Blends of nylon 6 with an ethylene-based multifunctional polymer. I. Rheology–structure relationships

An experimental study was conducted to investigate the rheological behavior of a heterogeneous polymer blend system consisting of nylon 6 and an ethylene-based multifunctional polymer (CXA 3101, DuPont Co.). For comparison purposes, we also investigated the rheological behavior of two additional blend systems, namely blends of nylon 6 with a chemically modified polyolefin (Plexar 3, Chemplex Co.) and blends of nylon 6 with ethylene–vinyl acetate copolymer (EVA). We have investigated the thermal and thermomechanical behavior of the blend systems, using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Also, we have attempted to identify the chemical structure of the functional groups present in the CXA 3101 and Plexar 3 resins, using infrared (IR) spectroscopy. This information has enabled us to interpret the observed rheological behavior. Furthermore, we have used both optical and scanning electron microscopies to investigate the state of dispersion of the constituent components in each of the blend systems. We have concluded that, during melt blending, chemical reactions have taken place between carboxyl or anhydride groups present in the CXA 3101 resin and the amino end groups of the nylon 6, forming a graft copolymer which then acted as an “interfacial agent.”     

Effect of nylon 6 inclusions on the crystalline morphology of polypropylene–nylon 6 blends

Crystallization behavior and crystalline morphology of plain polypropylene (PP) and its blend with 0 to 30 wt % nylon 6 were studied by the hot‐stage polarized light microscopy method. Radial growth rate and the size and number of PP spherulites were measured as a function of both the isothermal crystallization temperature and the nylon 6 content of the blend. The study revealed that a reduction in the isothermal crystallization temperature from 135 to 120°C, for both the plain PP and its blend with nylon 6, leads to the formation of a large number of fast‐growing, small spherulites. Moreover, the size and growth rate of PP spherulites decreased on increasing the nylon 6 content of the blend; whereas the number of PP spherulites decreased sharply on initial addition of 10% nylon 6 and, thereafter, increased slightly by further addition of nylon 6. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1769–1775, 2000     

Rheology-morphology relationships in nylon 6/liquid-crystalline polymer blends

Extrusion measurements have been carried out on blends of nylon 6 and a liquid-crystalline copolyesteramide (LCP). The flow curves at low temperature show a behavior similar to that of pure LCP with a rapid rise of the viscosity at low shear rates. At high shear rates the viscosity is lower than that for each of the two components. This minimum has been attributed to the lack of interactions between the two phases and to the formation of fibrils of the LCP phase. The SEM analysis shows, indeed, that fibrils of the LCP phase are produced in the convergent flow at the inlet of the capillary at high shear rates. These fibrils are lost during the flow in the long capillary.     

Blends of polyamide 6, polycarbonate,and poly(propylene oxide). I. Reactive compatibilization–morphology relationships

The relationship between reactive compatibilization and morphology of the polyamide 6–polycarbonate (PA6–PC) and polyamide 6–polycarbonate–poly(pro-pylene oxide) (PA6–PC–PPO) blends were investigated by means of torque values, scanning electron microscopy, and Fourier transform infrared spectroscopy. The micrographs show that the blends processed for a long period of time presented a PC domain of smaller size and better adherence between the phases than the blends processed for a short period of time. This fact can be related with the presence of the block copolymer of PA6–PC synthesized in situ by the reaction of PA6 and PC and depend on temperature and mixing time. The presence of PPO does not impede the formation of copolymer but interferes on the size of the domain. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 857–864, 1998     

Impact fracture morphology of nylon 6 toughened with a maleated polyethylene–octene elastomer

This study aimed at using scanning electron microscopy to study the Izod impact fracture surface morphology of super‐tough nylon 6 blends prepared by blending nylon 6 with a maleic anhydride‐grafted polyethylene‐octene elastomer (POE) in the presence of a multifunctional epoxy resin (CE‐96) as compatibilizer. The fracture surface morphology and the impact strength of the nylon 6 blends were well correlated. The fracture surface morphology could be divided into a slow‐crack‐growth region and a fast‐crack‐growth region. Under low magnification, the fractured surface morphologies of the low‐impact‐strength nylon 6 blends appeared to be featureless. The area of the slow‐crack‐growth region was small. There were numerous featherlike geometric figures in the fast crack growth region. The fractured surface morphologies of the high‐impact‐strength nylon 6 blends exhibited a much larger area in the slow‐crack‐growth region and parabola markings in the fast‐growth region. Under high magnification, some rubber particles of the low‐impact‐strength nylon 6 blends showed limited cavitation in the slow‐crack‐growth region and featherlike markings in the fast‐crack‐growth region. Rubber particles of high‐impact‐strength nylon 6 blends experienced intensive cavitation in the slow‐crack‐growth region and both cavitation and matrix shear yielding in the fast‐crack‐growth region, allowing the blends to dissipate a significant amount of impact energy. A nylon 6 blend containing 30 wt % POEgMA exhibited shear yielding and a great amount of plastic flow of the matrix throughout the entire slow‐crack‐growth region, thus showing the highest impact strength. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1285–1295, 2000     

Dye–polymer interaction in nylon 66

Absolute orientation factors of dye and the amorphous region of the polymer nylon 66 have been determined from the dichroism of the visible band and that of the characteristic amorphous infrared band of the polymer. It has been shown that the orientations show a linear relationship with unit slope irrespective of whether the film was stretched before dyeing (prestretched) or stretched after dyeing (poststretched). The relation is the same for reactive as well as nonreactive disperse dye. The effect of thermal treatment at constant length shows that the dichroism of the dye decreases whereas that of the polymer does not and that it is reversible. It is concluded that disperse reactive as well as nonreactive dyes have specific interaction sites with the polymer.     

Thermotropic glazings for overheating protection. II. morphology and structure–property relationships

This article completes a systematic strategy for formulation and optimization of thermotropic systems with fixed domains (TSFDs) for overheating protection purposes. Focus was on characterization of morphology and on revealing optimization potential. A comprehensive characterization of scattering domain size and shape was done applying optical microscopy and scanning electron microscopy. In general, scattering domains exhibited inappropriate size and/or shape for optimum overheating protection performance. Moreover, several TSFD displayed defects (vacuoles, voids) resulting from thermomechanical or physicochemical interaction of matrix material and thermotropic additive during manufacturing. Morphological features along with solar optical and thermorefractive properties allowed for establishment of structure–property relationships. Light‐shielding efficiency of TSFD correlated well with scattering domain size and shape. The majority of TSFD showing defects exhibited an increase of solar hemispheric transmittance upon heating. Several strategies to overcome defect formation and to improve scattering morphology were suggested and proof of concept was shown partially, thus indicating a significant optimization potential of the established TSFD. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39910.     

Blends of polyamide 6, polycarbonate,and poly(propylene oxide). II. Reactive compatibilization–thermal degradation relationships

The thermal degradation of some blends of polyamide 6/polycarbonate (PA6/PC) and polyamide 6/polycarbonate/poly(propylene oxide) (PA6/PC/PPO) were investigated. The copolymer formed during the mixing of polyamide 6 and polycarbonate, at 240°C, for 30 min, increases the thermal stability of PA6/PC and of PA6/PC/PPO blends. This increase in the thermal stability occurs due to the plasticizing effect of PPO, which increases the mobility of the molecules of PA6 and PC, and consequently increases the probability of the reaction between the —NH₂ and —O—CO—O groups of polyamide 6 and polycarbonate, respectively. The ternary blends with PPO (5–10% w/w) have lower thermal stability than PA6/PC blends. This is due to the decrease of miscibility between these polymers and the rise of the diluting effect. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2556–2562, 2001     

Blends of nylon 6 with a polyethylene functionalized by photooxidation

An easy and cheap method to prepare functionalized polyethylene is reported in which polyethylene is photooxidized and then melt-blended with nylon. Structural, rheological, and mechanical modifications indicate that carbonyl, formed during photooxidation, and amine groups react giving rise to copolymers which stabilize the blends. Photooxidized polyethylene from waste could be very effective in preparing polyethylene/polyamide blends with improved properties. This new approach improves over current methods in which compatibilization of polyolefines and polyamides is mostly performed by reacting functionalized polyolefines with polyamides in molten state. The functionalization is achieved by chemical modification of the polyolefines chains. This step could be very expensive.     

Acrylonitrile–butadiene–styrene toughened nylon 6: The influences of compatibilizer on morphology and impact properties

Polymer alloys have been used as an alternative to obtain polymeric materials with unique physical properties. Generally, the polymer mixture is incompatible, which makes it necessary to use a compatibilizer to improve the interfacial adhesion. Nylon 6 (PA6) is an attractive polymer to use in engineering applications, but it has processing instability and relatively low notched impact strength. In this study, the acrylonitrile–butadiene–styrene (ABS) triblock copolymer was used as an impact modifier for PA6. Poly(methyl methacrylate‐co‐maleic anyhydride) (MMA‐MA) and poly(methyl methacrylate‐co‐glycidyl methacrylate) (MMA‐GMA) were used as compatibilizers for this blend. The morphology and impact strength of the blends were evaluated as a function of blend composition and the presence of compatibilizers. The blends compatibilized with maleated copolymer exhibited an impact strength up to 800 J/m and a morphology with ABS domains more efi8ciently dispersed. Moderate amounts of MA functionality in the compatibilizer (～5%) and small amounts of compatibilizer in the blend (～5%) appear sufficient to improve the impact properties and ABS dispersion. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 842–847, 2003     

Laminar morphology development using hybrid EVOH–nylon blends

Properties of blends having two types of hybrid dispersed phases as laminar morphology were investigated. The hybrid dispersed phases were prepared by preblending nylon and ethylene–vinyl alcohol (EVOH) in solid state (E + N) and in melt state (E/N). Oxygen and toluene barrier properties through the hybrid-dispersed phases in low-density polyethylene (LDPE) matrix were analyzed considering the morphological changes (number and size of layers). Oxygen barrier properties of the blends of LDPE–E + N hybrid dispersed phase having separate domains of nylon and EVOH were found to be linearly dependent on EVOH composition in the blend, but toluene barrier properties of the blends exhibited negative deviation. The other hybrid dispersed phase (E/N) in LDPE matrix, having comingled dispersed phase of nylon and EVOH, exhibited positive deviations in both oxygen and toluene barrier properties. Tensile properties also showed positive deviation. Basic studies on the melt blend (E/N) of EVOH and nylon 6 showed some miscibility, which was revealed from melting point depression, and positive deviation in complex viscosity and tensile properties of the blend. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2001–2014, 1998     

Modification of nylon 6 with organochlorosilanes. II. Physical properties

The physical properties of nylon 6 yarn treated with dimethyldichlorosilane (DMCS) and vinylmethyldichlorosilane (VMCS) in nitrogen atmosphere or air in the presence and absence of an amine have been compared with those of ether-extracted parent yarn. Treatment with DMCS in nitrogen resulted in marginal improvement in breaking stress, considerable increase in breaking elongation, and elastic behavior, whereas initial modulus was decreased. A decrease in density, birefringence, and moisture regain with increase in per cent weight gain was observed. Mechanical damping was decreased considerably up to an optimum weight gain after which it was increased. Thermal properties were also determined, and results are discussed in relation to mechanical properties. The results indicate that the overall thermal stability has decreased in the chemically treated yarns. Treatment with organochlorosilanes in the presence of air results in a chain-scission reaction and a decrease in mechanical properties.     

Conducting polymer composites of zinc‐filled nylon 6

The present work is concerned with the effect of processing variables and filler concentration on the electrical conductivity, hardness, and density of composite materials prepared by compression molding of a mixture of zinc powder and nylon 6 powder. The electrical conductivity of the composites is <10^?12 S/cm, unless the metal content reaches the percolation threshold at a volume fraction of about 0.18, beyond which the conductivity increases markedly by as much as 10 orders of magnitude. The density of the composites was measured and compared with values calculated by assuming different void levels within the samples. Furthermore, it is shown that the hardness increases with the increase of metal concentration, but for values of filler volume fraction higher than about 0.30 the hardness of samples remains almost constant. Two parameters of molding process, temperature and time, were shown to have a notable effect on the conductivity of composites, whereas pressure has no influence on this property in the pressure range considered. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1449–1454, 2001     

Isothermal crystallization of copolyamides. I. Kinetics of crystallization of nylon 6–piperazine adipate and nylon 6–piperazine terephthalate random copolyamides

The kinetics of primary crystallization from the melt of nylon 6–piperazine adipate and nylon 6–piperazine terephthalate copolyamides were measured dilatometrically. It was found that the crystallization rate of the samples under investigation decreases with increase in the percentage comonomer content and rigidity of molecules over the entire temperature range investigated. The Avrami exponent n varied with temperature, values being from 2 to 4.     

Blends of a PPO–PS alloy with a liquid crystalline polymer

Blends of a PPO–PS alloy with a liquid crystalline polymer have been studied for their dynamic properties, rheology, mechanical properties, and morphology. This work is an extension of our previous work on PPO/LCP blends. The addition of the LCP to the PPO–PS alloy resulted in a marked reduction in the viscosity of the blends and increased processibility. The dynamic studies showed that the alloy is immiscible and incompatible with the LCP at all concentrations. The tensile properties of the blends showed a drastic increase with the increase in LCP concentration, thus indicating that the LCP acted as a reinforcing agent. The tensile strength, secant modulus, and impact strength of the PPO–PS/LCP blends were significantly higher than that of PPO/LCP blends. Morphology of the injection molded samples of the PPO–PS/LCP blends showed that the in situ formed fibrous LCP phase was preserved in the solidified form. A distinct skin–core morphology was also seen for the blends, particularly with low LCP concentrations. The improvement of the mechanical properties of the blends is attributed to these in situ fibers of LCP embedded in the PPO–PS matrix. The improvement in the properties of PPO–PS/LCP over PPO/LCP is also attributed to the addition of the PS which consolidates the matrix. © 1995 John Wiley & Sons, Inc.     

Interpenetrating polymer networks. II. Sunlight-induced polymerization of multifunctional acrylates

Protective coatings and glass laminates have been readily obtained by sunlight-curing of acrylate monomers dispersed in a poly(methyl methacrylate) matrix or in a styrene–butadiene rubber, in the presence of an acylphosphine oxide photoinitiator. The polymerization reaction was followed by infrared spectroscopy and by gel fraction measurements and was shown to proceed extensively within minutes. As expected, the inhibitory effect of atmospheric O₂ on such radical-initiated reactions was less pronounced in solid than in liquid samples. The monomer, photoinitiator, and plasticizer concentrations were found to have a strong influence on the rate of polymerization, the final degree of conversion, and the hardness of the sun-cured polymer. The adhesion of the cured coating on glass was substantially improved by the addition of an acrylate-grafted organosol silica. To produce strongly adhesive glass laminates, a photocurable acrylate resin was poured between two coated glass plates and exposed to sunlight for a few seconds. The same formulation can serve as a light-sensitive quick setting glue to bond glass to a variety of materials [polycarbonates, poly(vinyl chloride), aluminium, and steel]. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2269–2282, 1998     

Polyurethane–polyacrylate interpenetrating polymer networks. II

Two component topologically interpenetrating polymer networks of the SIN type (simultaneous interpenetrating networks) composed of a melamine-cured polyacrylate and three different polyether-based polyurethanes were prepared. The linear polymers and prepolymers were combined in solution, together with the necessary crosslinking agents and catalysts, films were cast and subsequently chain extended and crosslinked in situ. In all cases, maxima in tensile strength significantly higher than the tensile strengths of the component networks occurred at 50% polyurethane : 50% polyacrylate. This was explained by an increase in crosslink density resulting from interpenetration. One of the interpenetrating polymer networks showed only one glass transition temperature (T_g) (measured calorimetrically) intermediate in temperature to the T_g's of the components and as sharp as the component T_g's. This is indicative of phase mixing and indicates at least partial chain entanglement (interpenetration). Some enhancement of other physical properties was also noted.     

Fractionated crystallization in polyolefins–nylon 6 blends

The crystallization behavior of polyolefins–nylon 6 polymer blends was studied by differential scanning calorimetry (DSC) measurements. In these blends, the crystallization of the minor component often starts with distinctly deeper supercooling than that of the pure polymer, and proceeds in several separate steps. The origin of this phenomenon was studied and was related to the volume fraction of the dispersed phase and the compatibility between the dispersed phase and the matrix. © 1994 John Wiley & Sons, Inc.