Process-structure-property relationship of meltblown poly (styrene–ethylene/butylene–styrene) nonwovens

With the advance of the thermoplastic plastic elastomer (TPE) technology, there are growing interest and needs for using these materials in the meltblowing process where benefits of small fiber diameters of meltblowns can be combined with rubber-like elastic properties of elastomers. Performances and utilities of wide ranges of meltblown products such as facemask, medical barrier, wound-care, diaper can be drastically improved with additions of TPE. In this study, a new elastomeric meltblown fabric was successfully made with the styrene–ethylene/butylene–styrene (SEBS) block copolymer, and the relationship among structure, tensile properties, and meltblowing process parameters are studied. We found that median fiber diameter increases with the polymer mass throughout and decreases with air pressure, and fabric solidity has significantly influenced by die collector distance (DCD). The pore sizes of the fabrics are directly influenced by fiber diameters at the given DCD, but higher DCD increases the pore size due to their open structures. All SEBS nonwovens exhibit high strain at break, larger than 400%. Processing parameters significantly affect tensile properties, and this can be attributed to the fabric structure changes. The reduction of fiber diameter tends to increase the tensile strength of the fabric as it created more fiber-to-fiber bond points.     

纳米电气石/聚丙烯驻极熔喷非织造布的研制

研制了一种纳米电气石改性驻极体熔喷聚丙烯非织造布母粒,并采用电晕放电法制备出纳米电气石/聚丙烯驻极熔喷非织造布。探讨了纳米电气石在聚丙烯树脂中的分散状况及改性母粒的流变性能,同时对非织造布力学性能、表面电荷密度和过滤性能进行了测试。结果表明:电气石能较好地分散在聚丙烯树脂中;加入特种电气石之后,纤网的机械性能有所下降;驻极体熔喷非织造布的驻极效果大大改善,其表面电荷密度、过滤性能均有明显提高。     

Melt rheology and morphology of PP/SEBS/PC ternary blend

Melt rheological properties of the ternary blend of isotactic polypropylene (PP), styreneethylene–butylene–styrene terpolymer (SEBS), and polycarbonate (PC), PP/SEBS/PC, are studied in a wide range of composition, such that PP is the matrix and SEBS and PC are the minor components, with the proportion of one varying from 0 to 30% at various fixed compositions of the other. The respective binary blends, PP/SEBS and PP/PC, studied as the reference systems for interpretation of results on the ternary blends yielded interesting new information about the morphology development and its correlation with melt rheological properties of these binary blends. The studies include the measurement of melt rheological properties on a capillary rheometer in the shear rate range 10¹–10⁴ s^?1 at a fixed temperature of 240°C. The data presented as conventional flow curves are analyzed for the effect of blend composition and shear rate on pseudoplasticity, melt viscosity, and melt elasticity, and role of each individual component is identified. Morphology of dispersed phases of these blends is studied through scanning electron microscopy of the cryogenically fractured and suitably etched surfaces. Variations of morphology with blend composition and shear rate showed interesting correlation with melt rheological properties, which are discussed in detail. An important finding of the morphological studies is that in the PP/SEBS/PC ternary blend the SEBS phase forms two types of morphologies depending on the blend composition and shear rate: (i) simple droplets and (ii) boundary layer at the surface of the PC droplets. © 1993 John Wiley & Sons, Inc.     

Interface modification of compatibilized polyethylene terephthalate/polypropylene blends: Effect of compatibilization on thermomechanical properties and thermal stability

Polyethylene terephthalate (PET) and polypropylene (PP) are incompatible thermoplastics because of differences in chemical structure and polarity, hence their blends possess inferior mechanical and thermal properties. Compatibilization with a suitable block/graft copolymer is one way to improve the mechanical and thermal properties of the PET/PP blend. In this study, the toughness, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA) of PET/PP blends were investigated as a function of different content of styrene‐ethylene‐butylene‐styrene‐g‐maleic anhydride (SEBS‐g‐MAH) compatibilizer. PET, PP, and SEBS‐g‐MAH were melt‐blended in a single step using the counter rotating twin screw extruder with compatibilizer concentrations of 0, 5, 10, and 15 phr, respectively. The impact strength of compatibilized blend with 10 phr SEBS‐g‐MAH increased by 300% compared to the uncompatibilized blend. Scanning electron microscope (SEM) micrographs show that the addition of 10 phr SEBS‐g‐MAH compatibilizer into the PET/PP blends decreased the particle size of the dispersed PP phase to the minimum level. The improvement of the storage modulus and the decrease in the glass transition temperature of the PET phase indicated an interaction among the blend components. Thermal stability of the PET/PP blends was significantly improved because of the addition of SEBS‐g‐MAH. J. VINYL ADDIT. TECHNOL., 23:45–54, 2017. © 2015 Society of Plastics Engineers     

Comparison of mechanical properties of PP/SEBS blends at intermediate and high strain rates with SiO2 nanoparticles vs. CaCO3 fillers

The present article focuses on the effect of two types of inorganic fillers (SiO₂ and CaCO₃) on the mechanical properties of PP/SEBS blend. The nominal particle diameters of SiO₂ and CaCO₃ are 7 nm and 1 μm, respectively. The studied blend ratios were PP/SEBS/SiO₂ (CaCO₃) = 75/22/3 and 73/21/6 vol %. The morphology of polymer blends was observed and the distributions of the SEBS, SiO₂, and CaCO₃ particles were analyzed by transmission electron microscopy (TEM). Tensile tests were conducted at nominal strain rates from 3 × 10^?1 to 10² s^?1. The apparent elastic modulus has the local strain‐rate dependency caused by SiO₂ nanoparticles around SEBS particles in the blend of PP/SEBS/SiO₂. The yield stress has weak dependency of morphology. The absorbed strain energy has strong dependency of the location of SiO₂ nanoparticle or CaCO₃ fillers and SEBS particle in the morphology. It is considered that such morphology, in which inorganic nanoparticles are located around SEBS particles, can prevent the brittle fracture while the increased local strain rate can enhance the apparent elastic modulus of the blend at the high strain rate. On the basis of the results of this study, the location and size of inorganic nanoparticles are the most important parameters to increase the elastic modulus without decreasing the material ductility of the blend at both low and high strain rates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of polypropylene on the rheology of co‐continuous PS/SEBS blends

Polypropylene (PP) was added to a co‐continuous blend of polystyrene (PS) and styrene‐ethylene/butylene‐styrene (SEBS) to investigate the effect of PP on the morphology and rheological behavior of PS/SEBS blends. For this purpose, a reference blend of 50 wt% PS and 50 wt% SEBS was chosen and an isotactic PP was added to it by increments of 10 wt% up to a maximum of 50 wt% of the total weight. Environmental SEM (ESEM) studies on the PS/SEBS/PP blends showed that PP could be added up to 10 wt% without changing the morphology of the co‐continuous PS/SEBS blend, whereas at 20 wt% PP formed a separate discrete phase. The discrete PP phase finally formed a fully developed matrix structure from 40 wt% onwards. Dynamic rheological measurements showed that at low frequencies the storage modulus was largely unaffected by addition of PP in small concentrations (up to 10 wt%), showing a significant effect of the PP/SEBS interface at low deformation rates. Melt strength tests on the PS/SEBS/PP blends showed the existence of a proportional correlation with their corresponding storage moduli, measured at frequencies from 10–100 rad/s. POLYM. ENG. SCI., 45:1432–1444, 2005. © 2005 Society of Plastics Engineers     

SBS and SEBS block copolymers as impact modifiers for polypropylene compounds

Blends of polypropylene (PP) and thermoplastic elastomers (TPE), namely SBS (styrene‐butadiene‐styrene) and SEBS (styrene‐ethylene/1‐butene‐styrene) block copolymers, were prepared to evaluate the effectiveness of the TPE type as an impact modifier for PP and influence of the concentration of elastomer on the polymer properties. Polypropylene homopolymer (PP‐H) and ethylene–propylene random copolymer (PP‐R) were evaluated as the PP matrix. Results showed that TPEs had a nucleating effect that caused the PP crystallization temperature to increase, with SBS being more effective than SEBS. Microstructure characterization tests showed that in most cases PP/SEBS blends showed the smallest rubber droplets regardless of the matrix used. It was seen that SEBS is a more effective toughening agent for PP than SBS. At 0°C the Izod impact strength of the PP‐H/SEBS 30% b/w blend was twofold higher than the SBS strength, with the PP‐R/SEBS 30% b/w blend showing no break. A similar behavior on tensile properties and flexural modulus were observed in both PP/TPE blends. Yield stress and tensile strength decreased and elongation at break increased by expanding the dispersed elastomeric phase in the PP matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 254–263, 2005     

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     

Molecular simulation on relationship between composition and microstructure of PP/PC blend

Simulations based on molecular dynamics and mesodyn theories were used to investigate the compatibility, morphology evolution of polypropylene/polycarbonate (PP/PC) blends, and the relationship between the composition and microstructure. Results of Flory–Huggins interaction parameters, integral structure factor, X‐ray intensity, free‐energy density, and order parameters all indicated that phase separations occurred in all PP/PC blend systems, and poor compatibility was exhibited for this polymer pair. The systems of PP/PC = 54/46, PP/PC = 31/69, and PP/PC = 18/82 showed stronger immiscibility and the faster separation process, while the systems of PP/PC = 82/18 and PP/PC = 5/95 showed less immiscibility and a slower separation process. Compared with the results of mechanical properties tests, the appearance of a cocontinuous structure obtained from simulation corresponds to the transition point of impact strength and tensile strength. After transition, the mechanical properties of the blends depended on the properties of the PC matrix, and the impact strength and tensile strength were both clearly enhanced. As the simulation steps increased, the morphology of PP/PC = 54/46 blend developed into a double‐lamellar structure by coarsening of PC phase from initial homogeneous configuration. In addition, the compatibilizing effect of SEBS was also investigated at the microscale, and varying the content of PS block in SEBS has little effect on the morphology of blend. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Melt rheological properties of polypropylene/SEBS (styrene–ethylene butylene–styrene block copolymer) blends

Study of melt rheological properties of the blends of polypropylene (PP) with styrene–ethylene butylene–styrene block copolymer (SEBS), at blending ratios 5–20% SEBS, is reported. Results illustrate the effects of (i) blend composition and (ii) shear rate or shear stress on melt viscosity and melt elasticity and the extrudate distortion. In general, blending of PP with SEBS results in a decrease of its melt viscosity, processing temperatures, and the tendency of extrudate distortion. However, the properties depend on blending ratio. A blending ratio around 5–10% SEBS seems optimum from the point of view of desirable improvement in processability behavior.     

A strategy for the preparation of closed‐cell and crosslinked polypropylene foam by supercritical CO2 foaming

We report the preparation of a closed‐cell polypropylene (PP) foam material by supercritical carbon dioxide foaming with the assistance of γ‐ray radiation crosslinking. Styrene–ethylene–butadiene–styrene (SEBS) copolymer was added to PP to enhance radiation crosslinking and nucleation. Radiation effects on the foaming of the PP/SEBS blend with different ratios were investigated. A significant improvement in the foaming of the crosslinked PP/SEBS blend was achieved as compared to pristine PP. The cell density of the crosslinked PP/SEBS foam greatly increased at a dose of 10 kGy and a high closed‐cell ratio was obtained. The tensile strength of the crosslinked PP/SEBS foams (10 kGy) was improved from 14 to 20.7 MPa compared to pristine PP foam (0 kGy). In addition, the crosslinked PP/SEBS blend exhibited a wider foaming temperature window (10 °C) as compared to the non‐crosslinked ones (4 °C). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45809.     

关于PS/PP系共混物的研究——第1报 PS/PP共混体系的相容性和相态结构

本研究以苯乙烯—乙烯—丁烯—苯乙烯嵌段共聚物(SEBS)和苯乙烯—乙烯—丙烯嵌段共聚物(SEP)为界面活性剂(相溶化剂),研究聚苯乙烯等规聚丙烯(PS/PP)共混体系的相容性;研究PS/PP两成分体系和添加界面活性剂后三成分体系的相态结构及相界面形态。为制取结构稳定的PS/PP系共混物,进一步制取具有特殊性能约PS/PP共混纤维提供实用的工艺条件和理论依据。     

Crystallization of PP in PP/SEBS blends and its correlation with tensile properties

Crystallization of polypropylene (PP) in the blends of PP with styrene–ethylene butylene–styrene triblock copolymer (SEBS) is studied through differential thermal analysis (DTA) and X-ray diffraction measurements. Analysis of crystallization exotherm peaks in terms of crystallization nucleation and growth rates, crystallite size distribution, and crystallinity revealed differences in the morphology of PP component in the blend in the different regions of blend composition. Crystallinity determined by X-ray diffraction and DTA showed identical variations with blend composition. Variations in tensile properties of these blends with blend composition are also reported. Correlations of the various tensile properties with the crystallization parameters, viz., the crystallinity and crystallite size distribution, are presented, which confirm the influence of crystallization of PP component on the tensile properties of these blends.     

Morphological evolution and mechanical property enhancement of natural rubber/polypropylene blend through compatibilization by nanoclay

Nanocomposites of natural rubber (NR)/polypropylene (PP) (80/20 wt %) blends filled with 5 phr pristine clay were prepared by melt‐mixing process. Effects of clay incorporation technique via conventional melt‐mixing (CV) and masterbatch mixing (MB) methods on nanostructure and properties of the blend nanocomposites were investigated. The XRD, SAXS, WAXD, and TEM results showed that the clays in the NR/PP blend nanocomposites were presented in different states of dispersion and were locally existed at the interface between NR and PP as well as dispersed in the NR matrix. The presence of clay caused unique morphological evolution such as fine fibrillar PP domains. The tensile strength was improved over the unfilled NR/PP blends by 53% and 224%, and the storage modulus at 25 °C was increased by 78% and 120% for the NR/PP/clay nanocomposites prepared by CV and MB methods, respectively. Significant improvement in both properties was particularly obtained from the MB method due to finer dispersion fibrillar PP phase in the NR matrix and stronger interfacial adhesion between NR and PP fibers, as suggested from DMA. The oil resistance of blend nanocomposites was also improved over that of the unfilled NR/PP blend, and this property was further progressed by the masterbatch mixing method. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44574.     

动态硫化SBR/PP共混物力学性能的研究

研究了不同共混比,不同类型SBR及不同硫化体系对动态硫化SBR／PP共混物力学性能的影响,试验结果表明,SBR／PP共混物的最佳共混比为60／40,E－SBR／PP共混物的力学性能稍好于S－SBR／PP共混物;采用硫黄硫化体系的共混物的力学性能优于采用过氧化物和酚醛树脂硫化体系的共混物;动态硫化SBR／PP共混物的交联密度低于静态硫化SBR母炼胶的交联密度。     

Property enhancement in polypropylene ternary blend nanocomposites via a novel poly(ethylene oxide)‐grafted polystyrene‐block‐poly(ethylene/butylene)‐block‐polystyrene toughener–compatibilizer system

Synthesis and characterization of a novel toughener–compatibilizer for polypropylene (PP)–montmorillonite (MMT) nanocomposites were conducted to provide enhanced mechanical and thermal properties. Poly(ethylene oxide) (PEO) blocks were synthetically grafted onto maleic anhydride‐grafted polystyrene‐block‐poly(ethylene/butylene)‐block‐polystyrene (SEBS‐g‐MA). Special attention was paid to emphasize the effect of PEO‐grafted SEBS (SEBS‐g‐PEO) against SEBS‐g‐MA on morphology, static/dynamic mechanical properties and surface hydrophilicity of the resultant blends and nanocomposites. It was found that the silicate layers of neat MMT are well separated by PEO chains chemically bonded to nonpolar SEBS polymer without needing any organophilic modification of the clay as confirmed by X‐ray diffraction and transmission electron microscopy analyses. From scanning electron microscopy analyses, elastomeric domains interacting with MMT layers via PEO sites were found to be distributed in the PP matrix with higher number and smaller sizes than the corresponding blend. As a benefit of PEO grafting, SEBS‐g‐PEO‐containing nanocomposite exhibited not only higher toughness/impact strength but also increased creep recovery, as compared to corresponding SEBS‐g‐MA‐containing nanocomposite and neat PP. The damping parameter of the same nanocomposite was also found to be high in a broad range of temperatures as another advantage of the SEBS‐g‐PEO toughener–compatibilizer. The water contact angles of the blends and nanocomposites were found to be lower than that of neat hydrophobic PP which is desirable for finishing processes such as dyeing and coating. © 2018 Society of Chemical Industry     

Effect of SEBS on morphology, thermal, and mechanical properties of PP/organoclay nanocomposites

A simultaneously increase in stiffness and toughness is needed for improving polypropylene (PP) competitiveness in automotive industry. The aim of this paper is to investigate the effects of styrene-(ethylene-co-butylene)-styrene triblock copolymer (SEBS) on mechanical and thermal properties of PP, in the presence and the absence of nanoclay. The amount of SEBS in PP was ranged to obtain the matrix with the most favorable stiffness–toughness balance. For this purpose, SEBS domain size and distribution in PP/SEBS blends was determined by means of atomic force microscopy and correlated with mechanical properties. The influence of SEBS on the crystalline structure of PP in PP/organoclay nanocomposites was investigated by X-ray diffraction and differential scanning calorimetry, a synergistic effect of SEBS and nanoclay being pointed out. Moreover large improvement in the impact strength (almost 22 times) was obtained in the case of SEBS-containing nanocomposite in comparison with the composite without SEBS.     

A study on functionalizing SEBS through ozone treatment and the mechanical properties of its blend with polyamide 6

Two types of styrene‐b‐(ethylene‐co‐1‐butene)‐b‐styrene triblock copolymer (SEBS) were functionalized through ozone treatment. The structure and properties of ozonized SEBS and the mechanical properties of their blend with Polyamide 6 (PA6) were studied by FTIR spectroscopy, gel permeation chromatography, gel content measurement, contact angle measurement, SEM, and mechanical properties measurement. The experimental results show that through ozone treatment, some oxygen‐containing groups (mainly carbonyl groups) are introduced onto the molecular chains of SEBS. The polarity of SEBS is thus improved. Compared with star‐shaped SEBS602, SEBS503 of linear shape is more susceptible to ozone oxidation. The polarity of ozonized SEBS503 is higher than that of ozonized SEBS602. The improvement of mechanical properties of PA6/ozonized SEBS blend is attributed to the improvement of the dispersion of ozonized SEBS in PA6 matrix and the interfacial adhesion between PA6 and ozonized SEBS. Compared with that of PA6/ozonized SEBS602 blend, the size of dispersed phase in PA6/ozonized SEBS503 blend is smaller, and the interfacial adhesion is stronger. The notched Izod impact strength of PA6/ozonized SEBS503 (90 min) (90/10) blend is 49.6 kJ/m², is higher than that of PA6/ozonized SEBS602 (90 min) (90/10) blend, which is only 21.3 kJ/m². The impact strength of PA6/ozonized SEBS503 (90 min) (80/20) blend is 68.7 kJ/m², is still higher than that of PA6/ozonized SEBS602 (90 min) (80/20) blend, which is 60.2 kJ/m². © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Evaluation of mechanical properties of polypropylene/polycarbonate/SEBS ternary polymer blends using Taguchi experimental analysis

In this work, ternary polymer blends based on polypropylene (PP)/polycarbonate (PC)/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) (SEBS) triblock copolymer and a reactive maleic anhydride grafted SEBS (SEBS‐g‐MAH) at fixed compositions are prepared using twin‐screw extruder at different levels of die temperature (235‐245‐255°C), screw speed (70‐100‐130 rpm), and blending sequence (M1‐M2‐M3). In M₁ procedure, all of the components are dry blended and extruded simultaneously using Brabender twin‐screw extruder, whereas in M₂ procedure, PC, SEBS, and SEBS‐g‐MAH minor phases are first preblended in twin‐screw extruder and after granulating are added to PP continuous phase in twin‐screw extruder. Consequently, in M₃ procedure, PP and SEBS‐g‐MAH are first preblended and then are extruded with other components. The influence of these parameters as processing conditions on mechanical properties of PP/PC/SEBS ternary blends is investigated using L9 Taguchi experimental design. The responding variables are impact strength and tensile properties (Young's modulus and yield stress), which are influenced by the morphology of ternary blend, and the results are used to perform the analysis of mean effect as well. It is shown that the resulted morphology, tensile properties, and impact strength are influenced by extrusion variables. Additionally, the optimum processing conditions of ternary PP/PC/SEBS blends were achieved via Taguchi analysis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Studies on binary and ternary blends of polypropylene with SEBS,PS, and HDPE. II. Tensile and impact properties

Studies are reported on tensile and impact properties of several binary and ternary blends of polypropylene (PP), styrene-b-ethylene-co-butylene-b-styrene triblock copolymer (SEBS), high-density polyethylene (HDPE), and polystyrene (PS). The blend compositions of the binary blends PP/X were 10 wt % X and 90 wt % PP, while those of the ternary blends PP/X/Y were 10 wt % of X and 90 wt % of PP/Y, or 10 wt % Y and 90 wt % PP/X (PP/Y and PP/X were of identical composition 90:10); X, Y being SEBS, HDPE, or PS. The results are interpreted for the effect of each individual component by comparing the binary blends with the reference system PP, and the ternary blends with the respective binary blends as the reference systems. The ternary blend PP/SEBS/HDPE showed properties distinctly superior to those of PP/SEBS/PS or the binary blends PP/SEBS and PP/HDPE. Differences in the tensile yield behavior of the different samples and their correlation with impact strength suggested shear yielding as the possible mechanism of enhancement of impact strength. Scanning electron microscopic study of the impact fractured surfaces also supports the shear yielding mechanism of impact toughening of these blends.