Effect of ultrasonic oscillations on weld line strength of PS,PMMA, and their blends

The effect of ultrasonic oscillations on the weld line strength of amorphous polystyrene (PS), polymethyl methacrylate (PMMA), and PS/PMMA (20/80, 50/50, 80/20) blends at various temperatures was investigated. By facilitating the molecular diffusion across the weld line, the introduction of ultrasonic oscillations could evidently improve the weld line strength of PS, PMMA, and their blends. The different effects on the weld line strength of PS/PMMA (20/80, 50/50, 80/20) blends were investigated. The ultrasonic oscillations could greatly increase the weld line strength of PS/PMMA (80/20) by ～ 70%, but was less efficient to PS/PMMA (50/50, 20/80) blends, due to the great difference of weld line morphologies of these blends. The dispersed phase of PS/PMMA (80/20) in the weld line was spherical while two different morphologies in the weld line of PS/PMMA (50/50) were observed. And the stripe‐like morphology of PS perpendicular to the flow direction in the weld line of PS/PMMA (20/80) is responsible for the little effect of ultrasonic oscillations. The fractured surfaces of PS, PMMA, and PS/PMMA (80/20) with weld line became much rougher due to the introduction of ultrasonic oscillations. The morphology study of PS/PMMA (80/20) showed that the spherical dispersed phase of PS/PMMA at the skin turned smaller under ultrasonic oscillations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2990–2997, 2006     

Weld‐line characteristics of polycarbonate/acrylonitrile–butadiene–styrene blends. I. Effect of the processing temperature

The effects of the processing temperature on the morphology and mechanical properties at the weld line of 60/40 (w/w) polycarbonate (PC)/acrylonitrile–butadiene–styrene (ABS) copolymer blends were investigated. The influences of the incorporation of poly(methyl methacrylate) (PMMA) as a compatibilizer and an increase in the viscosity of the dispersed ABS domain phase were also studied. The ABS domain was well dispersed in the region below the V notch, and a coarse morphology in the core region was observed. When tensile stress was applied perpendicularly to the weld line, the fracture propagated along the weak region behind the weld part; there, the domain phase coalescence was significant because of the poor compatibility between PC and styrene–acrylonitrile (SAN). Phase coalescence became severe, and so the mechanical strength of the welded specimen decreased with an increasing injection‐molding temperature. The domain morphology became stable and the mechanical strength increased as the viscosity of the domain phase increased or some SAN was replaced with PMMA. That the morphology was well distributed behind the weld line and the mechanical properties of PC/ABS/PMMA blends were improved was attributed to the compatibilizing effect of PMMA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 689–699, 2005     

Effect of nanoclay on the morphology and properties of poly(methyl methacrylate)/high‐density polyethylene blends

The effect of nanoclay on the morphology and properties of poly(methyl methacrylate) (PMMA)/high‐density polyethylene (HDPE) blends was studied. A scanning electron microscopy study of the PMMA/HDPE (70/30 w/w) blends with nanoclay indicated a reduction in the average domain sizes of the dispersed HDPE phase and, hence, a better extent of mixing compared to that of the blends without any nanoclay. An X‐ray diffraction study and transmission electron microscopy revealed the localization of intercalated nanoclay in the PMMA matrix of the PMMA/HDPE (70/30 w/w) blend. However, the same effect of clay was not observed in the PMMA/HDPE (30/70 w/w) blend when HDPE became the matrix. In the PMMA/HDPE (30/70 w/w) blend, the addition of nanoclay increased the domain size of the dispersed PMMA domains by preferential location of the clays inside the PMMA domains. The addition of polyethylene‐grafted maleic anhydride in both compositions of the PMMA/HDPE blend effectively reduced the domain size of the disperse phases in the blend. However, the presence of clay increased the tensile strength and storage modulus of the PMMA/HDPE blends in both blend compositions. Thus, in the PMMA/HDPE blend, the clay platelets acted as a effective compatibilizer as long as they were dispersed mainly in the matrix phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A modified model predictions and experimental results of weld-line strength in injection molded PS/PMMA blends

In this paper, the model based on melt diffusion and Flory-Huggins free energy theory for predicting the weld-line strength of injection molded amorphous polymers and polymer blends parts were modified by considering the diffusion thickness in the interface as a function of contact time. The modified model for weld-line strength prediction of homopolymers and polymer blends were, respectively, used to evaluate the weld-line strength of Polystyrene (PS) and Poly(methylmethacrylate) (PMMA), and that of PS/PMMA blends. The model predictions show that the theoretic predictions as a function of temperature and contact time for PS, PMMA and PS/PMMA (80/20, 70/30) are in good agreements with corresponding experimental results. However, the model predictions for PS/PMMA (20/80, 30/70) blends are much higher than experimental results. The morphology in weld-line regions for PS/PMMA (20/80, 30/70) shows lack of dispersed PS phase. Near the weld-line regions, dispersed PS phase is highly oriented along the weld-line. In theoretic prediction for polymer blends, three kinds of diffusion: Polymer A-Polymer A and Polymer B-Polymer B self-diffusions and Polymer A-Polymer B mutual diffusion were considered. This is why model predictions for PS/PMMA (20/80, 30/70) blends are higher than experimental results.     

Ethylene Methacrylate (EMA) Co-polymer Toughened Polymethyl Methacrylate Blends: Physico-mechanical,Optical, Thermal and Chemical Properties

Polymethyl methacrylate (PMMA) was blended with ethylene methacrylate (EMA) copolymer in different compositions by melt mixing technique using Haake Rheochord twin screw extruder. The physico-mechanical, thermal, optical and chemical properties of PMMA/EMA blends were investigated with special reference to the blend compositions. The impact strength of the blends was found to increase significantly with increase in EMA content, without affecting the optical properties significantly. Optical micrograph images of the blends reveals that the rubbery phase dispersed as domains in the continuous PMMA matrix at 5 and 10 wt. % addition of EMA. The PMMA/EMA, 80/20 blend was found to exist as co-continuous system. Attempts have been made to correlate changes in morphology with mechanical properties. The influence of chemical ageing and heat ageing on the mechanical performance of PMMA/EMA blends has been studied. Four composite models such as series model, parallel model, Hapin-Tsai and Kerner's model have been used to fit the experimental tensile strength, tensile modulus and surface hardness.     

Melt rheology and interfacial properties of binary and ternary blends of PS,EOC, and SEBS

This works systematically investigates the interfacial properties of the binary and the ternary blends based on polystyrene (PS), ethylene octene copolymer (EOC), and styrene–ethylene–butylene–styrene (SEBS) by analyzing the melt linear rheological behavior of the blends and neat components. Moreover, the relationship between rheology, phase morphology, and mechanical properties of PS/EOC ternary blends with various quantities of SEBS were studied. The surface shear modulus (β) and interfacial tension values obtained by Palierne model indicated that the EOC/SEBS blend has the best interfacial properties, while the lowest interaction was found for PS/EOC blend. Based on the Palierne model and Harkin's spreading coefficients a core–shell type morphology with EOC phase encapsulated by the SEBS shell dispersed in the PS matrix was determined for the ternary blends. Scanning electron microscopy results revealed that both fibrillar and droplet forms of dispersed phase could be developed during the blending of PS and EOC in presence of SEBS. The extent of fibrillar morphology and interfacial interactions in PS/EOC/SEBS ternary blends was dependent on the SEBS content. The improvement of the mechanical properties of PS/EOC blends in the presence of SEBS was evidenced by the tensile and impact resistance experiments. The tensile strength reinforcement was more pronounced for the ternary blends with more fibrillar dispersed phase. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48791.     

Effect of organoclay on the morphology, phase stability and mechanical properties of polypropylene/polystyrene blends

The effect of organically modified clay on the morphology, phase stability and mechanical properties of polypropylene (PP) and polystyrene (PS) blends was studied using three molecular weight grades of PP. Maleated polypropylene was used, at a PP-g-MA/organoclay ratio of 1, to preferentially promote dispersion of the organoclay in the PP matrix. The MMT content was fixed at 3 wt% based on the PP/PP-g-MA/MMT phase and the PS content was varied from 0-100 wt% in the blend. All blends were processed using a twin screw extruder. The organoclay resides in the PP phase and at the PP/PS interface. The dispersed PS particle size is significantly reduced by the presence of MMT, with maximum decrease observed for the low viscosity PP compared to its blend without MMT. The blends with MMT did not show any change in onset of co-continuity, though MMT shifts the phase inversion composition toward lower PS contents. The phase stability of the blend was significantly improved by the presence of MMT; for blends annealed at 210 °C for 2 h the dispersed phase particle size increased by as much as 10x without MMT with little change was noted with MMT present in the blend. The tensile modulus of blends improved with the addition of MMT at low PS contents. Blends based on the highest molecular weight grade PP showed increase in the tensile yield stress up to 40 wt% PS in the absence of MMT. The tensile strength at break for blend increased slightly with MMT while elongation at break and impact strength decreased in the presence of MMT. Surface energy analysis model was used to predict the orientation and equilibrium position of the clay platelet at the interface based on the surface energies.     

拉曼Mapping成像研究聚苯乙烯/聚甲基丙烯酸甲酯共混体系的相态结构

利用拉曼光谱成像技术研究了聚苯乙烯/聚甲基丙烯酸甲酯（PS/PMMA）共混薄膜体系及其增容体系（增容剂为PS-b-PMMA嵌段共聚物）的相态结构及化学成分分布。实验结果表明,拉曼Mapping成像技术不仅可以得到PS/PMMA共混体系化学成分的精确分布图,同时也可以获取共混体系中分散相、界面相和连续相的分子指纹光谱。研究发现,共混体系中分散相和连续相组分分布与体系的组成紧密相关,当PS/PMMA质量比30/70时,分散相为PS,连续相为PMMA;当PS/PMMA质量比为50/50时,分散相为PS,但PS分子链仍存在于PMMA连续相中;当PS/PMMA质量比为70/30时,分散相为PMMA,连续相为PS。当增容剂PS-b-PMMA加入到PS/PMMA共混体系中后,分散相粒径减小、分布更加均匀、共混体系相容性指数（N_c）增大,说明PS/PMMA共混体系由完全不相容体系趋向变成半相容性体系,这是因为增容剂能增加PS和PMMA之间的相互作用,降低了体系的相分离程度,改善了共混体系的相容性。     

The effect of the viscosity ratio of dispersed phase to matrix on the rheological,morphological, and mechanical properties of polymer blends containing a LCP

The effect of the viscosity ratio of the dispersed LCP phase to the polystyrene/poly(phenylene oxide) (PS/PPO) thermoplastic matrix on the rheological, morphological, and resultant mechanical properties of the LCP blends was investigated. The viscosity of PS/PPO is largely dependent on the blend composition, so that different levels of viscosity ratios of dispersed LCP phase to PS/PPO thermoplastic matrix are obtained by using PS/PPO premixtures of different blend ratios as a thermoplastic matrix. When the viscosity of the LCP dispersed phase is lower than that of the thermoplastic matrix, finely distributed fibril structure of LCP is obtained. Tensile modulus of injection molded specimens show a positive deviation from the additive rule when the viscosity ratio (η_LCP/η_matrix) is smaller than unity. These improvements in tensile modulus are attributed to the formation of finely distributed LCP fibrils. © 1996 John Wiley & Sons, Inc.     

Phase morphology,thermomechanical, and crystallization behavior of uncompatibilized and PP‐g‐MAH compatibilized polypropylene/polystyrene blends

In this article, we discuss the phase morphology, thermal, mechanical, and crystallization properties of uncompatibilized and compatibilized polypropylene/polystyrene (PP/PS) blends. It is observed that the Young's modulus increases, but other mechanical properties such as tensile strength, flexural strength, elongation at break, and impact strength decrease by blending PS to PP. The tensile strength and Young's modulus of PP/PS blends were compared with various theoretical models. The thermal stability, melting, and crystallization temperatures and percentage crystallinity of semicrystalline PP in the blends were marginally decreased by the addition of amorphous PS. The presence of maleic anhydride‐grafted polypropylene (compatibilizer) increases the phase stability of 90/10 and 80/20 blends by preventing the coalescence. Hence, finer and more uniform droplets of PS dispersed phases are observed. The compatibilizer induced some improvement in impact strength for the blends with PP matrix phase, however fluctuations in modulus, strength and ductility were observed with respect to the uncompatibilized blend. The thermal stability was not much affected by the addition of the compatibilizer for the PP rich blends but shows some decrease in the thermal stability of the blends, where PS forms the matrix. On the other hand, the % crystallinity was increased by the addition of compatibilizer, irrespective of the blend concentration. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42100.     

Effect of composition on the linear viscoelastic behavior and morphology of PMMA/PS and PMMA/PP blends

Here, the effect of concentration on the morphology and dynamic behavior of polymethylmethacrylate/polystyrene (PMMA/PS), for PS with two different molecular weight, and polymethylmethacrylate/polypropylene (PMMA/PP) blends was studied. The blends concentrations ranged from 5% to 30% of the dispersed phase (PS or PP). The dynamic data were analyzed to study the possibility of inferring the interfacial tension between the components of the blend from their rheological behavior using Palierne [Palierne JF. Rheol Acta 1990;29:204-14] [1] and Bousmina [Bousmina M. Acta 1999;38:73-83] [2] emulsion models. The relaxation spectrum of the blends was also studied. The dynamic behavior of 85/15 PS/PMMA blend were studied as a function of temperature. It was possible to fit both Palierne and Bousmina's emulsion models to the dynamic data of PMMA/PS blends, to obtain the interfacial tension of the blend. This was not the case for PMMA/PP. The relaxation spectrum of both blends was used to obtain the interfacial tension between the components of the blends. The values of interfacial tension calculated were shown to decrease when the concentration of the blends increased. It was shown using morphological analysis that this phenomenon can be attributed to the coalescence of the dispersed phase during dynamic measurements that occurs for large dispersed phase concentration. When the ‘coalesced’ morphology is taken into account in the calculations the interfacial tension inferred from rheological measurement did not depend on the concentration of the blend used. The values of interfacial tension found analyzing the dynamic behavior of one of the PMMA/PS blend were shown to decrease with temperature.     

Composite droplets with core/shell morphologies prepared from HDPE/PS/PMMA ternary blends by twin‐screw extrusion

Ternary blends of PS and PMMA in a PE matrix were prepared by twin‐screw extrusion to investigate the core/shell encapsulation phenomenon in the composite droplet. The PS was found to encapsulate the PMMA to form composite droplets within the PE matrix as expected from the spreading coefficient theory. The effects of dispersed phase concentration, viscosity ratio, feeding sequence and twin‐screw operating conditions were investigated. The blend morphology was observed by scanning electron microscopy after selective extraction of either PS or PMMA, and average core and composite droplet diameters were determined by image analysis. Although it is known that the structure of composite droplet blends can be substantially altered through control of the volume fraction of the components in the dispersed phase, this study demonstrates that blends with a 1:1 composite droplet volume fraction are relatively stable to large variations in the minor phase viscosities and processing conditions. Twin‐screw extrusion thus provides a highly robust technique for the melt processing of blends possessing composite droplet morphologies. Polym. Eng. Sci. 44:749–759, 2004. © 2004 Society of Plastics Engineers.     

Response Surface Analysis of PS/EPDM/PA6 Ternary Blends: Effect of Mixing Sequence,Composition, and Viscosity Ratio on the Mechanical Properties

In this work, effect of three factors on the phase morphology and mechanical properties of ternary blends based on polystyrene (PS)/ethylene‐propylene‐diene terpolymer (EPDM)/polyamide6 (PA6) was investigated by response surface methodology (RSM). Results indicated that among the studied factors (i.e., mixing sequence, composition, and viscosity ratio of the minor phases), the first two have the greatest effect on the impact strength (75.6%) and tensile properties (tensile modulus (84.9%) and yield stress (88.9%); while EPDM/PA6 viscosity ratio has the least effect (≤ 2.1%) on the final mechanical properties. These achievements are, in fact, arising from the considerable changes in the phase morphology and the contribution share predicted by experimental design outputs. However, mixing sequences just affected on the size of dispersed particles, but samples with different compositions presented different morphology types. According to the mechanical characterization of PS/EPDM/PA6 blends, the maximum impact strength and tensile properties were not obtained simultaneously. Optimal levels of input factors, aimed to balance impact strength and tensile properties, are M1 simultaneous mixing sequence, C1 composition (70/10/20), and V1 viscosity ratio (PA6 with low viscosity). J. VINYL ADDIT. TECHNOL., 26:282–290, 2020. © 2019 Society of Plastics Engineers     

Correlation of viscosity ratio,morphology, and mechanical properties of polyamide 12/natural rubber blends via reactive compatibilization

Natural rubber (NR)-modified polyamide 12 (Nylon12/NR) was produced by melt blending Nylon12 and NR in the presence of polystyrene/maleated natural rubber (PS/MNR) copolymer as a reactive compatibilizer. The influence of compatibilizer loading on viscosity ratio, morphology, and mechanical properties of the blends was investigated. As a consequence of the reactive blend between Nylon12 and maleated NR in PS/MNR, the formation of amide and succinimide linkages was set at rubber-Nylon12 interfaces. Thus the dispersion of rubber particles was improved, and the particle coalescence was prevented so that the fine morphology with good interfacial adhesion was stabilized. This also resulted to enhance the blend viscosity and to lower viscosity ratio. The data revealed strong correlation between low viscosity ratio and fine spherical morphology of the compatibilized blends. An optimum PS/MNR compatibilizer content was at 7 phr to produce good dispersion of small rubber domains (size ≤0.3 μm) in Nylon12 matrix. Thermal properties by DSC revealed that crystallization temperature of Nylon12 was lowered by the presence of NR and crystallinity of Nylon12 was slightly affected by the PS/MNR content. An enhancement of mechanical properties, especially the impact energy was observed without suffering the tensile and flexural properties. Compared to the neat Nylon12, the compatibilized blends showed an increase in impact energy by a factor of 5. This large enhancement is successfully interpreted in term of the toughening effect by rubber phase of suitable dispersed size and the interparticle distance.     

Injection and compression molding of polystyrene/high-density polyethylene blends—phase morphology and tensile behavior

Processing and compatibilization effects on the phase morphology and the tensile behavior of blends of polystyrene and high-density polyethylene (PS/HDPE) were investigated. As predicted by theory, high shear rates encountered during extrusion blending led to efficient minor phase emulsification in immiscible PS/HDPE blends for which the viscosity ratio approaches unity. Consequently, the emulsifying effect of a styrene/ethylene-butylene/styrene (SEBS) compatibilizer was found to be negligible. In the subsequent molding process, disintegration, shape relaxation and coarsening of the minor phase domains were found to be responsible for the morphological evolution. In the compression molding process, morphological observations showed that the rate of minor phase coarsening followed the predictions of the Ostwald ripening theory, in agreement with the rheological analysis. In the injection molding process, minor phase coarsening was attributed to shear coalescence. Tensile tests performed on compression molded and injection molded blends showed that the mechanical behavior of PS/HDPE blends depend strongly upon the matrix orientation as well as the dispersed phase morphology and orientation. In both postforming operations, compatibilization effects on the morphological stability and the tensile behavior of PS/HDPE blends were found to be dependent upon the composition and the rheological behavior of the blend. Evidence of adhesion between the PS and HDPE phases was observed in the presence of SEBS in HDPE-rich blends.     

High density polyethylene/acrylonitrile butadiene rubber blends: Morphology,mechanical properties,and compatibilization

Polymer blends based on high-density polyethylene (HDPE) and acrylonitrile butadiene rubber (NBR) were prepared by a melt blending technique. The mixing parameters such as temperature, time, and speed of mixing were varied to obtain a wide range of properties. The mixing parameters were optimized by evaluating the mechanical properties of the blend over a wide range of mixing conditions. The morphology of the blend indicated a two-phase structure in which NBR phase was dispersed as domains up to 50% of its concentration in the continuous HDPE matrix. However, 70 : 30 NBR/HDPE showed a cocontinuous morphology. The tensile strength, elongation at break, and hardness of the system were measured as a function of blend compostion. As the polymer pair is incompatible, technological compatibilization was sought by the addition of maleic-modified polyethylene (MAPE) and phenolic-modified polyethylene (PhPE). The interfacial activity of MAPE and PhPE was studied as a function of compatibilizer concentration by following the morphology of the blend using scanning electron micrographs. Domain size of the dispersed phase showed a sharp decrease by the addition of small amounts of compatibilizers followed by a leveling off at higher concentrations. Also, more uniformity in the distribution of the dispersed phase was observed in compatibilized systems. The tensile strength of the compatibilized systems showed improvement. The mechanical property improvement, and finer and uniform morphology, of compatibilized systems were correlated with the improved interfacial condition of the compatibilized blends. The experimental results were compared with the current theories of Noolandi and Hong. © 1995 John Wiley & Sons, Inc.     

Effects of the addition of a liquid crystalline copolyester to polystyrenes on blending torque and mechanical properties of blends

Blending of polystyrenes (PS) with a thermotropic liquid crystalline polymer (LCP) was performed by using a continuous corotating twin screw extruder. The influence of LCP content on the blending process was studied by changing the barrel heater temperature and the screw speed. The torque of screw shafts, generated during the blending process, was influenced by LCP content and its influence was not simple. The torque generated during the blending process was not directly related to the apparent melt viscosity of blends. Further, the effects of the matrix viscosity on the morphology and mechanical properties of the PS/LCP blends were studied using three grades of PS as matrix resins. It was found that the size of the LCP dispersed phase decreased with increasing matrix viscosity. Consequently, the mechanical properties of the PS/LCP blend were improved. © 1993 John Wiley & Sons, Inc.     

On the presence of a critical shell volume fraction leading to pseudo-pure droplet behavior in composite droplet polymer blends

During melt mixing a ternary blend system comprised of a high density polyethylene matrix containing dispersed polystyrene and poly(methyl-methacrylate) spontaneously forms a composite droplet structure where the PS encapsulates the PMMA. This study demonstrates that the PS/PMMA composite droplet exhibits pure PS droplet behavior at a critical volume fraction of encapsulating phase (PS:PMMA∼0.6:0.4). This critical volume fraction is shown to be independent of the overall dispersed phase concentration, shell thickness or dispersed phase size. Furthermore, the effect is observed even though the PMMA is significantly more viscous than the encapsulating PS phase. Interfacial slip as well as the maintenance of a complete PS shell during deformation are proposed as being important factors related to this behavior. The blends were prepared via melt mixing using an internal mixer and the morphology was examined by electron microscopy.     

Mechanical properties and morphology of liquid crystalline copolyester-amide and amorphous polyamide blends

Blends of an amorphous polyamide (PA) and a liquid crystalline copolyesteramide (LCP), poly(naphthoate-aminophenoterephthalate) were prepared in a twin-screw extruder. Specimens for mechanical testing were prepared by injection molding. Morphological, thermal, mechanical, and rheological properties were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffractometry, capillary rheometry, and a tensile tester, respectively. The tensile mechanical behavior of the LCP/PA blends was found to be affected by their compositions and specimen thickness. Tensile testing revealed that the tensile mechanical behavior of the LCP/PA blends was very similar to that of polymeric composite and the tensile strength of the LCP/PA (50/50) blend was approximately two times of the value of PA homopolymer and exceeded that of pure LCP. The morphology of the LCP/PA blends was also found to be affected by their compositions. SEM studies revealed that the liquid crystalline polymer (LCP) formed finely dispersed spherical domains in the PA matrix and the inclusions were deformed into fibrils from the spherical droplets with increasing LCP content. It has been found that droplet and fiber formations lead to low and high strength material, respectively. In particular, at specific LCP content (50 wt%), the tensile strength of the LCP/PA blend exceeded that of pure LCP. The improvement in tensile properties is likely due to the reinforcement of the PA matrix by the fibrous LCP phase as observed by SEM. A distinct shell-core morphology was found to develop in the injection molded samples of these blends. This is believed to have a synergistic effect on the tensile properties of the LCP/PA blends. The rheological behavior of the LCP/PA blends was found to be very different from that of the parent polymers and significant viscosity reductions were observed for the LCP/PA (50/50) blend. Based upon DSC, these blends have shown to be incompatible in the entire range of concentrations.     

Phase morphology development and melt rheological behavior in nylon 6/polystyrene blends

Phase morphology development in immiscible blends of polystyrene (PS)/nylon 6 was investigated. The blends were prepared by melt blending in a twin‐screw extruder. The influence of the blend ratio, rotation speed of the rotors, and time of mixing on the phase morphology of the blends was carefully analyzed. The morphology of the samples was examined under a scanning electron microscope (SEM) and the SEM micrographs were quantitatively analyzed for domain‐size measurements. From the morphology studies, it is evident that the minor component, whether PS or nylon, forms the dispersed phase, whereas the major component forms the continuous phase. The 50/50 PS/nylon blend exhibits cocontinuous morphology. The continuity of the dispersed phase was estimated quantitatively based on the preferential solvent‐extraction technique, which suggested that both phases are almost continuous at a 50/50 blend composition. The effect of the rotor speed on the blend morphology was investigated. It was observed that the most significant breakdown occurred at an increasing rotor speed from 9 to 20 rpm and, thereafter, the domain size remained almost the same even when the rotor speed was increased. The studies on the influence of the mixing time on the blend morphology indicated that the major breakdown of the dispersed phase occurred at the early stages of mixing. The melt rheological behavior of the blend system was studied using a capillary rheometer. The effect of the blend ratio and the shear stress on the melt viscosity of the system was investigated. Melt viscosity decreased with increase in the shear stress, indicating pseudoplastic behavior. With increase of the weight fraction of PS, the melt viscosity of the system decreased. The negative deviation of the measured viscosity from the additivity rule indicated the immiscibility of the blends. The domain size versus the viscosity ratio showed a minimum value when the viscosities of the two phases were matched, in agreement with Wu's prediction. The morphology of the extrudates was analyzed by SEM. From these observations, it was noted that as the shear rate increased the particle size decreased considerably. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3537–3555, 2002