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.     

A new method of preparation of a rubber-modified polyamide directly during caprolactam polymerization

A new method to obtain a rubber-modified polyamide 6 (PA6) directly during the polymerization of the caprolactam (CL) is described. Binary and ternary blends containing ethylene-propylene random copolymers (EPM) and/or a fictionalized EPM rubber (EPM-g-SA) were prepared and their morphology as well as their mechanical properties were investigated as function of composition and reaction conditions. It was found that the morphology of the blends is strongly dependent on the method of preparation. More complex structures are observed in blends obtained with the “Solution” preparation. For a better resolution of the morphology, the smooth ultramicrotomed surfaces were exposed to boiling xylene before SEM (scanning electron microscopy) examination. The rubbery phases are selectively dissolved whereas the PA6 matrix is left. The tensile mechanical properties and the Izod impact behavior are related to the mode and state of dispersion of the rubbery components. The impact properties of ternary PA6/EPM/EPMg-SA (80/18/2) and (80/15/5) blends, prepared during the CL polymerization are comparable to those of similar blends obtained by usual melt mixing procedures.     

Crystallization,morphology, structure and thermal behaviour of nylon-6/rubber blends

An experimental study was carried out in order to investigate the morphological, kinetic, structural and thermodynamic properties of nylon-6/rubber (namely ethylene-propylene copolymer (EPM) and ethylene-propylene copolymer functionalized by inserting along its backbone succinic anhydride groups (EPM-g-SA)) blends. The morphology and the overall kinetics of crystallization of the blends strongly depend on the type of copolymer added to nylon and on the blend composition. The EPM-g-SA acts as a nucleating agent for the Ny spherulites and at the same time causes a drastic depression of the overall kinetic rate constant. This decrease is related to the increase of the melt viscosity observed in Ny/EPM-g-SA blends. The crystalline lamella thickness of the Ny phase in the blends is lower than that of pure Ny crystallized at the same T_c suggesting that the presence in the melt of an elastomeric phase disturbs the growth of the Ny crystals. The rubber does not influence the thermal behaviour of the nylon. The results found lead to the conclusion that in the melt nylon-6 is incompatible with both EPM and EPM-g-SA copolymers.     

PA6/EPM/EPM-g-MAH共混物结构与性能研究

采用二元乙丙橡胶接枝马来酸酐(EPM-g-MAH)作为二元乙丙橡胶(EPM)增韧聚酰胺6(PA6)的增容剂,研究了PA6/EPM/EPM-g-MAH三元共混物的流变性能、力学性能和微观形态。结果表明,EPM-g-MAH可以与PA6发生增容反应生成接枝共聚物,改善了PA6和EPM的界面相容性。随着EPM-g-MAH含量的增加,共混物中分散相粒径更加细化,共混物的熔融峰温下降,缺口冲击强度显著提高,当EPM/EPM-g-MAH的配比为10/10时,共混物的冲击强度达到最大为47 kJ/m2,比纯PA6提高了8倍。     

PA6/PP/SEBS-g-MAH共混物的相容性研究

采用马来酸酐接枝(氢化苯乙烯/丁二烯/苯乙烯)共聚物(SEBS-g-MAH)作为增容剂,研究了增容剂用量对尼龙6/聚丙烯(PA6/PP)共混体系相态结构、力学性能的影响,以及在相同增容剂用量下不同PA6、PP配比对体系相形态的影响。结果表明,SEBS-g-MAH中的酸酐基团能与PA6末端的氨基发生化学反应,在PA6和PP的内表面形成PA6-SEBS接枝共聚物,明显改善了两相的界面相容性,并使共混物的力学性能得到显著提高。共混物冲击断面形貌的分析表明,共混物发生了明显的脆韧转变。     

Crystallization and melting behavior of polypropylene in β-PP/polyamide 6 blends containing PP-g-MA

In this research, we used a twin-screw extruder to melt and blend PP-g-MA compatibilizer with β-polypropylene (PP)/polyamide 6 (PA6). The influences of the PA6 and PP-g-MA contents in PP/PA6 blends on crystallization and melting behavior of PP phase and morphology were investigated. The results showed that, when PP-g-MA copolymer was added to the β form of nucleated PP/PA6 blends, the anhydride groups in PP-g-MA and PA6 terminal amine groups react to form PP-g-PA graft copolymer in a two-phase interface. This reduces the interfacial tension, improves the interfacial adhesion, and reduces the size of PA6 domains in the blend. The generated PP-g-PA graft copolymer wrapped PA6 phase and buried the anhydride groups of PP-g-MA. When the proportion of PP-g-MA and PA6 was between 0.5 and 0.75, there was no longer interfering to the formation of β-crystals in the PP phase. The content of β-crystal of PP phase in blends was found to reach as large as 85.9%.     

尼龙1010／乙丙共聚物共混体系形态与性能研究

在过氧化二异丙苯（ＤＣＰ）的引发下，用反应挤出的方法制备了乙丙共聚物接枝甲基丙烯酸环氧丙酯（ＥＰＭ－ｇ－ＧＭＡ）。用Ｂｒａｂｅｎｄｅｒ单螺杆挤出机制备了不同组成的ＥＰＭ／尼龙１０１０及ＥＰＭ－ｇ－ＧＭＡ／尼龙－１０１０的共混物，用电子显微镜观察了不同共混组成的形态，与ＥＰＭ／尼龙１０１０共混体系相比，ＥＰＭ－ｇ－ＧＭＡ／尼龙１０１０体系中ＥＰＭ在尼龙１０１０中分散相尺寸明显降低，ＥＰＭ－ｇ－ＧＭＡ     

PA6/ABS共混物性能研究

将聚酰胺6（PA6）与市售的丙烯腈-丁二烯-苯乙烯（ABS）树脂共混,制备PA6/ABS共混物。研究了ABS树脂的用量对PA6/ABS共混物力学性能的影响;采用苯乙烯及丙烯腈共聚物（SAN）和ABS粉料熔融共混制得不同胶含量的ABS/SAN共混物。研究了不同胶含量的ABS/SAN共混物对PA6/ABS共混物力学性能的影响。在PA6/ABS/SAN共混物中引入苯乙烯-丙烯腈-马来酸酐共聚（SAM）树脂取代部分SAN树脂,研究了SAM树脂的加入及引入顺序的不同对共混物性能的影响。结果表明, ABS树脂的用量在50%～60%左右时共混物性能最佳。随ABS/SAN共混物胶含量提高,共混物的拉伸强度、弹性模量、弯曲强度和弯曲模量逐渐降低。随SAM树脂替代SAN量增加,共混物的拉伸和弯曲性能先降低后增加。但共混物熔体流动速率降低明显,而SAM树脂的引入顺序对共混物的力学性能影响不大。     

Polymer blends of carboxylated butadiene‐acrylonitrile copolymer (nitrile rubber) and polyamide 6 developed in twin screw extrusion

Polymer blends of carboxylated butadiene‐acrylonitrile copolymer (nitrile rubber) and polyamide 6 (PA6) were developed in twin screw extrusion. The rubber was cured with SP 1045 methylol phenolic resin during melt mixing in twin screw. Effect of degree of carboxylation in the rubber phase on blend properties has been assessed. Phase morphologies have been characterized using transmission electron microscopy. A compatibilizing NBR‐g‐Nylon 6 graft copolymer generated in situ during melt mixing via interfacial reaction between the ? COOH groups in NBR and the ? NH₂ end groups in nylon 6 has been effective in generating a fine and stable dispersion of the rubber within the polyamide matrix. The graft copolymer has been characterized by DMTA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 372–377, 2007     

Impact toughened blends of styrene-maleic anhydride copolymer,polyethylene, and ethylene-propylene copolymer

Impact-toughened, compatibilized binary blends of styrene-maleic anhydride (SMA) copolymer/amine functionalized ethylene-propylene (amine-EP) polymer and ternary blends consisting of SMA/amine-EP/high density polyethylene (HDPE) are described. In both blends 0.02 to 4 μm range rubbery inclusions, which toughen the SMA matrix, are formed. SMA sub-inclusions exist in the amine-EP phase. In the ternary blend substantially all of the polyethylene is embedded in the EP phase. Compatibilization of the SMA and the commingled polyolefin phase is promoted by a graft copolymer formed by the reaction of amine groups on the EP with the maleic anhydride groups on the SMA. We describe the morphology, rheology, aging characteristics and impact properties of these blends. SMA modification by SMA-g-(amine-EP) polymers formed in situ in the melt, with HDPE, has not been previously reported.     

Improved compatibility between polyamide and polypropylene by the use of maleic anhydride grafted SEBS

Blends containing equal weight fractions of polypropylene (PP) and polyamide (PA-6 and PA-6.6) and up to 25% of a compatibilizing thermoplastic elastomer, either polystyrene-block-poly(ethylene-stat-butylene)-block-polystyrene (SEBS) or SEBS modified by maleic anhydride (SEBS-MA), were prepared by melt mixing. In all these blends, PP formed the continuous matrix phase. Even at high concentrations, unmodified SEBS was found to be a poor compatibilizer, affecting mainly the properties of the matrix. The graft copolymer formed, by reaction between SEBS-MA and polyamide during melt mixing, strongly influenced the blend morphology, by forming an interphase, separating the PA phase domains from the matrix. The crystallization behaviour of PP indicated that full coverage required between 3% and 5% SEBS-MA at the intense mixing conditions used. Above this level, the total surface area of the polyamide domains seemed to increase in direct proportion to the concentration of SEBS-MA. The thickness of the interphase layer was estimated to be about 15 nm. At high concentrations of SEBS-MA, the PA domains agglomerated and formed extended structures held together by the interphase polymer. This was reflected by the stress–strain and rheological behaviour of the blends. In blends with PA domains of small volume, crystallization of PA was delayed. The rate of water absorption was very low in blends containing SEBS-MA, much lower than in corresponding blends containing SEBS.     

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.     

Thermoplastic natural rubber based on polyamide‐12: Influence of blending technique and type of rubber on temperature scanning stress relaxation and other related properties

Thermoplastic natural rubber based on polyamide‐12 (PA‐12) blend was prepared by melt blending technique. Influence of blending techniques (i.e., simple blend and dynamic vulcanization) and types of natural rubber (i.e., unmodified natural rubber (NR) and epoxidized natural rubber (ENR)) on properties of the blends were investigated. It was found that the simple blends with the proportion of rubber ～ 60 wt % exhibited cocontinuous phase structure while the dynamically cured blends showed dispersed morphology. Furthermore, the blend of ENR exhibited superior mechanical properties, stress relaxation behavior, and fine grain morphology than those of the blend of the unmodified NR. This is attributed to chemical interaction between oxirane groups in ENR molecules and polar functional groups in PA‐12 molecules which caused higher interfacial adhesion. It was also found that the dynamic vulcanization caused enhancement of strength and hardness properties. Temperature scanning stress relaxation measurement revealed improvement of stress relaxation properties and thermal resistance of the dynamically cured ENR/PA‐12 blend. This is attributed to synergistic effects of dynamic vulcanization of ENR and chemical reaction of the ENR and PA‐12 molecules. Furthermore, the dynamically cured ENR/PA‐12 blend exhibited smaller rubber particles dispersed in the PA‐12 matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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.     

One-step compatibilization of polyamide 6/ poly (ethylene-1-octene) blends with maleic anhydride and peroxide

Polyamide 6/poly(ethylene-1-octene) (POE) blends were prepared in the presence of both maleic anhydride and peroxide via melt blending. The intrinsic viscosity, mechanical properties, rheology, and phase morphology of blends were evaluated. Molau test was adopted to confirm the formation of a graft copolymer between PA 6 and POE, rheology property also indicated the graft reaction. The SEM analysis showed a significant reduction in particle size of seperation phase after one-step compatibilization. It provides a promising method to obtain toughened polyamide material.     

Nylon 6/ethylene propylene rubber (EPM) blends: Phase morphology development during processing and comparison with literature data

The morphology of immiscible blends of nylon 6 and ethylene propylene rubber blends (EPM) was studied. The blends were prepared by melt blending in a twin‐screw miniextruder and a Haake Rheocord mixer. The influence of the blend ratio, time of mixing, rotation speed of the rotors, mixing temperature, and quenching of the extruded melt at low temperature on the phase morphology of the blends was quantitatively analyzed. The morphology was examined by scanning electron microscopy (SEM) after preferential extraction of the minor phase. The SEM micrographs were quantitatively analyzed for domain‐size measurements. The morphology of the blends indicated that the EPM phase was preferentially dispersed as domains in the continuous nylon matrix up to 40 wt % of its concentration. A cocontinuous morphology was observed at 50 and 60 wt % EPM content followed by a phase inversion beyond 60 wt % of EPM where the nylon phase was dispersed as domains in the continuous EPM phase. The size, shape, and distribution of the domains were evaluated by image analysis as a function of the blend composition. The effect of the time of mixing on the phase morphology was studied up to 20 min for the 30/70 EPM/nylon blend. The most significant domain breakup was observed within the first 3 min of mixing followed by a leveling off up to 15 min. This may be associated with the equilibrium between the domain breakup and coalescence. The influence of rotor speed on the morphology was insignificant at a high rotor speed although a significant effect was observed by changing the rotor speed from 9 to 20 rpm. The influence of high‐temperature annealing, repeated cycles of extrusion, the molecular weight of the nylon matrix, and the nature of the mixer type (twin‐screw miniextruder versus Haake Rheocord mixer) on the morphology was also investigated in detail. The experimental results were compared with literature data. Finally, the extent of interface adhesion in these blends was analyzed by examination of the fracture‐surface morphology. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1405–1429, 1999     

Poly(ethylene‐graft‐ethylene oxide) (PE‐PEO) and poly(ethylene‐co‐acrylic acid) (PEAA) as compatibilizers in blends of LDPE and polyamide‐6

In a blend of two immiscible polymers a controlled morphology can be obtained by adding a block or graft copolymer as compatibilizer. In the present work blends of low‐density polyethylene (PE) and polyamide‐6 (PA‐6) were prepared by melt mixing the polymers in a co‐rotating, intermeshing twin‐screw extruder. Poly(ethylene‐graft‐polyethylene oxide) (PE‐PEO), synthesized from poly(ethylene‐co‐acrylic acid) (PEAA) (backbone) and poly(ethylene oxide) monomethyl ether (MPEO) (grafts), was added as compatibilizer. As a comparison, the unmodified backbone polymer, PEAA, was used. The morphology of the blends was studied by scanning electron microscopy (SEM). Melting and crystallization behavior of the blends was investigated by differential scanning calorimetry (DSC) and mechanical properties by tensile testing. The compatibilizing mechanisms were different for the two copolymers, and generated two different blend morphologies. Addition of PE‐PEO gave a material with small, well‐dispersed PA‐spheres having good adhesion to the PE matrix, whereas PEAA generated a morphology characterized by small PA‐spheres agglomerated to larger structures. Both compatibilized PE/PA blends had much improved mechanical properties compared with the uncompatibilized blend, with elongation at break (ε_b) increasing up to 200%. Addition of compatibilizer to the PE/PA blends stabilized the morphology towards coalescence and significantly reduced the size of the dispersed phase domains, from an average diameter of 20 μm in the unmodified PE/PA blend to approximately 1 μm in the compatibilized blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2416–2424, 2000     

R-SMA增容PA6/PP共混物的形态结构与流变行为

采用R-SMA为增容剂制备PA6/PP共混物,讨论了R-SMA对共混物形态结构和流变行为的影响。     

PP-g-(MAH/VAc)接枝物对PP/PA6体系的增容作用

通过扫描电镜、差示扫描量热仪和力学性能测试等方法研究了聚丙烯接枝马来酸配和酷酸乙烯酷(PP-g-MAH/VAc)对聚丙烯康酸胺6(80/20}共混体系的增容效果。结果表明,PP-g-(MAH/DAc)用于PP/PA6共混体系,分散相PA6的微区尺寸可以减小到5μm以下,相应地提高了共混物的断裂伸长率、拉伸强度和冲击强度。使用接枝率为5.3%的PP-g-(MAH/VAc)作为相容剂,当用量为8%时,体系的拉伸强度为60.88MPa,断裂伸长率为558%,冲击强度为5.28KJ/㎡.DSC分析表明,PP/PA6共混体系各组分相互促进成核,结晶度降低。FTIR结果表明,PP-g-(MAH/VAc)中的MAH上的酸配基团与PA6中的酸胺键发生了化学反应从而改善了体系的相容性。     

One-step functionalization and reactive blending of polyolefin/polyamide mixtures (EPM/PA6)

Diethyl maleate, maleic anhydride and dicumyl peroxide in different ratios were directly added to molten polymeric mixtures based on ethylene-co-propylene (EPM) and polyamide 6 (PA6) to perform in one-step the functional groups grafting and branched copolymer formation necessary to obtain compatibilized products.The characterization of the blends by selective solvent extraction and IR and NMR analysis of the various fractions allowed to evidence the occurrence of maleate grafting on both EPM and PA6 as well as the formation of graft copolymers at the interface. The effect of the reactions on phase morphology development and thermal properties was evaluated by SEM and DSC analysis respectively in order to investigate the compatibilization extent in comparison with the conventional two-steps procedure. Besides tests about mechanical properties of samples produced by the extrusion were carried out.