends was investigated. The hybrid compatibilizer integrating strengthening, toughening and compatibilization functions was prepared via one-step reactive extrusion using peroxidated ATP as the initiator. Then, the effects of compatibilizer dosage on the mechanical, thermal, rheological and morphological characteristics of blends were evaluated in detail. It was found that the hybrid compatibilizer resulted in the significantly enhanced compatibility and mechanical performance. Increased amount of compatibilizer content fractionated and almost wholly suppressed the crystallization process of PGA. The compatibilized blends showed higher thermal stability than pure PGA, and lower storage modulus and complex viscosity at higher shearing frequency. PGA in the blends presented a much lower degradation rate, which lead to the higher strength retention of 81% for the blend with 4 wt% of compatibilizer in buffer solution after 35 days.     

Effect of dispersed phase composition on morphological and mechanical properties of PET/EVA/PP ternary blends

Immiscible ternary blends of PET/EVA/PP (PET as the matrix and (PP/EVA) composition ratio = 1/1) were prepared by melt mixing. Scanning electron microscope results showed core‐shell type morphology for this ternary blend. Binary blends of PET/PP and PET/EVA were also prepared as control samples. Two grades of EVA with various viscosities, one higher and the other one lower than that of PP, were used to investigate the effect of components' viscosity on the droplet size of disperse phase. The effect of interfacial tension, elasticity, and viscosity on the disperse phase size of both binary and ternary blends was investigated. Variation of tensile modulus of both binary and ternary blends with dispersed phase content was also studied. Experimental results obtained for modulus of PET/EVA binary blends, showed no significant deviations from Takayanagi model, where considerable deviations were observed for PET/PP binary blends. Here, this model that has been originally proposed for binary blends was improved to become applicable for the prediction of the tensile modulus of ternary blends. The new modified model showed good agreement with the experimental data obtained in this study. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 251–259, 2010     

Thermal,rheological, morphological and mechanical properties of high density polyethylene/ethylene vinyl acetate copolymer (HDPE/EVA) blends

Thermal, rheological, morphological and mechanical properties of binary HDPE and EVA blends were studied. The results of rheological studies showed that for given HDPE and EVA, the interfacial interaction in HDPE-rich blends is higher than EVA-rich blends. Using three different rheological criterions, the phase inversion composition was predicted to be in 30 wt% of the EVA phase. This showed good agreement with morphological studies. The tensile strength for HDPE-rich blends showed positive deviation from mixing rule, whereas the EVA-rich blends played negative deviation. These results were in a good agreement with the results of viscoelastic behavior of the blends. The thermal analysis revealed that high co-crystallizaiton in 90/10 composition, which increased the tensile strength and decreased the elongation at break in this composition. Furthermore, the results of thermal behavior of the blends indicated that the melting temperatures of HDPE decrease due to the dilution effect of EVA on HDPE.     

Preparation and morphological,electrical, and mechanical properties of polyimide‐grafted MWCNT/polyimide composite

Precursor of polyimide, polyamic acid has been prepared sucessfully. Acid‐modified carbon nanotube (MWCNT) was grafted with soluble polyimide then was added to the polyamic acid and heated to 300 °C to form polyimide/carbon nanotube composite via imidation. Morphology, mechanical properties and electrical resistivity of the MWCNT/polyimide composites have been studied. Transmission electron microscope microphotographs show that the diameter of soluble polyimide‐grafted MWCNT was increased from 30–60 nm to 200 nm, that is a thickness of 70–85 nm of the soluble polyimide was grafted on the MWCNT surface. PI‐g‐MWCNT was well dispersed in the polymer matrix. Percolation threshold of MWCNT/polyimide composites has been investigated. PI‐g‐MWCNT/PI composites exhibit lower electrical resistivity than that of the acid‐modified MWCNT/PI composites. The surface resistivity of 5.0 phr MWCNT/polyimide composites was 2.82 × 10⁸ Ω/cm² (PI‐g‐MWCNT) and 2.53 × 10⁹ Ω/cm² (acid‐modified MWCNT). The volume resistivity of 5.0 phr MWCNT/polyimide composites was 8.77 × 10⁶ Ω cm (PI‐g‐MWCNT) and 1.33 × 10¹³ Ω cm (acid‐modified MWCNT).Tensile strength and Young's modulus increased significantly with the increase of MWCNT content. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3349–3358, 2007