Morphology and deformation of compatibilized polystyrene low density polyethylene blends

This investigation deals with the morphology and tensile behavior of polystyrene/low density polyethylene blends compatibilized by hydrogenated styrene‐b‐butadiene‐b‐styrene triblock copolymer. The stress‐strain measurements indicate that blends with excellent toughness were achieved, due to the compatibilizing role of the triblock copolymer in the system. The morphology of the blends was observed by scanning electron microscopy (SEM), and the results show that the state of polystyrene changes from continuous phase to dispersed phase with increasing LDPE content. The correlation between mechanical properties and morphology is discussed. The morphologies of the tensile bars were also examined by SEM, and the deformation mechanisms of the blend were further analysed according to fractography. © 1999 Society of Chemical Industry     

Melt rheology of compatibilized polystyrene/low density polyethylene blends

Investigations have been made on the melt rheological behaviors of compatibilized blends composed of polystyrene, low density polyethylene and hydrogenated (styrene‐butadiene‐styrene) triblock copolymer used as a compatibilizer. The experiments were carried out on a capillary rheometer. The effects of shear stress, temperature and blending ratio on the activation energy for viscous flow and melt viscosity of the blends are described. The study shows that the viscosity of the blends exhibits a maximum or minimum value at a certain blending ratio. The activation energy for viscous flow decreases with increasing LDPE content. Furthermore, the concept of equal‐viscosity temperature is presented and its role in the processing of the blend is discussed. In addition, the morphology of the extrudate sample of the blends was observed by scanning electron microscopy and the correlation between the morphology and the rheological properties is explored. © 1999 Society of Chemical Industry     

Mechanical behaviors of ethylene/styrene interpolymer compatibilized polystyrene/polyethylene blends

In this study, ethylene/styrene interpolymer was used as a compatibilizer for the blends of polystyrene (PS) and high‐density polyethylene (HDPE). The mechanical properties including tensile and impact properties and morphology of the blends were investigated by means of uniaxial tension, instrumented falling‐weight impact measurements, and scanning electron microscopy. Tensile tests showed that the yield strength of the PS/HDPE/ESI blends decreases considerably with increasing HDPE content. However, the elongation at break of the blends tended to increase significantly with increasing HDPE content. The excellent tensile ductility of the HDPE‐rich blends resulted from shield yielding of the matrix. Izod and Charpy impact measurements indicated that the impact strength of the blends increases slowly with HDPE content up to 40 wt %; thereafter, it increases sharply with increasing HDPE content. The impact energy of the HDPE‐rich blends exceeded that of pure HDPE, implying that the HDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of ESI compatibilizer. The correlation between the impact property and morphology of the blends is discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4001–4007, 2007     

Ultrasonic improvement of the compatibility and rheological behavior of high‐density polyethylene/polystyrene blends

The effects of ultrasonic oscillations on the rheological behavior, mechanical properties, and morphology of high‐density polyethylene (HDPE)/polystyrene (PS) blends were studied. The experimental results show that the die pressure and apparent viscosity of HDPE/PS blends are remarkably reduced in the presence of ultrasonic oscillations and that mechanical properties of the blends are improved. The particle size of the dispersed phase in HDPE/PS blends becomes smaller, its distribution becomes narrower, and the interfacial interaction of the blends becomes stronger if the blends are extruded in the presence of ultrasonic oscillations. Ultraviolet spectra and Soxhlet extraction results show the formation of a polyethylene‐PS copolymer during extrusion in the presence of ultrasonic oscillations, which improves the compatibility of HDPE/PS blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 23–32, 2002     

A new technique for preparing polyethylene/polystyrene blends with gradient structure

In this study, polyethylene (PE)/polystyrene (PS) polymeric gradient material with spatially gradient structure was prepared continuously by a new technique through coextrusion–gradient distribution–two‐dimensional mixing with conventional polymeric material processing facilities. The processing line from coextrusion, gradient distribution to two‐dimensional mixing was fulfilled by two extruders, gradient distribution unit, and two‐dimensional mixing units, respectively. The gradient distribution unit and two‐dimensional mixing units were designed separately in our group. The gradient variation of composition along the sample thickness direction was studied by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). DSC results indicated that a gradient variation of the content of PE was formed along the sample thickness direction. SEM results showed the direct evolution of morphology of each specimen along the sample thickness direction. The experimental results demonstrated that the processing method with coextrusion–gradient distribution–two‐dimensional mixing can be served as a new way to produce polymer blends with spatially gradient structure and worth to be further investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

The effect of the architecture and concentration of styrene–butadiene compatibilizers on the morphology of polystyrene/low‐density polyethylene blends

The effect of styrene–butadiene block copolymers (SB) with varying number of blocks and length of styrene blocks on the morphology, rheology, and impact strength of 4/1 polystyrene/low‐density polyethylene (PS/LDPE) blends was studied. The scanning and transmission electron microscopy and X‐ray scattering were used for determination of the size of LDPE particles and the localization and structure of SB copolymers in blends. It is shown that the dependence of the LDPE particle size on the amount of added SB and localization of SB copolymers in blends is predominantly controlled by the length of their styrene blocks. It follows from thermodynamic considerations that the reason is the difference in composition asymmetry between SB with short and long styrene blocks. Coalescence of particles of SB having short styrene blocks at the surface of LDPE droplets and movement of SB with long styrene blocks to the PS–LDPE interface were observed during annealing of PS/LDPE/SB blends. Pronounced migration of SB copolymer during annealing shows that their localizations in blends in steady state on long steady mixing and at thermodynamic equilibrium are different. The values of tensile impact strength of PS/LDPE/SB blends correlate well with the size of LDPE particles and the amount of SB at the interface. Viscosity of PS/LDPE/SB depends on molecular structure of SB copolymers by a manner different from that of tensile impact strength. The results of this study and literature data lead to the conclusion that the compatibilization efficiency of SB copolymers for a certain polystyrene‐polyolefin pair is a function of not only molecular parameters of SB but also of the polystyrene/polyolefin ratio, the amount of SB in a blend, and mixing and processing conditions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2803–2816, 2006     

Effect of a styrene–butadiene copolymer on the phase structure and impact strength of polyethylene/high‐impact polystyrene blends

The effect of a styrene–butadiene block copolymer on the phase structure and impact strength of high‐density and low‐density polyethylene/high‐impact polystyrene blends with various compositions was studied. For both the blends, the type of the phase structure was not affected by addition of a styrene–butadiene compatibilizer. The localization and structure of the compatibilizer in the blends were dependent on their composition. Addition of the compatibilizer improved impact strength of the blends in the whole concentration range. The improvement was the largest for blends with a low amount of the minor phase. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 570–580, 2001     

Blends of sulphonated polystyrene and polystyrene: Morphology and deformation modes

Blends of sulphonated polystyrene, neutralized with metal ions, have been prepared in various proportions with polystyrene homopolymer. Morphology, microstructure, and deformation modes of strained, cast thin films have been examined by transmission electron microscopy. Variables studied include blend composition and ion content. In blends of low ionomer concentration, the ionomer component phase-separates and takes the form of small dispersed particles. With the increase of ion content, the average particle size increases and, as crazes develop in the matrix, particles elongate and fibrillate. These ionic crosslinked particles adhere well to the matrix, share in carrying the applied stress and reinforce the matrix polymer. Implications of these results for mechanical performance of bulk samples are discussed.     

Morphology development in polypropylene/polystyrene blends during coalescence under shear

Morphology development during the coalescence under shear in polypropylene/polystyrene blends was studied in this article. The coalescence was performed by decreasing the shear rate after a fine morphology is obtained at higher shear rate. Time resolved SEM performance indicates that, because of the smaller capillary number, particles of the minor phase are almost spherical during the whole coalescence process. An original sizing method based on SEM is used to describe the time evolution of particle size and their distribution. Initially, the volume–average particle size increases rapidly and levels off before a steady state is obtained, while the number–average particle size increases slowly but monotonously during the whole coalescence process. This two‐step increase in volume average particle size is discussed in terms of coalescence efficiency. Further, an examination of scaling behavior shows that a master curve for particle growth with different compositions is observed by plotting the relative increase in particles size versus the shear strain, confirming that the evolution of particle size could be described by a scaling law. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 666–671, 2007     

Morphology of polystyrene/poly(methyl methacrylate) blends: Effects of carbon nanotubes aspect ratio and surface modification

Multiwalled carbon nanotubes (MWCNTs) with aspect ratios (ARs) ranging from 94 to 474 were incorporated into polystyrene (PS)/poly(methyl methacrylate) blends using solution mixing and melt mixing. Also, two functionalized MWCNTs were prepared from the nanotubes having AR 94: one was oxidized by nitric acid while the other was further modified with amine‐terminated PS attached to carboxyl groups to form amides. The two functionalized MWCNTs (1 wt %) were used to show that which phase the carbon nanotubes (CNTs) were located in could be controlled with nanotube surface chemistry. When nanotubes were confined to the minor phase, the size of the minor domain first decreased with adding low AR CNT as expected due to the increased viscosity of the minor phase. However, at higher ARs, the size increased beyond the size for the minor domain with no nanotubes, and at high enough AR, the shape of the minor domain changed from spherical to an elongated irregular shape. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3500–3510, 2015     

Morphology,thermomechanical properties,and biodegradability of low density polyethylene/starch blends

The biodegradability of low density polyethylene (LDPE)/starch and LDPE/starch/starch acetate (STAc) blends was tested and observed to be dependent on STAc content. The binary and ternary blends containing up to a maximum concentration of 30% starch were examined for their thermal, mechanical, and morphological properties. The blends with no STAc or 2.5% STAc show almost no adherence of two phases. With 10% STAc, dispersion of starch was observed to increase with some adherence to LDPE. Tensile strength, elongation at break, and Izod impact strength of the blends decreased with increased starch content. However, incorporation of STAc along with starch improved all these properties, particularly elongation at break and toughness. The melt flow index was also improved on partial substitution of starch by STAc. Maximum biodegradability was observed for the blends containing 30% (starch + STAc). Cell growth was observed to increase with increasing concentration of (starch + STAc) in the blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2791–2802, 1999     

Mechanical properties and creep resistance in polystyrene/polyethylene blends

Recycled plastics, predominantly high‐density polyethylene (PE), are being processed in the shape of dimension lumber and marketed as “plastic lumber.” One drawback to these products is their low creep resistance or high creep speed. The objective of this study was to examine the feasibility of reducing the creep speed of PE‐based products by blending the PE with a lower‐creep plastic, in this case polystyrene (PS). Various blends of PE and PS were prepared in either a laboratory extruder or a bowl mixer and then compression‐molded. The mechanical properties, creep behavior, morphology, and thermal properties of extruded and compression‐molded samples were determined. The modulus of elasticity of the extruded blends could be estimated by a weighted average of PS and PE, even in the absence of a compatibilizer. Processing strongly affected the morphology and mechanical properties of the blends. For 50% PS : 50% PE blends, the stress–strain curves of the extruded samples showed PE‐like behavior, whereas those from compression‐molded samples were brittle, PS‐like curves. Flexural strength was 50% higher in the extruded samples than in those from compression molding. The creep experiments were performed in three‐point bending. Creep speed was lower in 50% PS : 50% PE and 75% PS : 25% PE blends than in pure PS. Creep speed of 75% PS : 25% PE was lowest of all the extruded blends. PE formed the continuous phase even when the PS content was as high as 50 wt %. For a 75% PS : 25% PE blend, cocontinuous phases were observed in the machine direction. A ribbonlike PS‐dispersed phase was observed in the 25% PS : 75% PE and 50% PS : 50% PE samples. Blending low‐creep‐speed PS with high‐creep‐speed PE appeared to successfully improve the performance of the final composite. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1100–1108, 2000     

Structure development and property changes in high‐density polyethylene/calcium carbonate blends during pan‐milling

A new self‐designed mechanochemical reactor, inlaid pan‐mill, was used in studying high density polyethylene (HDPE) and calcium carbonate (CaCO₃) blends. The effects of CaCO₃ on the crushing and structure of HDPE matrix and the properties of HDPE/CaCO₃ blends were investigated. Scanning electron microscopy, Fourier transformed IR spectroscopy, dynamical mechanical testing analysis, capillary rheometer, and Instron material testing system were used to characterize the structure of HDPE and evaluate the properties of HDPE/CaCO₃ blends. The introduction of calcium carbonate during milling improved milling efficiency, and time needed for each cycle was greatly reduced. Oxygen‐containing groups on HDPE chains, which were produced during milling, increased interfacial interactions and improved the dispersion and distribution of calcium carbonate particles in HDPE/CaCO₃ blends. Rheological, thermal, and mechanical properties were also improved. The elongation at break of milled blends with high concentrations of calcium carbonate was significantly higher than that of unmilled blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1459–1464, 1999     

Compatibilization effects of styrenic/rubber block copolymers in polypropylene/polystyrene blends

Compatibilizing effects of styrene/rubber block copolymers poly(styrene‐b‐butadiene‐b‐styrene) (SBS), poly(styrene‐b‐ethylene‐co‐propylene) (SEP), and two types of poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS), which differ in their molecular weights on morphology and selected mechanical properties of immiscible polypropylene/polystyrene (PP/PS) 70/30 blend were investigated. Three different concentrations of styrene/rubber block copolymers were used (2.5, 5, and 10 wt %). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the phase morphology of blends. The SEM analysis revealed that the size of the dispersed particles decreases as the content of the compatibilizer increases. Reduction of the dispersed particles sizes of blends compatibilized with SEP, SBS, and low‐molecular weight SEBS agrees well with the theoretical predictions based on interaction energy densities determined by the binary interaction model of Paul and Barlow. The SEM analysis confirmed improved interfacial adhesion between matrix and dispersed phase. The TEM micrographs showed that SBS, SEP, and low‐molecular weight SEBS enveloped and joined pure PS particles into complex dispersed aggregates. Bimodal particle size distribution was observed in the case of SEP and low‐molecular weight SEBS addition. Notched impact strength (a_k), elongation at yield (ε_y), and Young's modulus (E) were measured as a function of weight percent of different types of styrene/rubber block copolymers. The a_k and ε_y were improved whereas E gradually decreased with increasing amount of the compatibilizer. The a_k was improved significantly by the addition of SEP. It was found that the compatibilizing efficiency of block copolymer used is strongly dependent on the chemical structure of rubber block, molecular weight of block copolymer molecule, and its concentration. The SEP diblock copolymer proved to be a superior compatibilizer over SBS and SEBS triblock copolymers. Low‐molecular weight SEBS appeared to be a more efficient compatibilizer in PP/PS blend than high‐molecular weight SEBS. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 291–307, 1999     

Cocontinuous morphologies in polystyrene/ethylene–vinyl acetate blends: The influence of the processing temperature

The influence of the compression‐molding temperature on the range of cocontinuity in polystyrene (PS)/ethylene–vinyl acetate (EVA) copolymer blends was studied. The blends presented a broad range of cocontinuity when compression‐molded at 160°C, and they became narrower when compression‐molded at higher temperatures. A coarsening effect was observed in PS/EVA (60:40 vol %) blends upon compression molding at higher temperature with an increase in the phase size of the cocontinuous structure. Concerning PS/EVA (40:60 vol %) blends, an increase in the mixing and molding temperatures resulted in a change from a cocontinuous morphology to a droplet–matrix morphology. This effect was observed by selective extraction experiments and scanning electron microscopy. The changes in the morphology with the molding conditions affected the storage modulus. An increase in the storage modulus in blends compression‐molded at 160°C was observed as a result of dual‐phase continuity. An EVA copolymer with a higher vinyl acetate content (28 wt %) and a higher melt‐flow index resulted in blends with a broader range of cocontinuity. This effect was more pronounced in blends with lower amounts of PS, that is, when EVA formed the matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 386–398, 2003     

Compatibilization of polypropylene/polystyrene blends with poly(styrene-b-butadiene-b-styrene) block copolymer

The compatibilizing effect of the triblock copolymer poly(styrene-b-butadiene-b-styrene) (SBS) on the morphology and mechanical properties of immiscible polypropylene/polystyrene (PP/PS) blends were studied. Blends with three different weight ratios of PP and PS were prepared and three different concentrations of SBS were used for investigations of its compatibilizing effects. Scanning electron microscopy (SEM) showed that SBS reduced the diameter of the PS-dispersed particles as well as improved the adhesion between the matrix and the dispersed phase. Transmission electron microscopy (TEM) revealed that in the PP matrix dispersed particles were complex “honeycomblike” aggregates of PS particles enveloped and joined together with the SBS compatibilizer. Wide-angle X-ray diffraction (WAXD) analysis showed that the degree of crystallinity of PP/PS/SBS slightly exceeded the values given by the addition rule. At the same time, addition of SBS to pure PP and to PP/PS blends changed the orientation parameters A₁₁₀ and C significantly, indicating an obvious SBS influence on the crystallization process in the PP matrix. SBS interactions with PP and PS influenced the mechanical properties of the compatibilized PP/PS/SBS blends. Addition of SBS decreased the yield stress and the Young's modulus and improved the elongation at yield as well as the notched impact strength in comparison to the binary PP/PS blends. Some theoretical models for the determination of the Young's modulus of binary PP/PS blends were used for comparison with the experimental results. The experimental line was closest to the series model line. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 2625–2639, 1998     

Morphology and tensile properties of high-density polyethylene/natural rubber/thermoplastic tapioca starch blends: The effect of citric acid-modified tapioca starch

The effect of citric acid on the tensile properties of high density polyethylene (HDPE)/natural rubber (NR)/thermoplastic tapioca starch (TPS) blends was investigated. The ratio between HDPE/NR was fixed at 70/30 and used as the matrix system. TPS loadings, after modification with citric acid (TPSCA) and without modification (TPS), were varied from 0 to 30 wt %. The morphologies and tensile properties of HDPE/NR blends were evaluated as a function of TPS loadings. The tensile strength, Young's modulus, and elongation at break were found to decrease with increasing TPS loading. However, a slight improvement in the tensile strength of HDPE/NR/TPSCA blends at 5 and 10 wt % TPS loadings were observed. TPS can be partly depolymerised to produce a low viscosity product when processed with citric acid. TPS with low viscosity can easily disperse in the thermoplastic natural rubber (TPNR) system and reduce the surface tension at the interphase of TPS-HDPE/NR as shown by scanning electron microscopy (SEM). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Compatibilization of high‐impact polystyrene/high‐density polyethylene blends by styrene/ethylene–butylene/styrene block copolymer

Compatibilization of polymer blends of high‐impact polystyrene (HIPS) and high‐density polyethylene (HDPE) blend by styrene/ethylene–butylene/styrene (SEBS) was elucidated. Polymer blends containing many ratios of HIPS and HDPE with various concentrations of SEBS were prepared. The Izod impact strength and elongation at break of the blends increased with increases in SEBS content. They increased markedly when the HDPE content was higher than 50 wt %. Tensile strength of blends increased when the SEBS concentration was not higher than 5 pphr. Whenever the SEBS loading was higher than 5 pphr, the tensile strength decreased and a greater decrease was found in blends in which the HDPE concentration was more than 50 wt %. The log additivity rule model was applied to these blends, which showed that the blends containing the HIPS‐rich phase gave higher compatibility at the higher shear rates. Surprisingly, the blends containing the HDPE‐rich phase yielded greater compatibility at the lower shear rates. Morphology observations of the blends indicated better compatibility of the blends with increasing SEBS concentration. The relaxation time (T₂) values from the pulsed NMR measurements revealed that both polymer blends became more compatible when the SEBS concentration was increased. When integrating all the investigations of compatibility compared with the mechanical properties, it is possible to conclude that SEBS promotes a certain level of compatibilization for several ratios of HIPS/HDPE blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 742–755, 2004     

Morphology and mechanical properties of blends of linear low density polyethylene and poly(ethene‐propene‐1‐butene)

Blends of linear low density polyethylene (LLDPE) and ethene‐propene‐1‐butene copolymer (t‐PP) were obtained through mechanical mixing using a single‐screw extruder with different compositions: 20, 40, 50, 60, and 80 wt % of t‐PP. For this, two types of polyethylene were used: 1‐hexene comonomer and 1‐octene comonomer based. The same blends were prepared in a batch mixer and the torque and temperature were analyzed. The torque showed a decrease with increasing t‐PP content, indicating better processability of the mixture in comparison with LLDPE. The morphology of the blends was analyzed by SEM and showed a composition dependence. The mechanical properties of the blends were evaluated by tensile tests. The results revealed that the best properties were obtained in a 20% t‐PP blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1255–1261, 2006     

Effect of molecular structure of styrene–butadiene block copolymers on morphology,rheological properties,and impact strength of polystyrene/polyethylene blends

The effect of molecular structure of six model styrene–butadiene (SB) block copolymers with various number of blocks and two lengths of styrene blocks on morphology, rheological properties, and impact strength of polystyrene (PS)/high‐density polyethylene (PE) blends was studied. It was found that location of SB copolymers in the blends is determined by the length of styrene blocks. The length of styrene blocks has similar effects on impact strength and linear viscoelastic properties of the blends. On the other hand, the correlation was not found between the effects of a number of blocks on impact strength and linear viscoelastic properties of the blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2303–2309, 2003