Crystallisation behaviour of HDPE in PA6/EPDM-g-MA/HDPE ternary blend with different phase morphology

Morphology of polyamide/maleic anhydride grafted ethylene-propylene-diene monomer/high density polyethylene (PA6/EPDM-g-MA/HDPE) blend and crystallisation behaviour of HDPE in PA6/EPDM-g-MA/HDPE blend were studied by scanning electron microscopy, transmission electron microscope and differential scanning calorimetry (DSC). Morphology observation revealed that core–shell morphology with shell of EPDM-g-MA and core of HDPE was formed in PA6 matrix. DSC test indicated that unexpected result of HDPE double crystallisation peaks emerged for ternary blend system. Also the low temperature crystallisation peak of HDPE was confirmed to be induced as a result of hindered nucleation of HDPE in fine dispersed core–shell particles and the process of crystalline shrinkage of PA6 matrix during cooling process. Furthermore, the factors influencing the crystallisation behaviour of HDPE were systematically studied in this work. The content of EPDM-g-MA and the time of melt mixing significantly affected the crystallisation behaviour of HDPE while the crystallinity of PA6 had a little effect on the crystallisation behaviour of HDPE. The results demonstrated an intimate relationship between phase morphology and crystallisation behaviour of HDPE.     

Morphology prediction and the effect of core‐shell structure on the rheological behavior of PP/EPDM/HDPE ternary blends

In this work, the morphologies of polypropylene (PP)/ethylene‐propylene‐diene (EPDM) rubber/high density polyethylene (HDPE) 70/20/10 blends were studied and compared with the predictions of the spreading coefficient and minimum free energy models. The interfacial tension of PP/HDPE, PP/EPDM, and HDPE/EPDM blends were obtained by fitting the experimental dynamic storage modulus data to Palierne's theory. The prediction results showed core‐shell morphology (core of HDPE and shell of EPDM) in PP matrix. The PP/EPDM/HDPE blends were respectively prepared by direct extrusion and lateral injection method. Core‐shell morphology (core of HDPE and shell of EPDM) could be obtained with direct extrusion corresponding to the predicted morphology. The morphology of PP/EPDM/HDPE blends could be effectively controlled by lateral injection method. For PP/EPDM/HDPE blend prepared by lateral injection method, HDPE and EPDM phase were dispersed independently in PP matrix. It was found that the different morphology of PP/EPDM/HDPE blends prepared by two methods showed different rheological behavior. When the core‐shell morphology (core of HDPE and shell of EPDM) appeared, the EPDM shell could confine the deformation of HDPE core significantly, so the interfacial energy contribution of dispersed phase on the storage modulus of blends would be weaken in the low frequency region. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Effect of core‐shell morphology evolution on the rheology,crystallization, and mechanical properties of PA6/EPDM‐g‐MA/HDPE ternary blend

In this article, polyamide 6 (PA6), maleic anhydride grafted ethylene‐propylene‐diene monomer (EPDM‐g‐MA), high‐density polyethylene (HDPE) were simultaneously added into an internal mixer to melt‐mixing for different periods. The relationship between morphology and rheological behaviors, crystallization, mechanical properties of PA6/EPDM‐g‐MA/HDPE blends were studied. The phase morphology observation revealed that PA6/EPDM‐g‐MA/HDPE (70/15/15 wt %) blend is constituted from PA6 matrix in which is dispersed core‐shell droplets of HDPE core encapsulated by EPDM‐g‐MA phase and indicated that the mixing time played a crucial role on the evolution of the core‐shell morphology. Rheological measurement manifested that the complex viscosity and storage modulus of ternary blends were notable higher than the pure polymer blends and binary blends which ascribed different phase morphology. Moreover, the maximum notched impact strength of PA6/EPDM‐g‐MA/HDPE blend was 80.7 KJ/m² and this value was 10–11 times higher than that of pure PA6. Particularly, differential scanning calorimetry results indicated that the bulk crystallization temperature of HDPE (114.6°C) was partly weakened and a new crystallization peak appeared at a lower temperature of around 102.2°C as a result of co‐crystal of HDPE and EPDM‐g‐MA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Ternary nylon-6/rubber/modified rubber blends: Effect of the mixing procedure on morphology, mechanical and impact properties

Ternary polyamide-based blends have been prepared by adding to nylon-6 (PA6) an ethylene-propylene random copolymer (EPM) and the same EPM functionalized by inserting onto its backbone maleic anhydride groups (EPM-g-SA). Two kinds of processing have been used: (a) one-step mixing in which the three components were simultaneously introduced in the mixer; (b) two-step mixing in which the two rubbers EPM and EPM-g-SA were separately premixed before the final mixing with PA6. Also binary PA6/EPM-g-SA blends have been prepared to compare their properties with those of the ternary one.

Mechanical tensile characterization at room temperature and impact Izod tests at different temperatures as well as a morphological analysis of smoothed samples have been performed on all the blends. It has been shown by a model reaction that both in binary and ternary blends an EPM-g-PA6 graft copolymer is formed, which acts as an interfacial agent between the rubbery dispersed phase and the polyamide matrix. The blends obtained by the one-step mixing showed a gross morphology and a very poor impact resistance, whereas the ones prepared by the two-step mixing exhibited very fine morphologies and excellent impact performances. In addition, as shown at least in the case of one ternary blend, there seems to be good morphological stability of these materials after a second processing. This has been attributed to the influence of the interfacial agent formed during the melt mixing of the two premixed rubbers with PA6.     

Microscopic Deformation Behavior and Crack Resistance Mechanism of Core–Shell Structures in Highly-Toughened PP/PA6/EPDM-g-MA Ternary Blends

Highly-toughened blends, comprising polypropylene, polyamide 6, and maleic anhydride-grafted ethylene-propylene-diene monomer rubber (PP/PA6/EPDM-g-MA), of core–shell morphology are prepared and impact of microstructural development, at different PA6:EPDM-g-MA weight ratios (fixed at 30 wt%), on macroscopic mechanical and fracture characteristics of blends is studied through in-depth analysis of micromechanical deformations operating in the blends. The role of dispersion state of modifier domains on nucleation and evolution of various microscopic deformations accompanying the fracture process under impact and quasi-static fracture tests is closely examined. Increase in EPDM-g-MA:PA6 ratio develops agglomerated core–shell domains in the form of extended island-like structures. While impact data show significant synergistic toughening effect of dispersed composite domains in ternary blends compared with PP/EPDM-g-MA (70/30) binary blend, fracture works show a sole dependence on rubbery fraction. Fractography examinations reveal deformation of dispersed domains, development of multiple voids, and highly deformed craze-like void-fibrillar structures within core–shell structures as well as at their interfaces with surrounding matrix. The importance of deformation zones in activation and promotion of matrix shear yielding is clarified, while their function as crack nucleation and subsequent crack propagation trajectories is highlighted. The stability of void-fibrillar zones is found essential for extensive plastic deformation and premature failure prevention.     

Towards Quantifying Interfacial Adhesion in the Ternary Blends with Matrix/Shell/Core-Type Morphology

We quantified interfacial adhesion in ternary blends with matrix/shell/core microstructure based on mechanical properties assessments. Various HDPE-based ternary blends containing PA-6/EVOH core/shell droplets were prepared by changing composition and processing temperature. The theoretical predictions of tensile properties were compared with experimental data; thereby considerable shift in experimental modulus from lower to upper limit observed over a 10°C increase in melting temperature. This confirmed the impact of blending temperature on matching the predicted values with experimental data. The meaningful trend observed in tensile characteristics of ternary blends simply gives an understanding of interfacial adhesion degree in ternary blend showing matrix/shell/core microstructure.     

Effect of EPDM‐g‐MAH on the morphology and properties of PA6/EPDM/HDPE ternary blends

The formation of core‐shell morphology within the dispersed phase was studied for composite droplet polymer‐blend systems comprising a polyamide‐6 matrix, ethylene‐propylene‐diene terpolymer (EPDM) shell and high density polyethylene (HDPE) core. In this article, the effect of EPDM with different molecular weights on the morphology and properties of the blends were studied. To improve the compatibility of the ternary blends, EPDM was modified by grafting with maleic anhydride (EPDM‐g‐MAH). It was found that core‐shell morphology with EPDM‐g‐MAH as shell and HDPE as core and separated dispersion morphology of EPDM‐g‐MAH and HDPE phase were obtained separately in PA6 matrix with different molecular weights of EPDM‐g‐MAH in the blends. DSC measurement indicated that there may be some co‐crystals in the blends due to the formation of core‐shell structure. Mechanical tests showed that PA6/EPDM‐g‐MAH/HDPE ternary blends with the core‐shell morphology exhibited a remarkable rise in the elongation at break. With more perfect core‐shell composite droplets and co‐crystals, the impact strength of the ternary blends could be greatly increased to 51.38 kJ m^?2, almost 10 times higher than that of pure PA6 (5.50 kJ m^?2). POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

十八烷基缩水甘油醚的合成及其增容尼龙6/高密度聚乙烯共混体系的研究

利用十八醇和环氧氯丙烷反应合成了十八烷基缩水甘油醚(OGE),并将其作为熔融共混方法中的增容剂,制备了尼龙6(PA6)/高密度聚乙烯(HDPE)共混材料。研究了OGE用量对共混物的热性能、结晶行为、形态结构、力学性能及吸水性的影响。结果表明,OGE促进了HDPE在PA6基体中的分散,在保持共混材料吸水率的同时,有效改善了共混物的力学性能,与未加入增容剂的PA6/HDPE共混物相比,OGE含量为2.9%(m/m)时,共混材料的缺口冲击强度、拉伸模量、断裂伸长率、弯曲强度分别提高了12%、33%、95%、6%,拉伸强度基本保持不变,而弯曲模量下降了8%。     

A probe into the status quo of interfacial adhesion in the compatibilized ternary blends with core/shell droplets: Selective versus dictated compatibilization

A simple approach was applied to probe into the situation of interfacial adhesion in the compatibilized ternary polymer blends with core/shell morphology. The performance of compatibilization was discussed in terms of thermal, rheological, and mechanical properties analyses for blends prepared through different mixing strategies for which maleic anhydride‐grafted high‐density polyethylene (HDPE‐g‐MAH) could be localized at the interface of HDPE/poly(ethylene‐co‐vinyl alcohol) copolymer (EVOH) or HDPE/polyamide 6 (PA‐6) in their ternary blends. Two mixing strategies, one simultaneously (one‐step or selective) and two sequentially (two‐step or dictated), were performed, compared, and discussed. It was found that mixing policy (dictated or selective) significantly changes the interfacial adhesion, as signaled by variations in rheological and thermal properties. In the case of mechanical properties, facilitation of stress transfer across the matrix/shell/core interfaces was detected by calculation of semi‐experimental models' coefficients. It was found that one‐step mixing or selective localization of HDPE‐g‐MAH helps in accumulation of more compatibilizer molecules at the interface HDPE/EVOH or EVOH/PA‐6. By contrast, addition of compatibilizer to minor phase (masterbatch of EVOH and PA‐6) or to HDPE matrix alone in case of two‐step blending causes imperfect stress transfer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45503.     

Elasticity or viscosity,which one is more influential on the internal structure of a core-shell morphology in ternary blends?

The goal of this research was to study the internal phase structure of core-shell morphology within a ternary blend and look into the affecting parameters. In this way, a series of SEBS/SAN/PA6 ternary blends representing core-shell morphology were prepared and effect of viscosity and elasticity of core-forming component on the phase structure of core droplets were investigated. Studies based on the scanning electron microscopy micrographs demonstrated that elasticity plays a more dominant role on the formation of single or multi-core droplets. In addition, it was inferred that absolute elasticity of core component is more influential rather than elasticity ratio of core and shell components. Furthermore, morphology of prepared samples compared with predictions of DIE and modified DIE conceptual models.     

制备HDPE/PA-6阻隔性共混合金工艺条件的研究

本文通过测试HDPE、PA 6的流变性能、共混合金的溶剂透过率和PCM,研究了制得阻隔性层状HDPE/PA 6共混合金工艺条件,如加工温度、剪切速率和混合时间等。结果表明:改变加工温度可以调节HDPE/PA 6共混组成粘度比,当PA 6与HDPE的粘度比较大时,能得到PA 6相呈层状分布结构的阻隔性共混合金;剪切作用有利于共混体系两相的分散,适当的剪切速率有利于使PA 6相形成层状结构。较高的剪切速率使PA 6相尺寸减,分散更均匀,但对提高共混物的阻隔性不利;较短的混合时间可以获得具有阻隔性的HDPE/PA 6共混合金体系     

Preparation,structural development,and mechanical properties of microfibrillar composite materials based on polyethylene/polyamide 6 oriented blends

The preparation of microfibrillar composites (MFCs) based on oriented blends of polyamide 6 (PA6) and high‐density polyethylene (HDPE) is described. By means of conventional processing techniques, the PA6 phase was transformed in situ into fibrils with diameters in the upper nanometer range embedded in an isotropic HDPE matrix. Three different composite materials were prepared through the variation of the HDPE/PA6 ratio with and without a compatibilizer: MFCs reinforced by long PA6 fibrils arranged as a unidirectional ply; MFCs containing middle‐length, randomly distributed reinforcing PA6 bristles; and a nonoriented PA6‐reinforced material in which the PA6 phase was globular. The evolution of the morphology in the reinforcing phase (e.g., its visible diameter, length, and aspect ratio) was followed during the various processing stages as a function of the blend composition by means of scanning electron microscopy. Synchrotron X‐ray scattering was used to characterize selected unidirectional ply composites. The presence of transcrystalline HDPE was demonstrated in the shell of the reinforcing PA6 fibrils of the final MFCs. The impact of the compatibilizer content on the average diameter and length of the fibrils was assessed. The influence of the reinforcing phase on the tensile strength and Young's modulus of the various composites was also evaluated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Viscoelastic,thermal, and morphological analysis of HDPE/EVA/CaCO<Subscript>3</Subscript> ternary blends

High density polyethylene (HDPE), calcium carbonate (CaCO₃), and ethylene vinyl acetate (EVA) ternary reinforced blends were prepared by melt blend technique using a twin screw extruder. The thermal properties of these prepared ternary blends were investigated by differential scanning calorimetry. The effect of EVA loading on the melting temperature (T _m) and the crystallization temperature (T _C) was evaluated. It was found that the expected heterogeneous nucleating effect of CaCO₃ was hindered due to the presence of EVA. The melt viscosities of the ternary reinforced blends were affected by the % loading of CaCO₃, EVA, and vinyl acetate content. Viscoelastic analysis showed that there is a reduction of the storage modulus (G′) with increasing of EVA loading as compared to neat HDPE resin or to HDPE/CACO₃ blends only. The morphology of the composites was characterized by scanning electron microscopy (SEM). The dispersion and interfacial interaction between CaCO₃ with EVA and HDPE matrix were also investigated by SEM. We observed two main types of phase structures; encapsulation of the CaCO₃ by EVA and separate dispersion of the phases. Other properties of ternary HDPE/CaCO₃/EVA reinforced blends were investigated as well using thermal, rheological, and viscoelastic techniques.     

Evolution of shell formation process in PP/PMMA/PS ternary blends: correlation between the melt rheology and phase morphology

Correlation between the melt rheology and phase morphology of PP/PMMA/PS ternary blends during the shell formation process were studied in detail. In this PP-matrix ternary system, theoretical predictions in agreement with the direct SEM observations demonstrated the core-shell morphology with PMMA and PS phases as core and shell phases, respectively. Morphological observations revealed that the complete shell formation takes place at about 12 and 9 wt% of PS minor phase in ternary blends composed of low and high viscosity PMMAs, respectively. In terms of rheological properties, this was corresponding to the maximum value on the storage modulus versus PS content (shell thickness) curves. Encapsulation of high viscosity PMMA core particles at lower PS contents was related to the bigger particles and low interfacial area in this system compared to the system with low viscosity PMMA core particles. At high PS contents, single and multi-core structures were observed for composite droplets of ternary blends containing low and high viscosity PMMAs, respectively. The single core morphology of low viscosity PMMA particles was related to the coalescence of core particles after the coalescence of the corresponding shells, while high viscosity PMMA cores are less likely to coalescence, leading to creation of multi-core morphology in latter system.     

Novel ternary blends of natural rubber/linear low-density polyethylene/thermoplastic starch: influence of epoxide level of epoxidized natural rubber on blend properties

Novel degradable materials based on ternary blends of natural rubber (NR)/linear low-density polyethylene (LLDPE)/thermoplastic starch (TPS) were prepared via simple blending technique using three different types of natural rubber (i.e., unmodified natural rubber (RSS#3) and ENR with 25 and 50 mol% epoxide). The evolution of co-continuous phase morphology was first clarified for 50/50: NR/LLDPE blend. Then, 10 wt% of TPS was added to form 50/40/10: NR/LLDPE/TPS ternary blend, where TPS was the particulate dispersed phase in the NR/LLDPE matrix. The smallest TPS particles were observed in the ENR-50/LLDPE blend. This might be attributed to the chemical interactions of polar functional groups in ENR and TPS that enhanced their interfacial adhesion. We found that ternary blend of ENR-50/LLDPE/TPS exhibited higher 100 % modulus, tensile strength, hardness, storage modulus, complex viscosity and thermal properties compared with those of ENR-25/LLDPE/TPS and RSS#3/LLDPE/TPS ternary blends. Furthermore, lower melting temperature (T _m) and heat of crystallization of LLDPE (?H) were observed in ternary blend of ENR-50/LLDPE/TPS compared to the other ternary blends. Also, neat TPS exhibited the fastest biodegradation by weight loss during burial in soil for 2 or 6 months, while the ternary blends of NR/LLDPE/TPS exhibited higher weight loss compared to the neat NR and LLDPE. The lower weight loss of the ternary blends with ENR was likely due to the stronger chemical interfacial interactions. This proved that the blend with ENR had lower biodegradability than the blend with unmodified NR.     

Melt Rheological and Thermoresponsive Shape Memory Properties of HDPE/PA6/POE-g-MAH Blends

High density polyethylene (HDPE)/nylon6 (PA6) blends were prepared by means of melt extrusion and using ethylene – octane copolymer graft maleic anhydride (POE-g-MAH) as a reactive compatibilizer. Phase morphology, rheological and thermoresponsive shape memory properties of the blends had been studied. The results showed that addition of POE-g-MAH could increase compatibility and phase-interfacial adhesion between HDPE and PA6, decrease the temperature sensitivity of the melt, improve the shape memory property and processability of HDPE/PA6 blends. The shape recovery rate of HDPE/PA6/POE-g-MAH (80/20/10) blend is 96.5% when the stretch ratio is 75% and optimal shape recovery response temperature is 135°C.     

Functionalized elastomeric compatibilizer in PA 6/PP blends and binary interactions between compatibilizer and polymer

Superior impact properties were obtained when maleic anhydride grafted styrene ethylene/butylene styrene block copolymer (SEBS-g-MAH) was used as a compatibilizer in blends of polyamide 6 (PA 6) and isotactic polypropylene (PP), where polyamide was the majority phase and polypropylene the minority phase. The optimum impact properties were achieved when the weight relation PA:PP was 80:20 and 10 wt% SEBS-g-MAH was added. The blend morphology was systematically investigated. Transmission electron microscopy (TEM) indicated that the compatibilizer forms a cellular structure in the PA phase in addition to acting as an interfacial agent between the two polymer phases. In this cellular-like morphology the compatibilizer appears to form the continuous phase, while polyamide and polypropylene form separate dispersions. In microscopy, PA appeared as a fine dispersion and PP as a coarse dispersion. The mechanical properties indicated that in fact PA, too, is continuous, and the blend can be interpreted as possessing a modified semi-interpenetrating network (IPN) structure with separate secondary dispersion of PP. The coarser PP dispersion plays an essential role in impact modification. Binary blends of the compatibilizer and one blend component were also investigated separately. The same cellular structure was observed in the binary PA/SEBS-g-MAH blends, and SEBS-g-MAH again appeared to form the continuous phase when the elastomer concentration was at least 10 to 20 wt%. By contrast, in PP/SEBS-g-MAH only conventional dispersion of elastomeric SEBS-g-MAH was observed up to 40 wt% elastomer. Impact strength was improved and the elastic modulus was lowered in both PA/SEBS-g-MAH and PP/SEBS-g-MAH blends when the elastomer content was increased. The changes in modulus indicate that the semi-IPN-like structure is formed in the binary PA/SEBS-g-MAH blends as well as in the ternary structure.     

Fabricating a partial wetting structure for improving the toughness of intumescent flame-retardant HDPE

A multistep processing method was developed to fabricate a partial wetting morphology for improving toughness of flame retardant polymer. In the first step, high-density polyethylene (HDPE) and nylon 6 (PA6) were melt-extruded with intumescent flame retardant (IFR) for fabricating HDPE/PA6/IFR blends with a core–shell structure (core: IFR, shell: PA6). At the second step, maleic anhydride-grafted-linear low-density polyethylene (LLDPE-g-MAH) was melted with HDPE/PA6/IFR at processing temperatures slightly below the melting temperature of PA6 to produce a partial wetting morphology in which LLDPE-g-MAH phase with the sphere was dispersed at the HDPE/PA6 interface. The effect of the LLDPE-g-MAH content on the impact strength was investigated, and high toughness was exhibited in the blend with 2 wt % LLDPE-g-MAH. Its elongation at break and notched impact strength were 43 and 270% higher, respectively, than that of neat HDPE. The unique interface failure mode was responsible for the high impact strength. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48735.     

Toughening of PA6/mEPDM Blends by two Methods of Compounding,Extruder and Internal Mixer: Rheological,Morphological and Mechanical Characterization

Blends of polyamide 6 with metallocene rubber as dispersed phase and grafted rubber as compatibilizer were prepared by two methods of compounding, extruder and internal mixer. Rheological measurements and morphological analysis were made in order to study the influence of compounding. The ternary blends with the same maleic anhydride content displayed similar rheological behaviour. On the other hand, the developed morphology is related to the compounding process and blend formulation. The better particle size distribution is achieved in both methods of compounding for blends with 20 wt% of EPDM-g-MA. The addition of EPDM-g-MA improves the mechanical properties compared to blends without compatibilizer. The results confirm that the mechanical properties are more influenced by the compounding process than by the blend composition.     

Interface evaluation in the ternary blends of HDPE/PA-6/EVOH

In this work, a quantitative evaluation on interface situation in HDPE/PA-6/EVOH ternary blends is presented. For this purpose, binary and ternary blends based on HDPE as continuous phase and PA-6 and EVOH as minor components with different weight ratios were prepared. The morphology of the blends was studied by SEM and their mechanical properties were measured. Then, through a theoretical/experimental approach, the tensile characteristics of HDPE/PA-6/EVOH ternary blends are discussed. The interface situation in the prepared blends is probed in such a manner that phenomenological models are successfully extended to the case of ternary blends and their parameters are obtained using available predictive schemes. In addition, the stress–strain curves of all prepared binary and ternary blends comprising different PA-6 to EVOH weight ratios in the minority phase are taken into account to study the yielding and toughening phenomena followed by quantitative evaluation of interfacial adhesion. The results provided support for the fact that the yielding behavior of prepared ternary blends is dependent on the minor component fraction possibly due to the formation of voids at the interface of polymers.