Effect of elastomer type and functionality on the behavior of toughened polyamide nanocomposites

The only shortcoming of PA6‐based nanocomposites is low toughness, which is the same as that of the matrix. This work is focused on optimization of toughening these nanocomposites by introduction of small amounts of finely dispersed elastomers. A comparison of reactively compatibilized and analogous nonreactive elastomer‐containing nanocomposites indicates the best‐balanced mechanical behavior for polar nonreactive elastomers such as NBR and E‐MA. This is explained by a significant compatibilizing effect of clay. Besides the elastomer particle size and its properties, the clay localization and its degree of ordering in the interfacial region also significantly influenced mechanical properties of the system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1571–1576, 2006     

Effect of montmorillonite modification on the behaviour of polyamide/polystyrene blends

BACKGROUND: In nanocomposites with multiphase matrices, the addition of layered silicate not only has a reinforcing effect, but also changes significantly the morphology, namely the size and the structure of the dispersed phase. In this paper, we focus on systems with polyamide 6 (PA6)/polystyrene (PS) matrices. The effect of clay was studied over the whole composition range together with the simultaneous variation of basic parameters influencing the structure and mechanical behaviour, i.e. the clay treatment type and mixing protocol. RESULTS: At all compositions, remarkable refinements of both particulate and co‐continuous structures by clay were found. This effect and a significant shift of the glass transition temperature of blend components were more pronounced for clay with less polar treatment as a result of distinct localization of clay in the interfacial area (due to its lower affinity for PA6 phase). An increase in modulus was found at all compositions, whereas strength and toughness were enhanced at low PS contents only, as a consequence of small particle size and enhanced interfacial bonding. CONCLUSIONS: The results presented indicate that nanosilicates can effectively influence the structure and properties of PA6/PS blends. Copyright © 2008 Society of Chemical Industry     

Preparation of thermoplastic elastomer nanocomposites based on polyamide‐6/polyepichlorohydrin‐co‐ethylene oxide

This work is aimed at determining the effect of nanoclay and polyepichlorohydrin‐co‐ethylene oxide (ECO) content on the microstructure and mechanical properties of PA6/ECO thermoplastic elastomers (TPEs). TPE nanocomposites were prepared in a laboratory mixer using polyamide 6 (PA6), ECO, and an organoclay by a two‐step melt mixing process. First, the PA6 was melt blended with Cloisite 30B and then mixed by ECO rubber. X‐ray diffraction results and transmission electron microscopy image showed that the nanoclay platelets were nearly exfoliated in both the phases. The SEM photomicrograph of PA6 with ECO showed that the elastomer particles are dispersed throughout the polyamide matrix and the size of rubber particles is less than 3 μm. Introduction of organoclay in the PA6 matrix increased the size of dispersed rubber particles in comparison with the unfilled but otherwise similar blends. The nanoscale dimension of the dispersed clay results in an improvement of the tensile modulus of the nanocomposites. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

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     

Novel morphologies of poly(phenylene oxide) (PPO)/polyamide 6 (PA6) blend nanocomposites

Poly(phenylene oxide) (PPO)/polyamide 6 (PA6) (50/50 w/w) blend nanocomposites were prepared by melt mixing of PPO, PA6, and organically modified clay. The morphology of PPO/PA6 nanocomposite with various amounts of clay has been investigated using scanning electron microscope (SEM), transmission electron microscope (TEM), and wide-angle X-ray diffraction (WAXD). For the PPO/PA6 blend without clay, PPO is dispersed in the PA6 matrix with an average particle diameter of about 4.2 μm. The domain size of the dispersed PPO phase is significantly decreased to about 1.1 μm by adding a small amount of clay (2%). However, when the amount of organoclay is more than 5%, the matrix-domain structure is found to transform into the co-continuous morphology. The TEM observation shows that all the organoclay is dispersed only in the PA6 phase with a high degree of exfoliation and there is no any clay detectable in the PPO phase for the nanocomposites regardless of the amount of clay. It is considered that the dispersed clay platelets play an important role in the control of the PPO/PA6 blend morphology. Firstly, the selective localization of clay in PA6 phase changes the viscosity ratio of the PPO and PA6 phases. Therefore, clay has significant effects on the morphology of the polymer blend. Secondly, the high aspect ratio of the clay platelets prevents the coalescence of domains during melt mixing.     

马来酸酐含量及制备工艺对PA6/POE-g-MAH/Nano-CaCO3复合材料形态及力学性能的影响

通过改变共混物中乙烯辛烯共聚物（POE）与马来酸酐接枝POE（POE-g-MAH）的比例,研究了MAH含量对聚酰胺6（PA6）/POE/POE-g-MAH/纳米碳酸钙（nano-CaCO3）复合材料的微观结构和力学性能的影响。结果表明,MAH含量较高时,POE-g-MAH与PA6基体的相容性好,复合材料的冲击强度最高;制备工艺对复合材料的形态及力学性能有很大影响,采用两步法制备的复合材料中nano-CaCO3分散效果更好,其增容作用使弹性体分散相直径增大约100 nm,冲击强度较一步法提高21 %。     

Influence of the component reactivity on the properties of ternary reactive blends Nylon 6/rigid brittle polymer/elastomer

The ternary reactive blend of Nylon 6 matrix with dispersed poly(styrene‐co‐maleic anhydride) and maleated SEBS or EPR represents a toughened system with enhanced strength and, at least, the retained stiffness of the matrix. In the present work, the influence of changed reactivity of dispersed phases, including the application of one or both nonreactive components, on the phase structure and related mechanical behavior is studied. Lowering of the reactivity of the elastomer caused a decrease of blend properties, whereas suitable dilution of SMA by PS brought better properties in comparison with a fully reactive system. With the nonreactive N6/PS/SEBS blend, the formation of blended bicontinuous inclusions causes worsening of toughness. This documents the importance of separate dispersion of both phases for good mechanical behavior in the system studied, which is shown to be assured by application of at least one reactive component. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1597–1603, 2000     

Nanoindentation and morphological studies on nylon 66 nanocomposites. I. Effect of clay loading

Nanoindentation technique has been used to investigate the mechanical properties of exfoliated nylon 66 (PA66)/clay nanocomposites in present study. The hardness, elastic modulus and creep behavior of the nanocomposites have been evaluated as a function of clay concentration. It indicates that incorporation of clay nanofiller enhances the hardness and elastic modulus of the matrix. The elastic modulus data calculated from indentation load-displacement experiments are comparable with those obtained from dynamic mechanical analysis and the tensile tests. However, the creep behavior of the nanocomposites shows an unexpected increasing trend as the clay loading increases (up to 5 wt%). The lowered creep resistance with increasing clay content is mainly due to the decrease of crystal size and degree of crystallinity as a result of clay addition into PA66 matrix, as evidenced by optical microscopy and X-ray diffraction. At lower clay concentration (here ≤5 wt%), morphological changes due to addition of clay plays the dominant role in creep behavior compared with the reinforcement effect from nanoclay.     

Effect of clay addition on the morphology and thermal behavior of polyamide 6

The nanostructure, morphology, and thermal properties of polyamide 6 (PA6)/clay nanocomposites were studied with X‐ray scattering, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The wide‐angle X‐ray diffraction (WAXD) and TEM results indicate that the nanoclay platelets were exfoliated throughout the PA6 matrix. The crystallization behavior of PA6 was significantly influenced by the addition of clay to the polymer matrix. A clay‐induced crystal transformation from the α phase to the γ phase for PA6 was confirmed by WAXD and DSC; that is, the formation of γ‐form crystals was strongly enhanced by the presence of clay. With various clay concentrations, the degree of crystallinity and crystalline morphology (e.g., spherulite size, lamellar thickness, and long period) of PA6 and the nanocomposites changed dramatically, as evidenced by TEM and small‐angle X‐ray scattering results. The thermal behavior of the nanocomposites was investigated with DSC and compared with that of neat PA6. The possible origins of a new clay‐induced endothermic peak at high temperature are discussed, and a model is proposed to explain the complex melting behavior of the PA6/clay nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1191–1199, 2007     

Thermoplastic elastomers of butadiene-acrylonitrile copolymer and polyamide. VI. Dynamic crosslinking by different systems

The dynamic crosslinking of butadiene-acrylonitrile copolymer (NBR) with polyamide 6 thermoplastic elastomer are studied. The effect of curing systems and the amount of curing agent are described. It is found that the NBR/PA6 60/40 ratio and phenolic curing system have a significant effect on the physical, mechanical, and thermal behavior of the elastomer. Scanning electron microscopy studies show that in the phenolic cured NBR/PA6 60/40 ratio the rubber phase is still the dispersed phase. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2057–2066, 2000     

Influence of microstructure and flexibility of maleated styrene-b-(ethylene-co-butylene)-b-styrene rubber on the mechanical properties of polyamide 12

The present investigation deals with the mechanical and morphological properties of binary polyamide 12/maleic anhydride-grafted styrene-b-(ethylene-co-butylene)-b-styrene rubber (PA12/SEBS-g-MA) blends at varying dispersed phase (SEBS-g-MA) concentrations. Tensile behavior, impact strength and crystallinity of these blend systems were evaluated. Influence of microstructure, dispersed phase particle size, and ligament thickness on the impact toughness of the blend was studied. DSC data indicated an increase in crystallinity of PA12 in the blends. Tensile modulus and strength decreased while impact strength and elongation-at-break increased with the elastomer concentration. The enhanced properties were supported by interphase adhesion between the grafted maleic groups of rubber with polar moiety of polyamide 12. Analysis of the tensile data employing simple theoretical models showed the variation of stress concentration effect with blend composition.     

Phase Morphology and Mechanical Properties of Rubber-Toughened Polypropylene Nanocomposites: Effect of Elastomer Polarity

The objective of this work was to investigate the effect of elastomer polarity on phase structure and mechanical properties of PP nanocomposites. The nonpolar and polar elastomers studied were polyethylene octene (POE) and polyethylene octene grafted maleic anhydride (POEgMAH), respectively. The results from mechanical studies showed that the POEgMAH-toughened polypropylene nanocomposites have higher Izod impact strength but lower tensile and flexural properties than the unmaleated ones. X-ray diffraction (XRD) was used to characterize the formation of nanocomposites. XRD studies revealed that intercalated rubber-toughened PP nanocomposites (RTPPNC) had been successfully prepared where the macromolecule segments PP were intercalated into the interlayer space of organoclay. XRD also indicated that the incorporation of polar POEgMAH elastomers into PP nanocomposites contribute to a better intercalation effect and formed a more exfoliated combinations structure compared to POE. Scanning electron microscope (SEM) was used for the investigation of the phase morphology and rubber particle size and particle-size distribution. SEM study revealed a two-phase morphology where POE as droplets dispersed finely and uniformly in the PP matrix. The POEgMAH-toughened PP nanocomposites shows a much finer dispersion of elastomer particles than POE-toughened PP nanocomposites.     

Reinforcement of polyolefins‐based nanocomposites: combination of compatibilizer with high shear extrusion process

The structure and properties of polypropylene (PP) and ethylene propylene copolymer (EPR) blends filled with nanosilica have been investigated. The nanocomposites were prepared via direct melt mixing using high shear corotating twin screw extruder. The effects of the process as well as adding amaleated‐Polyethylene MAPE compatibilizer were assessed by morphology studies, thermal analysis and mechanical testing. From SEM and TEM investigations, a separate dispersion of filler and rubber in the PP matrix prevails in the PP/EPR/SiO₂ systems. Encapsulation of the filler particles into the elastomer takes place when MAPE is used, promoting filler/polymer interactions and resulting in a simultaneous improvement in stiffness and toughness. Interestingly, the results indicated that high‐shear processing is an effective method to improve the dispersion of the EPR phase and fillers through the matrix. The dispersed phase droplet size was reduced with the increase of the shear rate by varying the screw rotation speed from 300 to 800 rpm, which induces a high shear stress exerted onthe materials. To sum up, what is expected from an efficient compatibilization‐process association is the reduction of the dispersed elastomer domains characteristic size, their stabilization by creation of an interphase and thus, enhanced mechanical properties. POLYM. ENG. SCI., 55:2328–2338, 2015. © 2015 Society of Plastics Engineers     

Effect of clay dispersion on the rheological properties and flammability of polyurethane‐clay nanocomposite elastomers

Polyurethane‐clay nanocomposite elastomers were synthesized using polyol‐clay blends with different levels of dispersion, which affected the final elastomer microstructure. A PU‐clay microcomposite elastomer containing partially dispersed clay showed poorer mechanical and similar fire properties to the unmodified polyurethane. More complete dispersion of the clay into the polyol led to an exfoliated structure in the final elastomer. This showed a higher modulus and kept a viscoelastic behavior to higher temperature than the pristine PU. The enhancement of mechanical and thermal properties in the nanocomposite elastomer can be attributed to the degree of clay exfoliation, and this also prevented dripping during the UL 94 fire test. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Characterization of microstructure and fracture behavior of polypropylene/elastomer blends containing small crystal in elastomeric phase

Fracture behavior of polypropylene (PP)/ethylene–propylene–rubber (EPR) blends containing small crystal in elastomeric phase was investigated. Various ethylene-α-olefin co-polymers (ECP) were used as crystal components and put into the elastomer phase of the blends. The crystallite size was controlled by changing the composition of the ECP. From thermal analysis and electron microscopic analysis, it was found that the ECP having a smaller crystal had better affinity to EPR and thus the crystal was finely dispersed in the elastomeric phase. The ECP with large crystallite size had poorer affinity to EPR and tended to segregate in the elastomeric phase. Scratch resistance and tensile elongation of blends were measured and it was found that the small crystal drastically improved the above properties while the large crystal deteriorated them. The dispersed small crystal was thought to act as a crosslinking point in the elastomeric phase. The reinforcement of the elastomeric phase by such quasi-crosslinking structure was the possible reason for the improvement of the mechanical properties of the blends. © 1995 John Wiley & Sons, Inc.     

The formation of fibrous structure of polyamide 6 induced by the three-step forming process and its prominent reinforcement in nitrile rubber

Nitrile rubber (NBR) blends with excellent performance have always been a hot research topic in petroleum field. Due to the excellent performance and compatibility of polyamide 6 (PA6), it provides an opportunity for the preparation of high-performance NBR/PA6 blends. In this article, NBR/PA6 blends were prepared by the three-step molding process. Experimentally, it was found that PA6 has a prominent reinforcement effect in NBR matrix. The variation of this mechanical property was investigated from different aspects of the crystal structure, crystallinities, phase morphology, and so on. It can be cleared that the formation of fibrous structure of PA6 phase is the main factor for reinforcement of the polymer blends. Meanwhile, the formation mechanism of the special phase structure induced by the three-step process is deeply expounded and its structural evolution schematic is established. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47472.     

Characteristics of impact modified polystyrene/organoclay nanocomposites

The poor impact resistance of Polystyrene (PS) was enhanced by the addition of elastomeric material, SEBS‐g‐MA. To prevent the reduction in strength and stiffness, organoclay Cloisite® 25A was used as filler and introduced into the matrix by a corotating twin screw extruder. Throughout the study, the clay content was kept at 2 wt%, whereas the content of SEBS‐g‐MA was varied between 5 and 40 wt%. It was found that Cloisite® 25A displays well dispersion in the ternary nanocomposites and the degree of dispersion increases with the elastomer content. The elastomeric phase has a greater viscosity than pure PS. Thus, as expected, at low elastomer contents, it forms the dispersed phase in the matrix as droplets. Transmission electron microscopy results show that the clay layers reside at the interphase between PS and elastomer and also inside the elastomeric phase. Owing to the location of the clay particles, the average elastomer domain size in ternary nanocomposites are found to be greater than that in the relative binary blends of PS‐(SEBS‐g‐MA). Moreover, with the organoclay addition, phase inversion point shifts to lower elastomer contents. The mechanical test results showed that the nanocomposites containing 15 and 20 wt% SEBS‐g‐MA have the optimum average domain size that results in high‐impact strength values without deteriorating the tensile properties. POLYM. COMPOS., 31:1853–1861, 2010. © 2010 Society of Plastics Engineers.     

Polyamide 6/clay nanocomposites using a cointercalation organophilic clay via melt compounding

Polyamide 6/clay nanocomposites (PA6CN) were prepared via the melt compounding method by using a new kind of organophilic clay, which was obtained through cointercalation of epoxy resin and quaternary ammonium into Na‐montmorillonite. The dispersion effect of this kind of organophilic clay in the matrix was studied by means of X‐ray diffraction (XRD) and transmission electron microscopy (TEM); the silicate layers were dispersed homogeneously and nearly exfoliated in the matrix. This was probably the result of the strong interaction between epoxy groups and amide end groups of PA6. The mechanical properties and heat distortion temperature (HDT) of PA6CN increased dramatically. The notched Izod impact strength of PA6CN was 80% higher than that of PA6 when the clay loading was 5 wt %. Even at 10 wt % clay content, the impact strength was still higher than that of PA6. The finely dispersed silicate layers and the strong interaction between silicate layers and matrix decreased the water absorption. At 10 wt % clay content, PA6CN only absorbs half the amount of water compared with PA6. The dynamic mechanical properties of PA6CN were also studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 953–958, 2003     

Toughness of nanoscale and multiscale polyamide‐6,6 composites

Fracture initiation and fracture propagation toughening (R‐curve behavior) of polyamide 6,6 (PA‐66) polymers with different types of layered silicate clay having nanoscale (fully dispersed) or multiscale (mixed nanoscale/microscale) structure were studied. These results were compared to fracture data for conventional kaolin clay particulate reinforcements and a PA‐66 polyblend containing rubber and rigid poly(styrene‐co‐acrylonitrile) particulates. The stiffness increase due to the intercalated clay was the same as would be predicted by classical models for conventional elongated reinforcements at the same volume fraction level. The special benefit of the nanoscale reinforcement derived from their high surface area of contact with the matrix. Toughness in layered silicate clay composites was enhanced by better dispersion of the clay, by exfoliation of the clay layers, and by a stronger clay/matrix interface. A multiscale microstructure was found to be the more desirable microstructure, combining toughness from the nanodispersed clay with resistance curve behavior from the micrometer‐sized particulates. Fracture toughness was proportional to the crack‐tip plastic zone size at fracture, indicating that the clay reinforcements, by influencing shear deformation in the crack tip region, played an important role in promoting toughness. There was indirect evidence for the formation of a zone of damage within the crack‐tip plastic zone that could explain why toughness was not optimal.     

Effect of poly(oxyalkylene)amines on structure and properties of epoxide nanocomposites

A shortcoming of most polymer nanocomposites is relatively low toughness. An effective method to eliminate this is the use of a suitable combination of polymeric impact modifiers with organoclay, which may impart synergistic effects on the mechanical behavior of both thermoplastic and thermoset matrix nanocomposites. This work focuses on the effect of various combinations of amine-terminated (APOP) and hydroxyl-terminated poly(oxypropylene) (POP) and layered silicates on the structure and mechanical behavior of epoxy nanocomposites. The combination of APOP and POP with 0.5−5% wt % of organoclay leads to some compositions that produce well balanced mechanical behavior of the epoxy nanocomposite. The higher toughening effectiveness of APOP/montmorillonite (MMT) compared with that of POP/MMT is a consequence of formation of blended domains consisting of clay tactoids and fine APOP inclusions. An increase in the dispersed particle size with clay content was observed to be a consequence of more significant clay-induced nucleation of phase separation at the expense of clay-induced accelerated curing. The best mechanical behavior was observed for materials using an adduct of APOP and MMT, which was obtained using the ion exchange of sodium ions of MMT by protonated APOP. The enhanced mechanical behavior was due to the formation of nanosized planar arrays by self-pilling of elastomer-modified clay and the corresponding increase in the T_g of the epoxy. The structure/property relationships of these systems indicate that this type of clay polymer combination provides an effective way of modifying the mechanical behavior of epoxy nanocomposites. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012