Effects of blend composition on the morphologies and physical properties of polycarbonate/acrylonitrile-butadiene-styrene blends

The morphologies and physical properties of twin-screw-extruded polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends with various blend ratios are studied. The needle-like co-continuous phase in PC-rich blends changes to the sea-island phase for blend ratios of more than 50 wt% ABS. While pure PC exhibits an almost-Newtonian flow behavior, PC/ABS blends exhibit the interesting rheological transition. The viscosities of the ABS-rich blends at low shear rates are almost equal to those of the pure ABS polymer. The yield stress for the PC/ABS blend ratio of 3:7 is the highest in composition. At the frequency of 10 rad/s, the PC-rich blends exhibit highly viscous properties, whereas the ABS-rich blends present highly elastic properties as the temperature increases. Moreover, the ABS polymer in the PC/ABS polymer blend induces significant change at the fracture surface of PC, transitioning from brittle to ductile nature.     

Dielectric properties of isotactic polypropylene/nitrile rubber blends: Effects of blend ratio,filler addition,and dynamic vulcanization

The dielectric properties of isotactic polypropylene/acrylonitrile–butadiene rubber blends have been investigated as a function of frequency with special reference to the effect of blend ratio. The dielectric properties measured were volume resistivity, dielectric constant (ϵ′), dissipation factor (tan δ), and loss factor (ϵ″). At high frequencies, a transition in relaxation behavior was observed whereby the dielectric constant of the blends decreased with frequency, whereas the loss tangent and loss factor increased on reaching a maximum. The variation of the dielectric properties with blend composition was correlated with blend morphology, and relationships were established with reference to blend composition. Experimental ϵ′ values were compared with theoretical predictions. The effect of the addition of fillers on the dielectric properties was also investigated for different fillers and filler loadings. It was found that silica filler increases the dissipation factor, whereas carbon black and cork gave a reverse trend. The variation in dielectric properties upon dynamic vulcanization of the rubber phase using different vulcanizing agents (such as sulfur, peroxide, and mixed systems) was also investigated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 255–270, 1999     

Influence of calcium carbonate filler and mixing type process on structure and properties of styrene–acrylonitrile/ethylene–propylene–diene polymer blends

The properties of styrene–acrylonitrile (SAN) and ethylene–propylene–diene (EPDM) blends containing different types of calcium carbonate filler were studied. The influence of mixing type process on the blend properties was also studied. Two different mixing processes were used. The first one includes mixing of all components together. The other process is a two‐step mixing procedure: masterbatch (MB; EPDM/SAN/filler blend) was prepared and then it was mixed with previously prepared polymer blend. Surface energy of samples was determined to predict the strength of interactions between polymer blend components and used fillers. The phase morphology of blends and their thermal and mechanical properties were studied. From the results, it can be concluded that the type of mixing process has a strong influence on the morphological, thermal, and mechanical properties of blends. The two‐step mixing process causes better dispersion of fillers in blends as well as better dispersion of EPDM in SAN matrix, and therefore, the finest morphology and improved properties are observed in blends with MB. It can be concluded that the type of mixing process and carefully chosen compatibilizer are the important factors for obtaining the improved compatibility of SAN/EPDM blends. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effect of interface characteristics on the morphology,rheology and thermal behavior of three‐component polymer alloys

Immiscible polymer blends are interesting multiphase host systems for fillers. Such systems exhibit, within a certain composition limits, either a separate dispersion of the two minor phases or a dispersion of encapsulated filler particles within the minor polymer phase. Both thermodynamic (e.g. interfacial tension) and kinetic (e.g. relative viscosity) considerations determine the morphology developed during the blending process. The effect of interfacial characteristics on the structure‐property relationships of ternary polymer alloys and blends comprising polypropylene (PP), ethylene‐vinyl alcohol copolymer (EVOH) and glass beads (GB), or fibers (GF), was investigated. The system studied was based on a binary PP/EVOH immiscible blend, representing a blend of a semi‐crystalline apolar polymer with a semicrystalline highly polar copolymer. Modification of the interfacial properties was obtained through using silane coupling agents for the EVOH/glass interface and compatibilization using a maleic anhydride grafted PP (MA‐g‐PP) for the PP/EVOH interface. The compatibilizer was added in a procedure aimed to preserves the encapsulated EVOH/glass structure. Blends were prepared by melt extrusion compounding and specimens by injection molding. The morphology was characterized using scanning electron microscopy (SEM) and high resolution SEM (HRSEM), the shear viscosity by capillary rheometry and the thermal behavior using differential scanning calorimetry (DSC). The system studied consisted of filler particles encapsulated by EVOH, with some of the minor EVOH component separately dispersed within the PP matrix. Modification of the interfaces resulted in unique morphologies. The aminosilane glass surface treatment enhanced the encapsulation in the ternary [PP/EVOH]GB blends, resulting in an encapsulated morphology with no separtely dispersed EVOH particles. The addition of a MA‐g‐PP compatibilizer preserves the encapsulated morphology in the ternary blends with some finely dispersed EVOH particles and enhanced PP/EVOH interphase interactions. The viscosity of the binary and ternary blends was closely related to the blend's morphology and the level of shear rate. The treated glass surfaces showed increased viscosity compared to the cleaned glass surfaces in both GB and GF containing ternary blends. Both EVOH and glass serve as nucleating agents for the PP matrix, affecting its crystallization process but not its crystalline structure. The aminosilane glass surface treatment completely inhibited the EVOH crystallization process in the ternary blend. In summary, the structure of the multicomponent blends studied has a significant effect on their behavior as depicted by the rheological and thermal behavior. The structure‐performance relationships in the three‐component blends can be controlled and varied.     

Influence of the morphology on the fire behavior of a polycarbonate/poly(butylene terephthalate) blend

Polycarbonate/Poly(butylene terephthalate) (PC/PBT) blends are used in various industrial sectors, particularly in the cable industry. In this work, the fire behavior of PC/PBT blends was studied for the entire range of blend composition to investigate the relation between fire properties and blend morphology. The morphology of the binary blends used presents a phase inversion point for 25–30 wt % PBT. Various tests have been performed to characterize the fire behavior [limiting oxygen index (LOI), epiradiator test, cone calorimeter, and pyrolysis combustion flow calorimeter (PCFC)]. A change in fire behavior has been observed when the PBT content increases from 20 to 30 wt %, corresponding to the phase inversion, from a continuous rich-PC phase to a continuous rich-PBT phase. Consequently, it can be suggested that the control of the morphology of binary polymer blends is crucial to improve their fire properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of blend composition and organoclay loading on the nanocomposite structure and properties of miscible poly(methyl methacrylate)/poly(styrene‐co‐acrylonitrile) blends

Organically‐modified montmorillonite clay nanocomposites of poly(styrene‐co‐acrylonitrile) (SAN), poly(methyl methacrylate) (PMMA) and SAN/PMMA miscible blend are investigated. Structure characteristics at the nanoscale and microscale and thermal and tensile properties are studied as a function of polymer blend composition and filler loading fraction. Blend miscibility and T_g are unaffected by up to 10% by wt. organoclay. Thermal degradation stability increases with SAN content and exhibits an optimum value of clay loading. Stiffness shows significant improvement. Tensile strength and elongation‐at‐break suffer as a result of nanocomposite formation. Modulus shows a maximum enhancement of 57% (5 ± 0.06 GPa at 10 wt% filler, 20/80 SAN/PMMA) and varies linearly with clay fraction for all compositions of matrix phase. Predictions of Halpin–Tsai composite model are in excellent agreement with the experimental behavior over full range of polymer blend composition. Fundamental aspects of a polymer blend–clay nanocomposite are clarified, such as lack of additional synergy between clay platelets and matrix, and tensile ductility reduction, compared with polymer–clay system. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Controlled CaCO3 stearate pre-treatment effects on the interphase adhesion in filled SAN/EPDM blend

Calcium carbonate (CaCO₃) fillers pre-treated with the increased amount of stearate were used in order to tune the surface energy for a selective filler migration to the interface in immiscible styrene-acrylonitrile/ethylene–propylene–diene (SAN/EPDM) polymer blends. Various models were used in order to predict the filler accommodation at the blend interface when the interfacial tension becomes low and the wettability is good. The results showed that under optimal thermodynamic conditions, the filler might act as a compatibilizer and significantly improve the blend morphology. The coarse morphology of the initially immiscible SAN/EPDM changed into a fine blend morphology with the addition of the selected CaCO₃ fillers with optimal surface energy. Due to the problem with filler agglomeration of initially nanosized CaCO₃ fillers, we used masterbatch (MB) compositions for the blend preparation in order to get the better filler distribution. In this paper, the comparison between two types of MB compositions based on SAN and/or EPDM as a surplus phase with the selected filler was made considering the model predictions and its effects on the blend morphology and properties. In the case of using MB(EPDM) in blend preparation, the fine blend morphology resulted in improved mechanical and thermal properties, while with MB(SAN) the coarse blend morphology and worsened properties illustrated the opposite effect.     

Dispersion of fillers and the electrical conductivity of polymer blends filled with carbon black

Dispersion state of carbon black(CB) was studied in polymer blends which are incompatible with each other. It was found that CB distributes unevenly in each component of the polymer blend. There are two types of distribution. (1) One is almost predominantly distributed in one phase of the blend matrix, and in this phase fillers are relatively homogeneously distributed in the same manner as a single polymer composite. (2) In the second, the filler distribution concentrates at interface of two polymers. As long as the viscosities of two polymers are comparable, interfacial energy is the main factor determining uneven distribution of fillers in polymer blend matrices. This heterogeneous dispersion of conductive fillers has much effect on the electrical conductivity of CB filled polymer blends. The electrical conductivity of CB filled polymer blends is determined by two factors. One is concentration of CB in the filler rich phase and the other is phase continuity of this phase. These double percolations affect conductivity of conductive particle filled polymer blends.     

Controlling morphology,electrical, and mechanical properties of polymer blends by heterogeneous distribution of carbon nanotubes

Electrical and mechanical properties of some new composites made of copolyamide/polypropylene/carbon nanotubes (CPA/PP/CNTs) in different ratios, in correlation with their morphology, were investigated. The polymer blends based on polypropylene and low melting point copolyamide filled with CNTs were prepared by two methods. In the first procedure, CNTs were orderly distributed into the heterogeneous polymer matrix where filler occupied only one polymer component creating a highly branched conductive phase that provides a low value of the percolation threshold. In second case, CNTs were randomly distributed in the heterogeneous polymer matrix created by the blend CPA/PP yielding in a higher value of percolation threshold. Four factors influence on the distribution of filler, namely: thermodynamics, kinetics, chemical factor, and processing. Both electrical and mechanical properties are defined by spatial distribution of the conductive nanofiller in the polymer blend. POLYM. COMPOS., 37:2467–2477, 2016. © 2015 Society of Plastics Engineers     

The effect of interface characteristics on the static and dynamic mechanical properties of three‐component polymer alloys

The effect of interfacial characteristics on the structure‐property relationships of ternary polymer alloys and blends comprising polypropylene (PP), ethylene‐vinyl alcohol copolymer (EVOH) and glass beads (GB) or fibers (GF) was investigated. The systems studied were based on a binary PP/EVOH immiscible blend, representing a blend of a semi‐crystalline apolar polymer with a semi‐crystalline highly polar copolymer. The ternary systems studied consisted of filler particles encapsulated by EVOH, with some of the minor EVOH component separately dispersed within the PP matrix. Modification of the interfacial properties was done using silane coupling agents for the EVOH/glass interface and compatibilization using a maleic anhydride grafted PP (MA‐g‐PP) for the PP/EVOH interface. Both glass fillers increased the dynamic modulus and decreased the damping of the neat polymers and of their binary blends, especially in the rubbery region. GF has a more profound effect on both the modulus and the damping. Glass surface treatments and compatibilization have only a marginal effect on the dynamic mechanical behavior of the ternary blends. Yet, compatibilization shifted the polymers' T_gS to higher temperatures. Both glass fillers increased the elastic modulus of the binary blends, where GF performed better than GB as a reinforcing agent. GF slightly increased the strength of the binary blends while, GB reduced it. Both fillers reduced the ductility of the binary blends. The blends' mechanical properties were related to the morphology and their components' crystallinity. The compatibilizer increases both stiffness and strength and reduces deformability.     

Yielding behaviour of thermoplastic/elastomer blends cured by gamma irradiation

Mechanical blends of thermoplastic medium density polyethylene (MDPE) and elastomeric ethylene propylene diene monomer (EPDM) have been prepared with a fixed composition of 60/40 wt%. They have been used either in their gum form or loaded with two different reinforcing fillers, high abrasion furnace (HAF) carbon black or precipitated SiO₂ (Hi Sil) of concentration 25–100 phr (parts per hundred parts of resin) with respect to the blend. Curing was achieved by gamma irradiation. Yielding properties (yield stress, yield strain and cold drawing) have been followed as a function of irradiation dose for different blend compositions. Yield stress values increased with irradiation dose and with the content of the reinforcing filler, but yield strain and cold drawing values decreased with irradiation dose and also with the filler content. The data obtained reveal that Hi Sil is more effective as a reinforcing filler, and the prepared blends are suitable for load‐bearing applications. © 2001 Society of Chemical Industry     

The role of organoclay in promoting co-continuous morphology in high-density poly(ethylene)/poly(amide) 6 blends

The effect of organically modified clay on the morphology, rheology and mechanical properties of high-density polyethylene (HDPE) and polyamide 6 (PA6) blends (HDPE/PA6 = 75/25 parts) is studied. Virgin and filled blends were prepared by melt compounding the constituents using a twin-screw extruder. The influence of the organoclay on the morphology of the hybrid was deeply investigated by means of wide-angle X-ray diffractometry, transmission and scanning electron microscopies and quantitative extraction experiments. It has been found that the organoclay exclusively places inside the more hydrophilic polyamide phase during the melt compounding. The extrusion process promotes the formation of highly elongated and separated organoclay-rich PA6 domains. Despite its low volume fraction, the filled minor phase eventually merges once the extruded pellets are melted again, giving rise to a co-continuous microstructure. Remarkably, such a morphology persists for long time in the melt state. A possible compatibilizing action related to the organoclay has been investigated by comparing the morphology of the hybrid blend with that of a blend compatibilized using an ethylene-acrylic acid (EAA) copolymer as a compatibilizer precursor. The former remains phase separated, indicating that the filler does not promote the enhancement of the interfacial adhesion. The macroscopic properties of the hybrid blend were interpreted in the light of its morphology. The melt state dynamics of the materials were probed by means of linear viscoelastic measurements. Many peculiar rheological features of polymer-layered silicate nanocomposites based on single polymer matrix were detected for the hybrid blend. The results have been interpreted proposing the existence of two distinct populations of dynamical species: HDPE not interacting with the filler, and a slower species, constituted by the organoclay-rich polyamide phase, which slackened dynamics stabilize the morphology in the melt state. In the solid state, both the reinforcement effect of the filler and the co-continuous microstructure promote the enhancement of the tensile modulus. Our results demonstrate that adding nanoparticles to polymer blends allows tailoring the final properties of the hybrid, potentially leading to high-performance materials which combine the advantages of polymer blends and the merits of polymer nanocomposites.     

Mechanical and morphological properties of lyocell blends: Comparison with lyocell nanocomposites (I)

The mechanical properties and morphologies of polyblends of lyocell with three different fillers are compared. Poly(vinyl alcohol) (PVA), poly(vinyl alcohol‐co‐ethylene) (EVOH), and poly(acrylic acid‐co‐maleic acid) (PAM) were used as fillers in blends with lyocell produced through solution blending. The variations of their properties with polymer matrix filler content are discussed. The ultimate tensile strength of the PVA/lyocell blend is highest for a blend lyocell content of 30 wt %, and decreases as the lyocell content is increased up to 40 wt %. The ultimate tensile strengths of the EVOH/lyocell and PAM/lyocell blends are highest for a lyocell loading of 20 wt %, and decrease with the increasing filler content. The variations in the initial moduli of the blends with filler content are similar. Of the three blend systems, the blends with PVA exhibit the best tensile properties. Lyocell/organoclay hybrid films were prepared by the solution intercalation method, using dodecyltriphenylphosphonium–Mica (C₁₂PPh‐ Mica) as the organoclay. The variation of the mechanical tensile properties of the hybrids with the matrix polymer organoclay content was examined. These properties were found to be optimal for an organoclay content of up to 5 wt %. Even polymers with low organoclay contents exhibited better mechanical properties than pure lyocell. The addition of organoclay to lyocell to produce nanocomposite films was found to be less effective in improving its ultimate tensile strength than blending lyocell with the polymers. However, the initial moduli of the nanocomposites were found to be higher than those of the polyblend films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Influence of magnesium carbonate loading on the compound properties of polychloroprene,natural rubber,and their blends

The effect of magnesium carbonate (MgCO₃) loading on the compound properties of polychloroprene (CR), natural rubber (NR), and their blends was investigated. The studied properties included Mooney viscosity, cure characteristics, and degree of filler–filler interaction. In addition to MgCO₃ loading, the effect of the blend ratio on such properties was simultaneously determined. The results reveal that, regardless of the rubber type and blend ratio, increasing MgCO₃ loading resulted in not only an increase in the compound viscosity, but also in the enhancements of the cure rate and state of cure. However, the effect of MgCO₃ loading on the overcured behavior was strongly dependent on the rubber type and blend ratio. For CR, the presence of MgCO₃ accelerated postcuring, whereas the opposite results were found for NR, in which the reversion rate was promoted. For CR/NR blends, a plateau behavior was obtained at a 50/50 blend ratio, where the degrees of postcuring and reversion were counterbalanced. The results also reveal that when MgCO₃ was loaded at low concentrations (≤20 phr), the degree of filler–filler interaction was very low and had no significant effect on the compound properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Reverse exfoliation in a polymer nanocomposite by blending with a miscible polymer

An investigation of the permeability to methanol of blends of a PA-6 nanocomposite and ethylene-vinyl alcohol copolymers (EVOH), containing approximately 32 mol% ethylene, has been conducted. Blends were prepared by melt compounding and permeation measurements were performed by gravimetric uptake methods. The nanocomposite polyamide exhibited significantly reduced permeability compared to the unmodified polymer. The blends exhibited permeability that was non-linear with blend composition. The nanoscale filler in a blend containing up to 50 wt% EVOH remained fully exfoliated, however, in a blend containing 75 wt% of EVOH there was little or no exfoliation and the blend had a measured permeability lower than that of either of the pure components. Electron microscopy and X-ray analysis has indicated a reversal of exfoliation of the nanocomposite filler particles to be responsible.     

Compatibilization of PUR/PVAC polymer blend by addition of calcium carbonate filler

The influence of untreated and stearic acid surface pretreated calcium carbonate (CaCO₃) nanofiller (U1 – untreated CaCO₃ and U1S2 – stearic acid treated CaCO₃) on the properties of polyurethane/poly(vinyl acetate) (PUR/PVAC) polymer blends was investigated. Adhesion between fillers and polymers in the polymer blend composite, and filler position in regard to the polymer phases, are predicted on the basis of calculated adhesion parameters and wetting factor ωa of PUR, PVAC, U1, and U1S2. U1 is located in the PUR matrix phase and U1S2 is located at the interface between matrix PUR domain and dispersed PVAC domain. Polymer blend composites with predominant U1S2 showed lower tensile strength and elongation compared to these of polymer blend composites with predominant U1 mainly due to the fillers' different surface properties, which confirmed that the mechanical properties of polymer blend composites were dependent on overall system morphology rather than the filler location. POLYM. COMPOS. 37:1274–1281, 2016. © 2014 Society of Plastics Engineers     

Blends of polypropylene and ethylene octene comonomer with conducting fillers: Influence of state of dispersion of conducting fillers on electrical conductivity

Blends of polypropylene/ethylene octene comonomer (PP/EOC) with conducting fillers viz., carbon black (CB) and multiwall carbon nanotubes (MWNT) were prepared using melt mixing technique with varying filler concentration and blend compositions. Thermo gravimetric analysis studies indicated that presence of filler enhanced the thermal stability of PP/EOC blends. Morphological analysis revealed the formation of matrix‐dispersed droplet and co‐continuous type of morphology depending on the blend compositions. Significant reduction in droplet size and finer ligament thickness in co‐continuous structure were observed in the blends with filler due to compatibilization action. Fillers were found to be aggregated in the EOC phase irrespective of blends compositions and could be related to the affinity of the fillers toward EOC phase. The electrical conductivity of PP/EOC blends with CB and MWNT was found to be highest for 80/20 composition and decreased as EOC content increased. The percolation threshold of CB was between 10 and 15 wt% for the 80/20 and 70/30 blends whereas it was 15–20 wt% for blends with EOC content higher than 30 wt%. The percolation threshold was 2–3 wt% MWNT for PP/EOC blends. This was attributed to the aggregated filler network preferentially in the EOC phase. The melt‐rheological behavior of PP/EOC blends was significantly influenced in presence of both the fillers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Investigation on the thermal and crystallization behavior of high density polyethylene/acrylonitrile butadiene rubber blends and their composites

The properties of a blend containing a crystallizable component depend largely on the extent of crystallinity and the crystallization behavior of that component in presence of the other. Here, the semi crystalline high density polyethylene (HDPE) is blended with the amorphous elastomer, acrylonitrile butadiene rubber (nitrile rubber or NBR) and we focus mainly on the crystallinity of HDPE/NBR immiscible blends and its variation in the presence of compatibilizer and filler. The effect of blend ratio, compatibilizer concentration, dynamic vulcanization, and filler incorporation were carefully evaluated from the crystallinity measurements using differential scanning calorimeter and the basic aim of this work lies in tuning these conditions. This study allows the elucidation of the influence of crosslink density in regulating the crystallinity of thermoplastic elastomer blends. The scanning electron micrographs provide blend morphology from which the reduced domain size and the influence of NBR particles as heterogeneous nuclei for crystallization are evidenced especially at 5% compatibilizer concentration. The crystallinity of blends was observed to be high at 30 phr carbon black filler addition. Finally, the thermal stability of blends and their composites are also addressed and correlated with the crystallization effect. POLYM. ENG. SCI., 55:1203–1210, 2015. © 2014 Society of Plastics Engineers     

Mechanical Properties and Thermooxidative Aging of a Ternary Blend,Pvc/Enr/Nbr,Compared with the Binary Blends of Pvc

In the quest to improve the thermooxidative aging of the poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend, nitrile rubber (NBR) was incorporated into the blend to yield a ternary blend of PVC/ENR/NBR. A Brabender Plasticorder with a mixing attachment was used to perform the melt mixing at 150°C and 50 rpm followed by compression molding. The mechanical properties, dynamic mechanical properties, and thermooxidative aging behavior of the ternary blend were compared with those of the binary blends (i.e., PVC/ENR and PVC/NBR). It was found that the ternary blend exhibits mechanical properties which are superior to those of PVC/ENR. A single glass transition temperature (T _g) obtained from dynamic mechanical analysis coupled with synergism in the modulus and some other mechanical properties indicate that PVC, ENR, and NBR form a single phase (miscible system) in the ternary blend. Di-2-ethyl hexylphthalate (DOP) plasti-cizer improves the aging resistance of the blends generally, whereas the presence of CaCO₃ as a filler only imparts minor influences on the properties and aging resistance of the blends.