Comparison between the efficiencies of two conductive networks formed in carbon black-filled ternary polymer blends by different hierarchical structures

Two different types of thermodynamically induced self-assembled hierarchical structures were formed in carbon black (CB)-filled POM/SAN/TPU and POM/SAN/PA6 ternary polymer blends when the minor third polymer components TPU and PA6, which have the highest affinity to CB among the three polymer components, were individually incorporated into CB-filled POM/SAN binary blend: TPU with imbedded CB forms the interphase, while PA6 with imbedded CB forms droplets inside the SAN phase. The efficiencies of the two types of conductive networks formed by these hierarchical structures are compared in terms of electrical percolation threshold. The percolation threshold of CB in POM/SAN (70/30) blend decreases by 59% and 54% when only 5 wt% of POM is replaced by TPU and PA6, respectively. The mechanisms of conductive network formation are different in the two cases and related to their blend morphology, one is double percolation in a tri-continuous blend and the other is triple percolation in a cocontinuous blend.     

Reactive blending of PE‐GMA/PA6 effect of composition and processing conditions

Blends of ethylene‐glycidyl methacrylate copolymer (PE‐GMA) and polyamide 6 (PA6) were prepared in a corotating twin screw extruder. Two processing temperatures were used in order to disperse PA6 in two forms: at high temperature in the molten state in molted PE‐GMA Matrix (emulsion type mixture) and at lower temperature as fillers in molted PEGMA matrix (suspension type mixture). Processed blends were analyzed by scanning electron microscopy and dynamic mechanical experiments to probe the reactivity in the extruder and the compatibilization phenomena. The dependence of the morphology and the rheological properties of PE‐GMA/PA6 blends on blend composition and screw rotational speed was also investigated and is discussed in the paper. The results show that dispersion of the two polymers in the molten state leads to a higher level of interfacial reaction. They also show that whatever the screw rotational speed and the temperature of extrusion are, the rate of interfacial reaction in PE‐GMA/PA6 blends is higher for 50/50 PE‐GMA/PA blends than for 70/30 PE‐GMA/PA blends. Copyright © 2015 John Wiley & Sons, Ltd.     

Detection of co-continuous structures in SAN/PA6 blends by different methods

This paper describes the 70/30 wt% composition of SAN/PA6 blends having different types of morphology, namely PA6 dispersed in SAN, a co-continuous structures of PA6 and SAN, and a “mixed structure” which exhibits PA6 particles in SAN which themselves form the matrix for smaller SAN particles. These morphologies were achieved by using different processing conditions during extrusion blending in a twin screw extruder, especially variation in the screw speed and by injection molding. Morphological analysis using SEM and TEM, solubility experiments, DMA, and oscillatory rheometry are presented. These methods were shown to be able to distinguish between the different types of morphology. In addition, DSC was used to detect the PA6 crystallization behavior.     

Morphology of PC/SAN blends: effect of reactive compatibilization,SAN concentration,processing, and viscosity ratio

This article examines the effects of dispersed phase concentration, processing apparatus, viscosity ratio, and interfacial compatibilization using an SAN–amine compatibilizer on the morphology of blends of bisphenol A–polycarbonate (PC) with styrene–acrylonitrile (SAN) copolymers. For uncompatibilized blends, the dispersed phase particle size increased significantly with SAN concentration, and was found to exhibit a minimum at a viscosity ratio of approximately 0.35 for a fixed concentration of 30% SAN in the blend. Although the morphology of uncompatibilized PC/SAN blends mixed in a Brabender mixer, single‐ and twin‐screw extruders were quite similar, the twin‐screw extruder produced significantly finer morphologies in blends containing SAN–amine. The average particle size for blends compatibilized with the SAN–amine polymer was approximately half that of uncompatibilized blends and was relatively independent of viscosity ratio and dispersed phase composition. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 71–82, 1999     

PA6/HIPS/PP-g-(GMA-co-St)反应共混体系的研究

通过扫描电镜、热分析、熔体流动速率、熔融扭矩和力学性能等测试方法研究了甲基丙烯酸缩水甘油酯(GMA)和苯乙烯(St)多单体熔融接枝聚丙烯[PP-g-(GMA-co-St)]对PA6/HIPS共混物的熔融流变性能、结晶行为、相形态和力学性能的影响.结果表明,在熔融共混过程中,PP-g-(GMA-co-St)中的环氧基与PA6的端氨基原位生成的接枝共聚物有效地降低了共混物的界面张力,提高了共混物的界面粘着力,使共聚物的流动速率降低,熔融扭矩提高;PA6分子链的规整性降低,结晶完善性变差.在PP-g-(GMA-co-St)的质量分数为10%时,共混物分散相的尺寸明显减少,力学性能得到较大提高;其中冲击强度超过纯PA6,达到HIPS水平.通过反应共混,制备了力学性能均衡的PA6/HIPS/PP-g-(GMA-co-St)共混物合金.     

Barrier,Mechanical, Morphological and Thermal Properties of Compatibilized High Density Polyethylene and Polyamide 6 Blends

Effectiveness of the content of maleic anhydride (MAH) and polyamide 6 (PA6) on mechanical, thermal, barrier (moisture and oxygen) properties of HDPE/PA6 blends was investigated. Blends of HDPE with PA6 were prepared by in situ method. Molau test and FTIR spectroscopy results confirmed the reactive compatibilization through grafting of MAH on HDPE and PA6 chains in PA6/HDPE blends. Low concentration of benzoyl peroxide (BPO) and MAH reduced the particle size, improved phase morphology and mechanical properties of PA6/HDPE blends. Decrease in mechanical properties of PA6/HDPE blends was observed at high concentration of BPO and MAH.     

Effect of poly(vinyl acetate) (PVAc) on thermal behavior and mechanical properties of poly(3-hydroxybutyrate)/poly(propylene carbonate) (PHB/PPC) blends

To assess the compatibility of blends of synthetic poly(propylene carbonate) (PPC), with a natural bacterial poly(3-hydroxybutyrate) (PHB), a simple casting procedure of blend was used. poly(3-hydroxybutyrate)/poly(propylene carbonate) blends are found to be incompatible according to DSC and DMA analysis. In order to improve the compatibility and mechanical properties of PHB/PPC blends, poly(vinyl acetate) (PVAc) was added as a compatibilizer. The effects of PVAc on the thermal behavior, morphology, and mechanical properties of 70PHB/30PPC blend were investigated. The results show that the melting point and the crystallization temperature of PHB in blends decrease with the increase of PVAc content in blends, the loss factor changes from two separate peaks of 70PHB/30PPC blend to one peak of 70PHB/30PPC/12PVAc blend. It is also found that adding PVAc into 70PHB/30PPC blend can decrease the size of dispersed phase from morphology analysis. The result of tensile properties shows that PVAc can increase the tensile strength and Young’s modulus of 70PHB/30PPC blend, and both the elongation at break and the tensile toughness increase significantly with PVAc added into 70PHB/30PPC.     

Brittle-Ductile Transition in Reactive PBT/SAN Blends

Toughening of reactive poly(butylene terephthalate) (PBT)/styrene-acrylonitrile copolymer (SAN) blends was studied. PBT/SAN with glycidyl methacrylate (SAN-GMA) (70/30) behaved in ductile manner on tensile test, while PBT/SAN (70/30) blend failed in brittle manner. Additionally, poly[methylene (phenylene isocyanate)] (PMPI) was added to the PBT/SAN-GMA blend, where it was expected that PMPI would assist the reaction between PBT and SAN-GMA, and then the strain at break was improved. PBT/SAN/PMPI (70/30/4) also behaved in ductile manner, although the interfacial adhesion strength between matrix and dispersed phase was extremely weaker than that in PBT/SAN-GMA blend. From the results, it was found that PMPI acted as a compatibilizer without copolymer formation at the interface and then PBT/SAN behaved in ductile manner in higher SAN content by PMPI effect.     

Reactive compatibilization of PA12/plasticized starch blends: Towards improved mechanical properties

Glycerol-plasticized starch (TPS)/polyamide 12 (PA12) blends were processed by melt mixing using two types of interfacial agent, i.e. diglycidyl ether of bisphenol A and a poly(ethylene-co-butyl acrylate-co-maleic anhydride) copolymer. Morphologies of the blends were tailored from the nature and amount of the interfacial agents. The average size of the dispersed phase was shown to decrease with the incorporation of the reactive agents and was proved to respect models, usually employed for conventional blends, for size predictions of the dispersed phase. By means of rheological experiments, it has been investigated whether the size reduction of the dispersed phase was coming from the compatibilization of the blend or from the viscosity changes due to chain extension in the matrix. The influence of the coupling agents on the viscoelastic behavior of the blend was characterized. Both interfacial agents led to increase the absolute complex viscosity but in the case of diepoxy reactive agent, the Newtonian flow behavior of complex viscosity totally disappeared in the low-frequency region. Mechanical properties of the TPS/PA12 blends were characterized and were proved to be strongly impacted by the use of interfacial agents. Elongation at break was enhanced as a consequence of a better adhesion between the matrix and the dispersed phase, whereas a decrease of the Young’s modulus was observed with increasing DGEBA content. Polyamide 12 crystallization in TPS/PA12 blends was found to be strongly dependent on DGEBA content while the introduction of maleic anhydride-grafted copolymer had no influence.     

Effect of PBT molecular weight and reactive compatibilization on the dispersed‐phase coalescence of PBT/SAN blends

Poly(butylene terephthalate) (PBT)/styrene‐acrylonitrile copolymer (SAN) blends were investigated with respect to their phase morphology. The SAN component was kept as dispersed phase and PBT as matrix phase and the PBT/SAN viscosity ratio was changed by using different PBT molecular weights. PBT/SAN blends were also compatibilized by adding methyl methacrylate‐co‐glycidyl methacrylate‐co‐ethyl acrylate terpolymer, MGE, which is an in situ reactive compatibilizer for melt blending. In noncompatibilized blends, the dispersed phase particle size increased with SAN concentration due to coalescence effects. Static coalescence experiments showed evidence of greater coalescence in blends with higher viscosity ratios. For noncompatibilized PBT/SAN/MGE blends with high molecular weight PBT as matrix phase, the average particle size of SAN phase does not depend on the SAN concentration in the blends. However noncompatibilized blends with low molecular weight PBT showed a significant increase in SAN particle size with the SAN concentration. The effect of MGE epoxy content and MGE molecular weight on the morphology of the PBT/SAN blend was also investigated. As the MGE epoxy content increased, the average particle size of SAN initially decreased with both high and low molecular weight PBT phase, thereafter leveling off with a critical content of epoxy groups in the blend. This critical content was higher in the blends containing low molecular weight PBT than in those with high molecular weight PBT. At a fixed MGE epoxy content, a decrease in MGE molecular weight yielded PBT/SAN blends with dispersed nanoparticles with an average size of about 40 nm. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Reactively and physically compatibilized immiscible polymer blends: stability of the copolymer at the interface

This paper reports on the interfacial behaviour of block and graft copolymers used as compatibilizers in immiscible polymer blends. A limited residence time of the copolymer at the interface has been shown in both reactive blending and blend compatibilization by preformed copolymers. Polystyrene (PS)/polyamide6 (PA6), polyphenylene oxide (PPO)/PA6 and polymethylmethacrylate (PMMA)/PA6 blends have been reactively compatibilized by a styrene-maleic anhydride copolymer SMA. The extent of miscibility of SMA with PS, PPO and PMMA is a key criterion for the stability of the graft copolymer at the interface. For the first 10 to 15 minutes of mixing, the in situ formed copolymer is able to decrease the particle size of the dispersed phase and to prevent it from coalescencing. However, upon increasing mixing time, the copolymer leaves the interface which results in phase coalescence. In PS/LDPE blends compatibilized by preformed PS/hydrogenated polybutadiene (hPB) block copolymers, a tapered diblock stabilizes efficiently a co-continuous two-phase morphology, in contrast to a triblock copolymer that was unable to prevent phase coarsening during annealing at 180°C for 150 minutes.     

Viscoelastic behavior of polypropylene/nitrile rubber thermoplastic elastomer blends: Application of Kerner's models for reactively compatibilized and dynamically vulcanized systems

The viscoelastic properties of binary blends of nitrile rubber (NBR) and isotactic polypropylene (PP) of different compositions have been calculated with mean‐field theories developed by Kerner. The phase morphology and geometry have been assumed, and experimental data for the component polymers over a wide temperature range have been used. Hashin's elastic–viscoelastic analogy principle is used in applying Kerner's theory of elastic systems for viscoelastic materials, namely, polymer blends. The two theoretical models used are the discrete particle model (which assumes one component as dispersed inclusions in the matrix of the other) and the polyaggregate model (in which no matrix phase but a cocontinuous structure of the two is postulated). A solution method for the coupled equations of the polyaggregate model, considering Poisson's ratio as a complex parameter, is deduced. The viscoelastic properties are determined in terms of the small‐strain dynamic storage modulus and loss tangent with a Rheovibron DDV viscoelastometer for the blends and the component polymers. Theoretical calculations are compared with the experimental small‐strain dynamic mechanical properties of the blends and their morphological characterizations. Predictions are also compared with the experimental mechanical properties of compatibilized and dynamically cured 70/30 PP/NBR blends. The results computed with the discrete particle model with PP as the matrix compare well with the experimental results for 30/70, 70/30, and 50/50 PP/NBR blends. For 70/30 and 50/50 blends, these predictions are supported by scanning electron microscopy (SEM) investigations. However, for 30/70 blends, the predictions are not in agreement with SEM results, which reveal a cocontinuous blend of the two. Predictions of the discrete particle model are poor with NBR as the matrix for all three volume fractions. A closer agreement of the predicted results for a 70/30 PP/NBR blend and the properties of a 1% maleic anhydride modified PP or 3% phenolic‐modified PP compatibilized 70/30 PP/NBR blend in the lower temperature zone has been observed. This may be explained by improved interfacial adhesion and stable phase morphology. A mixed‐cure dynamically vulcanized system gave a better agreement with the predictions with PP as the matrix than the peroxide, sulfur, and unvulcanized systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1417–1432, 2004     

Thermal degradation and crystallisation studies of reactively compatibilised polymer blends

The thermal degradation and crystallisation behaviours of polyamide12/isotactic polypropylene (PA12/PP) blends were studied. Effects of blend ratio and compatibiliser concentration on the thermal degradation properties of the blends were analysed. The activation energy for degradation in compatibilised and uncompatibilised blends computed using Horowitz-Metzger equation was reported. The blend ratio as well as the presence of compatibiliser has significant effect on the thermal stability of the blends. Phase morphology was found to be one of the decisive factors that affected the thermal stability of both uncompatibilised and compatibilised blends. Melting and crystallisation behaviours of the blends in the presence and absence of compatibiliser were evaluated. It was observed that blending has no significant effect on the melting and crystallisation properties of PA12 and PP. Compatibilisation of 70/30 and 50/50 PA12/PP blends didn't affect the crystallisation and melting behaviours of PA12 and PP even though some discrepancies were observed.     

Phase morphology development in PP/PA6 blends induced by a maleated thermoplastic elastomer

The effects of maleated thermoplastic elastomer (TPEg) on morphological development of polypropylene (PP)/polyamide 6 (PA6) blends with a fixed PA6 content (30 wt %) were investigated. For purpose of comparison, nonmaleated thermoplastic elastomer (TPE) was also added to the above binary blends. A comparative study of FTIR spectroscopy in above both ternary blends confirmed the formation of in situ graft copolymer in the PP/PA6/TPEg blend. Dynamic mechanical analysis (DMA) indicated that un‐like TPE, the incorporation of TPEg remarkably affected both intensity and position of loss peaks of blend components. Scanning electron microscopy (SEM) demonstrated that PP/PA6/TPE blends still exhibited poor interfacial adhesion between the dispersed phase and matrix. However, the use of TPEg induced a finer dispersion and promoted interfacial adhesion. Transmission electron microscopy (TEM) for PP/PA6/TPEg blends showed that a core‐shell structure consisting of PA6 particles encapsulated by an interlayer was formed in PP matrix. With the concentration of TPEg increasing, the dispersed core‐shell particles morphology was found to transform from discrete acorn‐type particles to agglomerate with increasing degree of encapsulation. The modified Harkin's equation was applied to illustrate the evolution of morphology with TPEg concentration. “Droplet‐sandwiched experiments” further confirmed the encapsulation morphology in PP/PA6/TPEg blends. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1050–1061, 2006     

Reactive compatibilization of nylon copolymer/EPDM blends: experimental aspects and their comparison with theory

In situ reactive compatibilization was first time applied to a low melting nylon (nylon 6 and 66 copolymer) and EPDM blend system. The effects of in situ compatibilization and concentration of compatibilizer on the morphology and mechanical properties of nylon/EPDM blends have been investigated. The influence of EPM‐g‐MA on the phase morphology was examined by the scanning electron microscopy (SEM) after preferential extraction of the minor phase. The SEM micrographs were quantitatively analyzed for domain size measurements. The compatibilizer concentrations used were 0, 1, 2.5, 5, and 10 wt%. The graft copolymer (nylon‐g‐EPM) formed at the interface showed relatively high emulsifying activity. A maximum phase size reduction was observed when 2.5 wt% of compatibilizer was added to the blend system. This was followed by a leveling‐off at higher loadings indicating interfacial saturation. The conformation of the compatibilizer at the interface was deduced based on the area occupied by the compatibilizer at the blend interface. The experimental compatibilization results were compared with theoretical predictions of Noolandi and Hong. It was concluded that the molecular state of compatibilizer at interface changes with concentration. The in situ compatibilized blends showed considerable improvement in mechanical properties. Measurement of tensile properties shows increased elongation as well as enhanced modulus and strength up on compatibilization. At higher concentrations of compatibilizer, a leveling‐off of the tensile properties was observed. A good correlation has been observed between the mechanical properties and morphological parameters. Copyright © 2007 John Wiley & Sons, Ltd.     

Nanocomposites based on a polyamide 6/maleated styrene-butylene-co-ethylene-styrene blend: Effects of clay loading on morphology and mechanical properties

The addition of up to 6% of an OMMT to a 70/30 polyamide 6 (PA6)/maleated styrene-ethylene/butylene-styrene (mSEBS) blend led to ternary compounds where the rigidifying effect of the clay and the toughening effect of the rubber came together. In fact, in the 70/30 blend with 3% OMMT supertough behaviour was accomplished with a modulus increase of 44% with respect to the pure PA6 matrix. When the changes in morphology of the dispersed rubber phase in presence of OMMT are discussed, the slight decrease in viscosity upon clay addition does not explain the increase in rubber particle size that indicates a decrease in the compatibilization level. Interactions between the surfactant of the OMMT and the maleic anhydride groups of modified rubber are proposed as the reason for the decrease in compatibility. The maximum impact strength attained is rather independent of the clay content and the testing temperature. The increase in modulus of the blend upon clay addition was similar to that observed for the pure PA6 matrix, while maintaining the ductile nature in the ternary PN’s, which is not always present in PA6/OMMT binary materials.     

Mechanical properties of PA6/PA12 blend specimens prepared by selective laser sintering

The use of polymeric blends can increase the range of structures and properties of selective laser sintering (SLS) parts. This study investigates the processing of a binary polar system using polyamide 6 (PA6) and polyamide 12 (PA12) by SLS. The mixture composition and processing conditions, and their influence on the dynamic mechanical properties of the specimens manufactured were evaluated. The maximum tan δ values suggest that PA6 and PA12 have similar visco-dissipative behavior. The PA6/PA12 blends behavior varied according to the relaxation phenomena of the pure components, proportionally to the blend composition. The creep test showed that blends with a higher amount of PA6 had greater plastic deformation and less elastic recovery. In the fatigue test the 20/80 and 50/50 blends presented good fatigue resistance under the test conditions.     

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.     

SiO2粒子对PMMA/SAN共混体系相分离行为的影响

采用小角激光光散射(SALLS)并结合动态流变学方法,考察了气相法二氧化硅(SiO2)粒子的加入对聚甲基丙烯酸甲酯/苯乙烯-丙烯腈无规共聚物(PMMA/SAN)共混体系相行为的影响,得到了添加SiO2粒子前后的相图,发现SiO2粒子对基体相行为的影响与基体的组成有关.对PMMA/SAN(60/40)体系,加入SiO2粒子后相分离温度上升,但并未改变相分离机理,仍为亚稳单相分解过程(spinodal decomposition,SD);而对于PMMA/SAN(30/70)体系,加入SiO2粒子后却降低了体系的相分离温度.该现象可能是SiO2粒子和基体组分界面间组成与PMMA/SAN共混物基体组成的差异造成的.     

Miscibility and Mechanical Behavior of SAN/NBR Blends

Summary: Aiming the development of high toughness polymer materials, blends of poly(styrene-co-acrylonitrile) (SAN) and poly(butadiene-co-acrylonitrile) (NBR) rubbers, with contents of acrylonitrile (AN) varying from 21 to 45%, were prepared by casting, coprecipitation and monoscrew extrusion followed by injection molding. SAN/NBR blends, prepared in the compositions (w/w) 90/10, 80/20, 70/30, 60/40, and 50/50, were characterized by differential scanning calorimetry (DSC) and Izod impact tests. DSC analyses showed that blends with 33% AN NBR prepared by casting, and with 39% AN NBR prepared by coprecipitation, are partially miscible at 60/40, 70/30 and 80/20 (SAN/NBR) compositions and immiscible for 50/50 compositions. On the other hand, 90/10 SAN/NBR systems were totally miscible. The blends with 45% AN NBR prepared by coprecipitation showed partial miscibility to 50/50, 60/40, 70/30 and 90/10 compositions and total miscibility to 80/20 composition. The NBR addition results in a significant increase in the impact resistance, strongly dependent on the blend composition and the NBR AN content. The best result of impact resistance — 75.2 ± 8.6 (kJ · m⁻²) — was obtained for SAN/NBR 50/50, using 45% AN NBR. This value is 15.7 times bigger than that for pure SAN -4.8 ± 0.7 (kJ · m⁻²).