Polyolefin/polystyrene in situ compatibilization using Friedel–Crafts alkylation

Polyolefin/polystyrene (PS) blends are difficult to compatibilize using in situ reactive compatibilization techniques, because neither of these polymers has any functional groups that one can use in the formation of a copolymer from these polymer components. In this study, the Friedel–Crafts alkylation was realized in a polyethylene/PS (PE/PS) melt blend, which resulted in improved compatibility between PE and PS. A number of Lewis acid compounds were tested as catalysts, among which the AlCl₃ was the most efficient. It was found in this study that the presence of a cocatalyst, such as a cationically polymerizable monomer or a halogenated alkane, significantly enhances the formation of PE-g-PS copolymer. The effects of blending parameters, such as temperature and blending time, on the in situ copolymer formation were investigated. The mechanical properties of compatibilized PE/PS blends were improved considerably. Such an in situ compatibilization technique has potential in the recycling of mixed polymer wastes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1385–1393, 1997     

Structure and properties of in situ compatibilized polystyrene/polyolefin elastomer blends

To increase the compatibility of polystyrene (PS) and polyolefin elastomer (POE) blends, a Lewis acid catalyst, aluminum chloride (AlCl₃), was adopted to initiate the Friedel–Crafts alkylation reaction for the formation of PS‐graft‐POE copolymer. Dynamic mechanical analysis indicated that PS/POE and PS/POE/AlCl₃ blends are partially miscible, and the formation of PS‐graft‐POE copolymer increased the compatibility between PS and POE. Scanning electron microscope and transmission electron microscope results showed that the domain size of the blends decreased dramatically and the size distribution became more uniform with the addition of AlCl₃. Such in situ compatibilization also induced hindrance to the macromolecular chain movement, as reflected by the results of the dynamic rheological analysis. The dynamic rheological behaviors of PS/POE and PS/POE/AlCl₃ blends under different temperature showed that in situ compatibilization weakened the effects of thermooxidation on PS/POE blends. Moreover, in situ compatibilization decreased the activation energy of viscous flow and reduced the influence of temperature on PS/POE blends. POLYM. ENG. SCI., 47:951–959, 2007. © 2007 Society of Plastics Engineers     

In situ compatibilization of polystyrene/polyolefin elastomer blends by the Friedel–Crafts alkylation reaction

Blends of polystyrene (PS) with polyolefin elastomer (POE) were prepared by a reactive extrusion method. In order to increase the compatibility of the two blending components, a Lewis acid catalyst, aluminium chloride (AlCl₃), was adopted to initiate the Friedel–Crafts alkylation reaction. Fourier‐transform infrared (FTIR) spectra of the PS/POE/AlCl₃ blends extracted with butanone verified the graft structure between the PS and POE. Because the in situ generated PS‐graft‐POE copolymers acted as compatibilizers, the mechanical properties of PS/POE blends were greatly improved. For example, after compatibilization, the Charpy impact strength of an 80/20 (wt%) PS/POE blend was increased from 6.29 to 8.50 kJ m^?2. Scanning electron microscopy (SEM) showed that the size of the droplets decreased from 9–10 µm to less than 2 µm with the addition of AlCl₃. Gel permeation chromatography (GPC) showed competition between the grafting reaction and the degradation of blending components in the presence of AlCl₃. Copyright © 2005 Society of Chemical Industry     

Studies on mechanical and morphological behavior of hybrid nanoclay‐reinforced EPDM‐g‐TMEVS/PS blends

A new copolymer of tris(2‐methoxyethoxy) vinylsilane (TMEVS)‐grafted ethylene–propylene–diene elastomer (EPDM‐g‐TMEVS) has been developed by grafting of TMEVS onto EPDM by using dicumylperoxide (DCP) initiator. The linear polystyrene blends (EPDM‐g‐TMEVS/PS) based on EPDM‐g‐TMEVS have been synthesized with varying weight percentages of polystyrene in a twin‐screw extruder. In a similar manner, the dynamically vulcanized and nanoclay‐reinforced polystyrene blends have also been developed using DCP and organically modified montmorillonite clay separately by means of a twin‐screw extruder. The grafting of TMEVS onto EPDM at allylic position present in the third monomer of EPDM has been confirmed by Fourier Transform infrared spectroscopy. The effect of silane‐grafted EPDM and concentration of nanoclay on mechanical properties of polystyrene blends has been studied as per ASTM standards. The morphological behavior of these blends has been investigated using scanning electron microscope. It was observed that the incorporation of silane‐grafted EPDM enhanced the impact strength and the percentage elongation of linear‐ and dynamically vulcanized blends. However, the values of tensile strength, flexural strength, flexural modulus, and hardness of the blends were found to be decreasing with the increase of silane‐grafted EPDM. In the case of nanoclay‐reinforced polystyrene blends, the values of impact strength, tensile strength, flexural strength, flexural modulus, and hardness were increased with an increase in the concentration of nanoclay. XRD studies have been carried out to confirm the formation of nanoclay‐reinforced EPDM‐g‐TMEVS/PS blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Rheology,morphology, and mechanical properties of reactive compatibilized polypropylene/polystyrene blends via Friedel–Crafts alkylation reaction in the presence of clay

Attempts were made to study the effect of reactive compatibilization via Friedel–Crafts alkylation reaction, using AlCl₃ as a catalyst, on rheology, morphology, and mechanical properties of polypropylene/polystyrene ( PP/PS) blends in the presence of an organoclay (Cloisite 15A). During the reactive compatibilization process, PS showed much more degradation than that of PP in the presence of AlCl₃. It was found that the effect of generation of PP‐g‐PS copolymer at the interface of the PP/PS blend dominates the effects of degradation of PS and PP phases, which manifested itself by increased toughness as well as uniform dispersion of the dispersed PS particles in the PP matrix. Generation of PP‐g‐PS copolymer was confirmed by using Fourier‐transform infrared analysis. By using rheological and X‐ray diffraction analyses, it was shown that the clay had higher affinity to PS than that of PP. It was also shown that the clay located at the interface of PP and PS phases, leading to increased relaxation time of the deformed PS dispersed particles, exhibited higher dispersion in PP/PS blend, which resulted in higher ductility of the blend. By using the results of rheological studies, it was concluded that during reactive compatibilization of the blend nanocomposite, the clay migrated into the dispersed PS phase, which was confirmed by scanning electron microscopy analysis. It was demonstrated that the rheological studies have a reliable sensitivity to the clay partitioning and phase morphology of the studied blends and blend nanocomposites . J. VINYL ADDIT. TECHNOL., 24:18–26, 2018. © 2015 Society of Plastics Engineers     

Dynamic mechanical properties of polypropylene‐g‐maleic anhydride and ethylene–propylene–diene terpolymer blends: Effect of blend preparation methods

In this work, we attempted two different ways of processing to improve interfacial adhesion of polypropylene (PP) and ethylene–propylene–diene terpolymer (EPDM) by introducing maleic anhydride (MAH); In one way, the in situ grafting and dynamic vulcanization (ISGV) were performed simultaneously from PP and EPDM with MAH in the presence of dicumyl peroxide (DCP) in an intensive mixer. In another way, PP was first grafted with MAH and then the PP‐g‐MAH was blended with EPDM in the intensive mixer in the presence of DCP by the dynamic vulcanization (DV). It was found that the glass transition temperatures (T_gs) of both PP and EPDM phases were shifted to higher temperature as the EPDM content increased for the blends prepared by both IGSV and DV methods, mainly due to the crosslinking of EPDM. The higher T_gs and larger storage moduli were observed for the blends prepared by the ISGV method than those prepared by the DV method, while the morphology showed that the size reduction of dispersed particles in latter blends was larger than that of the former blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2777–2784, 2000     

Drug‐release behavior of chitosan‐g‐poly(vinyl alcohol) copolymer matrix

Chitosan‐g‐poly(vinyl alcohol) (PVA) copolymers with different grafting percent were prepared by grafting water‐soluble PVA onto chitosan. The drug‐release behavior was studied using the chitosan‐g‐PVA copolymer matrix containing prednisolone in a drug‐delivery system under various conditions. The relationship between the amount of the released drug and the square root of time was linear. From this result, the drug‐release behavior through the chitosan‐g‐PVA copolymer matrix is shown to be consistent with Higuchi's diffusion model. The drug‐release apparent constant (K_H) was slightly decreased at pH 1.2, but increased at pH 7.4 and 10 according to the increasing PVA grafting percent. Also, K_H was decreased by heat treatment and crosslinking. The drug release behavior of the chitosan‐g‐PVA copolymer matrix was able to be controlled by the PVA grafting percent, heat treatment, or crosslinking and was also less affected by the pH values than was the chitosan matrix. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 458–464, 1999     

Dynamic mechanical and morphological behavior of blends of polystyrene and poly[acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene)‐g‐styrene] prepared by in situ polymerization of styrene

PS/AES blends were prepared by in situ polymerization of styrene in the presence of AES elastomer, a grafting copolymer of poly(styrene‐co‐acrylonitrile) – SAN and poly(ethylene‐co‐propylene‐co‐diene)–EPDM chains. These blends are immiscible and present complex phase behavior. Selective extraction of the blends' components showed that some fraction of the material is crosslinked and a grafting of PS onto AES is possible. The morphology of the noninjected blends consists of spherical PS domains covered by a thin layer of AES. After injection molding, the blends show morphology of disperse elastomeric phase morphology in a rigid matrix. Two factors could contribute to the change of morphology: (1) the stationary polymerization conditions did not allow the mixture to reach the equilibrium morphology; (2) the grafting degree between PS and AES was not high enough to ensure the morphological stability against changes during processing in the melting state. The drastic change of EPDM morphology from continuous to disperse phase has as consequence a decrease in the intensity of the loss modulus peaks corresponding to the EPDM glass transition. However, the storage modulus at temperatures between the glass transition of EPDM and PS/SAN phases does not change significantly. This effect was attributed to the presence of the SAN rigid chains in the AES. © 2009 Wiley Periodicals, Inc. Journal of Applied Polymer Science, 2009     

Synthesis of PS‐g‐POSS hybrid graft copolymer by click coupling via ”graft onto” strategy

Polystyrene (PS)‐incorporated polyhedral oligomeric silsesquioxanes (POSS) organic–inorganic hybrid graft copolymer could be achieved by click coupling reaction between alkyne groups in POSS and azido groups in PS via “graft onto” strategy. Alkyne‐functionalized POSS was synthesized via thiol‐ene facile click reaction and subsequent amidation reaction with very high yield. Azido‐multifunctionalized PS could be synthesized by chloromethylation and subsequent azido reaction. The chemical structures of PS‐(CH₂Cl)_m, PS‐(CH₂N₃)_m, and PS‐g‐POSS were determined by Fourier transform infrared and ¹H NMR characterization. PS‐g‐POSS presented a better hydrophobic property with contact angle of 113° than that of PS (85°). And PS‐g‐POSS with ≤5% of grafting degree had lower glass transition temperature (T_g) than that of PS and then it increased up to 112°C with grafting degree. An obvious aggregation of POSS phase with 10–80 nm in size was formed in PS‐g‐POSS matrix. In addition, 5 wt % of PS‐g‐POSS was added to general purpose polystyrene (GPPS) to remarkably improve its tensile strength from 45 to 57 MPa. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The study of polystyrene blends: The relationship of phases and structure in blends of polystyrene with ethylene–propylene diene monomer rubber and its grafted copolymer

Pressed films of blends of polystyrene (PS) with ethylene–propylene diene monomer rubber (EPDM) or grafted copolymer of styrene (St) onto EPDM (EPDM-g-St) rubber were examined by small-angle X-ray scattering (SAXS), and scanning electron microscope (SEM). Small-angle X-ray scattering from the relation of phase was analyzed using Porod's Law and led to value of interface layer on blends. The thickness of interface layer (σ_b) had a maximum value at 50/50 (PS–EPDM-g-St) on blends. The radius of gyration of dispersed phase (domain) and correlation distances a_c in blends of PS–EPDM-g-St were calculated using the data of SAXS. The morphology and structure of blends were investigated by SEM. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 805–810, 1998     

The dynamic mechanical analysis,impact, and morphological studies of EPDM–PVC and MMA‐g‐EPDM–PVC blends

The dynamic mechanical studies, impact resistance, and scanning electron microscopic studies of ethylene propylene diene terpolymer–poly(vinyl chloride) (EPDM–PVC) and methyl methacrylate grafted EPDM rubber (MMA‐g‐EPDM)–PVC (graft contents of 4, 13, 21, and 32%) blends were undertaken. All the regions of viscoelasticity were present in the E′ curve, while the E″ curve showed two glass transition temperatures for EPDM–PVC and MMA‐g‐EPDM–PVC blends, and the T_g increased with increasing graft content, indicating the incompatibility of these blends. The tan δ curve showed three dispersion regions for all blends arising from the α, β, and Γ transitions of the molecules. The sharp α transition peak shifted to higher temperatures with increasing concentration of the graft copolymer in the blends. EPDM showed less improvement while a sixfold increase in impact strength was noticed with the grafted EPDM. The scanning electron microscopy micrographs of EPDM–PVC showed less interaction between the phases in comparison to MMA‐g‐EPDM–PVC blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1959–1968, 1999     

Study on the relaxation of polystyrene,ethylene–propylene diene monomer,and the blends of polystyrene with ethylene–propylene diene monomer by thermally stimulated current

A thermally stimulated current (TSC) was used to study the relaxation of polystyrene (PS), the ethylene–propylene diene monomer (EPDM), and the grafted copolymer of EPDM with styrene (EPDM-g-St). The effect of the measuring conditions on the relaxation of PS is discussed. Some relaxation parameters of PS, EPDM, and EPDM-g-St were calculated in two different ways. In addition, the TSC spectra of PS/EPDM and PS/EPDM-g-St showed that PS/EPDM was an immiscible system, but there existed a special interaction between the plastic phase and the rubber one in PS/EPDM-g-St blends. The compatibility of PS blends was evaluated in terms of their compositions. The results of inverse gas chromatography (IGC) agreed well with those of the TSC measurements. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1199–1204, 1998     

Morphology,crystallization, and thermal behavior of isotactic polypropylene/polystyrene blends: Effects of the addition of a graft copolymer of propylene with styrene

Optical microscopy, differential scanning calorimetry, and small‐angle X‐ray scattering techniques were used to study the influence of crystallization conditions on the morphology and thermal behavior of samples of ternary blends constituted by isotactic polypropylene (iPP), atactic polystyrene (aPS), and a novel graft copolymer of unsaturated propylene with styrene (uPP‐g‐PS) with the purpose of assessing the uPP‐g‐PS capability to act as a compatibilizer for iPP/aPS materials. It was shown that the presence of the uPP‐g‐PS copolymer affects the interfacial tension between the iPP and aPS phases in the melt state, with the aPS particle size and the particle‐size distribution being, in fact, strongly modified. In samples of iPP/aPS/uPP‐g‐PS blends, isothermally crystallized from the melt at a relatively low undercooling in a range of the crystallization temperature of the iPP phase, the addition of the uPP‐g‐PS copolymer induced a drastic change both in the aPS mode and the state of dispersion and in the iPP spherulitic texture and inner structure of the spherulite fibrils. In particular, the phase structure developed in the iPP/aPS/uPP‐g‐PS materials was characterized by a crystalline lamellar thickness of the iPP phase comparable to that shown by the plain iPP. The extent of the induced modifications, that is, the degree of compatibilization achieved, resulted in a combined effect of composition and undercooling. Also, relevant thermodynamic parameters of the iPP phase, such as the equilibrium melting temperature (T_m) and the folding surface free energy (ς_e) of the lamellar crystals, were found to be influenced by the presence of the uPP‐g‐PS copolymer. A linear decrease of the T_m and ς_e values with increasing uPP‐g‐PS content was, in fact, observed. Such results have been accounted for by an increase of the presence of defects along the iPP crystallizable sequences and by the very irregular and perturbed surface of the crystals with increasing copolymer content. The observed decrease in T_m values revealed, moreover, that, in the iPP/aPS/uPP‐g‐PS blends, the iPP crystal growth occurs under comparatively lower undercooling, in line with higher crystalline lamellar thickness shown by SAXS investigation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1429–1442, 1999     

Thermal behavior and properties of polystyrene/poly(methyl methacrylate) blends

The thermal behavior and properties of immiscible blends of polystyrene (PS) and poly(methyl methacrylate) (PMMA) with and without PS‐b‐PMMA diblock copolymer at different melt blending times were investigated by use of a differential scanning calorimeter. The weight fraction of PS in the blends ranged from 0.1 to 0.9. From the measured glass transition temperature (T_g) and specific heat increment (ΔC_p) at the T_g, the PMMA appeared to dissolve more in the PS phase than did the PS in the PMMA phase. The addition of a PS‐b‐PMMA diblock copolymer in the PS/PMMA blends slightly promoted the solubility of the PMMA in the PS and increased the interfacial adhesion between PS and PMMA phases during processing. The thermogravimetric analysis (TGA) showed that the presence of the PS‐b‐PMMA diblock copolymer in the PS/PMMA blends afforded protection against thermal degradation and improved their thermal stability. Also, it was found that the PS was more stable against thermal degradation than that of the PMMA over the entire heating range. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 609–620, 2004     

Architecture of prototype copolymer brushes composed of alternating structure and intramolecular phase separation of side chains in solution

Atom transfer radical polymerization (ATRP) was applied to the synthesis of prototype copolymer brushes composed polystyrene/poly(t‐butyl methacrylate) (PS/PBMA) alternating structure. Dilute solution properties of prototype copolymer brush were investigated by static and dynamic light scattering (SLS and DLS) in tetrahydrofuran (THF). As a result, such prototype copolymer brush composed of short aspect ratio formed a star‐like single molecule in THF. To discuss the intramolecular phase separation of PS/PBMA brushes in solution, we determined the radius of gyration (R_g) and cross‐sectional radius of gyration (R_g,c) of prototype copolymer brush by small‐angle X‐ray scattering (SAXS) using Guinier's plots in THF and styrene. We used styrene as solvent to cancel each other out with the electron density of PS side chains. Both R_g and R_g,c obtained in styrene decreased drastically compared with those obtained in THF. These results indicated strongly that PS and PBMA side chains of prototype brushes formed intramolecular phase separation even in good solvent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Toughened poly(trimethylene terephthalate) by blending with a functionalized ethylene–propylene–diene copolymer

A series of blends of poly(trimethylene terephthalate) (PTT) with ethylene–propylene–diene copolymer grafted with maleic anhydride (EPDM‐g‐MA) were prepared in composition by weight 95/5, 90/10, 80/20, and 70/30. Their morphologies, crystallization behavior, and mechanical properties were investigated. Morphology observation shows the well‐dispersed domains of EPDM‐g‐MA in PTT matrix with weight‐average particle size from 0.98 to 3.64 μm when the EPDM‐g‐MA content increases from 5% to 30% (mass fraction) in the blends. The constancy of the crystallinity level indicates that the elastomeric phase does not disturb the crystallization process of PTT. The addition of rubbery EPDM‐g‐MA to PTT matrix increases the notched Izod impact strength, but impairs the tensile strength properties. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

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.     

Functionalization of ethylene–propylene–diene monomer rubber with maleic anhydride in the melt state through high‐shear stress‐induced initiation

The functionalization reactions of ethylene–propylene–diene monomer rubber (EPDM) with maleic anhydride (MAH) in melt state through high‐shear‐stress‐induced initiation by an increase in the screw rotation speed of the twin‐screw extruder and through compounded initiation by the addition of some initiator and an increase in the screw rotation speed were investigated. The results show that, with increasing screw rotation speed and reaction temperature, the percentage grafting and melt flow rate of the functionalized products (EPDM‐g‐MAH) were noticeably increased, and the viscosity‐average molecular weight decreased, which implied that the grafting reaction consisted of the chain scission and grafting reaction of the produced macroradicals with MAH. In the presence of a certain peroxide initiator, the crosslinking reaction during melt extrusion was suppressed by an increase in the screw rotation speed. The percentage grafting of EPDM‐g‐MAH amounted to 1.1%, its melt flow rate was between 0.3 and 4.0 g/10 min, and its gel content was less than 1.0%, depending on the screw rotation speed and reaction temperature. Impact testing and scanning electron microscopy showed that the functionalized product prepared through the high shear stress‐induced initiation had a higher blocking activity with the amide terminated of PA66 than that prepared through the peroxide initiation or through the compound initiation, and the impact strength of the PA66/EPDM blends, improved by the high‐shear‐stress‐induced product was noticeably higher than those of the peroxide‐initiated product or the compound‐initiated one. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Graft copolymerization of styrene and acrylonitrile onto EPDM

Acrylonitrile–EPDM–styrene (AES) graft copolymers were synthesized by solution graft polymerization of styrene (St) and acrylonitrile (AN) onto EPDM in an n‐hexane/benzene solvent with benzoyl peroxide (BPO) as an initiator. The structure changes were studied by an FTIR spectrophotometer. The grafting parameters were calculated gravimetrically. The influence of the polymerization conditions, such as the reaction time, concentration of the initiator, EPDM content, and weight ratio of St/AN, on the structure of the products was investigated. It was found that a proper initiator concentration and EPDM content will give a high grafting ratio of the AES resin. The thermal property of the copolymer was studied using programmed thermogravimetric analysis (TGA). The results showed that the copolymer has a better heat‐resistant property than that of ABS, especially for the initial decomposition temperature (T_in) and the maximum weight loss rate temperature (T_max). Also, the mechanism of the graft reaction was discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 428–432, 2002     

Synthesis of polypropylene graft copolymers from a hydroxyl‐groups‐containing polypropylene precursor via atom‐transfer radical polymerization

Isotactic polypropylene graft copolymers, isotactic[polypropylene‐graft‐poly(methyl methacrylate)] (i‐PP‐g‐PMMA) and isotactic[polypropylene‐graft‐polystyrene] (i‐PP‐g‐PS), were prepared by atom‐transfer radical polymerization (ATRP) using a 2‐bromopropionic ester macro‐initiator from functional polypropylene‐containing hydroxyl groups. This kind of functionalized propylene can be obtained by copolymerization of propylene and borane monomer using isospecific MgCl₂‐supported TiCl₄ as catalyst. Both the graft density and the molecular weights of i‐PP‐based graft copolymers were controlled by changing the hydroxyl group contents of functionalized polypropylene and the amount of monomer used in the grafting reaction. The effect of i‐PP‐g‐PS graft copolymer on PP‐PS blends and that of i‐PP‐g‐PMMA graft copolymer on PP‐PMMA blends were studied by scanning electron microscopy. Copyright © 2006 Society of Chemical Industry