The influence of microstructure on the dynamic mechanical behavior of polycarbonate/poly(styrene-co-acrylonitrile) blends

The influence of microstructure on dynamic mechanical behavior in the two phase blend of polycarbonate, (PC), with poly(styrene-co-acrylonitrile), (SAN), was studied by comparing the torsional response for injection and compression molded samples. A matrix component's glass transition (T_g) damping was only moderately altered by the presence of a dispersed phase although shifts in T_g, assigned to the local maxima in tan delta, indicated partial miscibility. In compression molded samples the onset of a co-continuous PC phase suppressed the damping characteristics of the SAN T_g on the high temperature side shifting the assignment of this T_g to lower temperatures. This suppression results from PC dominating the composite's response at temperatures above the SAN T_g. In injection molded samples the onset of PC co-continuity only partially suppressed the damping of the SAN T_g such that a doublet results. Co-continuity within the injection molded microstructure could be idealized as alternating sheets which, subsequently, in the dynamic mechanical measurement are arranged In series to a shearing stress during torsion. Above the T_g of SAN the presence of such a series phase arrangement allows the composite to strain approximately to that extent which would be exhibited by pure SAN alone. The response of the composite is thereby approximately the response of SAN with the almost full extent of its T_g damping process realized.     

Phase morphology characterization and ultimate mechanical properties of 60/40 PC/SAN blend: Influence of the acrylonitrile content of SAN

The tensile stress-strain properties of blends having a 60/40 weight ratio of polycarbonate of bisphenol-A (PC) and styrene-acrylonitrile copolymers (SAN) have been investigated for a range of SAN copolymers with different AN levels. It is clearly demonstrated that the phase morphology of these, blends and the acrylonitrile (AN) content of the SAN component are important factors with respect to the ultimate mechanical properties (tensile strength and elongation at fracture). Following injection molding, a very fine phase distribution is observed for blends with SAN components containing 15 to 29% AN. By annealing of the blends at 200°C, i.e. above T_g(PC), it has been possible to obtain different degrees of domain sizes. From this range of morphologies, quite similar phase structures can selected differing only in AN-content of the SAN blend components. This allows a systematic investigation of the effect of the AN-content on the tensile stress-strain. Properties of PC/SAN blends. The elongation at fracture exhibits an optimum for blends with SAN containing 24% AN. A coarsening of the phase morphology only results in a decrease of the ductility and not in a shift of the optimum. The maximum tensile stress exhibits a sigmoidal trend as a function of the AN-content. This parameter remains constant for a typical -PC/SAN blend with different morphologies.     

Effects of AN-contents and shear flow on the miscibility of PC/SAN blends

The miscibility of polycarbonate (PC) with styrene-co-acrylonitrile random copolymer (SAN) has been systematically investigated as functions of acrylonitrile content and shear flow. Various AN-contents ranged from 11 to 74 wt% and different simple shear flow values up to 90 s⁻¹ have been used to explore the effect of both material and proceeding parameters on the miscibility of PC and SAN blends. The finest phase dispersion of the SAN particles was observed at AN=25 wt% for PC/SAN=70/30 blends under the same processing condition using scanning electron microscope (SEM). The obtained morphologies indicated that PC and SAN could form a partial miscibility blend and the maximum miscibility occurred at AN=25 wt%. This observation was supported by considering the shifts in the glass processes of the two rich phases of the blend using the dynamical mechanical analysis (DMA) measurements. The optimum interaction of the two components at AN=25 wt% calculated from ellipsometric technique was found to be the only responsible parameter for the high miscibility of the blend. The viscoelastic properties of the pure polymer components were found to play a minor role in the obtained morphologies. The effect of simple shear flow on the morphology of PC/SAN-25=70/30 blend has been also investigated using a special shear apparatus of parallel plate geometry. It has been found that the dispersed phase of SAN was elongated and broken-up in the direction of flow with weaker contrast at high shear rates. The shear rate was found to enhance the miscibility of SAN (dispersed phase) in the PC matrix to a great extent as seen in the weak contrast of the two phases observed by transmission electron microscope (TEM).     

Co-continuous morphology development in partially miscible PMMA/PC blends

Poly(methyl methacrylate) (PMMA)/polycarbonate (PC) partially miscible blends were produced via melt blending in an internal mixer over the entire range of composition at two different viscosity ratios. The morphology of this low interfacial tension system was investigated by scanning electron microscopy, solvent extraction/gravimetry and surface area measurement (BET) after selective extraction. The partial miscibility of these blends was evaluated by T_g measurements from dynamic mechanical thermal analysis. The co-continuous morphology development curve obtained from gravimetry is commonly reported in the literature as the %continuity vs. the vol% fraction of the dispersed phase for fully phase separated systems. Such systems possess pure phases of A and B. Partially miscible blends on the other hand demonstrate immiscibility between an A-rich phase and a B-rich phase. Quantitative estimation of the partial composition of the minor components in each respective rich phase was calculated using the Fox equation. Using this data, an approach to correcting the gravimetry results to take into account the partial miscibility of the PMMA/PC system is proposed. The co-continuous morphology development curve is then presented as the %continuity vs. the vol% fraction of the PMMA-rich phase. This corrected curve demonstrates the features of a highly interacting polymer blend: a low percolation threshold and a broad co-continuity region. The BET technique shows that the pore size of the extracted co-continuous blends is dependent on composition, the pore diameter increases with total PMMA content. Use of a low molecular weight PC shifts the co-continuous morphology development curve to higher volume fraction values of PMMA-rich phase. It is suggested that this is the result of a lower dispersed phase thread stability due to the lower matrix viscosity.     

Studies on morphology and thermomechanical performance of ABS/PC/organoclay hybrids

In the present research, poly(acrylonitrile‐butadiene‐styrene)/polycarbonate (ABS/PC) blends were prepared in a twin screw extruder. An attempt to reinforce and promote compatibility of the above systems was made by the incorporation of organically modified montmorillonite (OMMT, Cloisite 30B), as well as by the addition of compatibilizer (ABS grafted with maleic anhydride, ABS‐g‐MAH), and the effect of those treatments on the morphology, thermal transitions, rheological, and mechanical properties of the above blends was evaluated. The addition of compatibilizer in ABS/PC blends does not significantly affect the glass transition temperature (T_g) of SAN and PC phases, whereas the incorporation of Cloisite 30B decreases slightly the T_g values of SAN and, more significantly, that of PC in compatibilized and uncompatibilized blends. The T_g of PB phase remains almost unaffected in all the examined systems. The obtained results suggest partial dissolution of the polymeric components of the blend and, therefore, a modified Fox equation was used to assess the amount of PC dissolved in the SAN phase of ABS and vice versa.Reinforcing with OMMT enhances the miscibility of ABS and PC phases in ABS/PC blends and gives the best performance in terms of tensile strength, modulus of elasticity, and storage modulus, especially in 50/50 (w/w) ABS/PC blends. The addition of ABS‐g‐MAH compatibilizer, despite the improvement of intercalation process in organoclay/ABS/PC nanocomposites, did not seem to have any substantial effect on the mechanical properties of the examined blends. POLYM. COMPOS., 35:1395–1407, 2014. © 2013 Society of Plastics Engineers     

Polycarbonate and co-continuous polycarbonate/ABS blends: influence of specimen thickness

The influence of specimen thickness on the fracture behaviour of polycarbonate (PC) and co-continuous PC/ABS (50/50) blends was studied in single edge notch tensile tests at 1 m/s and different temperatures (−80 to 130 °C). Specimen thickness ranged from 0.1 to 8 mm. In the co-continuous PC/ABS blends the rubber concentration in the ABS was 0, 15 and 30 wt%. The change in fracture toughness was typified by the change in brittle-to-ductile transition temperature (T_bd).T_bd of pure PC depended strongly on specimen thickness, leading to very low transition temperatures for thin PC specimens. PC/ABS 0%, a 50/50 blend of PC and SAN (i.e. ABS without polybutadiene (PB)), was a brittle blend and showed a very high T_bd close to the T_g of SAN. T_bd did not seem to be influenced by specimen thickness. PC/ABS blends with 15 and 30% PB in ABS showed improved T_bd compared to PC/SAN and PC, indicating effective rubber toughening. T_bd decreased with decreasing thickness for PC/ABS specimens thicker than 1.5 mm. However, T_bd increased with decreasing thickness for specimens below 1.5 mm thickness. In thin specimens, the rubber-filled blend is less effective rubber toughening. The plane strain stress condition needed for rubber cavitation is apparently not present in thin specimens.     

Thermal behavior,morphology, and some melt properties of blends of polycarbonate with poly(styrene-co-acrylonitrile) and poly(acrylonitrile-butadiene-styrene)

Blends of bisphenol-A polycarbonate (PC) with poly- (styrene-co-acrylonitrile) (SAN) and poly (acrylonitrile-butadiene-styrene) (ABS) prepared by screw extrusion and solution-casting were investigated by differential scanning calorimetry and scanning electron microscopy. From the measured glass-transition temperatures (T_g) and specific heat increments (ΔC_p) at the T_g, SAN appears to dissolve more in the PC-rich phase than does PC in the SAN-rich phase. Also, the decrease of T_g (PC) in PC/ABS blends is larger than in the PC/SAN blends. From the T_g behavior and the electron microscopy study, it is suggested that the compatibility increases more in the SAN-rich compositions than in the PC-rich compositions of the blends. In the study of extrudate swell of the PC/SAN blends and the PC/ABS blends, the maximum level of extrudate swell is reached at 0.5 weight fraction of PC for both blend systems. The Flory-Huggins polymer-polymer interaction parameter (χ12) between PC and SAN was calculated and found to be 0.034 ± 0.004. A similar value of χ for PC and SAN was found with the PC/ABS blends.     

High-performance semi-interpenetrating polymer networks based on acetylene-terminated sulfone. II. Phase separation and morphology

The dynamic mechanical behavior, phase separation, and morphology of high-performance semi-interpenetrating polymer network (semi-IPN) obtained from acetylene-terminated sulfone (ATS-C) and high-performance thermoplastics have been studied by torsional braid analysis (TBA) and scanning electron microscopy (SEM). All the ATS-C/thermoplastic blends studied are compatible before curing. The addition of ATS-C results in a dramatic reduction in the glass transition temperature (T_g) of the thermoplastic. As the reaction of cure proceeds, the initially compatible blend passes through a stage of partial compatibility to achieve a fully incompatible semi-IPN. SEM observation of the fracturedetched surface reveals the formation of a co-continuous two-phase structure in the semi-IPNs. The connected globule and network morphology of the cured ATS-C phase are dispersed in a matrix of the thermoplastic phase. The size of dispersed particles decreases with increasing T_g of the thermoplastic. The mechanism of phase separation is discussed. © 1994 John Wiley & Sons, Inc.     

Compatibility enhancement of ABS/PVC blends

The compatibilizing effect of poly(styrene-co-acrylonitrile) (SAN) whose acrylonitrile (AN) content is 25 wt % (SAN 25) in poly(acrylonitrile-co-butadiene-co-styrene) (ABS)/poly(vinyl chloride) (PVC) blend was studied when the AN content of the matrix SAN in ABS was 35 wt % (SAN 35). When some amount of matrix SAN 35 was replaced by SAN 25 in a ABS/PVC (50/50 by weight) blend, the mixed phase of SAN and PVC at the interface was thickened, and about a twofold increase of impact strength was observed. The changes in morphology, dynamic mechanical properties, and rheological properties by the compatibilizing effect of SAN 25 were observed. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 705–709, 1998     

Influence of a core/shell rubber phase on the morphology and the impact resistance of a PC/SAN blend (75/25)

At 75/25 concentration ratio, bisphenol a polycarbonate (PC)/styreneacry-lonitrile copolymer (SAN) blend has poor impact resistance compared to PC/ABS. A rubber phase methacrylate-butadiene-styrene (MBS) of core/shell type was dispersed in PC/SAN blend. The morphology of the unmodified and modified blend was investigated. The influence of the acrylonitrile ratio in the SAN on the microstructure was studied. It clearly shows that core/shell resides at the interface between PC and SAN. It seems that core/shell particles enhance the adhesion between the different phases. Their presence influences the interface mobility; i.e., the coalescence of the dispersed phase observed in pure PC/SAN is considerably reduced when the MBS particles are added. The impact resistance of the samples was correlated with the morphology.     

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.     

Characterization of polypropylene–poly(1-butene)–hydrogenated olygo(cyclopentadiene) ternary blends

Ternary blends containing polypropylene (PP), poly(1-butene) (PB), and hydrogenated oligo(cyclopentadiene) (HOCP) have been studied using microscopic calorimetric and dynamic mechanical techniques, with no phase separation having been observed in the melt for all the considered compositions. The morphology of the crystallized blends and spherulite growth rate of the PP component appeared to be influenced by the blend composition. The presence of one or two T_gs revealed by dynamic mechanical thermal analysis (DMTA) on quenched or crystallized blends has suggested that demixing phenomena can occur during the crystallization of the components. The blend composition has been found to affect the overall crystallization rate and the equilibrium melting temperature of the PP component. A parameter describing the enthalpic interactions between the PP component and the diluent fraction evidenced that the addition of HOCP to PP and PB increases the stability of the ternary blend. The above results suggest that the three components can form a miscible blend in the melt. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1659–1665, 1997     

Formation of co‐continuous PLLA/PC blends with significantly improved physical properties by reactive comb polymers

A kind of reactive comb (RC) polymer, which is constituted by poly(methyl methacrylate) backbone and side chains and a few epoxide groups that distribute randomly along the backbone, has been applied as compatibilizers for the thermodynamically immiscible poly(l ‐lactide) (PLLA)/polycarbonate (PC) blend (50/50, wt/wt). Phase morphology and physical properties of the compatibilized PLLA/PC blends are characterized by scanning electron microscopy, transmission electron microscopy, and tensile tests. It has been found that the morphologies of the PLLA/PC blends are significantly ameliorated with the addition of RC polymers. A type of PLLA/PC blend with stable co‐continuous morphology has been achieved by the incorporation of more than 3 wt % of RC polymers. The mechanical tests showed that the co‐continuous PLLA/PC blends have an excellent stiffness‐toughness balance with high modulus and significantly improved ductility. Especially, the elongation at break of the PLLA/PC blend compatibilized by 10 wt % of RC polymers is 10 times higher than that of neat PLLA, in which the blend exhibits a cocontinuous lamellar microstructure. Furthermore, the PLLA/PC blends with cocontinuous morphology exhibit dramatically improved thermal stability as compared to neat PLLA when the temperature is over the T_g of the PLLA phase. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46047.     

Conformational motions in immiscible blends of polycarbonate and styrene-acrylonitrile copolymers

Blends of commercial bisphenol-A -polycarbonate and styrene-acrylonitrile copolymers were prepared by precipitation in ethanol from the solution in methylene chloride in order to eliminate the low molecular weight substances contained in the commercial polymers, specially the oligomers contained in commercial SAN copolymers. Two glass transitions appear in the DSC thermograms of the blend at the same temperatures as in the pure components which, in principle, indicates that the blend consists of two phases formed by pure PC and pure SAN. In order to detect small changes in the glass transition process that could be indicative of different mobility of the polymer chains in the blend with respect to the pure polymers, blends of different compositions were subjected to different thermal treatments that included annealing at temperatures below both glass transitions, and then the DSC thermograms were recorded. A broadening in the peaks shown by the c_p(T) curves measured on annealed samples in the zone of the PC transition is detected while no significant differences are shown by the glass transition of the San phase of the blend with respect to pure SAN copolymer. Dielectric relaxation experiments in the frequency domain (from 100 to 3·10⁶Hz) were carried out on the blends. The dielectric relaxation spectrum in the zone of the SAN main relaxation process was fitted with the stretched exponential equation showing no significant difference between the blends and the pure SAN copolymer. The region of the main relaxation process of PC was not analyzed due to the small polar activity of PC and the overlapping with the relaxation of the SAN phase.     

Dynamic mechanical, thermal, physico-mechanical and morphological properties of LLDPE/EMA blends

The effect of blend composition on the morphology, dynamic mechanical properties, thermal and physico-mechanical properties of linear low density polyethylene (LLDPE)/ ethylene-co-methyl acrylate (EMA) blends were studied. The blend showed both dispersed and continuous phase morphology that depends on the blend composition. A co-continuous structure is formed for blends containing 50 wt% of EMA. Dynamic mechanical studies showed that flexibility of the blend enhanced with the expansion of the amorphous region as EMA content increased. However, two separate melting temperature peak observed in differential scanning calorimetry (DSC) analysis indicate that the blends are immiscible in crystalline region of the two polymers. X-ray diffraction (XRD) studies showed that crystallinity of blends decreases with increase in EMA content and negative deviation of tensile strength from the mixing rule indicates the poor interfacial adhesion between the two components. FTIR spectroscopy established the lack of chemical interaction between LLDPE and EMA, which support the SEM, DSC, DMA and XRD observations. Parallel-Voids model has been applied to characterize phase morphology of these blends.     

Anisotropy and instability of the co-continuous phase morphology in uncompatibilized and reactively compatibilized polypropylene/polystyrene blends

The present work describes the anisotropy and instability observed upon the formation of co-continuous phase morphologies in model polystyrene/polypropylene melt-extruded blends. Uncompatibilized and reactively compatibilized blends using amino-terminated polystyrene, PS-NH₂, and maleic anhydride grafted polypropylene, PP-MAh, reactive precursors were investigated. Differences in phase morphology are discussed based on the viscoelastic properties of the components used, the blend composition and, the type and content of the compatibilizer precursor employed. As expected, for the same polystyrene grade at a concentration in the blend below 20 wt%, a polypropylene matrix having a higher viscosity enables the formation of a more co-continuous phase morphology than a less viscous one, as quantified by solvent extraction. The co-continuous phase morphology developed was found to exhibit a highly elongated structure upon melt flow through the die of the extruder. Isotropic co-continuity, observed inside the barrel of extruder, was transformed into anisotropic phase co-continuity in the form of interconnected infinite strands of the minor phase highly oriented in the extrusion direction.When the blends were thermally annealed, a 50/50 PS/PP co-continuous blend exhibits a substantial phase coarsening from micro- to millimeter scale without alteration of the phase co-continuity. The reactive compatibilization of the polypropylene and the polystyrene phases using 5 wt% PP-graft-PS, reactively in situ generated was able to significantly retard the phase evolution process.     

PET/PC blends: Effect of chain extender and impact strength modifier on their structure and properties

Methylene diphenyl diisocyanate (MDI) affects the morphology, rheological, mechanical, and relaxation properties, as well as tendency to crystallize of PET in PET/PC/(PP/EPDM) ternary blends produced by the reactive extrusion. Irrespective of the blend phase structure, the introduction of MDI increases the melt viscosity (MFI dropped), resulting from an increase in the molecular weight of the polymer chains; the PET crystallinity was also reduced. MDI favors compatibility of PET with PC in PET/PC/(PP/EPDM) blends. This is explained by intensified interphase interactions on the level of segments of macromolecules as well as monomer units. The presence of MDI causes a substantial rise in the dynamic shear modulus within the high‐elastic region of PET (for temperature range between T_g,PET and that of PET cold crystallization); the processes of PET cold crystallization and melt crystallization become retarded; the glass‐transition temperatures for PET and PC become closer to each other. MDI affects insignificantly the blend morphology or the character of interactions between the disperse PP/EPDM blend and PET/PC as a matrix. PP/EPDM reduces the intensity of interphase interactions in a PET/PC/(PP/EPDM), but a rise in the degree of material heterogeneity. MDI does not change the mechanism of impact break‐down in the ternary blends mentioned above. Increased impact strength of MDI‐modified materials can be explained by higher cohesive strength and resistance to shear flow at impact loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Gloss reduction and morphological properties of polycarbonate and poly(methyl methacrylate‐acrylonitrile‐butadiene‐styrene) blends with SAN‐co‐GMA as a reactive compatibilizer

The gloss properties of the polycarbonate (PC)/poly(methyl methacrylate‐acrylonitrile‐butadiene‐styrene) (MABS) blend with styrene‐acrylonitrile‐co‐glycidyl methacrylate (SAN‐co‐GMA) as a compatibilizing agent were investigated. For the PC/poly(MABS)/SAN‐co‐GMA (65/15/20, wt %) blend surface, the reduction of gloss level was observed most significantly when the GMA content was 0.1 wt %, compared with the blends with 0.05 wt % GMA or without GMA content. The gloss level of the PC/poly(MABS)/SAN‐co‐GMA (0.1 wt % GMA) blend surface was observed to be 35, which showed 65% lower than the PC/poly(MABS)/SAN‐co‐GMA blend without GMA content. The gloss reduction was most probably caused by the insoluble fractions of the PC/poly(MABS)/SAN‐co‐GMA blend that were formed by the reaction between the carboxylic acid group in poly(MABS) and epoxy group in SAN‐co‐GMA. The results of optical and transmission electron microscope analysis, spectroscopy study, and rheological properties supported the formation of insoluble structure of the PC/poly(MABS)/SAN‐co‐GMA blend when the GMA content was 0.1 wt %. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46450.     

Effect of styrene–acrylonitrile on the electrical resistivity of polycarbonate/multiwalled carbon nanotube composites

Multiwalled carbon nanotube (MWCNT)‐filled polycarbonate (PC)/styrene–acrylonitrile (SAN) blends with a wide range of blend compositions were prepared by melt mixing in a rotational rheometer, and the effect of SAN on the electrical properties of the PC/MWCNT composites was studied. The structure/electrical property relationship was investigated and explained by a combination of MWCNT localization and blend morphology. Transmission electron micrographs showed selective localization of MWCNTs in the PC phase, regardless of the blend morphology. When the SAN concentration was 10–40 wt %, which corresponded to sea‐island (10–30 wt %) and cocontinuous (40 wt %) blend morphologies (PC was continuous in both structures), the electrical resistivity decreased with increases in the SAN content. The concept of an effective volume concentration of MWCNTs was used to explain this effect. When the SAN concentration was 70 wt % or higher, the electrical resistivity was very high because MWCNTs were confined in the isolated PC particles. In addition, SAN was replaced by other polymers [polystyrene, methyl methacrylate/styrene, and poly(methyl methacrylate)]; these yielded similar blend morphologies and MWCNT localization and showed the generality of the concept of effective concentration in explaining a decrease in the electrical resistivity upon the addition of a second polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Morphology and mechanical properties of ABS blends prepared from emulsion‐polymerized PB‐g‐SAN impact modifier with AIBN as initiator

A series of PB‐g‐SAN impact modifiers (polybutadiene particles grafted by styrene and acrylonitrile) are synthesized by seed emulsion copolymerization initiated by oil‐soluble initiator, azobisiobutyronitrile (AIBN). The ABS blends are obtained by mixing SAN resin with PB‐g‐SAN impact modifiers. The mechanical behavior and the phase morphology of ABS blends are investigated. The graft degree (GD) and grafting efficiency (GE) are investigated, and the high GD shows that AIBN has a fine initiating ability in emulsion grafting of PB‐g‐SAN impact modifiers. The morphology of the rubber particles is observed by the transmission electron microscopy (TEM). The TEM photograph shows that the PB‐g‐SAN impact modifier initiated by AIBN is more likely to form subinclusion inside the rubber particles. The dynamic mechanical analysis on ABS blends shows that the subinclusion inside the rubber phase strongly influences the T_g, maximum tan δ, and the storage modulus of the rubber phase. The mechanical test indicates that the ABS blends, which have the small and uniform subinclusions dispersed in the rubber particles, have the maximum impact strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007