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     

Toughening of polypropylene with styrene/ethylene‐butylene/styrene tri‐block copolymer: Effects of mixing condition and elastomer content

The effect of processing conditions and elastomer content on the toughening of Polypropylene (PP) by melt blending with styrene/ethylene‐butylene/styrene tri‐block copolymer (SEBS) in a twin‐screw extruder has been investigated. The parameters analyzed were: temperature profile, screw speed, and feed rate of the blend components. Their effect was evaluated through the mechanical properties (tensile strength and Izod impact resistance at room temperature) as well as the morphology of the dispersed phase by means of scanning electron microscopy (SEM). The results showed that the impact resistance increases with increasing rotor speed and feed rate and decreases when the temperature profile is increased. The parameter with the greatest effect on the mechanical properties was the variation in rotor speed. Despite the fact that impact resistance as high as 25 times that of neat PP has been achieved with blends containing 20 wt % SEBS, no significant modification in phase morphology has been observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2185–2193, 2001     

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 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     

Polypropylene/styrene‐ethylene‐butylene‐styrene thermoplastic elastomer nanocomposite films

Nanocomposite (polypropylene/styrene‐ethylene‐butylene‐styrene/organoclay) films were sheet‐extruded with differing clay concentrations. Blends were compounded using a high shear single screw reciprocating kneader. Results demonstrated that higher clay content increased the Shore A hardness of the films but induced a significant improvement in both O₂ and CO₂ barrier performance. J. VINYL ADDIT. TECHNOL., 13:46–52, 2007. © 2007 Society of Plastics Engineers.     

Toughened and stiffened nanocomposites based on an amorphous polyamide modified with both styrene/ethylene‐co‐butylene/styrene triblock copolymer and an organoclay

Polymer nanocomposites (PNs) based on an amorphous polyamide (aPA) modified with both a maleated rubber (mSEBS) for toughening, and with an organically modified organoclay for stiffening were obtained in the melt state. The PNs were highly dispersed and the organoclay was exclusively located in the aPA matrix. However, they showed a fine particle size that was larger than that of the corresponding blends. This indicates a lower compatibilization in the PNs that was attributed to a slight surfactant migration to the matrix during processing in the melt state. The increases in the modulus of elasticity upon organoclay (OMMT) addition were high enough to counteract the modulus decrease inherent to a 15% rubber addition. This allowed us to obtain a toughened aPA with a modulus similar to that of the unmodified aPA. The critical interparticle distance was lower in the PNs than in the corresponding blends. This decrease was attributed to the higher modulus of elasticity of the PNs matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Blends of styrene–butadiene–styrene triblock copolymer and isotactic polypropylene: morphology and thermomechanical properties

A set of blends of styrene–butadiene–styrene triblock copolymer (SBS) and isotactic polypropylene (i‐PP) in a composition range 0–100 % polypropylene by weight was prepared in a twin screw extruder. The morphology of the blends has been studied by transmission electron microscopy. The blends present phase separation. Dynamic mechanical measurements show an improvement of the mechanical properties of SBS when i‐PP is the dispersed phase. This reinforcing effect can be observed even at high temperatures when i‐PP is in the rubbery state. The mechanical properties of the blends have been interpreted using Takayanagi's block model. The melting and crystallization behaviour of the i‐PP in the blends has been studied by differential scanning calorimetry. The fractionated crystallization phenomenon has been observed in the blends where i‐PP forms the dispersed phase. The results are consistent with the morphology shown by the blends, in particular, with its phase inversion, which occurs at a composition near to 50% i‐PP. © 2000 Society of Chemical Industry     

Preparation and properties of styrene ethylene butylene styrene / polypropylene thermoplastic elastomer powder for selective laser sintering 3D printing

As one of the most important thermoplastic elastomer materials, the application of styrene ethylene butylene styrene (SEBS) in selective laser sintering (SLS) has not been reported. In this study, SEBS and polypropylene (PP) are blended and then pulverized at low temperatures. We find that SEBS with high molecular weight and styrene segment content is difficult to melt and flow under laser irradiation, which is not suitable for SLS 3D printing. SEBS with low molecular weight can be printed, and its tensile properties can reach 2.1Mpa and 134% elongation at break. We test the enhanced absorption effect of two different infrared absorbers and find that graphene (GE) can enhance absorption mainly rely on its special structure to increase the optical path of the laser. The absorption enhancement effect of each enhancer rises first and then decreases. 0.4‰ addition of GE can bring 22.5% enhancement. With the enhancement of GE, we get a product of 2.8 MPa tensile strength and 176% elongation at break.     

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     

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     

Molecular transport of alkanes through thermoplastic miscible blends of ethylene–propylene random copolymer and isotactic polypropylene

A new experimental protocol based on the measurements of sorption (S), desorption (D), resorption (RS), and redesorption (RD) has been used to study the molecular transport of aliphatic alkanes through the miscible blends of an ethylene–propylene random copolymer and an isotactic polypropylene over the temperature interval 25–70°C. Diffusion and activation parameters are evaluated and their dependencies on solvent size, shape, and nature are discussed. Estimated values of the molar mass between chain entanglements, kinetic rate constants, and overshoot index parameters have been influenced by the polymer–solvent interactions. The sorption–diffusion mechanism is found to be of anomalous type. © 1995 John Wiley & Sons, Inc.     

Thermoplastic elastomeric nanocomposites from poly[styrene–(ethylene‐co‐butylene)–styrene] triblock copolymer and clay: Preparation and characterization

Thermoplastic elastomer (TPE)–clay nanocomposites based on poly[styrene–(ethylene‐co‐butylene)–styrene] triblock copolymer (SEBS) were prepared. Natural sodium montmorillonite (MMT) clay was organically modified by octadecyl amine to produce an amine‐modified hydrophobic nanoclay (OC). Commercially available Cloisite 20A (CL20) and Cloisite 10A, tallow ammine modified nanoclays, were also used. The intergallery spacing of MMT increased on amine modification as suggested by the shifting of the X‐ray diffraction (XRD) peak from 7.6 to 4.5 and 3.8° in the cases of OC and CL20, respectively. The latter demonstrated no XRD peak when it was used at 2 and 4 parts phr in the SEBS system. Transmission electron microscopy studies showed the intercalation–exfoliation morphology in SEBS containing 4 parts of CL20₄–SEBS, agglomeration in SEBS having 4 parts of MMT, and mixed morphology in SEBS with 4 parts of OC systems. Locations of the clay particles were indicated by the atomic force micrographs. Mechanical and dynamic mechanical thermal analysis studies confirmed the best properties with the CL20₄–SEBS nanocomposites. Significant improvements in mechanical properties such as tensile strength, modulus, work to break, and elongation at break were achieved with the CL20₄–SEBS in polymer‐layered silicate nanocomposites. Dynamic mechanical studies further showed the affinity of the organoclays toward both segments of the TPE and a compatibilization effect with CL20 at a 4‐phr loading. Atomic force microscopy showed distinctly different morphologies in nanocomposites prepared through solution and melt processing. Comparisons of the mechanical, dynamic mechanical, and morphological properties of the nanocomposites prepared by melt and solution intercalation processes were done. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2040–2052, 2006     

Study on thermal expansion in injection‐molded isotactic polypropylene and thermoplastic elastomer blends

The linear thermal expansion coefficients (CLTEs) along flow direction (FD) for the injection‐molded blends composed of isotactic polypropylene (iPP) and various ethylenic thermoplastic elastomers (TPEs) were investigated using a thermo‐mechanical analyzer. The iPP/TPE blends with higher comonomer contents in the TPE showed extremely low CLTE. TEM observation revealed that the array of the TPE whose MFR was adjusted to be higher than the iPP matrix was in lamella‐like sheet stacked normal to normal direction (ND) with being elongated along both FD and transverse‐to‐flow direction. At higher magnification of TEM, the iPP lamellae in the blend with higher comonomer contents in the TPE deeply penetrated into the TPE phase as a consequence of the faster iPP crystallization before the completion of the phase‐separation. Hence, the location of the iPP amorphous chains would change depending on the comonomer contents in the TPE; in the case of the iPP/TPE blend with higher comonomer contents, large amount of the iPP amorphous chains would be trapped inside the TPE phase because of incomplete phase‐separation arrested by faster crystallization. Therefore, the extremely low CLTE for the iPP/TPE blend with higher comonomer contents was accounted for by the simultaneous suppression of the thermal expansions from both the TPE phase and the iPP amorphous chains trapped inside the TPE by rigid iPP crystalline lamellae connecting in parallel with the TPE phase. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical and morphological properties of white rice husk ash filled polypropylene/ethylene‐propylene‐diene terpolymer thermoplastic elastomer composites

The performance of white rice husk ash (WRHA) as filler for polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) thermoplastic elastomer (TPE) composites was investigated. The composites with different filler loadings were prepared in a Brabender plasticorder internal mixer. Both unvulcanized and dynamically vulcanized composites were prepared. Mixing and vulcanization processes of the composites were monitored through the typical Brabender torque‐time curves. The mechanical properties and morphology of the composites were also studied. The Brabender torque curves revealed that the dynamic vulcanization process employed was successful and incorporation of filler has no adverse effect on the processibility of the composites. Incorporation of WRHA improves the tensile modulus and flexural modulus and lowers tensile strength, elongation at break, tear strength, and toughness of both types of composites. Dynamic vulcanization significantly enhances the mechanical and TPE properties of the composites. Dynamic mechanical analysis (DMA) study revealed the existence of two phases in both types of composites. It further shows that neither dynamic vulcanization nor filler agglomeration has played a prominent role in the compatibility of the composites. Thermogravimetric investigation shows that dynamic vulcanization or WRHA loading has not adversely affected the thermal stability of the composites. The scanning electron micrographs provide evidence for the tendency to form filler agglomerates with increasing filler loading, better filler dispersion of dynamically vulcanized composites over unvulcanized composites, and effective vulcanization of elastomer phase of the composites in the presence of filler. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 438–453, 2002     

Maleic anhydride/styrene melt grafting and crosslinking onto ethylene‐octene copolymer

Melt grafting of the multimonomer system of maleic anhydride (MAH)/styrene (St) onto ethylene‐octene copolymer (POE) was performed by a twin‐screw extruder. The effects of St and initiator contents as well as MAH/St on the grafting reaction were investigated. The structure and properties of the grafted POE were characterized by the Fourier transform infrared spectroscopy, melt flow index, dynamic rheological behaviors, and thermogravimetric analysis. It is shown that the addition of St can significantly enhance MAH grafting degree onto POE. MFI values of grafted POE are affected not only by MAH/St copolymer concentration, but also by initiator concentration. These data indicate that the interaction and reaction between MAH and St monomers plays an important role in the grafting reaction. St improves the grafting reactivity of MAH and reacts with MAH before the two monomers graft onto POE. And high grafting degree can be obtained while the gel content is still low. Compared with neat POE, grafted POE shows different dynamic rheological behaviors and high thermal stability. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Rheological properties and morphological evolutions of polypropylene/ethylene‐butene copolymer blends

This work aims at studying the extensional rheological behavior of polypropylene (PP), ethylene‐butene copolymer (PEB) and their blends in the melt. The weight fraction of the PEB in the blend is 20 and 40%, respectively. Dynamic mechanical analysis shows that these two blends exhibit two tanδ peaks corresponding to the glass transitions of the PP and PEB, respectively. Differential scanning calorimeter results indicate that the presence of the PEB does not alter the melting and crystallization temperatures of the PP. Master curves at 170°C are constructed for the storage and loss modulus as well as complex viscosity. The extensional behavior of the PP, PEB, and their two blends is studied. The PEB enhances the strain hardening of the PP. Changes in the blend morphology during the extensional analysis are also studied. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Differential scanning calorimetry of copolymer of isotactic polypropylene backbone with grafted poly(ethylene‐co‐propylene) branches

A series of graft polymers having polypropylene (PP) backbone and poly(ethylene‐co‐propylene) (EPR) side chains was prepared. PP backbone molecular weight (M_n) was 28–98 kg/mol, EPR side chain M_n was 2.6–17 kg/mol, and EPR content was 0–16 wt %. In this work, thermal analysis of the copolymers was performed using differential scanning calorimetry (DSC). Nonisothermal crystallization was performed at different cooling rates. The DSC thermograms revealed multiple melting peaks for slowly cooled samples, most likely the result of the melting of thinner tangential lamellae followed by the melting of thicker radial lamellae. Equilibrium melting temperature (T_m⁰) was determined using the linear Hoffman–Weeks method. Another approach was also used for determining T_m⁰: melting temperature (T_m) and crystallization temperature (T_c) were plotted as functions of logarithmic cooling rate. Linear relationships were observed for all samples with the cross points as T_m⁰'s. As cooling rate decreased, T_c, T_m, and enthalpy of fusion (ΔH_f) increased. T_m and T_m⁰ increased with increasing PP M_n. T_c and T_m were unaffected by the grafting of EPR onto the PP backbone. T_m⁰ and ΔH_f decreased as EPR content increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3380–3388, 2006     

Dynamic‐mechanical and thermal characterization of polypropylene/ethylene–octene copolymer blend

Polypropylene/Ethylene–Octene copolymer (PP/EOC) blends were prepared by melt blending technique followed by compression molding. The effect of addition of EOC on the mechanical behavior of the PP matrix was investigated. Tensile and flexural strengths decreased with the incorporation of EOC. However, the impact strength of the matrix polymer increased in all the blend systems. The blends prepared at 30% EOC content showed an increase in the impact strength to the tune of 380% as compared with polypropylene (PP) matrix. The morphology of the fractured surfaces was investigated employing Scanning Electron Microscopy. SEM micrographs depicted the formation of biphase structure, wherein the EOC phases were homogeneously dispersed as small droplets within the PP matrix. WAXD patterns revealed that the α monoclinic form of isotactic PP does not show any significant change with the incorporation of EOC up to 70 wt %. DSC thermograms revealed a decrease in the melting temperature of the virgin matrix with the addition of EOC. The blend system at 50% EOC exhibited a broad crystallization exotherm at 75°C thus indicating multiple crystallization behavior primarily attributed to the difference in the nucleation process. Further DMA analysis showed presence of two different relaxation peaks corresponding to the T_g of EOC and PP matrix respectively, confirming the formation of a biphase structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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     

The effect of curing system on the properties of the thermoplastic elastomer foams of ethylene‐vinyl acetate copolymer and styrene‐butadiene and ethylene‐propylene‐diene monomer rubbers

Thermoplastic elastomer (TPE) foams have important application in electrical, toys, and other industries. Several foams were prepared by ethylene‐vinyl acetate copolymer (EVA) lonely, and in combination with styrene‐butadiene and ethylene‐propylene‐diene monomer rubbers (SBR and EPDM). The effects of crosslinking and foaming agents and EVA type on density and mechanical properties of the cured foams with two curing systems, peroxide and sulfur‐peroxide with potential use in automotive applications, were studied. The results showed that proposed compounds formulations were foamed properly. The viscosity of the EVA was a key factor for the density values of the formed foams. The densities of the cured foams with peroxide system with various SBR contents were higher when compared with cured foams with sulfur‐peroxide system. With increasing foaming agent, the densities of the foams were reduced for studied curing systems. The densities of the EVA–EPDM foams were lower than those of the EVA–SBR foams in the same studied conditions. Increasing rubber in foam formulation had adverse effect on tensile properties of the foams. The existence of the talc powder in foam formulation had important role on the shape and type of the formed cells and resulted in foams with mostly closed cells. The results of this study help the automotive article designer to produce suitable TPE foam. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45357.