Reactive blending of polyamides with epoxidized elastomers

Melt blending of aliphatic polyamides (PA6, PA66, PA12) with epoxidized and nonepoxidized elastomers (SBS, BS, PB) was investigated. IR and rheological studies have shown that epoxidized elastomers can simultaneously react both with polyamides and within their own phases during melt blending. Relative intensity of both processes is the main factor, which determines structure and properties of blends. SEM observations indicated that use of epoxidized elastomers improves blend homogeneity and decreases mean size of dispersed elastomer phase in comparison with nonepoxidized elastomers. Mechanical properties of epoxidized elastomers based blends are generally better with respect to similar blends with nonepoxidized elastomers. They depend on blend composition and type of polyamide and elastomer. Elastomer addition decreases tensile strength of all systems but in some cases, a considerable rise of impact strength was measured. Epoxidized SBS block copolymer was found to be the most effective modifier, especially with respect to PA6 and PA12. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Curing behaviour and mechanical properties of dicarboxylated telechelic poly(ε-caprolactone)s/styrene–(epoxidized butadiene)–styrene triblock copolymer reactive blends

End-carboxylated telechelic poly(ε-caprolactone)s (XPCLs) with different molecular weights were blended into a triblock copolymer of styrene–(epoxidized butadiene)–styrene (ESBS) to investigate the curing behaviour and the mechanical properties of the XPCL/ESBS binary reactive blend. It was found that the time–torque cure curve showed a significant torque increase after a very short induction period, in which the degree of the torque increase depended on the molecular weight of XPCL. This indicates that substantial crosslinking reaction takes place between the XPCLs and the epoxidized polybutadiene of the ESBS. Stress–strain curves of the blends after cure depended on the molecular weight of XPCL and the blend ratio. The XPCL/ESBS blends had sufficient thermal stability to show elastomeric behaviour at elevated temperature above the glass transition of the styrene domains of ESBS because of formation of crosslinking points between unlike polymer components by the reactive blending. © 1999 Society of Chemical Industry     

Amphiphilic styrene–butadiene–styrene triblock copolymer grafted with polyoxyethylene

A styrene–butadiene–styrene triblock copolymer (SBS) was grafted with polyoxyethylene via a ring‐opening reaction of an epoxidized styrene–butadiene– styrene triblock copolymer (ESBS) with monocarboxylic‐group‐terminated methoxypoly(ethylene glycol) (CMPEG). The latter was prepared through the esterification of methoxypoly(ethylene glycol) with maleic anhydride. The optimum conditions for the preparation of the graft copolymer were studied. The graft copolymer was characterized with Fourier transform infrared spectrophotometry. Its water absorbency, oil absorbency, emulsifying property, phase‐transfer catalysis property in the Williamson solid–liquid reaction, and use as a compatibilizer in the blending of SBS with oil‐resistant chlorohydrin rubber (CHR) were also studied. The optimum conditions were a CMPEG/epoxy group molar ratio of 1.5, an N,N‐dimethyl aniline/ESBS concentration of 5 wt %, and an ESBS concentration of 12–14 g/100 mL at 75–80°C for 10 h. The polyoxyethylene content could reach 0.27 mmol/g. The graft copolymer absorbed a certain amount of water, fairly resisted kerosene, and possessed good emulsifying and phase‐transfer catalysis properties, both of which were enhanced with increasing polyoxyethylene graft content. The graft copolymer could be used as a compatibilizer for a blend of SBS and CHR. A 3 wt % concentration of the graft copolymer based on a 50/50 blend could increase both the tensile strength and ultimate elongation of the blend about 1.7 times. The blend behaved like an oil‐resistant thermoplastic elastomer. Scanning electron microscopy demonstrated the improved compatibility of the two components by the graft copolymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Blends of polyamide 6 and epichlorohydrin elastomers. I. Graft copolymerization in the melt blending

With the purpose of improving the mechanical properties of the polyamides, the possibility of combining polyamides with elastomers has been used. The low compatibility of the resulting blends leads to deficient mechanical properties, and therefore, it is necessary to add the compatibilizer to the mixture or to produce the compatibilizer during the melting mixture. Usually, at least one of the components must contain a reactive functional groups. In the present work, blends of polyamide 6 (PA 6) and epichlorohydrin elastomers, polyepichlorohydrin (PEPI), and the equimolar copolymer poly(epichlorohydrin‐co‐ethylene oxide), ECO, with different compositions were prepared by mechanical mixture using a Banbury‐type mixer. The blends were characterized by rheological measurements, the Molau test, elemental analysis, Infrared Spectroscopy by Diffuse Reflectance, Transmission Electron Microscopy, and X‐ray Diffractometry. The blends of PA 6 with PEPI and ECO are heterogeneous, showing a morphology of elastomer particles dispersed in the polyamide matrix. The results of rheological measurements and the Molau test indicate a graft copolymerization in the interface between the polyamide and the elastomer, PA 6‐g‐elastomer, whose concentration decreases with the elastomer content. It was found that the grafting of PEPI and PA 6 changed the diffraction pattern of PA 6. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1827–1833, 1999     

Compatibilization of poly(vinyl chloride)/polystyrene blends with epoxidized styrene-butadiene-styrene block copolymers

The effectiveness of epoxidized styrene-butadiene-styrene (ESBS) block copolymer as a polymeric compatibilizer for the incompatible polystyrene/poly(vinyl chloride) (PS/PVC) blend was investigated. ESBS at two epoxidation levels (34 and 49 mol% oxirane units) was used and the study covered mainly compositions with up to 30 wt% PS content in the ternary blends. The results support the view that ESBS can serve as a compatibilizer at these levels of epoxidation and when added in amounts in excess of 5 wt%. Ternary blends may also have good elongation properties due to the thermoplastic elastomer character of ESBS.     

Effect of composition on the mechanical properties of blends of the copolymer ABS with polyamides 6 and 12

Temperature and concentration dependences of the dynamic modulus of blends of an acrylonitrile–butadiene–styrene (ABS) copolymer and polyamides in the range of main transitions of the components were investigated. Small additions of both components displace the transitions temperature into the intermediate region, and additional transitions appear for the acrylonitrile–styrene part of ABS and polyamides. The concentration change of the storage modulus of composites is not monotonic and shows extremes because of miscibility of the components at a low concentration of either component. The system separates into two phases in the range of the intermediate concentrations of components.     

Use of mid‐ and near‐infrared techniques as tools for characterizing blends of copolymers of styrene–butadiene and acrylonitrile–butadiene

There is increased technological interest in using blends of various dissimilar elastomers in applications for which service, material availability, or cost of a single elastomer do not provide the necessary processing, vulcanizate, or economic properties. The properties of these polyblends are sensitive to small variations in the amounts of the individual polymers used. Accurately estimating the elastomer composition of blends is of vital importance to the elastomer industry. This study illustrates the feasibility of using mid-infrared (MIR) and near-infrared (NIR) spectroscopy to estimate the amount of styrene–butadiene and acrylonitrile–butadiene copolymers in blends composed of varying ratios of the two elastomers. Sometimes it is difficult to obtain a film of an elastomer amenable to IR analysis; to address this problem, several techniques were developed in this study [MIR transmission of a film, attenuated total internal reflection (ATR)-FTIR of a chunk, and NIR using a fiber-optic probe]. A plot of the absorbance ratio (absorbance of the characteristic peak for styrene–butadiene rubber or acrylonitrile–butadiene rubber/absorbance of the CC stretching vibration of polybutadiene) versus the amount of each elastomer in the blend was used to predict the blend composition. In addition, the blends were also characterized by ATR-FTIR using a plot of the characteristic peak absorbance versus the polymeric content for a series of standards. A partial least-squares algorithm was used to develop a calibration curve for the NIR region. Finally, the accuracy of the test methods developed in this work is compared to results obtained by pyrolysis-GC/MS and thermogravimetric analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88:1653–1658, 2003     

Influence of properties and morphology of elastomeric phase on the behavior of ternary reactive blends of polyamide 6/rigid polymer/elastomer

A ternary blend of the PA6 matrix with a finely dispersed rigid polymer and elastomer is a system with well‐balanced mechanical properties. Its micromechanical behavior, especially that of the elastomer phase, apparently differs from corresponding binary mixtures. This study shows the influence of the elastomer type, modulus, and reactivity on the behavior of ternary blends in comparison with analogous binary PA6/elastomer combinations. The presence of rigid reactive poly(styrene‐co‐maleic anhydride) (SMA) enhanced the properties of all the systems studied. For nonreactive elastomers, the dominant effect was refinement of their size due to enhanced viscosity, whereas for functionalized low‐modulus elastomers, the very good balance of properties was due to synergistic influences of both finely dispersed phases. Of interest is the enhanced toughness of ternary blends also for more rigid elastomers having a low toughening efficiency in binary blends. An appropriate addition of rigid SMA together with an elastomer enhances the energy absorption of the matrix, probably without cavitation of very small elastomer particles. Of importance also is the simultaneous strain‐hardening effect of deformed rigid particles. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3647–3651, 2003     

Toughening of polyamide‐6 with little loss in modulus by block copolymer containing poly(styrene‐alt‐maleic acid) segment

Toughening of polyamide‐6 (PA6) by elastomers without sacrificing the modulus of blends has always been a challenge. In this study, PA6 was modified by poly(styrene‐alt‐maleic acid)‐block‐polystyrene‐block‐poly(n‐butyl acrylate)‐block‐polystyrene tetrablock copolymer (BCP) elastomer. The introduced acid groups in BCP resulted in the size of BCP inclusions down to nanometers in polyamide matrix. 10 wt % of BCP‐modified PA6 blends achieved five times increase in notched impact strength with almost no loss in modulus. Microscopic observations suggested the cavitation of elastomer particles and shear yielding of PA6 matrix to be the major toughening mechanism. This research provides a strategy to toughen polyamides by block copolymers at very low rubber content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44849.     

Rubber toughened and optically transparent blends of cyclic olefin copolymers

A study is presented of increasing the toughness of Cyclic Olefin Copolymer (COC) while maintaining its optical transparency. The COC consists of a random copolymer of ethylene and norbornene, and the impact modifiers consist of thermoplastic elastomers. It is shown that several requirements must be satisfied, namely: for toughening there is an optimum finite particle size, but in order to minimize light scattering the particles have to be as small as possible. In addition, the refractive index of the elastomer must be closely matched to COC over the visible wavelength range and use temperature. Also for toughening, there are additional requirements of the adhesion of the elastomer to COC and high molecular weight. It is found that styrene butadiene styrene (SBS) is the most effective elastomer in toughening COC while maintaining optical transparency. It is also found that the addition of an index matched styrene‐ethylene‐butylene‐styrene (SEBS) copolymer as a compatibilizer to the SBS elastomer is beneficial in increasing the toughness and lowering the optical haze. Finally, light scattering calculations are presented based on the Rayleigh Debye model to calculate the optical haze and transmission of these blends. These calculations take into account the refractive index of COC and the elastomer, the particle size distribution and volume fraction of the elastomer. It is shown that there is reasonable agreement between calculation and experimental results. It is possible to increase the toughness of COC to greater than 50 J/m (Notched Izod) while keeping the optical haze to below 5% with an elastomer loading of 5% (w/w). We also identify opaque blends of COC with a toughness of greater than 500 J/m with an elastomer loading of 20% (w/w).     

Thermal behavior and morphology of polyamide 6 based multicomponent blends

The thermal behavior and morphology of multicomponent blends based on PA6, polyamide 6 (PA6)/styrene–acrylonitirle copolymer (SAN), PA6/acrylonitrile–butadiene–styrene terpolymer (ABS), and their compatibilized blends with styrene–acrylonitrile–maleic anhydride copolymer (SANMA) were studied using DSC and SEM. The blends were prepared in a twin‐screw extruder under similar processing conditions, keeping the PA6 content fixed at 50 wt %. It was found that, in all the blends, the second component had a nucleating effect and improved the overall degree and rate of crystallization of PA6, whereas addition of a compatibilizer slightly diminished these effects and resulted in significant changes in the blend morphology. The nucleating effect and consequent changes in the crystallization behavior was attributed to the presence of SAN, which is a common component in all the blends. The T_g of PA6 in the blends with a cocontinuous morphology, due to the connectivity between the phases, is higher than in the blends with a disperse‐type morphology. The compatibilized blends have a lower crystallization rate and nucleation ability with a cocontinuous morphology, whereas the uncompatibilized blends have a higher crystallization rate with a higher nucleation ability and a disperse and/or a coarse cocontinuous morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2753–2759, 2002     

Properties and morphology of supertoughened polyamide 6 hybrid composites

In this study, supertoughened polyamide (PA) nanocomposites were prepared by the incorporation of epoxidized polyhedral oligomeric silsesquioxane (POSS) into the polyamide 6 (PA6)/methyl methacrylate–butadiene–styrene copolymer (MBS) blend via a melt‐blending method. The effect of POSS on the rheological properties, mechanical properties, water uptake, and morphology of the hybrid PA6 nanocomposites was studied. The results show that under impact loading, the hybrid PA6 composites exhibited significant improvements in both the crack initiation energy and the crack propagation energy. This hybrid composite showed supertough behavior. Meanwhile, the tensile strength and the water absorption resistance was also improved with the addition of epoxidized POSS. The capillary and torque rheological results indicated that the epoxidized POSS, which acted as nanoscale ball bearings, significantly decreased the melt viscosity of the matrices and facilitated the melting process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were performed to study the microstructure–property relationships of the hybrid PA6 composites. The TEM results showed that the MBS particles were dispersed homogeneously in the PA6 matrix. The mean diameter of the MBS particles decreased, and the size distribution of the MBS particles narrowed down with the introduction of the epoxidized POSS and compatiblizer. The SEM micrographs indicated that the impact fracture surfaces of the PA composites showed morphological characteristics of supertough polymers because of the synergistic effect of the functionalized POSS and compatibilized MBS particles. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Behavior of ionomers of sulfonated styrene–butadiene–styrene triblock copolymer in polymer blends with crystalline polyolefins and as compatibilizer

The blends of ionomers of sulfonated (styrene–butadiene–styrene) triblock copolymer with two polyolefins as well as the blends of polystyrene (PSt) with two polar, oil‐resistant elastomers, i.e., chlorohydrin rubber (CHR) and chlorosulfonated polyethylene (CSPE), using the ionomer as compatibilizer were studied. The blends of the ionomer with polypropylene or high density polyethylene showed synergistic effects with respect to tensile strength. With increasing PSt content, the blends change their behavior from thermoplastic elastomer to toughened plastics. The synergism is probably because of the thermoplastic interpenetrating polymer networks formed in the blend. The blends exhibited high resistance against diesel oil or toluene. When PSt was blended with CHR or CSPE using the ionomer as compatibilizer, only 2 or 3% ionomer was needed to enhance the mechanical properties of the blends. The effect is due to the ion–polar interaction of the ionomer with the polar polymer. The enhanced compatibility of the blends by the ionomer was demonstrated by DSC and Scanning electron micrograph. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1887–1894, 2006     

Recycling of blends of acrylonitrile–butadiene–styrene (ABS) and polyamide

The aim of this work is to evaluate routes to upgrade recycled engineering plastics, especially mixed plastics with acrylonitrile–butadiene–styrene copolymers (ABS) as the major component. A core‐shell impact modifier was successfully used to improve the impact strength of blends of ABS and ABS/polycarbonate (PC) blends recycled from the automotive industry. However, the presence of other immiscible components like polyamide (PA), even in small amounts, can lead to a deterioration in the overall properties of the blends. A styrene–maleic anhydride (SMA) copolymer and other commercial polymer blends were used to promote the compatibilization of ABS and PA. The core‐shell impact modifier was again found to be an efficient additive with regard to the impact strength of the compatibilized ABS/PA blends. The results obtained with fresh material blends were quite promising. However, in blends of recycled ABS and glass‐fiber‐reinforced PA, the impact strength did not exhibit the desired behavior. The presence of poorly bonded glass fibers in the blend matrix was the probable reason for the poor impact strength compared with that of a blend of recycled ABS and mineral‐filled PA. Although functionalized triblock rubbers (SEBS–MA) can substantially enhance the impact strength of PA, they did not improve the impact strength of ABS/PA blends because the miscibility with ABS is poor. The possibilities of using commercial polymer blends to compatibilize otherwise incompatible polymer mixtures were also explored giving promising results. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2535–2543, 2002     

Interfacial adhesion evaluation in (low‐density polyethylene)/elastomer blends

Low‐density polyethylene (LDPE) with different elastomers at a ratio of 50/50 wt% blends was prepared by using a co‐rotating twin‐screw extruder. Three kinds of elastomers were used: ground tire rubber (GTR), partially crosslinked butyl rubber (Kalar^®), and styrene‐butadiene‐rubber block copolymer (SBS; Kraton^®). For better characterization of interaction between polyethylene and elastomer, influence of the type of elastomer on the properties of compositions LDPE/elastomer was determined. In the studies, two types of partially crosslinked butyl rubber (differing over filler content and Mooney viscosity) and two types of SBS (differing over structure: linear/branched) were used. The influence of kind and type of elastomer on static mechanical properties (tensile strength, elongation at break, hardness), dynamic mechanical properties, thermal properties, and morphology of obtained compositions were characterized. LDPE/linear SBS copolymer blend had the best mechanical properties, as a result of better compatibility in comparison with other investigated blends. The reason for improved compatibility was an increase of mobility of chain segments in the amorphous phase of polyethylene associated with their partial plasticization by flexible polybutadiene blocks present in SBS copolymer. J. VINYL ADDIT. TECHNOL., 22:492–500, 2016. © 2015 Society of Plastics Engineers     

Fractionated crystallization in PA6/ABS blends: Influence of a reactive compatibilizer and multiwall carbon nanotubes

The 20/80 blends of polyamide 6 (PA6) and acrylonitrile–butadiene–styrene copolymer (ABS) in the presence of styrene–maleic anhydride copolymer (SMA) and multiwall carbon nanotubes (MWNT) were prepared using melt-mixing technique. Crystallization behavior of the PA6 phase in the blends was studied using DSC, WAXD and SAXS techniques. Blends' morphology was characterized by SEM. We observed fractionated crystallization of PA6 phase in 20/80 PA6/ABS blends. It was also observed that the phenomenon of fractionated crystallization was influenced by the presence of both SMA and MWNT. Blends' morphology revealed the presence of wide domain size distribution of PA6 droplets in the amorphous ABS matrix. On incorporation of either SMA or SMA modified MWNT, the average domain size of PA6 droplets was found to be finer up to 1 wt% SMA modified MWNT. Encapsulation of SMA copolymer layer on the MWNT surface was also evident from SEM micrographs. SAXS analysis revealed the formation of multiple lamellae stacking of PA6 phase in the presence or absence of SMA and MWNT in 20/80 PA6/ABS blends. This was attributed to the formation of less perfect crystallites formed during the cooling of melt at higher degree of supercooling.     

Enhancement of the tensile retraction properties of a styrenic block copolymer by melt blending with PA6

Styrene–ethylene‐propylene–styrene triblock copolymer (SEPS), a thermoplastic elastomer (TPE) was blended with polyamide‐6 (PA6) in an attempt to improve the retraction properties of the TPE. A maximum loading of 30 wt % of polyamide was incorporated into SEPS using twin‐screw compounding. Various reactive compatibilisers were also incorporated at a maximum loading of 10 wt %. The blends were evaluated in terms of their tensile, dynamic mechanical, and rheological behavior. Design of experiments (DOE) was used to study the effect of blending variables on the tensile properties of the blends. Complex interactions between these variables were identified using this approach. It was shown that by incorporating PA6 into SEPS, in conjunction with a compatibilizer, blends with superior retraction properties and increased tensile strength could be obtained. A mean hysteresis of 54.2 ± 0.7% was recorded for a blend containing 5 wt % PA6 and 4 wt % compatibilizer compared to 58.5 ± 0.5% for virgin SEPS. The tensile strength of this blend was almost 75% higher than virgin SEPS. Further evidence of the benefit of incorporating a reactive compatibilizer was the absence of a distinct polyamide relaxation in the dynamic mechanical thermograms for the compatibilized blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

New Pretreatment for Elastomers to Enhance Adhesion

The effects of various chemical pretreatments on the surface chemistry and adhesion performance of an additive-free styrene-butadiene block copolymer and an additive-free ethylene-propylene elastomer have been studied. Most of the powerful oxidising agents that are effective with hydrocarbon plastics were ineffective in enhancing the adhesion to elastomers despite causing major changes to their surface chemistries. The poor adhesion was attributed to the existence of weak boundary layers. Chlorinated agents were also examined and a new pretreatment for elastomers containing carbon-carbon double bonds has been identified. It was found that a mildly acidified dilute aqueous suspension of Chloramine-T was very effective at enhancing the adhesion performance of styrene butadiene copolymers.     

Effect of maleic anhydride grafted polybutadiene on the compatibility of polyamide 66/acrylonitrile‐butadiene‐styrene copolymer blend

The addition of maleic anhydride grafted polybutadiene (PB‐g‐MAH) can greatly improve the compatibility of polyamide 66 (PA66)/acrylonitrile‐butadiene‐styrene copolymer (ABS) blends. Unlike the commonly used compatibilizers in polyamide/ABS blends, PB‐g‐MAH is compatible with the ABS particles' core phase polybutadiene (PB), rather than the shell styrene‐acrylonitrile (SAN). The compatibility and interaction of the components in the blends were characterized by Fourier transform‐infrared spectra (FTIR), Molau tests, melt flow index (MFI), dynamic mechanical analyses (DMA), and scanning electron microscopic (SEM) observations. The results show that PB‐g‐MAH can react with the amino end groups in PA66 while entangle with the PB phase in ABS. In this way, the compatibilizer anchors at the interface of PA66/ABS blend. The morphology study of the fracture sections before and after tensile test reveals that the ABS particles were dispersed uniformly in the PA66 matrix and the interfacial adhesion between PA66 and ABS was increased significantly. The mechanical properties of the blends thus were enhanced with the improving of the compatibility. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Dynamic stress relaxation behavior of nanogel filled elastomers

Long-time stress relaxation behavior of virgin elastomers, chemically crosslinked nanogels and nanogel filled elastomers was studied with the help of a dynamic mechanical analyzer. Sulfur crosslinked natural rubber and styrene butadiene rubber nanogels and nanocomposite gels were prepared and characterized using different methods. These gels were added in to the virgin elastomer matrix at different concentrations. Presence of crosslinked gels in elastomer matrix greatly influenced its stress relaxation behavior. The effect of draw ratio, gel loading and temperature on the stress relaxation behavior of elastomers was investigated in detail. It was found that virgin elastomers displayed extremely long-term relaxation processes and the time required to achieve equilibrium dramatically decreased with the increase in crosslink density in the case of gels. Time-temperature superposition studies revealed that stress relaxation process was accelerated and relaxation time reduced with a rise in temperature. Finally, experimental stress relaxation data were fitted with the empirical Chasset and Thirion equation with good agreement. From the fitting parameters, the characteristic relaxation time and the material parameter were estimated in order to understand the mechanism of the relaxation processes in the gels and the gel filled elastomers.