Influence of nanoparticle-polymer interactions on the apparent migration behaviour of carbon nanotubes in an immiscible polymer blend

We investigate the influence of nanoparticle-polymer interactions on the apparent migration behavior of multiwall carbon nanotubes (CNTs) in an immiscible polymer blend of ethylene-acrylate copolymer (EA) and polyamide 12 (PA). The polymer-CNTs interaction is tuned by using different surface modification strategies, comprising grafting and coating. Poly(methyl methacrylate) (PMMA) and polystyrene (PS) are chosen as surface modifiers. The nanocomposite materials are prepared by melt-blending polymer-modified-CNTs in EA and PA. Polymer-grafted-CNTs tend to concentrate at the PA/EA interface, even if predispersed in PA, as opposed to pristine CNTs, which stay inside PA under the same circumstances. This new behavior is consistent with the morphology of PA/EA/(PMMA or PS) ternary blends and suggest a dominance of interfacial thermodynamics on CNTs localization. If we use polymer-coated-CNTs instead, the behavior depends on molar mass of the coating polymer. For low molar mass, it is similar to that of pristine CNTs and indicates desorption of the coating, owing to the weak interaction with the CNTs surface. Interestingly, we observe that long PS chains do not desorb and can drive the CNTs to the interface of the PA/EA blend. Moreover, the influence of kinetics is clearly observed through the dependence of CNTs interfacial confinement on dispersed droplet size.     

Factors influencing the efficacy of an interfacial modifier for the interface in an immiscible polymer blend

The modification of the interface in immiscible polymer blends is critical in order to optimize physical properties. Despite the great commercial importance of polymer blends, many aspects of the emulsification process remain unclear In this paper, it will be shown that an emulsification curve can be used to estimate the influence of the architecture molar mass of styrene/hydrogenated butadiene block copolymer interfacial modifiers on the emulsifion of polystyrene/ethylene-propylene rubber blends under melt processing conditions. An expression for eing the critical amount of copolymer to saturate the interface, as well as aspects concerning the localisation of the modifier in the blend system will also be addressed.     

Dispersion control of immiscible polymer blend using selective heating by infrared laser irradiation

In this study, a selective heating technique by irradiating an infrared laser to an immiscible polymer blend was proposed to actively control the distribution of the dispersed phase in the blend. In the technique, the viscosity ratio between the matrix and dispersed phases was not changed by the molecular weight or shear rate but was changed by the controlled temperature distribution due to selective heating. The feasibility of the proposed technique was investigated through a numerical simulation of the temperature field and an experimental study using a test blend. The results showed that the technique successfully caused the deformation of relatively large droplets and enhanced the micro‐scale dispersion. It was also confirmed that the droplet size of the dispersed phase could be estimated by a simple method similar to the conventional technique: the chart of capillary number change with respect to the viscosity ratio. From the obtained results, it was concluded that the technique proposed in this study is a promising candidate for the development of a new blend process. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Enthalpic interaction of diblock copolymers with immiscible polymer blend components

Summary An attempt is made to extend the model of Leibler for the emulsifying activity and interfacial properties of A-b-B diblock copolymers in incompatible blends of the homopolymers A and B-which are identical with the respective copolymer components- to enthalpically interacting C-b-D diblock copolymers, the block C being thermodynamically compatible with A and D with B. Due to the attractive enthalpic interaction the A/C-b-D/B compatibilized blends are promising for optimum phase adhesion (bold types for thermodynamically compatible partners). Thus, the extended model for a plane interfacial layer includes the enthalpic interaction of the compatible polymer pairs beside the entropic effects. The approach starts with the equillibrium supposition, not taking into consideration enthalpy driven migration effects of the block copolymer from the bulk to the interface, The model confirms a dominant role of the enthalpic interaction between blocks of the diblock copolymer and the respective homopolymers to the compatibilization of incompatible blend components. It is applicable also for blends compatibilized with block copolymers of unfavourable repulsive type interaction, A/C-b-D/B, and for blend systems with mixed type interactions, e. g. A/C-b-B/B or A/C-b-D/B.     

Control of carbon nanotubes at the interface of a co-continuous immiscible polymer blend to fabricate conductive composites with ultralow percolation thresholds

The concept of “double percolation”, i.e., conductive fillers are selectively located in one phase of a co-continuous polymer blend to form a percolated network in the selected phase, is widely used to reduce the percolation thresholds of conductive polymer composites to a fraction of their original values. However, it is expected that the percolation threshold can be significantly reduced further if the conductive fillers are only selectively distributed at the continuous interface of the co-continuous polymer blend, where only a very small amount of fillers are needed to build up the conductive percolated network. Multiwalled carbon nanotubes (MWCNTs) with very high aspect ratio (ca. 1000) are selectively distributed at a continuous interface of a co-continuous immiscible poly(lactic acid)/poly(ε-caprolactone) (PLA/PCL) blend at a weight ratio of 50/50 by controlling the migration process of MWCNTs from the unfavorable PLA to the favorable PCL phase. Compared to the PLA/PCL/MWCNTs composites by the traditional double percolation method (percolation threshold is ca. 0.97 wt%), the percolation threshold of PLA/MWCNTs/PCL composites (ca. 0.025 wt%) drops 2 orders of magnitude due to controlling the MWCNTs at the continuous interface between the PLA and PCL phases.     

Determination of unblended chain dynamic parameters of a polar discontinuous phase in an immiscible polymer blend

A method is described by which the relaxation characteristics of a polar polymer in an included phase of an immiscible polymeric blend can be determined from those of the composite. The necessary prerequisite is that the relaxation regions of the matrix and of the dispersed phase do not overlap. First, the dynamic relaxation data of the composite is fitted to the Havriliak-Negami function using a multi-response fitting method. Next, the relaxation function for the included phase is determined using composite mixing equations and the data for the pure matrix. This method is demonstrated for dielectric data on a polypropylene/polyurethane (PP/PUR) composite containing 20 wt% polar additive. The resulting unblended relaxation function parameters of PUR are discussed and compared to other unblended PUR literature data. Blending PUR with PP did not change the shape of the relaxation process, did shift the maximum frequency by about half a decade, and significantly reduced the limiting values of the dielectric constants.     

Carbon black self-networking induced co-continuity of immiscible polymer blends

This work aims to clarify the mechanism of nanoparticle-induced co-continuity in immiscible polymer blends. An industrially relevant system, carbon black (CB)-filled acrylonitrile-butadiene-styrene (ABS)/polyamide 6 (PA6) blends, is investigated via scanning electron microscopy, selective extraction tests, dynamic mechanical analysis, and electrical conductivity measurements. The CB particles are found to be preferentially localized in the PA6 phase, and with an increase in CB loading (Φ_CB), the critical volume fraction of PA6 (Φ_PA6) that is essential for building the co-continuous structure decreases. The product of Φ_PA6 and Φ_CB, n, remains constant for the given system, suggesting that there exists an intrinsic cooperative effect between the CB and the CB-localized polymer phase. A further decrease in Φ_PA6 is achieved either by loading CB with a higher self-networking capability or by isothermal post-treatments for sufficient self-agglomeration of the CB clusters. It is demonstrated that, under the direction of CB self-networking, the CB-localized polymer domains tend to fuse together into co-continuous organization with little phase coarsening. Therefore, CB self-assembly not only plays a key role in extending phase co-continuity over a much larger composition range but also acts on stabilizing the co-continuous polymer domains during the melt processing.     

聚合物改性炭黑的研究进展

炭黑在诸多领域有着广泛的应用,其在基体中良好的分散一直是研究的热点。从聚合物对炭黑的稳定机理出发,综述了近年来聚合物改性炭黑的三种技术——聚合物吸附改性、聚合物接枝改性以及聚合物包覆改性的最新研究进展。最后指出了聚合物改性炭黑相关领域有待解决的问题及发展方向。     

The polymer blend technique as a method for designing fine carbon materials

The polymer blend technique is proposed as a method for designing fine carbon materials. In principle a blend consisting of polymers with and without carbon residue after heating is subjected to melt-spinning, stabilization and finally carbonization. A combination of two polymers and control of the blend texture are important for using the technique successfully. In this paper, three prepared fine carbon materials are introduced, i.e. carbon fibers including thin and long pores aligned parallel to the fiber, thin carbon fibers 200-300 nm in diameter and carbon nanotubes with 10-20-nm outer diameter. In particular the carbon nanotubes are described in detail to emphasize the great potential of the polymer blend technique. Further possibilities of the technique are also discussed briefly.     

Influence of carbon black dispersion on the thermal diffusivity of an SBR vulcanizate

There are few investigations of the influence of filler dispersion on the thermal diffusivity of carbon black rubber compounds. In this article, experimental results of a cured styrene–butadiene rubber (SBR) compound are presented in the range of temperatures between 210 and 350 K at four levels of dispersion obtained in a laboratory mill. The results of thermal diffusivity measurements are discussed in the frame of competitive mechanisms appearing during mixing and involving the breakdown of agglomerates into aggregates and particles in the rubber matrix. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1379–1385, 1999     

Compatibilization of an immiscible blend of EPDM and POM with an Ionomer

Immiscible blends of ethylene-propylene-diene-monomer (EPDM) and polyoxymethylene (POM), when EPDM is the major phase were compatibilized on the addition of an ionomer, poly(ethylene-co-methacrylic acid). The inclusion of the ionomer reduced the interfacial tension between the two phases, such that the diameter of the POM domains were significantly reduced to between 0.5 and 2 μm, typical of that required to toughen ductile polymers. The mechanical properties of the resultant compatibilized blends were significantly enhanced with increases in Young's modulus (↑54%), tensile strength (σ, ↑139%), elongation at break (ε, ↑97%), and tensile toughness (↑500%) with increasing ionomer content, relative to EPDM rubber alone. The ShoreA hardness of the compatibilized blend was 70.1 compared with 56.8 for the immiscible binary blend and, 50.2 for neat EPDM rubber.     

炭黑填充NR/TPI并用胶的性能

研究炭黑品种对NR/反式1,4-聚异戊二烯(TPI)并用胶性能的影响。结果表明,随着炭黑粒径的增大,NR/TPI并用胶焦烧时间延长,交联程度下降;填充炭黑N330的NR/TPI并用胶具有较好的综合物理性能;随着炭黑粒径的增大,NR/TPI并用胶的损耗模量逐渐降低;随炭黑比表面积的增大,当温度低于0℃时,并用胶损耗因子减小,当温度高于0℃时,损耗因子增大。     

Use of ultrasound to determine variation of carbon dispersion in carbon black filled HDPE melts

Abstract

An ultrasonic technique was used to determine whether differences in the degree of dispersion of carbon filler in high density polyethylene (HDPE) melts could be identified. Ultrasonic transit time measurements were used to identify differences between three grades of HDPE with different degrees of filler dispersion (designated high, medium and low dispersion). Tests were carried out on static melts (off line) over a range of temperatures and pressures, and during extrusion (inline). Tests carried out on samples of static melt showed a significant increase in ultrasonic transit time for the poorly mixed (low dispersion) sample, compared with the medium and high dispersion samples. Differences measured during off line tests were not observed during extrusion tests.     

Surfactant‐dispersed carbon black in polyimide nanocomposites: Spectroscopic monitoring of the dispersion state in the polymer matrix

The effects of an anionic surfactant on the dispersion of carbon black (CB) for the purpose of forming conducting composite films were examined with ultraviolet–visible (UV–vis) absorption spectroscopy. To obtain a good dispersion and size reduction of aggregated CB in a polymer matrix, sodium dodecyl sulfate (SDS), used as a surfactant, was introduced into a CB suspension. A set of concentrations with various ratios of CB to SDS (ranging from 1 : 0.4 to 1 : 10) was established before mixing with poly(amic acid) (PAA), a precursor of pyromellitic dianhydride and oxydianiline, was performed. The CB/PAA solution mixtures were submerged under an ultrasonic bath for several hours, then cast onto dry plate glasses, and finally subjected to thermal imidization to produce CB/polyimide (PI) nanocomposite films with various CB weight fractions ranging from 0.025 to 0.50 wt %. A method for evaluating the absorbance at 500 nm of the CB/PI nanocomposite films was established. The absorbance of CB/PI nanocomposite samples of various thicknesses was also normalized to get rid of the effects of the different thicknesses. UV–vis spectra showed that the minimum weight ratio of CB to SDS in the nanocomposite films that achieved well‐dispersed CB and still had transparent properties was 1 : 2.0. Transmission electron microscopy demonstrated that CB was dispersed homogeneously in the PI matrix, and the size of the aggregated CB was affected by the amount of the surfactant. The dielectric properties of the nanocomposite films without the surfactant increased by approximately 2 orders of magnitude with an increasing mass weight fraction of CB and decreased when the surfactant was added. The surfactant also reduced the tensile strength of the CB/PI nanocomposites when the CB/SDS ratio was higher than 1 : 2.0. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

炭黑在橡胶中分散技术研究进展

对于炭黑补强橡胶复合材料,平衡生热、补强以及磨耗之间的关系是炭黑应用的瓶颈问题。炭黑在橡胶基体中的分散性是影响其补强的关键因素之一,从增强炭黑与橡胶之间的相互作用角度出发,炭黑在橡胶中分散技术的研究进展主要体现在炭黑改性、橡胶改性以及液相复合技术方面。重点阐述炭黑的表面改性、聚合物基体的功能化改性以及炭黑与橡胶湿法混炼制备母胶,旨在促进炭黑在橡胶中均匀纳米分散,提高炭黑对橡胶的补强作用,获得性能优异的炭黑/橡胶复合材料。     

Use of the spectrophotometer to control carbon dispersion quality in polyethylene

Renewed interest in the development of a quantitative optical technique for assessing the quality of carbon dispersion in weather-resistant polyethylene compositions has given fresh significance to the findings of a study conducted earlier by a task group of ATSM Committee D-20 but not previously reported in the literature. This group evolved and refined a spectrophotometric procedure which was shown to be capable of good interlaboratory reproducibility when the same film was measured by each of the participants in turn. When each laboratory prepared its own film specimen from a standard lot of pellets, however, this reproducibility dropped to a very unsatisfactory level. It was concluded that fine-grained inhomogeneities even in compounds considered to have excellent dispersion quality preclude reproducible test results when sample weights of only a few milligrams are involved. The problem is aggravated by the difficulty of preparing thin, uniform films and complicated by a nonlinear dependence of transmission on film thickness.     

Microwave absorbing properties of carbon black/silicone rubber blend

In the frequency range of 2–18 GHz, the microwave absorbing properties of a carbon black/silicone rubber blend were investigated by changing the carbon black content and the thickness. The real part (ε′) and the imaginary part (ε″) of permittivity of the blends were calculated from the S‐parameters measured by a network analyzer. The reflection loss was simulated by using ε′ and ε″. The reflection loss less than ?10 dB could be obtained in the frequency range of 9.6ε13.5 GHz from the sample with 10 wt% of carbon black at 1.9 mm of thickness.     

炭黑对硬PVC共混料性能的影响

详细探讨了炭黑填充聚氯乙烯以后对复合材料的电性能,力学性能、加工性能的影响。