Toughening of polypropylene with styrene/ethylene‐butylene/styrene tri‐block copolymer: Effects of reactive and nonreactive compatibilization

The effects of compatibilization on the toughening of polypropylene (PP) by melt blending with styrene/ethylene‐butylene/styrene tri‐block copolymer (SEBS) in a twin‐screw extruder were investigated. The compatibilizers used were SEBS functionalized with maleic anhydride (SEBS‐g‐MA), PP functionalized with acrylic acid (PP‐g‐AA), and bifunctional compound p‐phenylenediamine (PPD). The effects of the compatibilization were evaluated through the mechanical properties as well as through the determination of the phase morphology of the blends by scanning electron microscopy. Reactive compatibilized blends show up to a 30‐fold increase in impact strength compared with neat PP; likely the result of the reaction of the bifunctional compound (PPD) with the acid acrylic and maleic anhydride groups, this increase in strength rendered both morphological and mechanical stability to these blends. The addition of PPD to the blends significantly changed their phase morphologies, leading to larger average diameters of the dispersed particles, probably as a result of the morphological stabilization at the initial processing steps during extrusion, with the occurrence of chemical reactions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3466–3479, 2002     

Toughening of polypropylene with styrene/ethylene‐butylene/styrene triblock copolymer: Effects of reactive and nonreactive compatibilization

The effects of the compatibilization on the toughening of polypropylene (PP) by melt blending with styrene/ethylene‐butylene/styrene triblock copolymer (SEBS) in a twin‐screw extruder were investigated. The compatibilizers used were an SEBS functionalized with maleic anhydride, a PP functionalized with acrylic acid, and a bifunctional compound, p‐phenylenediamine (PPD). The effects of the compatibilization were evaluated through the mechanical properties and by the determination of the phase morphology of the blends by scanning electron microscopy. Reactive compatibilized blends show up to a 30‐fold increase in impact strength compared to neat PP, which was likely to have been due to the reaction of the bifunctional compound (PPD) with the acid acrylic and maleic anhydride groups, which rendered both morphological and mechanical stability to these blends. The addition of the PPD to the blends significantly changed their phase morphologies, leading to larger dispersed particles' average diameters, probably due to the morphological stabilization at the initial processing steps during extrusion, with the occurrence of the chemical reactions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1081–1094, 2003     

Highly transparent thermoplastic elastomer from isotactic polypropylene and styrene/ethylene‐butylene/styrene triblock copolymer: Structure‐property correlations

Polypropylene (PP) is one of the most useful general purpose plastics. However, the poor transparency and brittleness of PP restricts its applications in the field of medical and personal care where silicone and polyvinyl chloride (PVC) are presently used. This work concentrates on developing highly transparent elastomeric PP blends and also thermoplastic elastomer by blending isotactic polypropylene (I‐PP) with styrene/ethylene‐butylene/styrene (SEBS) triblock copolymer. PP/SEBS blend derived from high melt flow index (MFI) PP and high MFI SEBS exhibit remarkable transparency (haze value as low as 6%) along with good percentage of elongation and processability. The reduction in difference of refractive index (RI) between PP and SEBS has been observed by blending SEBS with PP. The wide angle X‐ray diffraction studies show that there is significant reduction in the percentage crystallinity of PP by the addition of SEBS block copolymer. Temperature‐dependent polarized light microscopy studies reveal the reduction in spherulites size by the addition of SEBS block copolymer. Transmission electron micrographs show that the SEBS polymer forms a fine lamellar structure throughout the PP matrix with phase inversion at higher SEBS concentration. Development of phase morphology, crystalline morphology, and crystallinity in different blends has been analyzed and microstructure‐haze correlations have been developed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

苯乙烯-二元乙丙橡胶嵌段共聚物增韧聚丙烯

考察了苯乙烯-二元乙丙橡胶嵌段共聚物（SEP）和三元乙丙橡胶（EPDM）对聚丙烯（PP）的增韧作用。结果表明，SEP比EPDM具有更好的增韧效果。SEP以核-壳形态分布于PP基质中，有效地诱导PP基质产生银纹和剪切屈服，消耗大量的冲击能，SEP用量为10份时，PP/SEP共混材料的缺口冲击强度较纯PP的提高7-8倍，超过了20份EPDM增韧PP的效果，是一种新型的PP抗冲增韧改性剂。     

Crystallization behavior and mechanical properties of polypropylene random copolymer/poly(ethylene‐octene) blends

New polymer blends of polypropylene random copolymer (PP‐R) and poly(ethylene‐octene) (POE) were prepared by melt‐blending process using a corotating twin‐screw extruder. The POE content was varied up to 35%. The toughening efficiency of POE for PP‐R was evaluated by the mechanical properties of the resulted PP‐R/POE blends. The crystallization behavior and morphology of the blends were also studied. Results show that POE acts as nucleation agent to induce the crystallization of PP‐R matrix at higher crystallization temperature. Super‐toughened PP‐R/POE blends (Izod impact strength more than 500 J/m) can be readily achieved with only 10 wt % of POE. The high toughness of PP‐R/POE is attributed to cavitation and shear yielding of matrix PP‐R, as revealed by the morphology studies. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Rheological,mechanical, thermal,and morphological properties of polypropylene/ethylene‐octene copolymer blends

Rheological and morphological studies were performed on polymer blends of ethylene‐octene copolymer [polyethylene elastomer (PEE)] and polypropylene (PP). The viscosities of PEE, PP, and PEE/PP blends were analyzed using an Instron capillary rheometer and a Rheometrics Dynamic Stress Rheometer, SR 200. A non‐Newtonian flow behavior was observed in all samples in the shear rate range from 27 to 2700 s⁻¹, whereas at shear rates in the range from 0.01 to 0.04 s⁻¹, a Newtonian flow behavior was verified. The scanning electron micrographs showed that dual‐phase continuity may occur between 50 and 60 (wt %) of PEE. This result is consistent with the Sperling's model. The mechanical analysis showed that PEE/PP, with 5 wt % of PEE, presented an increase on the mechanical properties and as the PEE content increased, a negative deviation in relation to an empirical equation was observed. Thermal analysis showed that there were no change in the crystallization behavior of the matrix when different elastomer contents were added. Dynamic mechanical thermal analysis showed that samples with low PEE contents presented only one peak, indicating a certain degree of miscibility between the components of these blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 692–704, 2000     

Toughening isotactic polypropylene and propylene-ethylene block copolymer with styrene-ethylene butylene-styrene triblock copolymer

Dynamic mechanical properties, low-temperature impact behavior, flexural modulus and heat distortion temperature (HDT) of isotactic polypropylene (i-PP) and propylene-ethylene block copolymer (Co-PP) toughened with styrene-ethylene butylene-styrene triblock copolymer (SEBS), at blending ratios of 0–30 phr, were studied and compared. A scanning electron microscopic morphology study of the impact-fractured surfaces demonstrated the changes in fracture mechanisms at various temperatures and SEBS contents. SEBS remarkably improves the impact endurance in the lower-temperature range when blended with Co-PP in comparison with i-PP, due to the increased compatibility in the interface between SEBS particles and the Co-PP matrix.     

Rheological study of polypropylene copolymer/polyolefinic elastomer blends

Blends of polypropylene copolymer (PP‐cp) and a polyolefinic elastomer (POE) were prepared by a melt‐blending process at 210°C and 60 rpm using a counterrotating twin‐screw extruder. The POE content was varied up to 25%. The shear viscosity over a wide range of shear rate was measured. All blend compositions showed well‐defined zero shear viscosity and shear thinning behavior. The melt viscosity values were between those of the principal components in all cases. Rheology of blends shows different behavior up to concentrations of POE corresponding to the tough–brittle transition. The linear viscoelastic properties (G′, G″, η*, η′, η″) were used to check the miscibility of the two components in the melt state. All blend compositions showed a good degree of miscibility over the range of POE concentrations studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 665–671, 2002; DOI 10.1002/app.10376     

Toughening and brittle‐tough transition in blends of an amorphous polyamide with a modified styrene/ethylene‐butylene/styrene triblock copolymer

Amorphous polyamide (aPA)/maleated styrene/ethylene‐butylene/styrene triblock copolymer (mSEBS) blends with a mSEBS content up to 25% were obtained in the melt state with the aim of toughening the notch sensitive pseudoductile matrix, and of studying the parameters that influence the morphology that leads to the brittle/tough transition. The increase in the T_g of the rubbery phase, which depended on the maleinized copolymer content, indicated the presence of reacted copolymers. These copolymers should decrease the interfacial tension, thus allowing the presence of a fine dispersed particle size. The impressive (27‐fold) toughness increase observed, which is among the largest observed in toughened blends, took place at 15% mSEBS content. The critical interparticle distance (τ_c) of the blends was smaller than that of polyamide 6 (PA6)/mSEBS blends tested at the same conditions. Having ruled out the possible influence of other parameters, the lower τ_c of the aPA/mSEBS blends of this study is attributed to their higher interfacial adhesion that was inferred by the calculation of the solubility parameters and by the measured interfacial toughness. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Isotactic polypropylene/polystyrene blends: Effects of the addition of a graft copolymer of propylene with styrene

A novel graft copolymer of unsaturated propylene with styrene (uPP-g-PS) was added to binary blends of isotactic polypropylene (iPP) and atactic polystyrene (aPS) with a view to using such a copolymer as compatibilizer for iPP/aPS materials. Differential scanning calorimetry, optical microscopy, scanning electron microscopy (SEM), wide angle X-ray scattering, and small angle X-ray scattering (SAXS) techniques have been carried out to investigate the phase morphology and structure developed in solution-cast samples of iPP/aPS/uPP-g-PS ternary blends. It was found that the uPP-g-PS addition can provide iPP/aPS-compatibilized materials and that the extent of the achieved compatibilization is composition-dependent. Blends of iPP and aPS exhibited a coarse domain morphology that is characteristic of immiscible polymer systems. By adding 2% (wt/wt) of uPP-g-PS copolymer a very broad particle-size distribution was obtained, even though the particles appeared coated by a smooth interfacial layer, as expected according to a core–shell interfacial model. With increasing uPP-g-PS content (5% wt/wt), a finer dispersion degree of particles, together with morphological evidence of interfacial adhesion, was found. With further increase of uPP-g-PS amount (10% wt/wt) the material showed such a homogeneous texture that neither domains of dispersed phase nor holes could be clearly detected by SEM. The type of interface developed in such iPP/aPS/uPP-g-PS blends was accounted for by an interfacial interpenetration model. The iPP crystalline texture, size, neatness, and regularity of iPP spherulites crystallized from iPP/aPS/uPP-g-PS blends were found to decrease when the copolymer content was slightly increased. Assuming, for the iPP spherulite fibrillae, a two-phase model constituted by alternating parallel crystalline lamellae and amorphous layers, it was shown by SAXS that the phase structure generated in iPP/aPS/uPP-g-PS blends is characterized by crystalline lamellar thickness (L_c) and interlamellar amorphous layer thickness (L_a) higher than that shown by plain iPP; the higher the copolymer content, the higher the L_c and L_a. It should be remarked that considerably larger increases have been found in L_a values. Such SAXS results have been accounted for by assuming that a cocrystallization phenomenon between propylenic sequences of the uPP-g-PS copolymer and iPP occurs and that during such a process PS chains grafted into copolymer sequences remain entrapped in iPP interlamellar amorphous layers, where they form their own separate domains. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1539–1553, 1997     

Super‐toughed polymer blends derived from polypropylene random copolymer and ethylene/styrene interpolymer

In this article, blends of polypropylene random copolymer (PP‐R) with a novel impact modifier, namely ethylene/styrene interpolymer (ESI), were prepared to evaluate the effectiveness of ESI in toughening PP‐R and the influence of ESI content on the mechanical, thermal, and rheological properties of polymer blends. Results showed that super‐toughened PP‐R/ESI blends (ca. Izod impact strength ≥ 500 J/m) were readily achieved with only 5 wt % ESI. The blends exhibited significant improvement in both impact strength and elongation, while small loss in tensile strength and elastic modulus when increasing ESI content. ESI had a nucleating effect that caused PP matrix to crystallize at higher temperatures, whereas PP‐R/ESI blends presented lower melting temperatures (T_m) than PP‐R matrix and T_m decreased with the increment of ESI content. Rheology study indicated that both PP‐R matrix and PP‐R/ESI blends presented shear thinning behaviors during melt processing. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Impact modification of polypropylene copolymer with a polyolefinic elastomer

Polypropylene copolymer (PP‐cp) has a large number of applications and is preferred over the homopolymer due to its higher impact strength. These impact properties can be further improved by blending with polyolefinic elastomer (POE). Blends were prepared by using commercially available POE (Engage® EG 8150, Dupont–Dow Elastomers), by varying POE content up to 25%. The effect of processing conditions on the properties of the blends was studied. Although impact strength increased, flexural modulus decreased. Dicumyl peroxide caused chain scission of PP‐cp rather than crosslinking of POE. The results seem to indicate that there may be optimum concentration of POE around 10% for the polymers used in the present work. The grade of PP‐cp used in this work contained about 10–11% ethylene content (rubber phase around 17–18%). These results match with general observations that brittle–tough transition for PP occurs when total elastomer content is about 20–25%. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1480–1484, 2000     

Melting,nonisothermal crystallization behavior and morphology of polypropylene/random ethylene—propylene copolymer blends

The melting, nonisothermal crystallization behavior and morphology of blends of polypropylene (PP) with random ethylene–propylene copolymer (PP‐R) were studied by differential scanning calorimetry, polarized optical microscopy, scanning electron microscopy, and X‐ray diffraction. The results showed that PP and PP‐R were very miscible and cocrystallizable. Modified Avrami analysis was used to analyze the nonisothermal crystallization kinetics of the blends. The values of the Avrami exponent indicated that the crystallization nucleation of the blends was heterogeneous, the growth of the spherulites was tridimensional, and the crystallization mechanism of PP was not affected by PP‐R. The crystallization activation energy was estimated using the Kissinger method. An interesting result was obtained with the modified Avrami analysis and the Kissinger method, whose conclusions were in good agreement. The addition of a minor PP‐R phase favored an increase in the overall crystallization rate of PP. Maximum enhancing effect wass found to occur with a PP‐R content of 20 wt %. The relationship between the composition and the morphology of the blends is discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 670–678, 2006     

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     

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     

A novel combination of sandwich and co‐continuous structure based on polypropylene and styrene‐butadiene‐styrene block copolymer formed with wide range of polypropylene content

The styrene–butadiene–styrene block copolymer (SBS)/polypropylene (PP) blends with a unique sandwich layered co‐continuous structure were prepared by melt compounding. Differing from single conventional co‐continuous and sandwich structure, this structure was formed, where pure PP and co‐continuous SBS/PP phase acting as the face sheets and core. Even though the volume content was 20 or 10 vol %, PP always amazingly formed a continuous phase in SBS/PP blends, whereas the morphology of SBS phase relatively changed from dispersed particles to continuous network as its content increased to 50 vol %. For immiscible SBS/PP blends, due to the huge difference of complex viscosity and surface tension between SBS and PP, a pure PP layer existed on the surface of blends which can be ascribed to the PP enrichment. Herein, the structure of blends with more than 50 vol % SBS was presented as sandwich layered co‐continuous structure by combining the pure PP layer and co‐continuous structure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46580.     

Morphology and mechanical properties of binary blends of polypropylene with statistical and block ethylene‐octene copolymers

In the present work, statistical (EOCs) and block (OBCs) ethylene‐octene copolymers, with similar densities and crystallinities, were used as impact modifiers of isotactic polypropylene (iPP), and the toughening effects of these two types of elastomers were compared. The viscosity curves of EOCs were similar to those of OBCs with equivalent melt flow rate (MFR), enabling a comparison of the viscosity ratio and elastomer type as independent variables. No distinct differences on the crystal forms and crystal perfection of iPP matrix in various blends were observed by thermal analysis. Morphological examination showed that OBCs form smaller dispersed domains than EOCs with similar MFRs. The flexural modulus, yield stress, stress and strain at break showed the same variation tendency for all the investigated polypropylene/elastomer blends. However, the room temperature Izod impact toughness of iPP/OBC blend was higher than that of iPP/EOC blend containing elastomer with the similar MFRs. The experimental results indicated that the compatibility of iPP/OBCs was much higher than that of iPP/EOCs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of nylon 6 on fracture behavior and morphology of tough blends of poly(2, 6‐dimethyl‐1,4‐phenylene oxide) and maleated styrene‐ethylene‐butadiene‐styrene block copolymer

Ternary blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO), nylon 6, and styrene‐ethylene‐butadiene‐styrene block copolymer grafted with maleic anhydride (SEBS‐g‐MA) were prepared via a melt extrusion, and the fracture behavior, morphology, mechanical properties, and rheology were studied. The compatibilization of the blended components was confirmed by differential scanning calorimetry (DSC) analysis. Mechanical properties evaluation demonstrated that incorporation of nylon 6 resulted in an improvement of the tensile strength, but reduction of both the notched Izod impact strength and elongation at break. Transmission electron microscopy (TEM) observation revealed that the network structure of SEBS‐g‐MA domain was gradually destroyed by incorporating the nylon 6. A conversion of SEBS‐g‐MA domain from the network to the irregular dispersed phase took place when the nylon 6 content reached 20 wt %, which resulted in a reduction of the impact strength. Fracture morphology implied that increase of the tensile strength was caused by the plastic deformation of matrix. Rheology investigation indicated that the melt viscosities could be reduced significantly with increasing the content of nylon 6; thus, the processability was improved. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99:3336–3343, 2006     

Thermo‐oxidative decomposition kinetics of elastomeric composites based on styrene‐(ethylene‐butylene)‐styrene triblock copolymer and organomontmorillonite

The elastomeric nanocomposites based on organomontmorillonite (OMMT) and styrene‐(ethylene‐butylene)‐styrene (SEBS) thermoplastic elastomer were prepared by melt processing using maleic anhydride grafted SEBS (SEBS‐g‐MA) as compatibilizer. Thermo‐oxidative decomposition behavior of the neat components and the nanocomposites were investigated using thermogravimertic analysis (TGA) in air atmosphere. The isoconversional method is employed to study the kinetics of thermo‐oxidative degradation. The heating modes and the composition of nanocomposites were found to affect the kinetic parameters (E_a, lnA and n). The E_a and lnA values of SEBS, OMMT, and their composites are much higher under dynamic heating than under isothermal heating. The reaction order (n) of OMMT was lower than those of SEBS and their composites. The obtained TG profiles and calculated kinetic parameters indicated that the incorporation of OMMT into SEBS significantly improved the thermal stability both under dynamic heating and under isothermal heating. The simultaneously obtained DSC data showed that the enthalpy of thermal decomposition decreased with OMMT loading. No significant change in the nonisothermal and isothermal stability of the nanocomposites with addition of SEBS‐g‐MA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Correlation of miscibility and mechanical properties of polypropylene/olefin block copolymers: Effect of chain composition

This study examines the miscibility and mechanical properties of isotactic polypropylene (iPP) and olefin block copolymer (OBC) blends (70/30 wt %). The blends exhibit phase-separated morphology. The OBC domain size decreases with increasing the 1-octene content in the soft segment. The crystallization, melting behavior, and the long spacing of the iPP component in the blends are nearly the same as those of neat iPP, while the T_g of the iPP component shifts slightly to lower temperature. “Blocky” OBC is immiscible with iPP, while the soft segment rich polymers in OBC could be partially miscible with iPP. The impact strength of the blends is greatly increased with increasing the 1-octene content in the OBC soft segment. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012