Polyamide Content Research Articles

UK: Hubron — plastics masterbatch

Masterbatches of reactive polymers containing carbon nanotubes are used to prepare nanocomposites by reactive blending. By mixing masterbatches of low molecular-weight amino-terminated polyamide-6 (PA6) containing ∼10 wt% or ∼17 wt% of multi-walled carbon nanotubes (MWNT) with maleic anhydride functionalized polyethylene (PE*) at temperatures above melting of PA6 it is possible to obtain fine and homogeneous dispersions of carbon nanotubes. In the PA6 concentration range explored, from 19 wt% to 37 wt%, nanostructured co-continuous blend morphologies are achieved. Selective extractions show that a high amount of graft copolymer PE*-g-PA6 is synthesized during mixing. The swelling experiments in selective solvents demonstrate co-continuous blend morphologies. Electron microscopy confirms good quality of MWNT dispersion and shows structures on mesoscopic scales. Fine dispersion of carbon nanotubes and the matrix co-continuity concur to yield a unique combination of properties such as solvent resistance, electrical conductivity, mechanical strengthening and ductility.

EPDM/polyamide TPV compatibilized by chlorinated polyethylene

A thermoplastic vulcanizate (TPV) of ethylene-propylene-diene (EPDM) and polyamide (PA) with excellent mechanical properties was prepared by dynamic vulcanization. The effects of the vulcanizing agents, compatibilizer, PA content, aging and reprocessing on mechanical properties of EPDM/PA thermoplastic vulcanizate were investigated. Experimental results indicate that chlorinated polyethylene has a better effect in compatibilizing the EPDM/copolyamide blends compared with the other compatibilizers, including maleic anhydride grafted ethylene propylene rubber (MAH-G-EPR), maleic anhydride grafted EPDM (MAH-G-EPDM) and epoxidised ethylene-propylene-diene rubber. Tensile strength and elongation at break go through a maximum value at a compatibilizer resin content (on total rubber content) of 20%. EPDM/PA TPV using sulfur as a vulcanizing agent has higher tensile strength and elongation than that of TPVs using a brominated tert-butyl phenolic resin or peroxide as vulcanizing agent. Tensile strength and elongation at break increase with PA content. DMA results indicated a phase separation in the blend system of EPDM/CPE/PA. The glass transition temperature (Tg) of PA moves towards a high temperature with increasing CPE content, but the Tg of EPDM changes very slightly toward a lower temperature. The loss factor, tanδ, of PA also increases with increasing CPE content. In the blend EPDM/CPE/PA, small PA contents do not cause an immediate increase of storage modulus (E′). Scanning electron microscopy was used to examine the phase morphology of the blends; the results show that the particles of the dispersed EPDM phase have an average size of 2 μm in the dynamically vulcanized EPDM/CPE/PA TPV.

Thermal behavior and morphology of polyamide 6 based multicomponent blends

AbstractThe thermal behavior and morphology of multicomponent blends based on PA6, polyamide 6 (PA6)/styrene–acrylonitirle copolymer (SAN), PA6/acrylonitrile–butadiene–styrene terpolymer (ABS), and their compatibilized blends with styrene–acrylonitrile–maleic anhydride copolymer (SANMA) were studied using DSC and SEM. The blends were prepared in a twin‐screw extruder under similar processing conditions, keeping the PA6 content fixed at 50 wt %. It was found that, in all the blends, the second component had a nucleating effect and improved the overall degree and rate of crystallization of PA6, whereas addition of a compatibilizer slightly diminished these effects and resulted in significant changes in the blend morphology. The nucleating effect and consequent changes in the crystallization behavior was attributed to the presence of SAN, which is a common component in all the blends. The Tg of PA6 in the blends with a cocontinuous morphology, due to the connectivity between the phases, is higher than in the blends with a disperse‐type morphology. The compatibilized blends have a lower crystallization rate and nucleation ability with a cocontinuous morphology, whereas the uncompatibilized blends have a higher crystallization rate with a higher nucleation ability and a disperse and/or a coarse cocontinuous morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2753–2759, 2002

Multicomponent blends based on polyamide 6 and styrenic polymers: morphology and melt rheology

The role of each blend component on blend morphology and melt rheological properties was investigated for multicomponent compatibilized blends of polyamide 6 (PA6) and acrylonitrile–butadiene–styrene terpolymer (ABS). Blends with PA6 content of 50 wt% were prepared at similar processing conditions on a ZSK 30 twin screw extruder. PA6/styrene–acrylonitrile co-polymer (SAN) blends showed a dispersed morphology with PA6 as matrix. Addition of reactive compatibilizer, styrene–acrylonitrile–maleic anhydride co-polymer (SANMA), up to 5 wt%, changed the morphology from a dispersed to a co-continuous structure. PA6/ABS, having a part of the SAN substituted by rubber, exhibited a coarse co-continuous structure which could be explained with the yield stress of the ABS. Addition of the compatibilizer to this system refined the co-continuous structure and increased the viscosity as well as the elasticity.

Caracterização Mecânica de Compósitos de Poliamida/Fibra de Carbono Via Ensaios de Cisalhamento Interlaminar e de Mecânica da Fratura

Compósitos termoplásticos a partir de poliamidas 6 e 6,6 e tecido de fibras de carbono com 40, 50 e 60 % em volume de reforço foram processados via moldagem por compressão a quente e caracterizados por ensaios mecânicos destrutivos (cisalhamento interlaminar em três pontos (short-beam), cisalhamento interlaminar por compressão (CST) e ensaios de mecânica da fratura) e por inspeção não-destrutiva (ultra-som e microscopias óptica e eletrônica de varredura). Os resultados obtidos mostraram que os compósitos termoplásticos processados apresentaram uma distribuição homogênea do polímero no reforço. Entretanto, nos compósitos com maior quantidade de poliamida (40 % de reforço) foram observadas regiões ricas em matriz entre as camadas de tecido. Os ensaios de mecânica da fratura (DCB e ENF) e de cisalhamento interlaminar em três pontos não apresentaram falha interlaminar, não sendo observada a propagação de trincas de forma homogênea e retilínea no interior do material. Em função destes resultados foi utilizado o ensaio de cisalhamento por compressão, desenvolvido no Institute of Polymer Research Dresden da Alemanha, que permitiu uma caracterização mais precisa dos compósitos termoplásticos estudados. Foi observado também, a partir dos ensaios de CST, que os compósitos obtidos da poliamida 6,6 apresentaram um aumento no valor do cisalhamento interlaminar de até 20 % com o aumento do volume de fibras.

Transport of Water through Polyamide-Nitrile Rubber Blends and its Influence on Mechanical Properties

Polyamide-nitrile rubber blends of high polyamide content (100/0, 70/30, 50/50) were prepared by melt mixing in a Haake Rheocord. The diffusion of water through the blends was investigated at various temperatures; 28, 45, 65 and 75°C. The temperature dependence of the diffusion characteristics indicates that the transport mechanism varied with blend composition, morphology and temperature. The weight gain curves for pure polyamide and blends rich in polyamide showed a maximum followed by a decrease (overshoot effect). The enthalpy and entropy of sorption have been computed from the sorption data. Transport was found to follow the Fickian type mechanism. The effects of water uptake on the mechanical behaviour of the blends have also been analysed. The mechanical properties were found to decrease considerably as a result of water absorption.

Hydrogen bonding in polyamide toughened novolac type phenolic resin

The hydrogen bonding, miscibility, and thermal stability of polyamide toughened novolac type phenolic resin were investigated. The intermolecular force of the resin increased with the content of the soft segments of polyamides (nylon 6, nylon 66) that absorb the loads in the network of brittle phenolic resin. IR (IR region) spectra and differential scanning calorimetry results confirmed that the phenolic/polyamide blend was completely miscible. Its thermal degradation temperature was higher than 400°C and increased with the increasing of polyamide content. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2283–2289, 1999

Mechanical properties, morphology, and flame retardance of glass fiber-reinforced polyamide-toughened novolac-type phenolic resin

The mechanical properties (tensile, flexural modulus, and impact strength) and the flame retardance of glass fiber-reinforced novolac-type phenolic resin modified with polyamide (PA-6, PA-66) were investigated. Results show that polyamide improves the mechanical properties of composites, especially for the impact strength up to 1.5-fold which shows a maximum value at 7 wt % of polyamide content. The interface between the matrix and glass fiber is increased due to the hydrogen-bonding function present in the polyamide chain. This modified phenolic composite shows excellent flame retardance, that is, UL-94, V-0, and LOI is higher than 55.

Mechanical properties, morphology, and flame retardance of glass fiber-reinforced polyamide-toughened novolac-type phenolic resin

The mechanical properties (tensile, flexural modulus, and impact strength) and the flame retardance of glass fiber-reinforced novolac-type phenolic resin modified with polyamide (PA-6, PA-66) were investigated. Results show that polyamide improves the mechanical properties of composites, especially for the impact strength up to 1.5-fold which shows a maximum value at 7 wt % of polyamide content. The interface between the matrix and glass fiber is increased due to the hydrogen-bonding function present in the polyamide chain. This modified phenolic composite shows excellent flame retardance, that is, UL-94, V-0, and LOI is higher than 55. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 881–887, 1999

Reactive compatibilisation of A/(B/C) polymer blends. Part 2. Analysis of the phase inversion region and the co-continuous phase morphology

The blend polyamide 6 (PA-6)/poly(methyl methacrylate) (PMMA) can be compatibilised by means of the reactive copolymer styrene-maleic anhydride with 20 wt% maleic anhydride (SMA20). The region of phase co-continuity has been analysed for the non-compatibilised and the compatibilised blends with scanning electron microscopy (SEM). The blend composition range of phase co-continuity was shifted to a lower PA-6 content when compatibiliser (SMA20) was added and the co-continuous structures were observed over a much narrower composition range. The effect of the molecular weight of PA-6 on the composition range of phase co-continuity was also analysed; it was found to be shifted to lower PA-6 content with decreasing molecular weight of PA-6. This shift could be interpreted by measuring the melt-viscosity of the different polymers using capillary rheometry. The analysis of the dynamic mechanical properties of the blends confirmed the results obtained with SEM; a clear change in storage modulus (log E′) and damping (tan δ) was observed in the phase inversion region. Finally, the crystallisation behaviour of PA-6 in the blends was investigated during cooling from the melt with differential scanning calorimetry. Fractionated crystallisation was observed in the blends where PA-6 forms the dispersed phase.

Pervaporation of aqueous ester solutions through hydrophobic poly(ether-block-amide) copolymer membranes

The pervaporation of three ethyl esters (aroma model compounds) in aqueous solutions was studied with poly(ether-block-amide) copolymer (PEBA) membranes of different compositions. The ester flux increases linearly with the ether-unit (tetramethylene oxide) content. The slope of the increase changes from a low to a higher value at 50 wt% polyether content. This behavior is explained by a change in the membrane structure from a continuous polyamide matrix structure to a polyether matrix one. The ester flux from saturated aqueous solutions increases from butyrate to propionate, then to acetate. This order differs from that of the poly(dimethylsiloxane) (PDMS) membrane whose flux was highest for butyrate and lowest for propionate ester. The PEBA membrane permeability and selectivity to the esters increase significantly with the polyether content. However, the best PEBA membrane had lower flux and selectivity to esters in aqueous solutions than the PDMS membrane. The activation energy for ester permeation was always lower than that for water permeation; its value was the highest for the PEBA membrane with the highest polyamide content.

Dynamic rheological properties of binary PP/PA and ternary PP/PA/GF blends

AbstractThe dynamic rheological behavior was investigated for binary polypropylene (PP) ‐ polyamide‐6 (PA‐6) and ternary PP‐PA‐6‐glass fiber (GF) blends. The observed trends are related to the blend morphology and the partitioning of the GF within the three component blends. The dynamic and shear viscosity results show a good overlap for the PP homopolymer, within the shear rates studied. The addition of PA‐6 and/or glass fibers to the PP causes significant deviations between the two rheological behaviors. This reflects the fibrillation of PA‐6 and the orientation of glass fibers during shear rheometry, which reduce the blends' shear viscosity. The effect of PA‐6 content on dynamic viscosity is less significant than for shear viscosity, owing to the absence of morphological structuring. The addition of PA‐6 to PP increased the principal relaxation time of the binary blends. The addition of GF to these binary blends gave a further increase in the principal relaxation time.

Synthesis and processing of the (ethylene‐vinyl acetate‐vinyl alcohol) terpolymer and its blends with a polyamide and styrene copolymers

In this article, the synthesis and properties of the (ethylene-vinyl acetate-vinyl alcohol) terpolymer are studied in detail. A transesterification reaction with alcohols was conducted on poly(ethylene-vinyl acetate) to obtain terpolymers with varying hydroxide contents through three different routes: in solution, in a mixing chamber, and in a twin-screw extruder. The kinetics of the reaction in the mixing chamber are compared with those of the twin-screw extruder. Mechanical and rheological properties of the terpolymer are examined as a function of conversion. Blends of the terpolymer with polyamide (Nylon-6) were prepared for various compositions. They show a steep reduction in the equilibrium torque with respect to that of the polyamide. A region of compatibility at high polyamide contents gives rise to an increase of some mechanical properties above the simple mixing rule (Young's modulus). On the other hand, blends with poly(styrene-acrylonitrile) and poly(styrene maleic anhydride) show a region of compatibility at equal proportions of the styrene copolymers and with 10% terpolymer content, induced by the reaction of the hydroxide and maleic anhydride groups. This reaction is inhibited at high styrene-acrylonitrile concentrations due to interference presented by the effect of interactions between the maleic anhydride and acrylonitrile groups. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1071–1083, 1998

Synthesis and processing of the (ethylene-vinyl acetate-vinyl alcohol) terpolymer and its blends with a polyamide and styrene copolymers

In this article, the synthesis and properties of the (ethylene-vinyl acetate-vinyl alcohol) terpolymer are studied in detail. A transesterification reaction with alcohols was conducted on poly(ethylene-vinyl acetate) to obtain terpolymers with varying hydroxide contents through three different routes: in solution, in a mixing chamber, and in a twin-screw extruder. The kinetics of the reaction in the mixing chamber are compared with those of the twin-screw extruder. Mechanical and rheological properties of the terpolymer are examined as a function of conversion. Blends of the terpolymer with polyamide (Nylon-6) were prepared for various compositions. They show a steep reduction in the equilibrium torque with respect to that of the polyamide. A region of compatibility at high polyamide contents gives rise to an increase of some mechanical properties above the simple mixing rule (Young's modulus). On the other hand, blends with poly(styrene-acrylonitrile) and poly(styrene maleic anhydride) show a region of compatibility at equal proportions of the styrene copolymers and with 10% terpolymer content, induced by the reaction of the hydroxide and maleic anhydride groups. This reaction is inhibited at high styrene-acrylonitrile concentrations due to interference presented by the effect of interactions between the maleic anhydride and acrylonitrile groups. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1071–1083, 1998

Polypropylene/Polyamide 6 in situ Composite

The in situ composite consisting of polypropylene (PP) and polyamide 6 (PA6) was obtained with extrusion method in a single screw extruder. It was found that PA6 being the dispersed phase could fibrillated in PP matrix and fibrillation occurred in the channel of the extruder. The notched impact strength increased with the increasing content of PA6 while the tensile strength decrease. The average diameter of the fibrils changed hardly with the changing content of PA6 under the investigated condition. Increasing the draw rate and the impact strength and tensile strength increased obviously. When increasing the rotating speed of screw the dimension of the fibrils also became finer. The mechanical properties decreased with the increasing processing temperature and the average diameter of fibrils increased.

Carbon–epoxy composites based on fibers coated with nylon 6,6: hygrothermal ageing versus interlaminar shear strength

AbstractCarbon fibers were coated in situ with a thin film of polyhexamethylene adipamide by an interfacial polycondensation technique. The modified fibers were used for the preparation of epoxy‐based unidirectional composites. Specimens of these materials were immersed in water until equilibrium conditions were attained. The weight gain at equilibrium was determined as a function of the immersion temperature, the fiber volume fraction and the polyamide content deposited on the fibers. Water penetration in specimens made with uncoated carbon fibers increases when the volume fraction decreases. Introduction of the polyamide interlayer initially increases the water absorption, but reduces it at higher immersion temperatures and/or higher polyamide contents. The treated specimens were subjected to the short beam test to determine the interlaminar shear strength (ILSS). The data show that the ILSS decreases with water penetration but increases when the immersion temperature increases from 40 to 70°C. The overall performance encountered is discussed in terms of the possible roles of the polyamide interphase while taking into account mechanisms concerned with matrix plasticization, interphase degradation and residual stress relaxation.

The role of a polyamide interphase on carbon fibres reinforcing an epoxy matrix

Carbon fibres were pretreated by means of an interfacial in-situ polyamidation technique resulting in a polyamide coating of the fibres. The procedure followed involved successive application to the carbon fibres of two immiscible solutions of hexamethylenediamine and adipoyl chloride. Previous work conducted in our laboratory on chrysotile/epoxy composites coated with Nylon 6,6 provided interesting results when the tensile performance was evaluated. This behaviour was attributed to the improved affinity between matrix and asbestos fibres as a result of the well-known compatibility between polyamide and the epoxy phase. In this study emphasis is given to the coating of long carbon fibres such as are used for the preparation of unidirectional carbon/epoxy composites. The mechanical properties of uniaxial laminates with varying fibre volume fractions and polyamide contents are then compared with those of uncoated carbon fibres.

Polyamide coating on carbon fibres and potential application in carbon/kevlar/epoxy hybrid composites

Hybrid unidirectional composite materials, consisting of alternately laminated layers of Kevlar-49 fibres and carbon fibres in an epoxy resin, have been studied. Before embedding, the carbon fibres were coated with a Nylon 6,6 film by an interfacial in-situ polymerization technique. Emphasis is given to the mechanical properties of the hybrid composites based on coated carbon, with those based on uncoated carbon, for various values of partial volume fraction of the carbon fibres, V cf, polyamide content deposited on the carbon fibres, C N, and total fibre (Kevlar + carbon) volume fraction, V f.

Blends of polyamide 6 and bisphenol‐A polycarbonate. Effects of interchange reactions on morphology and mechanical properties

AbstractBlends of polyamide 6 (PA6) and polycarbonate (PC) were prepared in a Brabender mixer, at 240°C, applying long mixing time, for 45 min. It was observed that the morphology and the mechanical properties tend to resemble those of a homogeneous material as the mixing time and PA6 concentration increase. This is attributed to chemical reactions taking place between the two homopolymers. Acidolysis, amidolysis, and aminolysis, catalyzed by the terminals and the amide groups of the polyamide, should in principle be possible. Our results indicate that the aminolysis is the main process, inducing simultaneously scission of PC chains and formation of PC‐PA6 copolymer chains. The latter act as interfacial agents between incompatible PA6 and PC, improving the mechanical properties of PA6‐rich blends, in agreement with the predictions of some theoretical models assuming good phase interpenetration. © 1992 John Wiley & Sons, Inc.

The effect of fiber coating on the tensile properties of ionomer‐based composites

AbstractAsbestos fibers, of the chrysotile variety, were coated with a thin polyamide film by an in situ polycondensation technique. Ionomer‐based composites were prepared containing the so‐modified asbestos fibers in a random in‐plane orientation; results of testing the tensile properties of these asbestos/polyamide/ionomer composites are presented. Parameters investigated comprise the asbestos content in the composite and the polyamide content deposited on asbestos. A significant improvement in the tensile performance was established, especially at the intermediate polyamide content of 3.4 phr. The behavior is discussed in terms of possible interactions between the phases present in the composite material.