Linear viscoelastic properties of high‐density polyethylene/polyamide‐6 blends extruded in the presence of ultrasonic oscillations

Blends of high‐density polyethylene (HDPE) and polyamide‐6 (PA6) were produced by ultrasonic extrusion. Ultrasonic irradiation leads to degradation of polymers and in situ compatibilization of blends as confirmed by variations in linear viscoelastic properties. The results showed that the effect of ultrasonic irradiation on dynamic rheological properties depends on the composition and experimental temperature. At the same time, the relationship between storage modulus and loss modulus indicated the effect of ultrasonic irradiation on compatibility of HDPE/PA6 blends. Based on an emulsion model, the interfacial tension between the matrix and the dispersed phase was predicted. The data obtained showed that ultrasonic irradiation can decrease the interfacial tension and then enhance the compatibility of HDPE/PA6 blends. This finding was consistent with our previous work. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1260–1269, 2005     

The effect of polyethylene addition on the morphology of polystyrene/polyamide blends

The effect of a small admixture of high‐density polyethylene (HDPE) with a high or low viscosity to polystyrene/polyamide (PS/PA) blends of various compositions was studied. PS/PA blends with composition near 50/50 form sheet‐like or fiber‐like morphology at mixing that passes to the cocontinuous structure during compression molding. Ternary PS/PA/HDPE blends with PS/PA ratio about 50/50 show similar behavior. Generally, neither continuity nor shape of PS and PA phases was changed qualitatively by the addition of a small amount of HDPE. In agreement with existing rules for ternary blends, HDPE particles prefer a contact with PS phase to PA phase. On the other hand, none of these rules explains why a number of small HDPE subinclusions were dispersed into PS particles instead of HDPE‐PS core‐shell structure with a lower Gibbs free energy. Quantitative evaluation of the size of PA particles in blends with PS matrix showed that the previously proposed rule stating, that the addition of a small amount of a third immiscible component leads to a strong decrease in the size of dispersed particles, was not valid for the blends studied in this work. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2158–2170, 2009     

Barrier,Mechanical, Morphological and Thermal Properties of Compatibilized High Density Polyethylene and Polyamide 6 Blends

Effectiveness of the content of maleic anhydride (MAH) and polyamide 6 (PA6) on mechanical, thermal, barrier (moisture and oxygen) properties of HDPE/PA6 blends was investigated. Blends of HDPE with PA6 were prepared by in situ method. Molau test and FTIR spectroscopy results confirmed the reactive compatibilization through grafting of MAH on HDPE and PA6 chains in PA6/HDPE blends. Low concentration of benzoyl peroxide (BPO) and MAH reduced the particle size, improved phase morphology and mechanical properties of PA6/HDPE blends. Decrease in mechanical properties of PA6/HDPE blends was observed at high concentration of BPO and MAH.     

Does nanoclay addition always lead to amelioration? Dual effects of the nanoclay on the PA‐6/EVOH/SEBS ternary blends

This work presents the investigation of properties of polyamide‐6 (PA‐6)/ethylene vinyl alcohol (EVOH)/styrene‐ethylene‐butylene‐styrene (SEBS) ternary blends and related nanocomposites with nanoclays. In this way, the effect of the mixing protocol and nanoclay type on the morphology, mechanical, and rheological properties of the blends was comprehensively studied. Scanning electron microscopy (SEM) observation revealed that, for the neat ternary blends, core‐shell droplets were formed in which SEBS droplets were encapsulated by EVOH phase in the PA‐6 matrix. In this regard, experimental observations were compared and discussed with the predictions of phenomenological models. According to the X‐ray diffraction analysis, the distribution and degree of dispersion of the nanoclays were significantly influenced by mixing protocol. It was demonstrated that competition between the intrinsic effect of the nanoclay on the physical properties and its inhibiting effect on the interactions between PA‐6 and EVOH phases led to some interesting observations for the rheological and mechanical properties of the ternary blends. The results revealed that optimum properties could be obtained by selecting appropriate nanoclay and mixing protocol.     

Effect of compatibilizer on morphology and properties of HDPE/Nylon 6 blends

The compatibilization effect of linear low‐density polyethylene‐grafted maleic anhydride (LLDPEgMA) and high‐density polyethylene‐grafted maleic anhydride (HDPEgMA) on high‐density polyethylene (HDPE)/polyamide 6 (Nylon 6) blend system is investigated. The morphology of 45 wt %/55 wt % polyethylene/Nylon 6 blends with three compatibilizer compositions (5 wt %, 10 wt %, and 15 wt %) are characterized by atomic force microscopic (AFM) phase imaging. The blend with 5 wt % LLDPEgMA demonstrates a Nylon 6 continuous, HDPE dispersed morphology. Increased amount of LLDPEgMA leads to sharp transition in morphology to HDPE continuous, Nylon 6 dispersed morphology. Whereas, increasing HDPEgMA concentration in the same blends results in gradual morphology transition from Nylon 6 continuous to co‐continuous morphology. The mechanical properties, oxygen permeability, and water vapor permeability are measured on the blends which confirm the morphology and indicate that HDPEgMA is a better compatibilizer than LLDPEgMA for the HDPE/Nylon 6 blend system. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 281–290     

Thermal studies on polypropylene/polyamide‐6 blends modified by succinic anhydride and succinyl fluorescein grafted polypropylenes

This study investigates the role played by two different interface agents on the basis of atactic polypropylene in the continuous/disperse phase polypropylene/polyamide‐6 (PP/PA6) system. The two agents used were obtained at the authors' laboratories from an atactic polypropylene byproduct derived from industrial polymerization reactors and consist of two grafted polymers containing either succinic anhydride (a‐PP‐SA) or both succinyl‐fluorescein and succinic anhydride grafted groups (a‐PP‐SF/SA). The role of these grafted polymers as compatibilizers in PP/PA6 polymer blends has been confirmed in previous investigations on the basis of their macroscopic behavior. This work investigates the thermal study of these blends where polypropylene acts as the polymer matrix and polyamide as the dispersed phase. Under isothermal conditions, thermal analysis agrees with the changes in the overall system behavior caused by the presence of the interface agents. These aspects were confirmed by polarized light microscopy that showed the morphology of the blends before and after modification with a‐PP‐SA or a‐PP‐SF/SA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1307–1315, 2002     

Friction and wear mechanisms of polyamide 66/high density polyethylene blends

Polyamide 66 (PA66)/high density polyethylene (HDPE) blends having miscible structure were produced by compatibilization of HDPE grafted with maleic anhydride (HDPE‐g‐MAH). Mechanical and tribological properties of blends in different compositions were tested. It was found that the polymer blends greatly improved the mechanical properties of PA66 and HDPE. Blending HDPE with PA66 significantly decreased the friction coefficient of PA66; the friction coefficients of blends with different compositions were almost the same and approximately equal to that of pure HDPE; the blends with 80 vol % PA66 exhibited the best wear resistance. The transfer films, counterpart surfaces, and wear debris formed during sliding were investigated by Scanning Electron Microscopy (SEM), and Differential Scanning Calorimetry (DSC) analysis was further carried out on wear debris. These investigations indicated that the thermal control of friction model is applicable to PA66/HDPE blend, that is the friction coefficient of blend is governed by the HDPE component, which possesses a lower softening point relative to the PA66 component in this system. The wear mechanism of PA66/HDPE blend transforms from PA66 to HDPE as the HDPE content increases. PA66, as the component with higher softening point, increases the hardness of blend, enhances the ability of blend to form a transfer film on the counterface, and inhibits the formation of larger belt‐like debris of HDPE, at the same time, the presence of self‐lubricating HDPE in the system decreases the friction coefficient and the frictional heat, all of these factors are favorable for the wear resistance of PA66/HDPE blend. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2514–2523, 2005     

Development of morphology and properties of injection‐molded bars of HDPE/PA6 blends along flow direction

The structure and mechanical properties of injection‐molded bars of high‐density polyethylene (HDPE)/PA6 blends were studied in this article. The experimental results showed that the morphologies of injection‐molded bars change gradually along the flow direction, which is tightly related to the melt viscosity and processing conditions. The higher melt viscosity, lower mold temperature, and shorter packing time, restricting the macromolecular relaxation, enhance the difference in morphologies and properties at near and far parts of a mold. An injection‐molded bar (namely H2C5), consisting of 75 wt % of HDPE, 20 wt % of PA6, and 5 wt % of compatibilizer (HDPE‐g‐MAH), showed a greater difference in mechanical properties at near and far parts because of its higher melt viscosity. A clear interface between the skin and core layers of near part in it leads to a much higher impact strength than that of far part. And tensile tests show that its tensile strength of near part is higher than that of far part due to the higher orientation degrees of HDPE matrix and PA6 dispersed phase in near part. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 184–195, 2007     

Phase morphology development in PP/PA6 blends induced by a maleated thermoplastic elastomer

The effects of maleated thermoplastic elastomer (TPEg) on morphological development of polypropylene (PP)/polyamide 6 (PA6) blends with a fixed PA6 content (30 wt %) were investigated. For purpose of comparison, nonmaleated thermoplastic elastomer (TPE) was also added to the above binary blends. A comparative study of FTIR spectroscopy in above both ternary blends confirmed the formation of in situ graft copolymer in the PP/PA6/TPEg blend. Dynamic mechanical analysis (DMA) indicated that un‐like TPE, the incorporation of TPEg remarkably affected both intensity and position of loss peaks of blend components. Scanning electron microscopy (SEM) demonstrated that PP/PA6/TPE blends still exhibited poor interfacial adhesion between the dispersed phase and matrix. However, the use of TPEg induced a finer dispersion and promoted interfacial adhesion. Transmission electron microscopy (TEM) for PP/PA6/TPEg blends showed that a core‐shell structure consisting of PA6 particles encapsulated by an interlayer was formed in PP matrix. With the concentration of TPEg increasing, the dispersed core‐shell particles morphology was found to transform from discrete acorn‐type particles to agglomerate with increasing degree of encapsulation. The modified Harkin's equation was applied to illustrate the evolution of morphology with TPEg concentration. “Droplet‐sandwiched experiments” further confirmed the encapsulation morphology in PP/PA6/TPEg blends. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1050–1061, 2006     

Largely enhanced ductility of immiscible high density polyethylene/polyamide 6 blends via nano‐bridge effect of functionalized multiwalled carbon nanotubes

Immiscible polymer blends usually exhibit negative deviation in mechanical properties compared with the corresponding pure polymers due to the weak interfacial bonding between the two polymers. Due to the bridge effect of the oriented carbon nanotubes (CNTs) on the craze and crack development at the load of stress, CNTs have been proved to be efficient toughening agent for polymers. In this work, functionalized multiwalled carbon nanotubes (FMWCNTs) have been introduced into immiscible high density polyethylene/polyamide 6 (HDPE/PA6) blends through different sample preparation methods. The mechanical measurements demonstrate that, when the nanocomposite is prepared from the HDPE master batch, the sample exhibits excellent tensile strength and toughness simultaneously. For all the nanocomposites, FMWCNTs tend to migrate and/or maintain in PA6 particles, leading to the variation of the crystallization behavior in PA6 phase. Further results based on morphologies characterization indicate that the intensified interfacial adhesion between HDPE and PA6, which is realized by the nano‐bridge effect of FMWCNTs in the interfaces, is the main reason for the largely improved ductility. Copyright © 2010 John Wiley & Sons, Ltd.     

Solid-state morphology,structure, and tensile properties of polyethylene/polyamide/nanoclay blends: Effect of clay fraction

The effect of nanoclay fraction on the linear and non-linear tensile properties of a polyethylene/polyamide 12 blend with droplet morphology was investigated. All ternary blends were prepared at a fixed polyamide (PA) weight fraction of 20%, and at clay volume fractions varying from 0.5 to 2.5% relative to PA. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the blends and the clay interphase structure. The nanoclay content was shown to strongly influence both linear and non-linear tensile properties. Young's modulus, elongation at yield, yield strength, tensile strength and elongation at break as a function of clay fraction were studied and discussed in terms of morphological changes and strain-induced structural reorganization of the clay interphase.     

Ester–amide exchange in blends of liquid‐crystalline copolyester and polyamide 6

The kinetics of the ester–amide exchange in solution blends of the random liquid‐crystalline polyester copoly(oxybenzoate‐terephthalate) (P64) and polyamide 6 (PA6) were studied with carbon nuclear magnetic resonance. With second‐order reversible reactions assumed, the activation energy of the ester–amide interchange in 30/70, 50/50, and 70/30 P64/PA6 blends were all about 24.0 kcal/mol. The pre‐exponential factors for the ester–amide exchange in 30/70, 50/50, and 70/30 P64/PA6 blends were 2.01 × 10¹¹, 2.59 × 10¹⁰, and 2.74 × 10¹² min⁻¹, respectively. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2124–2135, 2000     

Influence of preparation methods on the structures and properties for the blends between polyamide 6co6T and polyamide 6: Melt‐mixing and in‐situ blending

Two blends between polyamide 6 (PA6) and Polyamide 6co6T (PA6co6T, a random copolymer between polyamide 6 and polyamide 6T) were fabricated by melt‐mixing on a twin‐screw extruder and the subsequent injection molding, or through the in‐situ polymerization of ε‐caprolactam in the presence of PA6co6T. As far as the former method is concerned, there exist an obvious decline of toughness and a slight increase in strength and modulus; however, for the latter, there appear a remarkable improvement in toughness and a simultaneous moderate increase in strength and modulus. A series of characterizations were carried out including scanning electron microscopy, wide‐angle X‐ray diffraction, polarized optical microscopy, differential scanning calorimetry, dynamic mechanical analysis, and Fourier transform infrared spectrometry. It is found that both blends exhibit single glass transition on DMA tan δ curves. However, contrary to that of the melt‐mixed blends, the glass transition temperature (T_g) of the in‐situ ones decreases with increasing PA6co6T content. It is suggested that different mixing levels are the main reasons. Moreover, the addition of PA6co6T containing linear rigid segments conducts remarkable refinement of spherulites for the blends. Significantly different changes in the crystallographic form, spherulite size, crystalline content and perfection due to the introduction of PA6co6T for the two blends are ascribed to their varied thermomechanical histories and the presence of interchange reaction only for the in‐situ blends. On the basis of the characterizations of the microstructures, the different trends of changes in the mechanical properties with the addition of PA6co6T for the two fabrication methods are discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 201–211, 2008     

Impact properties,phase structure,compatibility, and fracture morphology of polyamide‐1010/thermoplastic poly(ester urethane) elastomer blends

Blends of polyamide‐1010 (PA1010) and a thermoplastic poly(ester urethane) elastomer (TPU) were prepared by melt extrusion. The impact properties, phase structure, compatibility, and fracture morphology under impact were investigated for PA1010/TPU blends. The results indicated that TPU enhanced the impact strength of PA1010, and the best impact modification effect of the blends was obtained with 20 wt % TPU. The phase structure was investigated with scanning electron microscopy, and the compatibility was investigated with dynamic mechanical analysis and small‐angle X‐ray scattering. The study of the fracture morphology of PA1010/TPU blends indicated that the fracture surface of the blends had special features, consisting of many fibrillar elastomer particles and a conglutination–multilayer structure, as well as many small tubers on this structure. These fracture phenomena could not be found on the fracture surface of pure PA1010. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1177–1185, 2005     

Barrier property enhancement of polyamide 6 by blending with a polyhydroxyamino‐ether resin

In this work, the transport properties of the system formed by polyamide 6 (PA6) and polyhydroxyamino‐ether resin (PHAE) have been studied after characterizing the miscibility behavior. A single glass transition has been observed using differential scanning calorimetry that usually means total miscibility, but measurements by solid‐state cross‐polarization magic angle spinning NMR have shown that this system is only partially miscible, in good agreement with phase behavior reported before. Both carbon dioxide and water vapor transport properties of PA6/PHAE blends have been measured. For both penetrants, permeability coefficient shows an interesting negative deviation from the additive value, even the barrier character to carbon dioxide of pure PHAE is maintained up to 60 % in PA6 composition. Besides, PHAE reduces the plasticization effect of water in PA6. These improvements are very interesting for the PA 6 due to its wide use in packaging applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1625–1634, 2009     

Photo-oxidation behaviour of polyethylene/polyamide 6 blends filled with organomodified clay: Improvement of the photo-resistance through morphology modification

The impact of small amounts of organomodified clay (OMMT) on the photo-degradation behaviour of two blends obtained by mixing either low-density polyethylene (LDPE) or high density polyethylene (HDPE) with polyamide 6 (PA6) (LDPE/PA6 and HDPE/PA6 75/25 wt-%) was studied. The complex photo-degradation behaviour was followed by monitoring the main physical-mechanical properties of the blends. In particular, mechanical and spectroscopic tests were performed in conditions of accelerated artificial aging. An accurate mechanical and morphological characterization was previously carried out. The presence of the OMMT promotes the unexpected formation of a co-continuous morphology for the HDPE/PA6 blend without significantly improving the interfacial adhesion. Differently, the OMMT-filled LDPE/PA6 blend exhibits a finely distributed morphology, and some apparent improvement of the interfacial adhesion was noticed. Probably due to these differences in microstructure, a different impact of the nanoparticles on the photo-resistance behaviours was observed for the two families of samples. In particular, the HDPE-based nanocomposite blend exhibits an improved photo-resistance, while the opposite occurs for the LDPE-based system.     

Rheological behavior of PET/HDPE in situ microfibrillar blends: Influence of microfibrils' flexibility

Poly(ethylene terephthalate) (PET)/high‐density polyethylene (HDPE) in situ microfibrillar reinforced blends were prepared via a slit die extrusion‐hot stretch‐quenching process. The in situ PET microfibrils contain various contents of a segmented thermoplastic elastomer, Hytrel 5526 (HT), hence having different flexibility as demonstrated by dynamic mechanical analysis. It is interesting that the simple mixing leads to nanoscale particles of the HT phase in PET phase, and the size of the HT particles is almost independent of the HT concentration, as observed from the scanning electron microscope micrographs which show that the microfibrils with different HT concentrations have almost the same diameter and smooth surfaces. The static rheological results by an advanced capillary rheometer show that the entrance pressure drop and the viscosity of the microfibrillar blends both reduced with increasing the microfibrils' flexibility. Furthermore, the data obtained by the temperature scan of the PET/HT/HDPE microfibrillar blends through a dynamic rheometer indicates that the more flexible microfibril leads to lower melt elasticity and slightly decreases the viscosities of blends, presenting a consistent conclusion about influences of the microfibrils' flexibility on the rheological behavior from the static rheometer measurements. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1205–1216, 2007     

Thermal oxidative stability and effect of water on gas transport and mechanical properties in PA6‐EVOH films

The thermal oxidative stability and the effect of water on gas transport and mechanical properties of blends of polyamide 6 (PA6) with ethylene‐co‐vinyl alcohol (EVOH) and EVOH modified with carboxyl groups (EVOH‐COOH) have been investigated. The presence of EVOH reduces water vapor and oxygen gas permeability of polyamide, as well as small amounts of EVOH‐COOH further improve barrier properties, especially to oxygen. This has been explained in terms of improved interactions of the blend constituents in the amorphous phase, due to ionic linkages between the polyamide amino groups and the carboxyls of modified EVOH. The permeation to gases was found to increase with the amount of sorbed water. The morphology of the samples was found to have an effect on barrier properties, as the presence of EVOH causes the PA6 α crystalline form to increase, lowering the permeability to oxygen and water vapor. Mechanical properties are strongly affected by water sorption, as tensile modulus and strength decrease with increasing water content. Chemiluminescence (CL), infrared spectroscopy (FTIR), and tensile test were employed in order to assess the correlation between chemical composition and the thermal oxidative stability of the films aged at 110 °C in air. CL experiments suggest that the presence of EVOH and EVOH‐COOH efficiently inhibits the formation of peroxidized species during the processing, and increases the thermal oxidative stability of the films. Infrared spectroscopy showed a build‐up of carbonyl absorption in the range 1700–1780 cm^?1, due to the formation of oxidation products, which is greater in the case of the pure polymer. Tensile tests on films revealed a reduction in ductility as a result of ageing for neat PA6, whereas in comparison the blends exhibit a far better long‐term stability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 840–849, 2007     

Effect of the microstructure on the dye diffusion and mechanical properties of polyamide‐6 fibers

The morphology, mechanical properties, and dye diffusion of drawn and heat‐set polyamide‐6 (PA6) yarns were examined. Correlations between the microstructure of PA6 yarns and the dye diffusion coefficients and mechanical properties were established. The crystallinity of PA6 yarns was estimated with density and Fourier transform infrared spectroscopy measurements. A decrease in the γ crystallinity and an increase in the γ‐crystallite size with the draw ratio were observed and attributed to the disappearance of small crystallites and an increase in the average γ‐crystallite size population during the deformation process. The scouring treatment increased the total crystallinity, almost entirely as a result of an increase in the α fraction. Thermally induced crystallization involved increases in both crystalline phases (α and γ) and did not involve crystal‐to‐crystal transformation, whereas drawing PA6 yarns involved both crystallization of the amorphous phase in the α form and γ→α transformation. A sharp decrease in the diffusion coefficient with an increasing draw ratio of PA6 yarns was correlated with an increasing amorphous orientation. The influence of thermally induced crystallinity on the diffusion coefficient seemed exceptionally strong. The mechanical properties of PA6 yarns were examined and correlated with structural changes. It was demonstrated that the crystallinity had a direct correlation with the terminal modulus and extension at break, whereas there was no correlation with the initial modulus. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 349–357, 2007     

Reactive compatibilization of polyamide‐6 (PA 6)/polybutylene terephthalate (PBT) blends by a multifunctional epoxy resin

A multifunctional epoxy resin has been demonstrated to be an efficient reactive compatibilizer for the incompatible and immiscible blends of polyamide‐6 (PA 6) and polybutylene terephthalate (PBT). The torque measurements give indirect evidence that the reaction between PA and PBT with epoxy has an opportunity to produce an in situ formed copolymer, which can be as an effective compatibilizer to reduce and suppress the size of the disperse phase, and to greatly enhance mechanical properties of PA/PBT blends. The mechanical property improvement is more pronounced in the PA‐rich blends than that in the PBT‐rich blends. The fracture behavior of the blend with less than 0.3 phr compatibilizer is governed by a particle pullout mechanism, whereas shear yielding is dominant in the fracture behavior of the blend with more than 0.3 phr compatibilizer. As the melt and crystallization temperatures of the base polymers are so close, either PA or PBT can be regarded as a mutual nucleating agent to enhance the crystallization on the other component. The presence of compatibilizer and in situ formed copolymer in the compatibilized blends tends to interfere with the crystallization of the base polymers in various blends. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 23–33, 2000