Nylon Matrix Research Articles

Effects of molecular weights and compatibilizing agents on the morphology and properties of blends containing polypropylene and nylon‐6

AbstractPolymer blends containing nylon‐6 of different molecular weights (MW) and polypropylene (PP) were prepared by using a twin screw extruder in order to examine the effects of molecular weights of nylon and the influences of different types of compatibilizing agents on the phase morphology and the properties. The morphology of the resulting blends was characterized by using both scanning electron microscope (SEM) and optical microscope and the properties measured included Izod impact strength, melt flow index (MI), flexural modulus, and heat distortion temperature (HDT). It was found that the molecular weights of the nylon matrix had a significant effect on the phase morphology. The fracture surface of the low MW nylon blend demonstrated a uniformed phase morphology with the dispersed PP particles of dimensions in the range of 1 μm in diameter embedded in the nylon matrix, suggesting an improved compatibility as compared with the high MW nylon system, even though these two constituents were incompatible in nature. Three different types of compatibilizers, including maleic anhydride modified PP (MA‐g‐PP), acrylic acid modified PP (AA‐g‐PP), and ethylene glycidyl methacrylate copolymer (EGMA), were used to examine their effects. It seemed that blends compatibilized with MA‐g‐PP exhibited the most homogeneous phase morphology and superior mechanical properties among the three. In the blends containing low MW nylon as the matrix phase, the Izod impact strength was shown to have increased by about 40% as compared with the noncompatibilized blend, while a 20% increase of the impact strength was measured in the high MW nylon system. The effects of nylon's molecular weights and the compatibilizers were also studied in systems of PP/nylon blends reinforced with silane‐treated glass fibers. It was shown that the properties of the composites relied on the phase morphology which, in turn, was affected by both the molecular weight of nylon and the compatibilizing agents. © 1995 John Wiley & Sons, Inc.

Genetically modified skin to treat disease: potential and limitations.

Molecular definition of disease at the level of the gene and advances in recombinant DNA technology suggest that many diseases are amenable to correction by genes not bearing the defective elements that result in disease. Many questions must be answered before this therapy can be used to correct chronic diseases. These questions fall into safety and efficacy categories. Experience with transplanting cellular elements of skin or skin substitutes (defined as skin that possess the cell types and a dermal structure to develop into a functioning skin) to athymic rodents is considerable and is seen as a system where these questions can be answered. This paper reviews these questions and presents our early analysis of genetically modified cells in skin substitutes in vivo and in vitro. Experimental data demonstrate that both a matrix of woven nylon, housing a fibroblast generated collage, and dead dermis can be utilized to shuttle genetically modified human fibroblasts from the laboratory to an in vivo setting. Genetically modified fibroblasts do not migrate from the shuttle to the surrounding tissue. The survival of significant numbers, approximately 70%, of genetically modified fibroblasts for at least 6 weeks in these shuttles, supports this general approach as having clinical utility. It is also concluded that skin substitute systems can be used to generate a genetically modified skin in vitro that has the capacity to develop into functional skin in vivo. Further, as genetically modified keratinocytes differentiate there is increased production by the transgene, supporting the concept that keratinocytes have true potential as shuttles for therapeutic genes. This work demonstrates that transplantation of systems containing genetically modified cells of the skin can be used to experimentally define many aspects of gene therapy using skin before this technology is taken to the clinic. Examples include determining the effect of gene transduction and expression on structure and function of the genetically modified skin as well as on distant skin and an assessment of the translational capacity of the transgene as function of time and cell number.

Genetically Modified Skin to Treat Disease: Potential and Limitations

Molecular definition of disease at the level of the gene and advances in recombinant DNA technology suggest that many diseases are amenable to correction by genes not bearing the defective elements that result in disease. Many questions must be answered before this therapy can be used to correct chronic diseases. These questions fall into safety and efficacy categories. Experience with transplanting cellular elements of skin or skin substitutes (defined as skin that possess the cell types and a dermal structure to develop into a functioning skin) to athymic rodents is considerable and is seen as a system where these questions can be answered. This paper reviews these questions and presents our early analysis of genetically modified cells in skin substitutes in vivo and in vitro. Experimental data demonstrate that both a matrix of woven nylon, housing a fibroblast generated collage, and dead dermis can be utilized to shuttle genetically modified human fibroblasts from the laboratory to an in vivo setting. Genetically modified fibroblasts do not migrate from the shuttle to the surrounding tissue. The survival of significant numbers, approximately 70%, of genetically modified fibroblasts for at least 6 weeks in these shuttles, supports this general approach as having clinical utility. It is also concluded that skin substitute systems can be used to generate a genetically modified skin in vitro that has the capacity to develop into functional skin in vivo. Further, as genetically modified keratinocytes differentiate there is increased production by the transgene, supporting the concept that keratinocytes have true potential as shuttles for therapeutic genes. This work demonstrates that transplantation of systems containing genetically modified cells of the skin can be used to experimentally define many aspects of gene therapy using skin before this technology is taken to the clinic. Examples include determining the effect of gene transduction and expression on structure and function of the genetically modified skin as well as on distant skin and an assessment of the translational capacity of the transgene as function of time and cell number.

Mechanical properties and morphology of nylon-6/acrylonitrile-butadiene-styrene blends compatibilized with imidized acrylic polymers

The mechanical properties and phase morphology of blends of nylon-6 with various acrylonitrile-butadiene-styrene (ABS) materials and compatibilizers are explored. The main focus was on nylon-6/ABS blends compatibilized with one particular imidized acrylic polymer that is miscible with the styrene-acrylonitrile (SAN) matrix of the ABS and has nearly optimal content of functional groups (anhydride and free acid) for reaction with nylon-6 to form graft copolymers in situ at the polymer-polymer interfaces. The effects of compatibilizer content, rubber concentration and the mixing protocol on the mechanical properties of these blends were extensively explored. In general, the most efficiently dispersed ABS domains in the nylon matrix led to the lowest ductile-brittle transition temperatures and the maximum tensile modulus for the super-tough nylon-6/ABS blends. The effects of varying the functionality and miscibility characteristics of imidized acrylic polymers on the mechanical properties and morphology of nylon-6/ABS blends were also investigated. Some other types of polymers with a high anhydride content were also tested as compatibilizers for this system. It appears that compatibilizers with high levels of reactive functinality are not very effective; hence, there is an optimal level of functionality.

Structure development during dynamic vulcanization of hydrogenated nitrile rubber/nylon blends

AbstractThe factors that influence the morphology and the interfacial parameters during dynamic vulcanization of hydrogenated nitrile rubber/nylon blends are examined. The particle size of the dispersed phase (R̄) and the correlation distance (ξ) of a 50 : 50 blend decreased with increasing mixing time at 250°C, attained a minimum value, and then increased. The increase in the number of particles with time (dn/dt) may be expressed as (dn/dt) = k'nm, where n is the number of dispersed particles at time t, and m and k' are constants. R̄ and ξ gradually increased as the mixing temperature was increased from 250 to 300°C at a constant mixing time of 10 min. The particle size increased also with the increasing gel fraction of the rubber. At a constant mixing time of 10 min at 250°C, the particles were larger when the addition of the cross‐linker was delayed. These observations can be explained with the help of a hypothetical model, similar to that proposed by Wu, considering the breaking down of rubber particles, coagulation and coalescence of droplets, and droplet rupture in a matrix of nylon. On vulcanization, the thickness of the interface (λ) reduced from 62 to 48 nm. The interaction parameter and interfacial tension, as estimated from λ, for a bilayer specimen vulcanized in situ, at 250°C were 2.8 × 10–3 and 0.24 mN/m, respectively. The high value of λ for the dissimilar polymer pair may be due to polymer‐polymer graft formation at high temperature. © 1993 John Wiley & Sons, Inc.

Transformations between polyiodide structures in a nylon 6 matrix

Iodide because of its high electronegativity, is extensively used as an active cathode material in dry lithium galvanic cells. Nylon 6 (N6) can incorporate up to 1.4 times its weight of iodine, and this is the highest reported for any polymer-iodine complex. Structures of these complexes are investigated by X-ray diffraction. Iodine exists in the N6 matrix as iodide ions between hydrogen bonded sheets. The heavily iodinated N6 (1.25 mol of iodine/chemical repeat of N6) shows an equatorial period of 23 [angstrom] which we attribute to the presence of I[sub 5][minus] arrays perpendicular to the chain axis. The complex rapidly loses iodine during initial aging and becomes fairly stable once a concentration level of ca. 0.75 mol of iodine is reached. During this initial aging, the I[sub 5][minus] arrays transform into I[sub 3][minus] species but maintain their orientation and thus result in a structure with an equatorial 15.6 [angstrom] repeat. As the concentration of the iodide ions is further reduced by continued aging (0.25 moles), the I[sub 5][minus] columns are established parallel to the chain axis, resulting in a structure with an equatorial repeat of 8 [angstrom]. Thermal data show that the transition from I[sub 3][minus]([perpendicular]) to I[sub 3][minus]([parallel]) ismore » the result of [open quotes]melting[close quotes] and [open quotes]recrystallization[close quotes] of the iodide ion arrays. The [gamma] form of N6 is obtained as the iodide ions are removed from the 8-[angstrom] structure. A lattice match between the I[sub 5][minus]([parallel]) ions and the chain-axis structure of N6 in the final stage of the complex is thought to be responsible for the formation of the [gamma] crystalline form of N6 from the iodinated complex. 15 refs., 19 figs.« less

Percolation Model of Brittle-Ductile Transition in PP/EPDM Blends

1 Introduction S. Wu reported the brittle-ductile transition master curve for the relation between the notched izod impact strength of Nylon-6/EPDM blends and rubber fractions. It was interpreted by the strong interaction between polar Nylon-6 matrix and modified EPDM dispersed phase. However, similar brittle-ductile transition master curve in non-polar PP/EPDM blends was also observed in this laboratory (Fig. 1).

Relaxational and Interfacial Properties of Ultrafine Particles-Polymer Composite.

Nylon composites containing ultrafine particles such as gold, silver and copper (I) oxide, were prepared by the RAD process. Various properties of the composites such as optical, mechanical, and electrical properties were studied in order to examine the interfacial properties between ultrafine particles and nylon matrix. The composites showed such colloidal colors as red (Au), yellow (Ag), and yellowish green (copper (I) oxide) which were all uniformly transparent without metalic luster. Both solid film of the composite and m -crezol solution of the composite maintained its colloidal color for a long time without agglomeration or aggregation of the particles. The mechanical relaxation of the composites suggested that the rigid nylon region around particle was formed by strong interaction between particles and nylon molecules. This region stably kept holding ultrafine particles in nylon matrix, and it also prevented particles from agglomerating. The composites showed interesting elecrical properties different from those of nylon alone because the rigid region of nylon polarized very slowly by applying the electric field. The time lag in the electrical response was caused by slow relaxation of the interfacial region.

Water penetration in nylon 6,6: Absorption, desorption, and exchange studied by NMR microscopy

AbstractThe uptake of water by nylon 6,6 [42DB Adipure (trade name of Dupont Canada Inc.)] at 100°C has been monitored by a combination of one‐dimensional proton NMR spectroscopy, relaxation time (T1 and T2) measurements and proton microscopic NMR imaging techniques. The relaxation times of the water absorbed into the nylon matrix are very short at room temperature, (T2 < 1 ms and T1 ≈ 1 s) indicating that the water is located in a highly restricted environment and suggesting that strong interactions exist between the absorbed water and the polymer. The diffusion profiles measured at room temperature indicate that the diffusion of water into nylon 6,6 at 100°C is Case I Fickian diffusion. The spatial dependence of the T2 relaxation time constant and its variation with the water content was also examined. The results reveal that both T2 and T2* decrease toward the center of the sample in samples that have a concentration gradient of sorbed water. In fully saturated samples, no spatial dependence was observed. The overall values of T2 and T2* are also observed to increase as a function of exposure time. An evaluation of the desorption process at room temperature and at 100°C was performed. A continuous, exponentially decreasing solvent profile was observed for the desorption process which again indicates Case I Fickian kinetics. The exchange process of external bulk and atmospheric water with deuterium oxide (D2O) saturated nylon rods has also been studied using the microscopic imaging technique. © 1993 John Wiley & Sons, Inc.

Interphase Bond Strength and Energy Absorption of Injection-Molded Rubber-Coated Glass/Nylon Composites

The use of a thin rubber coating on the fiber in a fibrous composite has been shown to increase the composite low-speed impact resistance [1,2]. The coating used was very thin compared to the fiber diameter, in order to preserve the other composite properties. From elastic consideration, the thin rubber coating was understood to have a direct effect upon the reduction of the stress concentration in the region near the fiber/matrix interface, especially at the chopped fiber end or at the matrix crack front reaching the fiber [3,4]. If the possible existence of localized high stress zones is reduced, the material can be subjected to higher loading before global failure occurs. With the rub ber coating the high stress zones inside the material can spread out to a larger volume. There will be less chance for local damage to initiate under the same loading level. The material will therefore exhibit higher resistance to failure, i.e., it will absorb more energy before failure. Three injection-molded glass/nylon composites were tested for tensile fail ing energy. One is reinforced with bare chopped fibers and the other two are with rubber- coated fibers. Tensile experiments showed significant increase of energy absorption in one sample with a rubber coating. Micrograph study was extensively carried out on the failed samples to identify the parameters of this desirable consequence. The rupture of the rub ber interphase and the limited plastic flow of the nylon matrix on the fractured surface of failed specimens were clearly evidenced. Meanwhile, interfacial bonding measured through microdebonding tests [4] revealed reasonable relation of the characteristic inter facial bonding and the energy absorption.

Effect of polyamide functionality on the morphology and toughness of blends with a functionalized block copolymer

Previous work has shown that blends of a maleic anhydride functionalized triblock copolymer (with an ethylene/butene mid-block and styrene end-blocks, or SEBS- g-MA) with nylon-6,6 gives super-tough materials with complex-shaped rubber particles that are just below the upper critical particle size for toughening. Similar blends of SEBS- g-MA with nylon-6 are not toughened because the rubber particles are evidently too small, i.e. below a proposed lower critical size for toughening. It was further proposed that this difference in morphology stems from the difunctional (nylon-6,6) versus monofunctional (nylon-6) character of these polyamides for reaction with anhydrides. This proposal is supported here by the observation that blends of SEBS- g-MA with nylon-12,12 give large complex rubber particles like those in nylon-6,6 while nylon-11 and nylon-12 give smaller particles like nylon-6. Further support of this notion is provided by blending nylon-6 with other polyamides in an attempt to produce a chemically modified matrix. Addition of 10% nylon-6,6, poly( m-xyle adipamide) (MXD6) and nylon-12,12 to the nylon-6 matrix (under conditions that cause phase homogenization by interchange reactions) leads to rubber particle enlargement and toughening, while addition of nylon-11 or nylon-12 does not lead to either particle enlargement or toughening. Possible effects of rheological factors, extent of interchange reactions, interfacial tension and end-group contents are discussed.

Effect of water absorption on the behavior of E‐glass fiber/nylon‐6 composites

AbstractThe effect of water absorption on the stress transferability across E‐glass fiber/nylon 6 interface has been studied using the embedded single fiber composite technique. The behavior of silane coated fiber and untreated fiber composites after periods of water immersion were compared. The silane coating provided both higher interfacial shear stress transferability and protection from permanent water damage in the interphase region. It was found that water absorption in the nylon matrix reduced the shear stress transferability through plasticization of the matrix, weakening of the interface, and the development of tensile swelling stresses at the phase boundaries. In untreated materials the shear stress transferability was limited by decoupling of the matrix from the broken fiber ends by either interface slippage or local plane strain fracture in the interphase region near the fiber end. In the silane treated materials the shear stress transferability was limited by constrained yielding of the polysiloxane/nylon interphase at the fiber end, thus indicating plasticization of the matrix was the primary factor. After 20 days of water immersion, there was permanent deterioration of stress transferability in the untreated samples, but very little permanent damage in the treated samples.

Circus movement atrial flutter in canine sterile pericarditis model. Activation patterns during entrainment and termination of single-loop reentry in vivo.

Recently, we used a custom designed "jacket" electrode with 127 bipolar electrodes in a flexible nylon matrix to map the total atrial epicardial surface in the in situ canine heart. Atrial flutter in dogs with sterile pericarditis was shown to be due to a single wave front circulating around a combined functional/anatomic obstacle, with the arc of functional conduction block contiguous with one or more of the atrial vessels. In the present study, this model was used to analyze the activation pattern during pacing-induced entrainment and termination of single reentrant loops in a syncytium without anatomically predetermined pathways. Sustained atrial flutter was induced in five dogs with 3-5-day-old sterile pericarditis. Atrial pacing at a cycle length 5-30 msec shorter than the spontaneous cycle length entrained the arrhythmia and could result in a "classical" activation pattern, characterized by an antidromic stimulated wave that collided with the reentrant orthodromic wave front of the previous beat at a constant site. However, two variations of this classical activation pattern were also observed: 1) Pacing at short cycle lengths could lead to localized conduction block in antidromic direction, forcing a change in the pathway of the antidromic wave front. This could prevent the expected shift of the site of collision in antidromic direction. 2) The stimulated orthodromic wave front could also use a pathway different from that of the original reentrant impulse, so that a different circuit was active during the pacing period. Termination of atrial flutter by rapid atrial stimulation was associated with progressive slowing and finally blocking of the paced orthodromic wave front and a progressive shift of the site of collision in antidromic direction. The occurrence of conduction block was determined by the cycle length of stimulation and the number of stimulated beats. A longer train at the critical cycle length or the critical number of beats at a shorter cycle length could reinduce the same reentrant circuit or a different reentrant circuit, respectively, during stimulated cycles following the beat that terminated reentry. The epicardial activation sequence during entrainment of reentrant arrhythmias does not necessarily follow a standard activation pattern. Instead, the stimulated orthodromic as well as the antidromic wave front might use a pathway different from that of the original reentrant wave front. The mechanisms of termination, failure of termination, and reinitiation of single-loop reentry are similar to those in the "figure-eight" reentrant circuit.

Structure development during flow of polyblends containing liquid crystalline polymers

AbstractThe microstructure development during capillary flow of polyblends containing Liquid Crystalline Polymers (LCPs) was studied. In the present investigation the wholly aromatic LCP constituent was the minor phase suspended in polycarbonate (PC), poly(butyleneterephthalate) (PBT) or Nylon 6 (N‐6), in addition to previously studied amorphous nylon matrix Experimental results showed that the viscous forces acting at the components' interface are predominating the elongational deformation and the resulting structure development of the LCP phase. In cases where the viscosity of the suspending matrix was higher than the LCP one (PC, amorphous nylon) scanning electron micrographs indicated that fibrillar structure developed. In cases where the viscosity of the matrix polymers was lower than the LCP suspended phase, fibrous structures developed only at very high shear rates. Due to velocity rearrangement effects at the capillary exit a skin core morphology was observed. Since the polymers viscosity depends both on shear rate and temperature, the in situ composite structure development depends on the specific processing methods and conditions that the LCP containing polyblends experience.

Microstructure and mechanical properties ofin-situ network composite fibres of PBZT with nylon

A method for preparing composite fibres by infiltrating nylon into swollen poly(p-phenylene benzobisthiazole) (PBZT) fibre is described. PBZT fibre forms a microfibrillar network structure during the coagulation process.In-situ network composite (IC) fibres may be prepared by exchanging the coagulant with a solution containing the desired matrix material. These new composite fibres exhibit nearly identical mechanical properties and similar thermomechanical properties to those of so-called molecular composite (MC) fibres prepared from isotropic solutions of PBZT and nylon in methane sulphonic acid (MSA), The mechanical properties of these fibres were determined before and after heat treatment under tension. The structure of pure PBZT and its composite fibres (ICs' and MCs') were characterized using nitrogen adsorption (Brunauer-Emmett-Teller (BET) experiments), small-angle X-ray scattering, and scanning and transmission electron microscopy (SEM and TEM, respectively). The structure of both composite fibres was found to be a microfibrillar network of PBZT in a matrix of amorphous nylon. The average diameters of the PBZT microfibrils were in the range of 10 to 20 nm forin-situ network composites and approximately 4 nm for molecular composites.

Circus movement atrial flutter in the canine sterile pericarditis model. Activation patterns during initiation, termination, and sustained reentry in vivo.

The mechanisms of single-loop reentry in a syncytium without anatomically predetermined pathways have not been shown. Using a "jacket electrode" with 111 bipolar electrodes in a nylon matrix, we mapped in situ the atrial epicardial surface during atrial flutter in dogs with sterile pericarditis. Of 21 episodes of reentrant atrial flutter, only four showed double-loop ("figure-eight") reentry, whereas in 17 episodes a single loop was present. During initiation of single-loop reentry, an arc of functional block extended to the atrioventricular (AV) ring. This forced activation to proceed as a single wave around the free end of the arc, before breaking through the arc close to the AV ring. Activation continued as one loop around an arc close to the AV ring (in eight episodes) or around a combined functional and anatomic obstacle (in nine episodes) when the arc joined an atrial vessel. A zone of slow conduction was consistently bordered by the arc of block and the AV ring or by the anatomic obstacle and the AV ring. Spontaneous termination occurred when conduction failed in this area and the arc rejoined the AV ring. High-density recordings (2 mm) along the arc of block showed double potentials separated by an isoelectric interval, interpreted as local activation and electrotonus due to activation on the opposite side of the arc. Histologically, a diffuse inflammatory reaction involved 50-80% of the atrial wall. A transitional layer of myocardial bundles with preserved cross striation, but separated by edema and inflammatory cells, was enclosed between an epicardial layer of fragmented myocytes and an endocardial layer of grossly intact myocardium. There were no distinctive features at sites of functional conduction block or slowed conduction. In conclusion, single-loop reentry is the common pattern during atrial flutter in this model. Its induction depends on an interaction of the AV ring, a functional arc of block, and a zone of slow conduction. The location of the inferior vena cava predisposes the lower right atrium to this type of reentry.

Preparation and characterization of heterophase blends of polycaprolactam and hydrogenated polydienes

AbstractThe preparation, analysis, testing, and structure determination of ultrahigh impact rubber‐toughened polycaprolactams (nylon 6) are described. Partially unsaturated hydrocarbon rubbers were used for this purpose. They were functionalized by reaction either in solution or in bulk with maleic anhydride to give rubbery “ene” adducts containing varying amounts of pendnet succinic anhydride. Tough, rigid, thermoplastic engineering resins with notched Izod impact strengths of 750–1000 J/m were prepared by briefly melt‐blending these adducts with nylon 6. Properties of the blends could be affected by the type and amount of elastomer used, the anhydride content, the type of nylon, the mixing conditions and the test conditions. Fractionation by coacervation in m‐cresol/cyclohexane of a typical resin containing 20% by weight of functionalized rubber showed approximately 35% of a rubber–nylon graft, along with a few percent of free rubber dispersed in the nylon 6 matrix. A comb‐block copolymer structure for the graft and a model for its formation are proposed, consistent with analyses of the fractions. Some of the blends prepared with partially hydrogenated medium vinyl polybutadiene–maleic anhydride adducts displayed a retention of impact properties at low temperatures which was superior to that obtainable with a similarly prepared EPDM‐modified nylon 6. Transmission electron microscopy of a blend containing an anhydride‐modified hydrogenated medium vinyl polybutadiene showed a morphology consisting of a nylon matrix containing finely dispersed, irregularly shaped, 0.03–0.55 μm rubber domains in which were found even smaller domains of nylon.

Influence of structure on the impact behaviour of nylon‐rubber blends

AbstractBlends of nylon‐6 and EPDM rubber were prepared by reaction blending to study the influence of rubber concentration, rubber particle size and interfacial adhesion on the impact strength. Rubber particles induce a sharp brittle‐tough transition which is independent of the glass transition of the nylon matrix. Increasing the rubber concentration or decreasing the particle diameter shifts the brittle‐tough transition temperature for notched Izod impact tests to lower values.A toughening mechanism is proposed in which the interparticle distance, the rubber modulus and the temperature play crucial roles.

“In-Situ Network” Composite Fibers of Pbzt/Nylon

ABSTRACTA novel method of preparing PBZT/nylon composite fibers by infiltrating nylon into pure PBZT fiber is described. The pure PBZT fiber formed a microfibrillar network structure during coagulation, which is effective in reinforcing the matrix in the “in-situ network” composite fibers (designated IC). These new composite fibers exhibit nearly indistinguishable mechanical properties as those of “molecular” composite fibers (MC) prepared from isotropic solutions before and after tension heat-treatment (E = 44 GPa, σ = 430 MPa, ε = 1.2 %, σc = 250 MPa, G = 1.75 GPa) for PBZT/nylon weight ratios equal to unity.The fine structure of pure PBZT and its composite fibers spun from isotropic solutions was characterized using techniques based on nitrogen adsorption, small-angle X-ray scattering, scanning and transmission electron microscopies. The structure of both type of composites was found to be a microfibrillar network of PBZT in a matrix of amorphous nylon. The average diameters of the PBZT microfibrils were in the range of 10 to 20 nm for the IC and 4 nm for the MC.

Brittle-tough transition in nylon-rubber blends: effect of rubber concentration and particle size

Blends of nylon-6 and EPDM-rubber were prepared with various rubber contents (0–20 wt%) and particle sizes (0.3–1.6 μm). The effects of rubber concentration and particle size on the tensile modulus, torsion modulus, yield stress and notched impact strength of the blends were studied. Blend structures and fracture surfaces were investigated by scanning electron microscopy. Rubber particles induce a sharp brittle-tough transition which is independent of the glass transition temperature of the nylon matrix. The brittle-tough transition temperature for notched Izod impact tests shifts to lower values when the rubber content is increased or the particle size is decreased. A correlation was found between the brittle-tough temperature and the interparticle distance. Two deformation modes were observed: voiding and shear yielding. Particle size and interfacial adhesion affect neither the yield stress nor the modulus of the blends.