Comparison of some butadiene-based impact modifiers for polycarbonate

The relationship of blend morphology to deformation mechanisms and notched Izod impact strength was studied with three butadiene-based impact modifiers for polycarbonate (PC). The impact modifiers were a linear polybutadiene (PB), a styrene–butadiene–styrene block copolymer (SBS), and a structured latex particle having a PB core and methyl methacrylate/styrene shell (MBS). The particle-size distribution in the blends was determined from transmission electron micrographs (TEM). Fractographic analysis combined with TEM examination of thin sections from impacted specimens provided insight into the failure mechanisms. Good impact was achieved with PC/MBS blends when cavitation of the core–shell particles relieved triaxiality and enabled the matrix to fracture by the plane stress ductile tearing mode that is characteristic of thin PC. The best impact properties were obtained with PC/SBS blends when the modifier was dispersed as aggregates of small particles. Cavitation at the weak internal boundaries relieved triaxiality, but subsequent coalescence of cavitated particles during ductile drawing of the matrix created critical size voids and the resulting secondary cracks reduced the toughness of the blend. In general, PB did not significantly enhance the impact strength of PC. © 1994 John Wiley & Sons, Inc.     

The toughness and morphology of (chlorinated poly[vinyl chloride])/(methyl methacrylate‐butadiene‐styrene) blends

A series of methyl methacrylate‐butadiene‐styrene (MBS) graft copolymers were synthesized via seeded emulsion polymerization techniques by grafting styrene and methyl methacrylate on poly(butadiene‐co‐styrene) (SBR) particles. The chlorinated poly(vinyl chloride) (CPVC)/MBS blends were obtained by melting MBS graft copolymers with CPVC resin, and the effect of the core/shell ratio of MBS graft copolymer and SBR content of CPVC/MBS blends on the mechanical properties and morphology of CPVC/MBS blends was studied. The results showed that, with the increase in the core/shell ratio, the impact strength of the blend increased and then decreased. It was found that, when the core/shell ratio was 50/50, the impact strength was about 155 J/m, and the tensile strength evidently increased. The toughness of the CPVC/MBS blend was closely related to the SBR content of the blend, and with the increasing of SBR content of blend, the impact strength of the blend increased. The morphology of CPVC/MBS blends was observed via scanning electron microscopy. Scanning electron microscopy indicated that the toughness of CPVC/MBS blend was consistence with the dispersion of MBS graft copolymers in the CPVC matrix. J. VINYL ADDIT. TECHNOL., 22:501–505, 2016. © 2015 Society of Plastics Engineers     

Distribution of MBS emulsion particles in immiscible polystyrene/SAN blends

The effect of mixing technique and sequence on the distribution of methacrylated-butadienestyrene (MBS) emulsion particles in immiscible blends of polystyrene (PS) and a styrene/acrylonitrile copolymer (SAN) was examined using transmission electron microscopy. The shell of the emulsion particle is essentially poly(methyl methacrylate) (PMMA), which is miscible with SAN but immiscible with PS. In simple thermodynamic terms, the MBS particle should have an affinity for SAN over PS. It was found, however, that the sequence of mixing had a strong influence on the location of the MBS particles. If the PS-SAN interface is established before the addition of the MBS particles, the MBS particles are located exclusively in the SAN phase. If the MBS particles are present at the time the PS-SAN interface is formed, then the particles line up at the interface.     

增韧PC/聚酯合金研究

对增韧聚碳酸酯(PC)/聚酯[聚对苯二甲酸乙二醇酯(PET)和聚对苯二甲酸丁二醇酯(PBT)]合金进行了研究,结合合金的相形貌结果,分别选择PC和聚酯是连续相的合金进行了研究,同时对比了相同树脂比例下PC/PET和PC/PBT之间性能的差别。增韧剂选择甲基丙烯酸甲酯-丁二烯-苯乙烯共聚物(MBS)或MBS和接枝环氧基团的丙烯酸酯类增韧剂(X-GM A)复配物。结果表明,使用相同的增韧剂,PC是连续相的情况下,冲击强度更高,相同树脂比例情况下,PC/PET合金冲击强度比PC/PBT的差,拉伸和弯曲强度相差不大,PC/PET合金的熔体稳定性能比PC/PBT的差,PC是连续相合金的熔体稳定性比聚酯是连续相的要好,含有X-GMA的合金熔体稳定性能更好,这些结果和酯基的热分解、PET分子链运动活性比PBT的差以及酯交换程度的差异等有直接的关联。     

Morphology development of PC/PE blends during compounding in a twin-screw extruder

The morphological development of a polycarbonate/polyethylene (PC/PE) blend in a twin-screw extruder was studied using a scanning electron microscope (SEM). The effects of extrusion temperature, viscosity ratio (the ratio of the viscosity of the dispersed phase to that of the matrix), and the screw configuration on the morphology of the PC/PE blend during the extrusion were discussed in detail. It was found that the morphology of the dispersed particles and the interfacial adhesion between the dispersed phase and matrix were both influenced by the extrusion temperature. The dispersed phase had a spheroidal shape and a small size during the high temperature processing, and an irregular shape and a large size when it was processed at low temperature. The PC phase with a lower viscosity was easier to disperse and also to coalesce. Therefore, the deformation of the low-viscosity dispersed phase during the processing was more intense than that of the high-viscosity dispersed phase. By comparing the effects of the different screw configurations on the morphology development of the PC/PE blend, it was found that the melting and breaking up of the dispersed phase were mainly affected in the initial blending stages by the number of the kneading blocks. While a kneading block with a 90 degree staggering angle was used, the size of the dispersed particles decreased and the long fibers were shortened, the large particles were drawn by the additional kneading zone. Finally, all of these structures were completely changed to the short fibers. POLYM. ENG. SCI., 47:14–25, 2007. © 2006 Society of Plastics Engineers     

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).     

Morphology and mechanical behaviors of rigid organic particles reinforced polycarbonate

For the purpose of promoting mechanical properties of bisphenol-A polycarbonate (PC) reinforced by rigid organic styrene–acrylonitrile copolymer (SAN) particles, styrene/acrylonitrile/glycidyl methacrylate terpolymer (SAG) was synthesized and applied as compatibilizer for PC/SAN blends. It is found that the phase morphology of PC/SAN/SAG blends is closely related with their mechanical properties. Large continuously distributed SAN phase or spherical dispersed SAN particles with average diameter over 2 μm tend to trigger premature tensile failure of blends due to stress concentration. The incorporation of SAG can simultaneously reinforce and toughen PC/SAN blends by controlling the size and distribution of the dispersed SAN particles. For the blends with fixed PC/SAN ratio, the elongation at break and fracture energy are markedly improved when SAN domain size is reduced by adding appropriate amount of SAG. Typically, for blends with a PC/SAN ratio of 75/25, adding 3 wt% SAG will cause the average diameter of SAN particles to reduce from 2.35 ± 1.20 to 0.74 ± 0.25 μm, meanwhile up to 95% increment in elongation at break and 115% increment in fracture energy is achieved.     

Influence of the viscosity ratio in PC/SAN blends filled with MWCNTs on the morphological,electrical, and melt rheological properties

Co-continuous polycarbonate (PC)/poly(styrene-acrylonitrile) (SAN) = 60/40 wt.% blends were filled with 1 wt.% multi-walled carbon nanotubes (MWCNTs), which selectively localized within the PC component. To study the influence of the viscosity ratio, PCs with different viscosities were selected resulting in PC/SAN viscosity ratios (at 100 rad/s) between 1.2 and 4.5. With increasing viscosity ratio, smaller blend structures were observed. Furthermore, optical microscopy revealed that the filler dispersion was improved with decreasing PC viscosity. The highest electrical conductivity was achieved for the blend composite with the coarsest morphology, containing the low viscosity PC and having the lowest PC/SAN viscosity ratio. Transmission electron microscopy analysis indicated that for the composite prepared with high viscosity PC, not all of the incorporated MWCNTs were able to localize completely into the PC component. Instead, some MWCNTs were found to be stacked at the interface of the two polymers, indicating that the high PC melt viscosity had a restricting effect on the movement of the MWCNTs. Moreover, with electrical conductive atomic force microscopy, it was proven that small, spherical PC particles, even if filled with CNTs, do not take part in the conductive network of the blend composites. Rheological analyses showed a correlation with the morphological analysis and the electrical conductive behavior of the blend composites. In summary, a lower viscosity ratio between the blend components, in which upon addition due to thermodynamic reasons the CNTs localize (here PC), and the other component (here SAN) is favorable for high electrical conductivity values.     

Effect of core-shell particles dispersed morphology on the toughening behavior of PBT/PC blends

Methyl methacrylate-co-styrene-co-glycidyl methacrylate grafted polybutadiene (PB-g-MSG) and styrene-co-glycidyl methacrylate grafted polybutadiene (PB-g-SG) core-shell particles were prepared to toughen poly (butylene terephthalate) (PBT) and polycarbonate (PC) blends. The compatibilization reaction between the epoxy groups of glycidyl methacrylate and the carboxyl groups of PBT induced the PB-g-SG particles dispersed in the PBT phase. On the other hand, the good miscibility between PMMA (the shell phase of PB-g-MSG) and PC induced the PB-g-MSG particles dispersed in the PC phase. The different phase morphology led to different toughening behavior. The PBT/PC/PB-g-MSG blends with the PC encapsulated morphology showed much lower brittle-ductile transition core-shell particles content (10-15 wt% or 15-20 wt%) compared with the PBT/PC/PB-g-SG blends (20-25 wt%). The difference between the toughening efficiency of the core-shell particles was due to the change of deformation mechanisms. In PBT/PC/PB-g-MSG blends, the cavitation of PB rubber phase led to the occurrence of shear yielding of the matrix. While in the PBT/PC/PB-g-SG blends, the debonding between PBT and PC interface induced the shear yielding of the matrix. The variation of the core-shell particles dispersed phase morphology also affected the crystallization properties and DMA results of the PBT/PC blends. Modification of the phase morphology provided an useful strategy to prepare PBT/PC blends with higher toughening efficiency.     

Electroconductive polyblend fibers of polyamide‐6/polypropylene/polyaniline: Electrical,morphological, and mechanical characteristics

Melt spun drawn fibers were prepared using a ternary blend of PP/PA6/PANI‐complex (polypropylene/polyamide‐6/polyaniline‐complex). Their electrical and mechanical properties were compared to those of binary blend fibers of PP/PANI‐complex. The results of the morphological studies on 55:25:20 PP/PA6/PANI‐complex ternary fibers were found to be in accordance with the predicted morphology for the observed conductivity vs. fiber draw ratio. The scanning electron microscopy (SEM) micrographs of the ternary blend illustrated at least a three‐phase morphology of a matrix/core‐shell dispersed phase style, with widely varying sizes of droplets. This resulted in a dispersed morphology that, in some parts of the blend, approached a bicontinuous/dispersed phase morphology due to coalescence of the small droplets. The matrix was PP and the core‐shell dispersed phase was PA6 and PANI‐complex, in which a part of the PANI‐complex had encapsulated the PA6 phase and the remaining was solved/dispersed in the PA6 core, as later confirmed by X‐ray mapping. When the ternary blend fibers were compared to the binary fibers, the formers were able to combine better conductivity (of an order of 10^?3 S cm^?1) with a greater tensile strength only at a draw ratio of 5. This indicated that the draw ratio is more critical for the ternary blend fibers, because both conductivity and tensile strength depended on the formation of fibrils from the core‐shell dispersed phase of the PA6/PANI‐complex. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Effect of blending sequence on the morphology and impact toughness of poly(ethylene terephthalate)/polycarbonate blends

The morphology of PET/PC/E‐GMA‐MA blends made by different mixing sequences was studied by transmission electron microscopy (TEM). The results suggest that migration of the E‐GMA‐MA copolymer from the PET phase to the PC phase occurred during the mixing of the (PET/E‐GMA‐MA) pre‐blend with the PC at 10% copolymer content. As a result of the migration, the E‐GMA‐MA particles are located in the PC phase rather than in the PET phase. This finding is not in agreement with the prediction made previously by others based on the possible reaction between the epoxy group of GMA and carboxyl group of PET. Core‐shell (PC/E‐GMA‐MA) particles formed in situ during blending and the size of the core‐shell particles was controlled by the blending sequence used. Mechanical properties of the ternary blends were tested at various temperatures. Although the blending sequence does not have a noticeable effect on the yield strength and modulus of the blends, it has a strong influence on the morphology formed, which determines the impact toughness. For blends made under optimum processing conditions, the brittle‐ductile transition occurred at a lower temperature and lower elastomer content. A study of the toughening mechanism suggested that the major toughening events were cavitation plus matrix shear yielding. It is postulated that the very high impact toughness found with the (PC/E‐GMA‐MA)/PET blend (at 10% E‐GMA‐MA) originated from the bimodal particle size distribution of the core‐shell particles formed in situ.     

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.     

Structure–property relationships in ternary polymer blends with core–shell inclusions: revisiting the critical role of the viscosity ratio

Structure–property relationship in typical polypropylene/polycarbonate/poly[styrene-b-(ethylene-co-butylene)-b-styrene] (PP/PC/SEBS) ternary blends containing maleated SEBS (SEBS-g-MAH) was investigated. Three grades of PC with different melt viscosities were used, and changes in blend morphology from PC/SEBS core–shell particles partially surrounded by SEBS-g-MAH to inverse SEBS/PC core–shell particles in PP matrix were observed upon varying the viscosity ratio of PC to SEBS. It was found that the viscosity ratio completely controls the size of the core–shell droplets and governs the type, population, and shape of the dispersed domains, as evidenced by rheological, mechanical, and thermomechanical behavioral assessments. Dynamic mechanical analysis of samples with common (PC–SEBS) and inverse (SEBS–PC) core–shell particles revealed that they show completely different behaviors: blends containing PC–SEBS presented a higher storage and loss modulus, while blends containing SEBS–PC exhibited a lower β-transition temperature. Moreover, ternary blends with PC cores showed the highest Young’s modulus values and the lowest impact strength, due to the different fracture modes of the blends containing PC–SEBS and SEPS–PC core–shell droplets, which present debonding and shell-fracture mechanisms, respectively. Morphological observations of blends with high-molecular-weight PC demonstrated the presence of detached droplets and rods of PC in the PP matrix, along with composite core–shell and rod-like particles. Micrographs of the fracture surfaces confirmed the proposed mechanisms, given the presence of stretched (debonded) PC (SEBS) cores encapsulated by SEBS (PC), which require more (less) energy to achieve fracture. The correlation between the mechanical and morphological properties proves that decreasing core diameter and shell thickness has positive effects on the impact strength but decreases the Young’s modulus.     

A study on the effects of SEBS‐g‐MAH on the phase morphology and mechanical properties of polypropylene/polycarbonate/SEBS ternary polymer blends

In this work, five ternary blends based on 70% by weight (wt %) of polypropylene (PP) with 30% wt of polycarbonate (PC)/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene)(SEBS) dispersed phase consists of 15 wt % PC and 15 wt % reactive (maleic anhydride grafted) and nonreactive SEBS mixtures at various ratios were prepared in a co‐rotating twin screw extruder. scanning electron microscopy (SEM) micrographs showed that the blends containing only nonreactive SEBS exhibited a fine dispersion of core‐shell particles. With decreasing the SEBS/SEBS‐g‐Maleic Anhydride (MAH) weight ratio, the morphology changed from the core‐shell particles to a mixed of core‐shell, rod‐like and individual particles. This variation in phase morphology affected the thermal and mechanical properties of the blends. DSC results showed that the blends containing only nonreactive SEBS exhibited a minimum in degree of crystallinity due to the homogeneous nucleation of core‐shell particles. Mechanical testing showed that in the SEBS/SEBS‐g‐MAH weight ratio of 50/50, the modulus and impact strength increased compared with the PP matrix while the yield stress had minimum difference with that of PP matrix. These effects could be attributed to the formation of those especial microstructures revealed by the SEM studies. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

SAN及MBS改性氯化聚氯乙烯的研究

研究了稳定体系、ＳＡＮ及ＭＢＳ对氯化聚氯乙烯共混物力学性能、耐热性及加工行为的影响。结果表明：采用钡／镉复合稳定体系可获得较好的综合性能；提高ＭＢＳ用量可以增加共混物的冲击强度和断裂伸长率，耐拉伸强度下降；ＳＡＮ用量增加，共混物的拉伸强度上升，而冲击强度和断裂伸长率下降，加入ＳＡＮ和ＭＢＳ。共混物的耐热性略有下降，但能改善共混物的辊上加工行为。     

核—壳共聚物对光盘级聚碳酸酯的增韧研究

研究了甲基丙烯酸甲酯－丁二烯－苯乙烯共聚物（MBS）对光盘级聚碳酸酯的增韧作用，结果表明，MBS对PC增韧效果显著，且MBS分散性越好，达到晚一韧转变时所需的MBS含量越少，求得达到脆－韧转变时的临界粒间距为50nm，对共混物损伤机制的研究表明，MBS增韧PC共混物的增韧机理为MBS粒子的空洞化引发基体的剪切屈服。     

The Influence of the compatibilizer Characteristics on the interfacial characteristics and phase morphology of aPA/SAN blends

The main objective of this work is study the influence of the methyl mathacrylate maleic anhydride copolymer (MMA-MA) compatibilizer properties such as molecular weight and maleic anhydride content in the characteristics of amorphous polyamide and styrene acrylonitrile copolymer (aPA/SAN) blends, correlating their interfacial characteristics and phase morphology. The blends aPA/SAN, with and without the compatibilizer, prepared were characterized by transmission electron microscopy (TEM) and small angle X-rays scattering (SAXS). The results show that the maleic anhydride concentration has a more significant effect on the blend properties than the molecular weight of the MMA-MA copolymer. Even though the system aPA/SAN is thermodynamically immiscible, it shows morphology of phases with small particles of SAN. The addition of MMA-MA copolymer with high degrees of MA led to an increase of the SAN phase particle size. With SAXS technique, it was possible to determine the interface thickness and the results shows that the characteristics of the interface do not change with the variation of the compatibilizer characteristics. The results observed in this work indicate that the viscosity ratio is very important factor on the formation of the phase morphology.     

Design of a super‐ductile polypropylene/polycarbonate blend with high heat resistance by using reactive plasticizer

High‐performance blend of polypropylene (PP) and polycarbonate (PC) has not been explored. The difficulty is caused by the big differences in melt viscosity (PP: low viscosity vs. PC: high viscosity) and polarity (PP: nonpolar vs. PC: polar). We put forth a new approach using a reactive plasticizer which is preferentially soluble with PC and polymerizable by organic peroxide. As the plasticizer, diallyl phthalate and triallyl cyanurate (TAC) were used. By reactive extrusion of PP/PC/plasticizer/dicumyl peroxide (e.g., 80/14/6/0.12 wt. ratio), reaction‐induced phase decomposition took place in the dispersed PC particles to develop a regularly phase‐separated nanostructure and the graft copolymer of PP and polymerized plasticizer was in situ generated at the interface. The extruded blend showed an excellent ductile behavior with about 500%‐elongation at break. TAC was very effective to elevate the heat resistance. Then, a super‐ductile PP/PC blend with high heat resistance was successfully developed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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.     

The influence of the internal structure of core–shell particles on poly(vinyl chloride)/(methyl methacrylate–butadiene–styrene) blends

Methyl methacrylate–butadiene–styrene (MBS) core–shell particles were prepared by grafting styrene and methyl methacrylate onto polybutadiene seeds via emulsion polymerization. All the MBS particles were designed with the same chemical composition, similar grafting degree but different internal structures. The difference in internal structure was realized by controlling the ratio of ‘external grafting’ and ‘internal grafting’ of styrene. The work focused on the influence of the internal structure of MBS core–shell particles on the properties of poly(vinyl chloride)/MBS blends. From transmission electron microscopy, three different internal structures were observed: rare sub‐inclusions, a large number of small sub‐inclusions and large sub‐inclusions. The results of dynamic mechanical analysis illustrated that the different internal structures greatly affected the glass transition temperature T_g of the rubber phase and the storage modulus of the core–shell particles. The notched Izod impact test results showed that the MBS with large sub‐inclusions had the lowest brittle–ductile transition temperature, while the transparency test revealed that the presence of sub‐inclusions in the rubbery phase reduced the transparency of the blend. Copyright © 2012 Society of Chemical Industry