Structural and rheological investigation of interphase in polyethylene/polyamide/nanoclay ternary blends

This study aims at investigating and characterizing the interphase in Polyethylene (PE)/Polyamide (PA) blends with nodular morphology, filled with organically modified Montmorillonite (C30B), using structural and rheological experimental techniques. PE/PA/C30B blends have been prepared by simultaneous mixing at a dispersed phase fraction (PE or PA) of 20% and a clay fraction ranging from 1 to 6%. Structural properties of the interphase have been investigated using XRD combined with TEM micrographs. The presence of numerous interphase defects is evidenced, and the effect of interphase disorder is discussed. Linear viscoelastic properties show the contribution of the interphase in PE matrix ternary blends at all clay fractions, whereas interphase effects are masked by the contribution of dispersed nanoclay particles in PA matrix ternary blends.     

Characterization and properties of polyphthalamide/polyamide blends and polyphthalamide/polyamide/polyolefin blends

Polyphthalamide(PPA)/polyamide(PA) blends were analyzed to determine the effect of PA addition to PPA on melting point, glass transition temperature, dynamic modulus, and heat distortion temperature. Results indicate that the choice of PPA and the choice of PA for the blend systems affects not only the above properties but also the miscibility of the blend systems. In general, PA addition to PPA lowers the melting point and glass transition, which potentially makes these blend materials easier to process. Also, the PPA/PA blends were observed to have dynamic modulus curves with transitions shifted to lower temperatures and crystalline plateaus shifted to lower modulus. PPA/PA/polyolefin(PP) systems were investigated to determine if a useful balance of properties could be obtained, even though the blend components would have to be processed at unusually high processing temperatures (in excess of 320°C). Morphological characterization indicates that small dispersed domains of PP are obtained. The modifiers utilized in these systems were either found at the interface of the PP domain or dispersed within the PP domain. The properties of PPA/PA/PP blends indicates that these systems are ductile and have a good balance of strength, stiffness, impact, and thermal performance.     

The role of repulsive interactions in polyamide blends

Phase phenomena in mixtures containing any combination of aliphatic and aromatic polyamides can be formulated by the application of a mean-field binary interaction model. This has been achieved by the quantitative analysis of the solubility of an aromatic polyamide, denoted as nylon 3Me6T, in a homologous series of aliphatic polyamides. A critical feature of this development required an estimation of the upper and lower bound concentration of methylene units of the latter for which the aromatic polyamide moved from a miscible to immiscible condition. The fabrication of random copolyamides of caprolactam-laurolactam and 2-pyrrolidinone-caprolactam, respectively, has allowed an accurate determination of these critical limits. A survey of the behavior of polyamide blends will be discussed in light of this improved quantitative definition of the model. A principal feature of these analyses is the exclusion of a role for hydrogen bonding interactions. Details concerning the nature of interactions in these systems and how they are influenced by chemical structure are discussed.     

Morphology of polyamide and polyether block amide blends

The morphology of polyamide 12 and polyether block amide blends was investigated by electron microscopy and dynamic mechanical techniques. The blends are not miscible, and phase segregation is observed. In each phase, the lamellar structure of the pure components is observed. The stability of these micro phases is pointed out. When the mass ratio of the hard and soft sequences in the block copolymer is about 4, a partial miscibility takes place.     

Reinforcement factors in fibers from block copolyamides and polyamide blends

The modulus of a fiber can be increased by plying with it a higher-modulus fiber. In this case, the modulus of the combination is characterized by a springs-in-parallel model, and the modulus of the composite is a linear function of the per cent of the second fiber in the composite. Another method of obtaining reinforcement is to melt-blend a higher-modulus polymer with the substrate polymer. With polyamides, this leads to a certain degree of amide interchange and block copolymer formation which depends on the compatibility of the polymers as well as on the usual kinetic factors. If the dispersion of the higher-modulus polymer is such that aggregate size is relatively large (e.g., ≥500 Å) and if the adhesion between the two polymers is good, a springs-in-parallel-type reinforcement is the best which can be obtained. In melt-blend polyamides, a “nonclassical” phenomenon in reinforcement has been noted when the diameters of the dispersed aggregates are ≤500 Å and when there are a relatively high number of hydrogen bonding sites on both polymer components. In this case, it appears that moduli appreciably higher than predicted from a springs-in-parallel model are obtained as well as higher than expected T_g values. A mechanism is proposed to account for this “nonclassical” behavior along with data to support it. Another type of anomaly is observed when the components of the blend are isomorphous. In this case, the reinforcement is considerably less than expected.     

Oxazoline‐containing compatibilizers for polyamide/SAN and polyamide/ABS blends

Polyamide (PA) and acrylonitrile/butadiene/styrene copolymer (ABS) may appear as a mixture in the recycled plastic stream. The incompatibility of these blends results in a blend with poor mechanical properties. The aim of this work is to partially convert the nitrile groups of the acrylonitrile/styrene copolymer (SAN) into oxazoline groups by reaction with aminoethanol (AE). Such modified SAN (SAN‐m) can react with the amine or carboxylic acid end groups of PA, and therefore used as compatibilizers for blends of PA with ABS. SAN‐m was found to reduce the SAN‐domain size in the PA/SAN‐blends. The initial acrylonitrile content of SAN‐m had a strong influence on the degree of conversion into oxazoline groups and on the compatibilizing effect. Mechanical properties of SAN‐m compatibilized PA/ABS blends were investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 449–455, 2002     

Pyrolysis-field ionization mass spectrometry of polyamide copolymers and blends

Nylon foils of PA 6, PA 66, PA 69, PA 12, the copolymer PA 666, and nine blends based on these polymides have been investigated by in-source pyrolysis (Py)–field ionization mass spectrometry (FIMS). These polymers and blends can be distinguished by characteristic molecular ions of oligomers, protonated amines and nitriles, and products terminated by olefinic end groups. Series of ions are formed differing in the number of additional monomeric units. Thus, polymers containing different chemical subunits were easily distinguished from each other in the spectra of the blends. Mass signals, only expected for copolymers, were found in the integrated blend spectra, indicating that amide exchange reactions occur under the experimental conditions employed. This observation was confirmed by pyrolysis of mixtures of pure polymers in the same crucible and under the same experimental conditions. Hence, the distinction by Py–MS alone between blends and copolymers with an identical averaged number of identical chemical subunits is not possible.     

Structural organization and transport properties of iPP/LLDPE blends solidified at controlled cooling rates

The structural organization of blends of isotactic polypropylene (iPP) and linear low‐density polyethylene (LLDPE), with different compositions, was studied and correlated with the thermal history followed by the samples during solidification from the molten state. The materials were cooled at two extreme controlled rates: 0.1 and 500°C/s. The resulting structure was investigated both in the crystalline and the amorphous phases. In particular, attention was focused toward the analysis of the diffusion parameters of dichloromethane vapors, and the morphological organization of the amorphous phases was interpreted using models that consider them (in terms of resistance to diffusion) combined in series and in parallel. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2237–2244, 2001     

Thermal and mechanical behavior of polyamide 6/polyamide 6I/6T blends

The thermal and mechanical properties of blends, obtained by mixing polyamide 6 (PA6) and an amorphous aromatic copolyamide G21 (ISO nomenclature PA 6I/6T), were investigated by differential scanning calorimetry, dynamic mechanical analysis, and mechanical tensile tests. Quenched blends show a single glass transition temperature; the T_g-composition trend was interpreted by means of the Gordon–Taylor equation. The half-time of crystal-lization decreases by increasing the G21 content and this indicates a depression of the overall crystallization rate. A small decrease in the equilibrium melting temperature of PA6 in the blends was observed; this finding suggests that the interaction parameter in PA6/G21 blends is probably very small. The dynamic mechanical analysis of crystallized blends suggests the presence of a homogeneous amorphous phase even if the crystallization of PA6 occurred. The tensile mechanical properties reveal that G21 acts as stiffener of PA6. The collected experimental data suggest that PA6 and G21 are miscible in the composition range investigated. © 1996 John Wiley & Sons, Inc.     

Synthesis and properties of reactively compatibilized polyester and polyamide blends

The functionalization of poly(butylene terephthalate) (PBT) has been accomplished in a twin screw extruder by grafting maleic anhydride (MA) using a free radical polymerization technique. The resulting PBT‐g‐MA was successfully used as a compatibilizer for the binary blends of polyester (PBT) and polyamide (PA66). Enhanced mechanical properties were achieved for the blend containing a small amount (as low as 2.5 %) of PBT‐g‐MA compared to the binary blend of unmodified PBT with PA66. Loss and storage moduli for blends containing compatibilizer were higher than those of uncompatibilized blends or their respective polymers. The grafting and compatibilization reactions were confirmed using FTIR and ¹³C NMR spectroscopy. The properties of these blends were studied in detail by varying the amount of compatibilizer, and the improved mechanical behaviour was correlated with the morphology with the help of scanning electron microscopy. Morphology studies also revealed the interfacial interaction in the blend containing grafted PBT. The improvement in the properties of these blends can be attributed to the effective interaction of grafted maleic anhydride groups with the amino group in PA66. The results indicate that PBT‐g‐MA acts as an effective compatibilizer for the immiscible blends of PBT and PA66. © 2000 Society of Chemical Industry     

Phase behavior study of chitosan/polyamide blends

Blends of chitosan with strongly crystalline polyamides (nylon-4 and nylon-6) and weakly crystalline polyamides (caprolactam/laurolactam and Zytel®) were investigated. Phase behavior, morphology, interactions with water, mechanical properties, and catalytic reactivity were studied. Films were made from formic acid solutions with the chitosan concentrations ranging from 5% to 95% (w/w). The 80% deacetylated chitosan is in the salt, neutral, or copper chelate form. All the blends have higher relative water contents than does the pure chitosan. Dry neutral chitosan shows a relaxation centered at approximately 90°C which is attributed to local motion. The phase behavior of the blends is influenced by preparation conditions such as the drying temperature. Characterization of blends by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) suggests partial miscibility of chitosan with nylon-4 and lack of miscibility in the remaining cases. Blending with nylon-4 enhances mechanical properties with marked antiplasticization in blends containing 90% chitosan. Catalytic activity of the chitosan is enhanced by blending with nylon-4. Salt and neutral forms of chitosan appear to be equally effective. © 1996 John Wiley & Sons, Inc.     

Compatible blends of polypropylene with an amorphous polyamide

Compatible polymer blends of polypropylene (PP) with an amorphous polyamide (aPA) were obtained through reactive compatibilization by adding 20% maleic anhydride‐modified copolymer (PP‐g‐MA) to the blends. The blends were made up of a pure PP phase and an aPA‐rich phase where very small amounts of PP were detected. The dispersed phase particle size decreased considerably indicating that compatibilization occurred. Young's modulus of the compatibilized blends increased with respect to that of the uncompatibilized ones. The compatibilized blends were highly ductile, and the impact strength also improved, proving that compatibilization occurred under a broad range of experimental conditions. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013     

PS/PA6共混体系的研究进展

综述了国内外聚苯乙烯与尼龙6共混的研究进展,分析了共混物的相容性、相形态、结晶性能和流变性能。重点介绍了增容剂对聚苯乙烯与尼龙6共混的增容作用和共混物相形态的变化。     

Morphological studies of glass-microbead-filled polyamide 6.6-polypropylene blends

This article deals with the study of the morphology of glass bead (10% in volume) reinforced compatibilized blends of polypropylene (PP) and polyamide (PA) 6.6. The morphology, as well as some physical and mechanical properties, are determined. The blends are studied in relation with the PP-PA ratio and according to the glass bead's sizing. We have seen the existence of a boundary PA-glass beads interface (independently of the sizing), and the best compatibilization effect is obtained with PP size glass beads and for 50% PP content. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 201–208, 1998     

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     

Crystallization,melting, and rheology of reactive polyamide blends

The crystallization and melting characteristics of a series of polyamide blends based on PA 4,6 and PA 6I were investigated by calorimetric methods; preparation of the samples was conducted so as to control the extent of transamidation occurring in the melt before crystallization. Blend samples with minimal prior thermal history displayed a modest degree of melting point depression compared to the equilibrium melting temperature of PA 4,6 (T = 309.5°C). Application of the Nishi–Wang equation indicated a value of χ = ?0.25 for the blends. PA 4,6 and the blends followed Avrami crystallization kinetics with exponents in the range 2.0 to 2.5; no systematic variation of n with blend composition was observed. The influence of transamidation was investigated for samples exposed to varying melt temperatures and melt times with the extent of transreaction quantified using ¹³C‐NMR. Increasing extents of transreaction led to a decrease in both the rate of crystallization and the overall bulk crystallinity of the blends owing to a reduction in the length and number of crystallizable blocks present along the polymer chains. Capillary rheometry studies indicated a strong sensitivity to time in the melt for the PA 4,6 homopolymer, and the mechanism responsible for the observed decrease in apparent viscosity was also operative in the blend samples. As such, it was not possible to independently assess the influence of transreaction on the rheology of the blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1245–1252, 2004     

Structure-property relationships in polyamide/acrylonitrile-butadiene-styrene (ABS) blends

The structures and physical properties of four blends of poly(acrylonitrile-co-styrene-g-butadiene) (ABS) materials with polycaprolactam (PA6) have been characterized. The blends were separated into components by selective solvent extraction and were found to contain different structures: Blend A contained no PA6 grafts. Blend B contained PA6 grafted onto both soluble and insoluble ABS. Blend C contained PA6 grafted onto soluble poly(styrene-co-acrylonitrile) (p-SAN). In Blend D, PA6 was grafted onto both the insoluble ABS and the p-SAN phases. Transmission electron microscopy showed different morphologies in the blends. Blend A had a co-continuous, somewhat laminar structure, while Blend D consisted of an ABS phase dispersed in a PA6 continuum. Blends B and C had intermediate structures. All four blends, however, had very similar rheological and physical properties despite the variation in structure.     

Effects of composition of modified polyamide on barrier properties of polyethylene/modified polyamide blends

A systematic study on the effects of types and contents of compatibilizer precursors (CPs) on degrees of crystallinity (W_c), melt shear viscosities (η_s), and permeation barrier properties of modified polyamides (MPAs) and on their corresponding morphology and barrier properties of bottles blow-molded from polyethylene (PE)/MPA blends is reported. Two alkylcarboxyl-substituted polyolefins were selected as CPs to modify PA and to improve its permeation resistance to xylene by the “reactive extrusion” process. The barrier improvements of MPAs prepared in this study depend significantly on the type and content of CP present in the MPA. A maximum improvement in barrier properties of each MPA series samples were found as the contents of CP reached an “optimum” value. On the other hand, it is interesting to note that bottles blow-molded from PE/MPA series samples exhibited better barrier properties because the MPAs used were associated with better permeation resistance to xylene. The melt shear viscosities of MPAs were found to depend on the type of CP used and increase with increasing CP contents. In contrast, the W_c of MPAs decreased with increasing CP contents. Further analysis of the fracture surfaces of bottles blow-molded from PE/MPA blends also indicated that the morphology of MPA laminas depended on the type of CP present in the MPA, and these MPA laminar structures became clearer as the contents of CPs increased. Possible mechanisms accounting for the interesting behaviors described above are discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1531–1540, 1997     

Polyarylate/polyamide 6 blends: A calorimetric study

Summary A calorimetric study has been done of the miscibility of blends composed of polyarylate (PAr) and poly(-caprolactam) (polyamide 6, nylon 6). The thermal transitions of blends subjected to two different thermal treatments have been determined. Two glass transitions have been observed in the blends irrespective of the thermal history. These glass transitions indicate the existence of two amorphous phases in the blends, a practically pure nylon phase and a mixed PAr/nylon 6 phase. The variation of the melting temperature of nylon with the blend composition is in good agreement with the existence of phase separation in the blends. However, the melting heat shows a slightly positive deviation from linearity when it is represented against the blend composition.     

Fusion bonding of maleated polyethylene blends to polyamide 6

Blends of linear low-density polyethylene (LLDPE) and linear low-density polyethylene–grafted maleic anhydride (LLDPE-gMA) were used to promote the adhesion to polyamide 6 (PA) in a three-layer coextruded film without using an additional adhesive or tie layer. The effect of bonding time and molecular weight (MW) of different maleated polyethylenes on the peel strength of the joints was analyzed. Direct evidence of a copolymer formed in-situ at the interfaces is also considered. The peel strength of fusion bonded layers of LLDPE/LLDPE-gMA blends with PA strongly depends on bonding time and molecular weight of the maleated polymer. Tensile properties of three-layer films, made up of PA as the central layer and LLDPE/LLDPE-gMA blends as the two external layers, are improved with increases in the maleic anhydride (MA) content in the blend. The in-situ formation of a copolymer between the MA in the blend and the terminal amine groups of the PA was confirmed by the Molau test, infrared (IR) spectroscopy, and thermal analysis (DSC).