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     

Gasoline permeation resistance of the as‐blow‐molded and annealed polyethylene,polyethylene/polyamide,and polyethylene/modified polyamide bottles

An investigation of the gasoline permeation resistance of the as‐blow‐molded and annealed polyethylene, polyethylene (PE)/polyamide (PA), and polyethylene/modified polyamide (MPA) bottles is reported. The gasoline permeation resistance improves dramatically after blending PA and MPA barrier resins in PE matrices during blow‐molding, and the order of barrier improvement corresponds to the order of barrier improvement of the barrier resins added in PE. Somewhat unexpectedly, the gasoline permeation rates of the annealed PE and/or PE/PA bottles annealed at 90°C or higher temperatures increase significantly with the annealing temperature and time. On the contrary, the gasoline permeation resistance of the annealed PE/MPA bottles increase significantly as the annealing temperature and/or time increase. For instance, the gasoline permeation rate of the PE/MPA bottle annealed at 120°C for 32 h is about 190 times slower than that of the as‐blow‐molded PE bottle. Further investigations found that, after blending the MPA and PA barrier resins in PE matrices, the relatively nonpolar hydrocarbon components present in the gasoline fuels were significantly blocked, without permeation during the permeation tests, in which the as‐blow‐molded PE/MPA bottle inhibited the permeation of hydrocarbon components more successfully than did the as‐blow‐molded PE/PA bottle. In contrast, the amounts of polar components that permeated through the as‐blow‐molded PE/PA and PE/MPA bottles were very small and about the same as the amount that permeated through the as‐blow‐molded PE bottle. Possible mechanisms accounting for these interesting behaviors are proposed in this study. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2827–2837, 2001     

Compatibility of poly(vinylidene fluoride) (PVDF)/polyamide 12 (PA12) blends

Poly(vinylidene fluoride) (PVDF)/polyamide 12 (PA12) blends showed new peaks in XRD profile with increasing PA12 and the crystallinity of PA12 significantly decreased with the addition of PVDF. PVDF showed three relaxation regions at about −40, 40, and 100°C, respectively, and glass transition temperature (T_g ) of PA12 increased in blends (10.8→30.14°C) and α‐relaxation of PVDF decreased from 100.26 to 86.46°C. Complex viscosities (η*) vs. composition curve showed a great positive deviation in PVDF‐rich and a small negative deviation in PA12‐rich blends. The N—H and C=O stretching band of PA12 shifted slightly toward higher wavelength, and from curve‐fitted data the area of hydrogen‐bonded C=O stretching bands of PA12 decreased with the addition of PVDF, especially in the 30/70 blend, implying the existence of interactions between the β‐hydrogen atom of PVDF and amide carbonyl group of PA12 in the blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1374–1380, 2000     

Compatibilization of polyethylene/polyamide 6 blends with oxazoline‐functionalized polyethylene and styrene ethylene/butylene styrene copolymer (SEBS)

Study was made of the compatibilization of polyethylene/polyamide 6 (PE/PA6) blends with a ricinoloxazoline maleinate grafted polyethylene and styrene ethylene/butylene styrene copolymer. The blends were prepared in a twin‐screw midiextruder, and the specimens for mechanical tests were injection molded with a mini‐injection molding machine. The effect of compatibilizing on the mechanical properties and the morphology of the blends was studied. The toughness and ductility of the blends were substantially improved as a result of the compatibilization. Simultaneously, the strength and stiffness were slightly reduced. Morphological studies showed that the particle size was reduced and the adhesion of the dispersed phase to the matrix was improved by the compatibilization. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1443–1450, 1999     

Effects of polyethylenes on the morphology,barrier, and impact properties of polyethylene/modified polyamide blends

An investigation of the influence of the melt shear viscosities of polyethylenes (PE) on the morphology, barrier, and impact properties of polyethylene/modified polyamide PE/MPA bottles is reported. The melt shear viscosities of polyethylenes exhibited a significant influence on the deformation and morphology of MPAs during the blow molding of polyethylene/modified polyamide (PE/MPA) blends. Some obscure MPA laminars were observed in PE/MPA bottles as the value of melt shear viscosity ratio of MPA to PE (VR) deviated significantly from the “optimum” range. In contrast, clear and elongated laminar structures of MPAs were found as the value of VR reached the “optimum” range. Similarly, the total impact energies (Ets) and permeation barrier properties of PE/MPA samples improved with the value of VR until it reached the “optimum” range, after which value Ets and permeation barrier properties of PE/MPA samples reduced significantly with further increasing VR. Possible mechanisms accounting for these interesting behaviors are presented in this study.     

Barrier resistance of polyethylene,polyethylene/modified polyamide,and polyethylene/blends of modified polyamide and ethylene vinyl alcohol bottles against permeation of polar and nonpolar mixed solvents

The main objective of this study is to investigate the barrier properties and mechanisms of polyethylene (PE), PE/modified polyamide (MPA), and PE/blends of MPA and ethylene vinyl alcohol copolymer (MPAEVOH) bottles against permeation of polar/nonpolar (acetone/white spirit) mixed solvents. The mixed solvent permeation resistance improves dramatically after blending MPA and MPAEVOH barrier resins in PE matrices during blow molding. By using the proper MPAEVOH compositions, the white spirit permeation rate of PE/MPAEVOH bottles at 40°C can be about 145 times slower than that of the PE bottle specimen; however, it is still 2.5 times faster than that of the PE/MPA bottles. In contrast, the rate of polar acetone solvent permeation through the PE bottle is much slower than that of white spirit and only slightly faster than that through the PE/MPA and PE/MPAEVOH bottle specimens. In contrast, the permeation rates of acetone/white spirit mixed solvents into PE/MPA bottles are at least 20–60 times faster than the summation permeation rates calculated using the simple mixing rule when the acetone contents in the mixed solvents are between 10 and 70 wt %. It is somewhat interesting that, after blending the proper amounts of EVOH in MPA, the mixed solvent permeation rates of PE/MPAEVOH bottles are dramatically reduced and are very close to the summation permeation rates calculated using the simple mixing rule when the acetone contents are in the particular “window” range. These interesting barrier properties of PE/MPA and PE/MPAEVOH bottle specimens were investigated in terms of the free volumes, barrier properties, molecular interactions in the amorphous phases of the barrier resins, and their resulting morphological structures that present in their corresponding bottles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1333–1344, 2005     

Permeation mechanisms of xylene in blow-molded bottles of pure polyethylene,polyethylene/polyamide and polyethylene/ modified polyamide blends

The hydrocarbon permeation mechanisms of polyethylene/ modified polyamide (PE/ MPA). PE/PA blends and pure PE, were investigated over a range of testing temperatures. In addition to the permeation resistance to xylene, the weight of xylene absorbed per gram of dry polymers (Sx) and the diffusion coefficient (D) of xylene in these bottles were determined. At each fixed testing temperature, the steady permeation rates (Ps) and D of xylene in PE/MPA bottles is significantly lower than those of pure PE bottles, and that of PE/PA bottles is slightly lower. This significantly improved permeation resistance of PE/MPA to xylene at each testing temperature is mainly attributed to the significantly reduced diffusion coefficient of xylene in PE/ MPA bottles, but not due to the slight change in the amount of xylene absorbed in these three bottles. The temperature dependence of steady permeation rates and diffusion coefficient of xylene in each bottle is very similar, and, in fact, some clear transition points were found on the plots of Ps and D versus testing temperatures for PE. PE/PA and PE/MPA bottles. These interesting behaviors along with the temperature dependence of Sx in each bottle were discussed and correlated with the free volume, molecular relaxation motions of these polymers and the vapor pressure of xylene at varying testing temperatures.     

Effects of compatibilizer precursors on the barrier properties and morphology of polyethylene/polyamide blends

Summary A systematic investigation on the effects of type of compatibilizer precursors (CP) upon the barrier properties and morphology of PE/PA blends was reported. Three alkyl carboxyl-substituted polyolefins were selected to modify PA in a twin screw extruder by reactive extrusion process. The barrier property of the modified PA (MPA) was better than pure PA, and the amount of barrier improvement of the blend of PE and MPA dependended significantly on the barrier property of the MPA prepared. The extent of mixing PE and MPA before blow-molding has a significant effect on its corresponding barrier properties. Further analysis of the fracture surfaces indicated that a more demarcated laminar structure of MPA dispersed in PE matrix is essential for better barrier properties of PE/MPA blends. It is not completely clear how the type of CP added affects the barrier properties of MPAs. However, it is suggested that long PA sequence with shorter grafted CP chain and high normalized grafting efficiency of MPA are essential for preparing a clear laminar structure of MPA, and a good barrier properties of PE/MPA blends.     

HDPE、改性HDPE与PA6,6共混物的机械性能和结构形态

研究了HDPE、改性HDPE与PA6,6的共混比、制备方法及增容剂对共混物性能的影响。结果表明,改性HDPE与PA6,6共混,能够得到很好的相容性(特别是在共混比是50/50时),并在很多方面(拉伸强度、屈挠强度、伸长率)得到良好的性能;两步法得到的共混物中,HDPE与PA6,6获得良好的相容;一步法得到的共混物可得到较高的屈挠强度。     

Effects of preparation conditions on the morphology and gas permeation properties of polyethylene (PE) and ethylene vinyl acetate (EVA) films

In this study, the effect of film preparation conditions on the gas permeation properties of polyethylene (PE) and ethylene vinyl acetate (EVA) films (containing 18 and 28 wt% vinyl acetate) was investigated. Film blowing and phase inversion methods were applied in the production of PE and EVA films, respectively. The permeation of pure oxygen and carbon dioxide gases was measured at room temperature. The results indicated that with the increase of PE film thickness, permeability and solubility of O₂ and CO₂ in these films decreased; but the diffusivities of gases through PE films increased. In addition, in the case of EVA copolymers, by increasing the content of vinyl acetate, the permeability of CO₂ increased. The rate of increase in CO₂ permeability was different for samples having different preparation conditions. For example, the samples prepared using chloroform as the solvent instead of THF, showed lower CO₂ permeability. Also, the morphological studying of film structure indicated that the higher CO₂ permeability for the samples made from THF solvent is due to the existing of higher porosity in the under layer polymer area. Also scanning electron microscopy (SEM) micrographs showed that with the usage of phase inversion method, there will be a thin dense layer near to the glass substrate.     

Blending and white spirit permeation properties of the blends of modified polyamide and ethylene vinyl alcohol with varying vinyl alcohol contents

The blending and white spirit permeation properties of the MPAEVOH blends of modified polyamide (MPA) and ethylene vinyl alcohol copolymer (EVOH) were systematically investigated in this study. Three types of EVOHs with varying vinyl alcohol contents were used to prepare the MPAEVOH resins by melt blending them with the MPA resin, respectively. The peak melting temperatures and percentage crystallinity (W_c) values of the EVOH specimens increase significantly as their vinyl alcohol contents increase. The X‐ray diffraction patterns of the melt‐crystallized EVOH crystals transform from monoclinic to orthorhombic lattice as their vinyl alcohol contents are equal to or less than 56 wt %. After blending EVOH in MPA resins, the main melting endotherms and characteristic X‐ray diffraction patterns of both monoclinic and orthorhombic lattices of EVOH crystals originally present in MPAEVOH specimens almost disappear completely, when the weight ratios of MPA to EVOH are equal to or greater than 4. The free‐volume properties and white spirit permeation rates of the EVOH specimens reduce significantly as their vinyl alcohol contents increase. A noticeable “negative deviation” was found on the plots of white spirit permeation rates, annihilation intensity (I₃), and/or fractional free‐volume (F_v) versus MPA contents as the MPA contents of each MPAEVOH sample series reach about 80 wt %. Possible reasons accounting for these interesting blending and barrier properties of MPAEVOH specimens are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1224–1233, 2006     

Structure and properties of polyamide 6 blends with low‐density polyethylene grafted by itaconic acid and with neutralized carboxyl groups

A comparative study of the structure and properties of two‐phase blends of polyamide 6 (PA6) and low‐density polyethylene (LDPE) modified in the course of reactive extrusion, by grafting of itaconic acid (IA) without neutralization of carboxyl groups (LDPE‐g‐IA) and with neutralized carboxyl groups (LDPE‐g‐IA^?M⁺) was carried out. It was shown that 30 wt % of LDPE‐g‐IA^?M⁺ introduced to PA6 resulted in blends of higher Charpy impact strength compared with that of PA6/LDPE‐g‐IA blends. The maximum increase was achieved when Mg(OH)₂ was used as a neutralizing agent. The blend morphology has a two‐phase structure with blurred interphases because of increased adhesion between the phases. The neutralization of carboxyl groups in grafted IA did not lead to two‐phase morphology of blends, which had a negative influence on the mechanical properties. It is believed that the differences in the impact strength were caused by the influence of the added neutralizing agents on the structure of interphases, which depends on both the interfaces adhesion and structural effects resulting from the nucleating behavior of the neutralizing agent. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1702–1708, 2004     

Permeation barrier properties of polyethylene/modified blends of polyamide and polyvinylalcohol containers against methanol/gasoline fuels

One commercial grade of polyamide and/or polyvinylalcohol resins were modified by a compatibilizer precursor to make various compositions of modified polyamide (MPA) and/or modified blends of polyamide/polyvinylalcohol (MPAPVA) through reactive extrusion. Good methanol/gasoline fuel permeation resistance together with clearly defined MPAPVA and MPA laminar structures were found on containers blow‐molded from the blends of polyethylene PE/MPAPVA and PE/MPA, respectively. The compositions of MPAPVA and MPA resins were found to exhibit a significant influence on the methanol/gasoline fuel permeation resistance and morphology of PE/MPAPVA and PE/MPA containers, respectively. Possible mechanisms are proposed to explain these interesting phenomena. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2158–2169, 1999     

Effect of compatibilization on the oxygen‐barrier properties of poly(ethylene terephthalate)/poly(m‐xylylene adipamide) blends

The improvement of the oxygen‐barrier properties of poly(ethylene terephthalate) (PET) via blending with an aromatic polyamide [poly(m‐xylylene adipamide) (MXD6)] was studied. The compatibilization of the blends was attempted through the incorporation of small amounts of sodium 5‐sulfoisophthalate (SIPE) into the PET matrix. The possibility of a transamidation reaction between PET and MXD6 was eliminated by ¹³C‐NMR analysis of melt blends with 20 wt % MXD6. An examination of the blend morphology by atomic force microscopy revealed that SIPE effectively compatibilized the blends by reducing the MXD6 particle size. Thermal analysis showed that MXD6 had a nucleating effect on the crystallization of PET, whereas the crystallization of MXD6 was inhibited, especially in compatibilized blends. Blending 10 wt % MXD6 with PET had only a small effect on the oxygen permeability of the unoriented blend when it was measured at 43% relative humidity, as predicted by the Maxwell model. However, biaxially oriented films with 10 wt % MXD6 had significantly reduced oxygen permeability in comparison with PET. The permeability at 43% relative humidity was reduced by a factor of 3 in compatibilized blends. Biaxial orientation transformed spherical MXD6 domains into platelets oriented in the plane of the film. An enhanced barrier arose from the increased tortuosity of the diffusion pathway due to the high aspect ratio of MXD6 platelets. The aspect ratio was calculated from the macroscopic draw ratio and confirmed by atomic force microscopy. The reduction in permeability was satisfactorily described by the Nielsen model. The decrease in the oxygen permeability of biaxially oriented films was also achieved in bottle walls blown from blends of PET with MXD6. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1361–1370, 2005     

PET/PA nanocomposite blends with improved gas barrier properties: Effect of processing conditions

The aim of this research is to develop nanocomposite polyethylene terephthalate‐polyamide blends (PET/MXD6 blends) with low oxygen permeability. Particular attention has been paid to the relation between barrier properties and the processing route adopted and therefore four different strategies were considered. Mechanical characterization shows that clay may effectively act as reinforcing filler in PET/MXD6 blends. Morphological characterization shows the strong effect of the processing strategy on clay dispersion and its distribution between the PET and polyamide phases. Barrier properties of PET/MXD6 nanocomposite blends are enhanced with respect to neat PET polymer as well as PET/MXD6 blends. The significant effect of processing techniques on barrier properties is also revealed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Compatibility of reactively compatibilized polyamide 11 (nylon 11)/polyethylene (PE) alloys

The compatibility of nylon 11/polyethylene (PE) alloys on addition of reactive maleated ethylene‐propylene‐diene copolymer (EPDM‐graft‐MAH) was investigated by differential scanning calorimetry, morphological observations and rheology. The decrease in the differential volume of the melting temperature of nylon 11 and PE with increasing compatibilizer suggests that the addition of EPDM‐graft‐MAH affects the crystalline behavior of nylon 11 and PE. The decreased particle size of the dispersed phase also confirmed the improvement in the compatibility. The rheological behavior revealed that the addition of the compatibilizer enhanced the apparent viscosity of the melting blends, which resulted from the increasing interaction between the chains due to the improvement in compatibility of nylon 11 and PE. Copyright © 2004 Society of Chemical Industry     

Structure and properties of bio-based poly(trimethylene terephthalate)/polyamide 56 blends prepared by melt mixing

The extensive use of conventional petroleum-based polymers consumes large amounts of energy and emits a lot of carbon dioxide. Therefore, the development and popularization of bio-based polymer materials are highly significant for ecological reasons. Herein, a series of poly(trimethylene terephthalate)/polyamide 56 (PTT/PA56) blends with different weight ratios were prepared by melt blending of two bio-based polymers, PTT and PA56. The phase structure, miscibility, crystallization and melting behaviors, crystal structure, and mechanical and water absorption properties of PTT/PA56 blend systems were investigated. The results showed that PTT and PA56 were immiscible in the whole range of compositions. The immiscibility of the blend system intensified with the increase of dispersed phase content. As PA56 content increased, tensile strength and elongation at break of samples assumed an increasing trend, whereas impact strength initially remained almost unchanged and then gradually decreased. In contrast, increasing PA56 content gradually increased water absorption of samples. Comprehensive analysis indicated that the best combination of different properties was obtained for the PTT/PA56 blends including 60–80 wt% PA56.     

HDPE-g-MAH对HDPE/PA 11性能的影响

以马来酸酐(MAH)接枝高密度聚乙烯(HDPE)(HDPE-g-MAH)作为相容剂,通过熔融共混法制备了HDPE/聚酰胺11(PA 11)共混物.研究了HDPE-g-MAH对HDPE/PA 11共混物的增容作用以及对共混物性能的影响.结果表明,HDPE-g-MAH对共混体系有明显的增容作用,共混物的拉伸强度和冲击强度得到提高;相容剂的加入,使共混物的结晶温度升高.     

Effects of polyphenylene oxide content on morphology,thermal, and mechanical properties of polyphenylene oxide/polyamide 6 blends

A series of composites of PPO/PA 6 with improved toughness were synthesized by using ε‐caprolactam as a reactive solvent. Inserting minor PPO macromolecules (1–3 wt %) into PA 6 matrix obviously reduced the crystallinity of PA6. Two crystallization temperatures were found when 6 wt % PPO was added. SEM revealed that the phase morphology of the composites could be manipulated by varying the content of PPO in PA 6. As a consequence, the impact strength and the elongation of PPO/PA6 were improved with maintenance of tensile strength when quite small content of PPO (1–3 wt %) was incorporated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006