Addition compatibilization of PP/PS blends by tailor‐made copolymers

The thermoplastic polymer blends of commercial interest generally need a phase compatibilization to reduce the interfacial tension, to stabilize the morphology, and to increment the interfacial adhesion. This work deals with the compatibilization of PP/PS blends by addition of a tailor‐made copolymer, which is prepared from the pure homopolymers by a Friedel‐Crafts reaction. This addition compatibilization process comes out as an economic alternative applicable to the recycling of mixed plastics from urban and industrial wastes. The influence of compatibilizer concentration and blending time on the emulsifying effect, morphology, and mechanical properties of the resulting blends are analyzed. The compatibilization process effectiveness is assessed through the improvement in phase adhesion, emulsification and ductility of the compatibilized with respect to the physical blends. An increase of three times in ductility is achieved using very low compatibilizer concentrations (0.5–0.7 wt%). No appreciable detriment in yield strength or modulus is observed in these compatibilized blends. POLYM. ENG. SCI. 46:329–336, 2006. © 2006 Society of Plastics Engineers     

Effect of the molecular structure of ethene–propene and styrene–butadiene copolymers on their compatibilization efficiency in low‐density polyethylene/polystyrene blends

The effect of the molecular structure of styrene–butadiene (SB) block copolymers and ethene–propene (EPM) random copolymers on the morphology and tensile impact strength of low‐density polyethylene (LDPE)/polystyrene (PS) (75/25) blends has been studied. The molecular characteristics of SB block copolymers markedly influence their distribution in LDPE/PS blends. In all cases, an SB copolymer is present not only at the interface but also in the bulk phases; this depends on its molecular structure. In blends compatibilized with diblock copolymers, compartmentalized PS particles can also be observed. The highest toughness values have been achieved for blends compatibilized with triblock SB copolymers. A study of the compatibilization efficiency of SB copolymers with the same number of blocks has shown that copolymers with shorter PS blocks are more efficient. A comparison of the obtained results with previous results indicates that the compatibilization efficiency of a copolymer strongly depends both on the blend composition and on the properties of the components. The compatibilization efficiency of an EPM/SB mixture is markedly affected by the rheological properties of the copolymers. The addition of an EPM/SB mixture containing EPM with a higher viscosity leads to a higher improvement or at least the same improvement in the tensile impact strength of a compatibilized blend as the same amount of neat SB. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Compatibilization efficiency of styrene–butadiene triblock copolymers in polystyrene–polypropylene blends with varying compositions

The compatibilization efficiency of two styrene‐butadiene‐styrene triblock copolymers with short (SB1) and long (SB2) styrene blocks was studied in polystyrene (PS)–polypropylene (PP) blends of composition 20, 50, and 80 wt % PS. The supramolecular structure of the blends was determined by small‐angle X‐ray scattering, and the morphology was studied with transmission electron microscopy and scanning electron microscopy. Structural changes in both the uncompatibilized and compatibilized blends were correlated with the values of tensile impact strength of these blends. Even though the compatibilization mechanisms were different in blends with SB1 and SB2, the addition of the block copolymers to the PS–PP 4/1 and PS–PP 1/4 blends led to similar structures and improved the mechanical properties in the same way. These block copolymers had a very slight effect on the impact strength in PS–PP 1/1 blends, exhibiting a nearly cocontinuous phase morphology. The strong migration of SB2 copolymers to the interface and of SB1 copolymers away from the interface were detected during the annealing of compatibilized PS–PP 4/1 blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2431–2441, 2004     

The influence of styrene–butadiene diblock copolymer on styrene–butadiene–styrene triblock copolymer viscoelastic properties and product performance

The effects of the styrene–butadiene (SB) diblock copolymer on the viscoelastic properties of styrene–butadiene–styrene (SBS) triblock copolymers were examined in both in the the neat state and within specific product applications. The addition of the SB diblock copolymer into a pure SBS triblock copolymer resulted in a significant decrease in the plateau storage modulus and a quantitative linear rise in tan delta. In a pure triblock, in which all endblocks are anchored in polystyrene domains, all entanglements are physically trapped. The SB diblock embodies untrapped polybutadiene endblocks that are able to relax stress by chain reptation through the rubbery polybutadiene matrix. The SB diblock copolymer quantitatively lowered the microphase separation temperature (MST) of the SBS triblock copolymer. These changes in linear viscoelastic behavior manifest themselves into a reduction in the efficiency and performance of the SBS triblock copolymer in asphalt pavement binders and hot-melt adhesive blends. Specifically, the SB diblock diminished the complex shear modulus and elasticity of a polymer-modified asphalt, which translated into lower predicted rutting specification values. The increase in diblock content altered the viscoelastic response of the hot-melt adhesive blend, translating into a reduction in the shear holding power and shear adhesion failure temperature. The lack of network participation, coupled with the relaxation of the polybutadiene endblocks, accounts for the lower strength and greater temperature susceptibility of the diblock-containing systems. © 1995 John Wiley & Sons, Inc.     

Improvement of mechanical properties for PP/PS blends by in situ compatibilization

The effect of the in situ compatibilization on the mechanical properties of PP/PS blends was investigated. The application of Friedel-Crafts alkylation reaction to the PP/PS-blend compatibilization was assessed. Styrene/AlCl₃ was used as catalyst system. The graft copolymer (PP-g-PS) formed at the interphase showed relatively high emulsifying strength. Scission reactions, occurring in parallel with grafting, were verified for PP and PS at high catalyst concentration, but no crosslinking reactions were detected. Tensile tests were performed on dog-bone specimens of the blends. Both elongation at break and toughness increased with catalyst concentration. At 0.7% AlCl₃, a maximum was reached, which amounted to five times the value of the property for the uncompatibilized blend. At higher catalyst concentrations these properties decreased along with the PP molecular weight due to chain-scission reactions. On the other hand, the tensile strength did not change with the catalyst concentration. The in situ compatibilized blends showed considerable improvement in mechanical properties, but were adversely affected by chain scissions at high catalyst contents.     

Assessment of compatibilization efficiency of SEBS in the PP/PS blend

The compatibilization efficiency of styrene–ethylene/butylene–styrene (SEBS) triblock copolymer in immiscible polypropylene (PP)/polystyrene (PS) 20/80 blends was evaluated in terms of not only morphology, but also rheology and fractionated crystallization behavior. Besides varying SEBS loading, four different mixing protocols were used to vary SEBS dispersion state. PP²/PS/SEBS blend, prepared by two‐step method mixing PS and SEBS primarily, presents the largest droplet size (1.278 μm) at the critical compatibilizer concentration (CCC = 1 wt %). However, the CCC of blends prepared by the other protocols is 2 wt %. And at the CCC, PP/PS²/SEBS (two step method mixing PP and SEBS primarily) shows the smallest droplet size (0.908 μm), followed by PP/PS/SEBS (one step method). The rheology and crystallization behavior of PP/PS blends could also be utilized to assess the compatibilization efficiency of SEBS, but only in the case of mixing under the same protocol and the content of SEBS below a CCC. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46244.     

Characterization of sulfur-cured styrene–butadiene copolymer rubbers and their polybutadiene blends

Dissolution of sulfur-cured, carbon black-loaded copolymers and their blends with cis-1,4-polybutadiene (PBD) are brought about by boiling with o-dichlorobenzene which contains a small amount of 2,2′-dibenzamidodiphenyl disulfide. The resulting slurries are subjected to a sequence of separations which include high-speed centrifugation to remove solids, and solvent precipitation followed by filtration to isolate the precipitates. The precipitates are washed with solvent to remove soluble organic materials followed by carbon disulfide washing to dissolve the polymers. Cast films of the polymers are obtained by evaporating the carbon disulfide washings onto sodium chloride discs. The infrared spectra of the cast films of these preparations are very similar to those of their respective polymers prior to loading and curing. Calculations for relative concentrations of bound styrene and PBD microstructures permit nominal identification of the kinds of styrene–butadiene rubber and the amounts of cis-1,4-PBD used in a cured rubber formulation. Absorption bands used are near 3.35 μ for cis-1,4-PBD, 6.65μ for bound styrene, 10.35 μ for trans-1,4-PBD; and 11.0 μ for vinyl-1,2-PBD. Efforts are being made to improve the data by using a grafting infrared instrument and also to extend the calibrations to include other rubber blends.     

Synthesis of a difunctional organolithium compound as initiator for the polymerization of styrene‐butadiene/isoprene‐styrene triblock copolymer

A difunctional organolithium compound was prepared by the addition of butyllithium (BuLi) to 1,4‐bis(4‐methyl‐1‐phenylethenyl)benzene (MPEB). The effects of the solvent, polar modifier (THF), butyl lithium structure, and reaction time on the formation of the difunctional organolithium compound were studied. Results showed that toluene as solvent was in favor of the addition reaction over cycohexane, in the absence of the polar modifier. However, cycohexane was a better option as solvent for the addition reaction, when polar modifier was employed. A small amount of polar modifier could efficiently accelerate the reaction rate and have no significant effect on the structure of the polydiene, which was initiated by the polar modifier containing organolithium compound. Results also showed that isobutyl lithium was more active in the addition reaction than n‐butyl lithium, because of inductive effect. The optimum molar ratio of THF/Li+ was determined as 4. The THF containing difunctional organolithium cyclohexane solution was sequentially used in the step‐wise polymerization of triblock thermoplastic copolymer SIBS. The so‐prepared SIBS shared the similar phase separation structure with SBS and exhibited excellent mechanic properties. As the content of the central polyisoprene block increases, the tensile strength of the copolymer is decreased, and the elongation at break is increased. The glass transition temperature T_g of the central block was correlated with its content as T_g = 0.33 × ?62.81, where × is the wt % of the central block, based on the triblock copolymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1395–1402, 2006     

Reactive compatibilization of PE/PS blends. Effect of copolymer chain length on interfacial adhesion and mechanical behavior

This paper deals with in situ compatibilization of PE/PS blends via Friedel-Crafts reaction, performed at the interphase. Two polyethylenes having different molecular weights, and the same PS, were used along a wide range of catalyst concentration. The influence of the graft copolymer architecture and content on the efficiency of blend compatibilization was studied. The emulsifying effect, morphological aspects and mechanical behavior were also assessed for these blends. The amount of copolymer formed increases with catalyst concentration and the short chain length fraction of the homopolymers. The high molecular weight (MW) copolymers behaved as better compatibilizers as they showed, at the cmc, greater graft copolymer concentration than the low MW ones. A substantial increase in interfacial adhesion and particle size reduction was observed, even at catalyst concentrations as low as 0.3 wt%. In correspondence, mechanical properties, like ductility and yield strength, were enhanced by the effect of this Friedel-Crafts reaction's compatibilization.     

Effect of the mixing conditions on the phase structure of PP/PS blends

The effect of the rate and time of mixing in a batch mixer on the phase structure of polypropylene/polystyrene (PP/PS) blends with various rheological properties of the components was studied. Regions with substantially different average sizes of the dispersed particles were found in the studied blends. Differences between the average size of the particles in individual regions of the samples persist in all blends and mixing conditions under study. No dependence of the average particle size on the rate of mixing has been obtained for the PP/PS (75/25) blends. On the other hand, decrease of the average particle size with increasing rate of mixing has been found for the PP/PS (95/5) blend. These results are discussed as a consequence of the competition between the breakup and coalescence of the dispersed particles. © 1996 John Wiley & Sons, Inc.     

Deformation and alignment of lamellae in melt extension of blends of a styrene‐butadiene block copolymer with polystyrene

The development of the morphology and the alignment of lamellae in melt elongation of blends of an asymmetric linear styrene‐butadiene block copolymer (LN3) and polystyrene (PS 158K) was investigated. PS 158K and LN3 formed two‐phase polymer blends with PS 158K resp. LN3 inclusions, depending on the concentration of polystyrene. The block copolymer was arranged in a lamellar phase with a lamellae thickness of ～ 13 nm. Our rheological experiments revealed that the complex modulus, the elongational viscosity and the recovered stretch of the blends primarily resulted from a superposition of the properties of the blend components. In melt elongation, pure LN3 started to crumple at a small Hencky strain. In the blends, the presence of the PS 158K inclusions led to a macroscopically more uniform elongation, but with an anisotropic Poisson ratio. The LN3 inclusions in the PS 158K matrix were deformed into a filament‐like shape. In the blends with a LN3 matrix the alignment of the block copolymer lamellae parallel to the loading direction increased with applied extensional strain. In the latter case, the lamellae thickness did not decrease significantly. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Fracture toughness of modified polypropylene/poly(styrene‐ran‐butadiene) blends

Fracture toughness of polypropylene (PP)/poly(styrene‐ran‐butadiene) rubber (SBR) blends as a function of concentration of maleic anhydride (MA) in the maleated polypropylene (MAPP) compatibilizer was investigated under uniaxial static and impact loading conditions. The addition of MAPP to the unmodified PP/rubber blend enhanced the tensile modulus and yield stress as well as the Charpy impact strength. The maximum values were recorded at 1.0 wt% grafted MA in the compatibilizer. V‐shaped blunt‐notched specimens exhibited typical ductile behavior and no breakage of the specimens occurred during the impact fracture tests. Sharp‐notched specimens of uncompatibilized and low‐content MA blends broke in a semibrittle manner, supported by a rapid crack propagation process. Increasing MA content in the blends led to semibrittle‐to‐ductile transition characterized by stable crack propagation. Fracture mechanics experiments, supplemented by scanning electron microscopy (SEM), were also employed to obtain a better understanding of the fracture and deformation behavior. Copyright © 2005 Society of Chemical Industry     

In‐situ ultrasonic compatibilization of unvulcanized and dynamically vulcanized PP/EPDM blends

Dynamically vulcanized PP/EPDM blends were treated by high‐intensity ultrasonic waves during extrusion. These blends were compared with unvulcanized PP/EPDM blends that were treated by ultrasound during extrusion and then dynamically vulcanized. Die pressure and power consumption were measured. The effects of different gap sizes, ratio of components, and number of ultrasonic horns were investigated. The rheological properties, morphology and mechanical properties of the blends with and without ultrasonic treatment were compared. The results obtained indicated that ultrasonic treatment induced thermo‐mechanical degradation, causing enhanced molecular transport and chemical reactions at the interfaces, thus leading to in‐situ compatibilization, which is evident by the morphological and mechanical property studies. Processing conditions were established for enhanced in‐situ compatibilization of the PP/EPDM blends that were either originally dynamically vulcanized and then ultrasonically treated or first treated and then dynamically vulcanized. Polym. Eng. Sci. 44:2019–2028, 2004. © 2004 Society of Plastics Engineers.     

Molecular architectures of four‐arm star‐shaped styrene‐butadiene copolymer

To understand the molecular architectures of styrene‐butadiene four‐arm star (SBS) copolymers, a size exclusion chromatography combined with laser light scattering (SEC‐LLS) has been used to determine their weight‐average molecular weight (M_w) and radius of gyration (〈S²〉^1/2), and a new method for the establishment of the Mark‐Houwink equation from one sample has been developed. Based on the Flory viscosity theory, we successfully have reduced the 〈S²〉^1/2 values of numberless fractions estimated from many experimental points in the SEC chromatogram to intrinsic viscosities ([η]). For the first time, the dependences of 〈S²〉^1/2 and [η] on M_w for the four‐arm star SBS in tetrahydrofuran at 25°C were found, respectively, to be 〈S²〉^1/2 = 2.62 × 10^?2 M (nm) and [η] = 3.68 × 10^?2 M (mL/g) in the M_w range from 1.4 × 10⁵ to 3.0 × 10⁵. From data of [η] and 〈S²〉^1/2 for linear and star SBS, we have obtained the information about the branching, namely, the ratios (g and g′) of 〈S²〉 and [η] for star SBS to that of the linear SBS of the same molecular weight, which agree with theoretical predictions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 961–965, 2005     

Synthesis of a maleic anhydride grafted polypropylene–butadiene copolymer and its application in polypropylene/styrene–butadiene–styrene triblock copolymer/organophilic montmorillonite composites as a compatibilizer

A maleic anhydride grafted propylene–butadiene copolymer (MPPB) was prepared. Fourier transform infrared spectroscopy and ¹H‐NMR results indicate that the maleic anhydride molecules reacted with the double bond in the butadiene unit of the propylene–butadiene copolymer (PPB), and the grafting percentage increased with the butadiene content in the initial copolymer. The gel permeation chromatography results show that the introduction of butadiene in the copolymer prevented the degradation of PPB. The MPPB was applied in polypropylene (PP)/styrene‐butadiene‐styrene triblock copolymer (SBS)/organophilic montmorillonite (OMMT) composites as a compatibilizer. In the presence of 10‐phr MPPB, the impact strength of the composite was improved by about 20%. X‐ray diffraction patterns indicated the formation of the β‐phase crystallization of PP in the presence of MPPB, and a significant decrease in the spherulite size was observed. Transmission electron microscopy (TEM) images showed that the OMMT was better dispersed in the matrix upon the inclusion of MPPB. A better distribution of the rubber phase and a rugged fracture surface were observed in the scanning electron microscopy images as the MPPB proportion was increased. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of the type of nylon chain‐end on the compatibilization of PP/PP‐GMA/nylon 6 blends

Polyamide and polypropylene (PP) are two important classes of commercial polymers; however, their direct mixing leads to incompatible blends with poor properties. Polypropylene functionalized with glycidyl methacrylate (PP‐GMA) was used as a compatibilizer in blends of PP and nylon 6, because of the possible reaction of ? NH₂ and ? COOH groups with the epoxide group of GMA. Two types of nylon 6 with different ratios between ? NH₂ and ? COOH groups were used. The one with higher concentration of ? COOH groups was less compatible with PP in a binary blend. When PP‐GMA was used as a compatibilizer, a better dispersion of nylon in the PP matrix was obtained together with better mechanical properties for both nylons used in this work. © 2001 Society of Chemical Industry     

PP接枝聚合物对PP/PS共混物相形态的影响

通过原子转移自由基反应合成了聚丙烯(PP)接枝聚苯乙烯(PS) (PP-g-PS),研究了PP-g-PS对PP/PS共混物相形态的影响.采用扫描电子显微镜、偏光显微镜观察了共混物的断面形貌和等温结晶形态.结果表明: 加入PP-g-PS对PP/PS共混物起到了良好的增容作用,表现在两相界面模糊,分散相尺寸减小.当PP-g-PS中x(PS)为5.10% 左右时即可起到增容改善相界面的作用.相容性的提高改善了PP/PS共混物的发泡性能.     

Conductive IPN based on polyaniline and silicon‐crosslinked styrene‐isoprene‐styrene triblock copolymer

A series of new conducting interpenetrating polymer networks (IPNs) are prepared by sequential crosslinking reactions of tetraethyl orthosilicate with silicon‐grafted functional styrene‐isoprene‐styrene triblock copolymer (SIS) and polyaniline (PANI) doped with dodecylbenzenesulfonic acid (DBSA). The various factors affecting the properties of conductive IPNs are investigated. The conductivity is found to increase only slightly after the IPN films are treated at 140 ° C . The thermal stability of the IPNs is much better than that of the pure polymer under nitrogen atmosphere, as shown by the results from thermal gravimetry analysis (TGA). © 1999 Society of Chemical Industry     

Aggregate structure and effect of phthalic anhydride‐modified soy protein on the mechanical properties of styrene‐butadiene copolymer

The aggregate structure of phthalic anhydride (PA) modified soy protein isolate (SPI) was investigated by estimating its fractal dimension from the equilibrated dynamic strain sweep experiments. The estimated fractal dimensions of the filler aggregates were less than 2, indicating that these particle aggregates have a distorted or broken two‐dimensional sheet‐like structure. The results also indicated that the aggregate structure has a greater effect on the composite reinforcement than the overall aggregate size. Tensile strength, elongation, Young's modulus, and toughness of hydrolyzed/modified soy composites are comparable with those of carbon black reinforced composites at 10–15% filler fraction. The moduli of PA‐modified SPI composites were less sensitive to the pH of the composite preparation compared to the unmodified SPI. The composites prepared at acidic pH, with lower filler fraction, or filled with hydrolyzed/modified SPI are more elastic and less fatigue. The composites of PA‐modified SPI had better recovery properties when prepared at acidic instead of alkali pH. PA‐modified hydrolyzed SPI composites prepared at acidic pH showed a similar recovery property to that of carbon black reinforced composites, but with greater shear elastic moduli. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011