Search

The objective of this paper is to investigate the debonding behavior of the interface between continuously and discontinuously fiber reinforced thermoplastics using the climbing drum peel test. The study emphasizes on the importance of considering different climatic boundary conditions on the properties of thermoplastics. Specimens with varying moisture contents, from 0 m. % up to above 6 m. % are prepared and tested. It is observed that an increase in moisture content from 0 m. % to 2 m. % results in an increase of the fracture surface energy from 1.07 · 10 3 J / m 2 to 2.40 · 10 3 J / m 2 required to separate the two materials, but a further increase in moisture to 6.35 m. % conversely results in a subsequent decrease of the required energy to 1.91 · 10 3 J / m 2 . The study presents an explanatory model of increasing plasticization of the polymer due to increased polymer chain mobility, which results in more deformation energy being required to propagate the crack, which is corroborated in SEM investigations of the fracture surface. A further increase in humidity leads to polymer degradation due to hydrolysis, which explains the subsequent reduction of the fracture energy. The experimental set up is modeled numerically for the first time with cohesive surfaces, which could successfully reproduce the effective force-displacement curve in the experiment by varying the interface parameters in the model over an influence length, allowing the conclusion of a process induced variation in the interface properties over a specific consolidation length. [ABSTRACT FROM AUTHOR]

Highlights Fiberglass‐reinforced composites are extensively utilized in a diverse range of fields. Nonetheless, relying on the high shear forces generated during twin screw extruder processing to enhance the dispersion and distribution of glass fibers (GFs) can result in GF breakage and the degradation of the molecular chains of polyamide (PA). Consequently, this leads to a diminished performance of the composite material. In this study, high‐performance PA6/GF composites were effectively fabricated through the utilization of a dual‐speed non‐twin screw extruder operating within a chaotic field. Furthermore, optimization was achieved by substituting the kneading block (KB) with a perturbation ring element (PRE). In this paper, a comparative analysis was conducted between the flow fields and experimental results obtained from varying thread arrangements. The result indicates that, in comparison to KB with discontinuous structures and sudden geometric shapes, PRE elements possessing open structure in both the transverse and longitudinal directions effectively mitigated the shear effect and residence time during processing. This led to the significant enhancement of the residual length of the GF, molecular weight of PA6, heat distortion resistance and thermal stability of the composites. Additionally, enhanced performance was observed in PA6/GF composites prepared using the PRE configuration. Specifically, PA6/GF composites prepared by PRE S3 configuration showed outstanding impact strength of 13.3 kJ/m2 and a tensile strength of 151.6 MPa, representing respective increases of 15.7% and 6.9% compared with those prepared using the twin screw extruder (TSE). This work introduced an innovative device and molding technique for the production of high‐performance fiber‐reinforced polymer composites. High‐performance PA/GF was successfully manufactured by non‐twin screw extruder. The modified non‐twin screw leaded to better dispersion and distribution of GF. The damage of fiberglass and the degradation of PA were significantly reduced. The mechanical properties were significantly improved without using additives. The heat distortion resistance and thermal stability of PA/GF were improved. [ABSTRACT FROM AUTHOR]

Achieving high thermal conductivity in composites with low filler content is a major challenge in current research. In this paper, polypropylene (PP) and polyamide 6 (PA6) were used as polymer matrix, and the hybrid thermal conductive filler, formed by hexagonal boron nitride (h‐BN) and aminated carbon nanotubes (NH2‐CNTs), was integrated into matrix for the fabrication of thermal conductive composites (PP/PA6/h‐BN and PP/PA6/h‐BN@CNTs) via two‐step melt blending technology. The thermal conductive fillers were selectively distributed in a phase of the polymer matrix with a co‐continuous structure, forming a thermal conductive path with a three‐dimensional network structure. The results show that when the content of h‐BN reaches 25 wt%, the thermal conductivity of the PP/PA6/h‐BN and PP/PA6/h‐BN@CNTs composites was 199% and 300% higher than that of PP/PA6, respectively. Through testing the volume resistivity of the composites, it was confirmed that PP/PA6/h‐BN@CNTs composites maintain good electrical insulation. Both composites demonstrated remarkable thermal conductivity and outstanding electrical insulation. This research provides a facile way to prepare highly thermal conductivity polymer composites with excellent processing performances and electrical insulation. Highlights: h‐BN@CNTs hybrid fillers with sandwich structure were prepared.A two‐step blending method was used to control the selective distribution of hybrid fillers in a phase of the polymer matrix with a co‐continuous structure.The hybrid filler formed a thermal conductive path with a three‐dimensional network structure in the collective.PP/PA6/h‐BN@CNTs composites demonstrated remarkable thermal conductivity, outstanding electrical insulation and favorable processing performances. [ABSTRACT FROM AUTHOR]

This paper presents the results of examinations of the structure and crystallinity of polyamide (PA6) modified with fly ash from biomass combustion in a fluidized-bed boiler. Composites based on a PA6 matrix were examined. They contained 5, 10, and 15 wt% fly ash. Fourier-transform infrared with attenuated total reflectance spectroscopy (FTIR-ATR) was used to identify the characteristic functional groups present in the chemical structure of polyamide and composites based on its matrix. Structural analysis was performed using a differential scanning calorimeter (DSC) and microscopic examinations. Analysis of the values of thermal effects determined using the DSC technique allowed for the evaluation of the degree of crystallinity of the materials studied. Polyamide is usually considered to be a two-phase system consisting of crystalline and amorphous regions. The addition of the filler in the form of fly ash reduced the degree of crystallinity of the studied specimens. Based on the FTIR-ATR spectra and the recorded DSC curves, it was found that the α-phase was the dominant crystalline phase in the studied materials. Microscopic examinations were conducted to analyze the microstructure of the materials, providing information on the distribution and shape of the filler particles. Most of the particles ranged in size from a few to tens of micrometers. Furthermore, the use of scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS) allowed for the analysis of the distribution of chemical elements in selected filler particles. [ABSTRACT FROM AUTHOR]

The newly-developed thermoplastic-based fibre metal laminates (T-FML) show good prospects for their application in the automotive industry because of their lightweight potential and thermal formability. This paper focuses on describing the tensile and bending properties of this hybrid material as structural components for load-bearing parts in vehicles. For this purpose, the uniaxial tensile and four-point bending behaviours of steel/glass fibre-reinforced polyamide 6 (GF-PA6)/steel-laminates are investigated. The effects of cover/core layer thickness ratio and fibre weaving style on their tensile and bending properties are considered, while the span-to-thickness ratio was kept constant. Testing of the mono-materials and laminates of Metal/PA6/Metal (MPM) is performed to be considered as a reference. Further, the analytical method is validated to predict the bending properties of the laminates. A good agreement between the analytical values and experimental results regarding the bending strength and modulus is revealed. T-FML showed better tensile and bending properties with increasing fibre content compared to the GF-PA6 mono-organosheet and MPM. [ABSTRACT FROM AUTHOR]

This paper focuses on investigating the forming behaviour of sandwich materials composed of steel sheets and glass fibre-reinforced polyamide 6 (GF-PA6), i.e., thermoplastic-based fibre metal laminates (FML). Stretching and forming limit curve (FLC) determination of FML with different cover/core layer thickness ratios at various forming temperatures, i.e., at room temperature (RT), 200 and 235 °C, are the main approaches for characterizing their formability. In addition, the formability of mono-materials and non-reinforced sandwich materials is investigated as a reference. For a successful test and reliable results, several technical issues are considered, such as the suitable lubrication configuration and digital image correlation at elevated forming temperatures. The results revealed that the formability of non-reinforced sandwich materials with different core layer thicknesses exhibited compared formability to their monolithic steel sheet and no remarkable improvement in their formability with increasing the temperature up to 200 °C. Conversely, the formability of FML shows significant improvement (approx. 300%) with increasing temperature with a forming depth of about 33 mm at 235 °C compared to only 12 mm at RT. [ABSTRACT FROM AUTHOR]

In order to investigate the type IV hydrogen storage bottle with better hydrogen storage capacity, the polymer lining of the hydrogen storage bottle was further developed. In this paper, the molecular dynamics method was used to simulate the helium adsorption and diffusion processes within a modified montmorillonite (OMMT)-filled polyamide 6 (PA6) system. The effects of the barrier properties of the composites were investigated at different filler contents (3%, 4%, 5%, 6% and 7%), different temperatures (288 K and 328 K) and different pressures (0.1 MPa, 41.6 MPa, 52 MPa and 60 MPa) for certain contents. It was found that when the filler content was 5%, the permeability coefficient of the material was lower than 2 × 10−13 cm3∙cm/(cm2∙s∙Pa) and the barrier performance was the best. The modified filler with 5% OMMT/PA6 at 328 K still had the strongest barrier performance. When the pressure increased, the permeability coefficient of the modified material first decreased and then increased. In addition to this, the effect of the fractional free volume on the barrier properties of the materials was also investigated. This study provides a basis and reference for the selection and preparation of polymer linings for high-barrier hydrogen storage cylinders. [ABSTRACT FROM AUTHOR]

Laser structuring is by far the most investigated metal surface-pretreatment method for creating adhesion in polymer–metal hybrids. Especially, cone-like protrusions show excellent wetting behaviour as well as high compound strength. However, the processing time is extremely high. Therefore, this paper assesses a process strategy for creating pin structures with scalable height by single pulse drilling with an Nd/YVO4 nanosecond laser system on EN AW-6082 aluminium alloy. The strength testing is carried out by butt-bonded hollow cylinder torsion. The samples are manufactured by heat-conduction thermal joining with polyamide 6. Ten different surface structures with two different ablation diameters are investigated and compared to cone-like protrusions in terms of processing time, wetting behaviour, shear strength and fracture behaviour. The experimental results show that pulse drilling pins structures with high aspect ratio reach-strength values close to cone-like protrusions but with 31 times higher processing rate. [ABSTRACT FROM AUTHOR]

With the application of hot-pressing technology, polyamide 6 (PA6) was successfully directly adhered to the aluminum alloy. The relationship between the bonding property and microstructures of PA6 and anodized AA5754 aluminum alloy hybrid were explored in the paper. The results showed that the honeycomb-like porous oxide film was prepared by anodic oxidation, which resulted in the decreased surface energy of the aluminum alloy, so that PA6 easily wetted on the aluminum alloy surface, and the maximum tensile shear strength and fracture work reached 8.24 MPa and 9.27 kJ m−2, respectively. Improved bonding strength was attributed to micro- and nanoscale honeycomb-like microstructures and large roughness on the anodized aluminum alloy surface. [ABSTRACT FROM AUTHOR]

It is highly expected to develop a simple and effective method to reinforce polyamide 6 (PA6) to enlarge its application potential. This is challenging because of frequently encountered multi-component phase separations. In this paper, we propose a novel method to solve this issue, essentially comprising two steps. Firstly, a kind of poly (amide-block-aramid) block copolymers, i.e., thermotropic liquid crystalline polymer (TLCP)-polyamide 6 (TLCP-PA6), that contains both rigid aromatic liquid crystal blocks, and flexible alkyl blocks were synthesized. It is unique in that TLCP is chemically linked with PA6, which is advantageous in excellent chemical and physical miscibility with the precursors of monomer casting polyamide 6 (MCPA6), i.e., ε-caprolactam. Secondly, such newly synthesized block copolymer TLCP-PA6 was dissolved in the melting ε-caprolactam, and followed by in situ polymerization to obtain composite polymer blends, i.e., MCPA6/TLCP-PA6. The thermodynamic, morphological, and crystalline properties of MCPA6/TLCP-PA6 can be easily manipulated by tailoring the loading ratios between TLCP-PA6 and ε-caprolactam. Especially, at the optimized condition, such MCPA6/TLCP-PA6 blends show an excellent miscibility. Systematic characterizations, including nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimeter (DSC), and polarizing optical microscope (POM), were performed to confirm these statements. In view of these results, it is anticipated that the overall mechanical properties of such PA6-based polymer composites will be satisfactory, which should enable applications in the modern plastic industry and other emerging areas, such as wearable fabrics. [ABSTRACT FROM AUTHOR]

The stepped isostress method (SSM) is an advanced technique which allows the prediction of the long-term behavior and enables the construction of creep master curves of materials with short-term experimental tests. However, the performance of this method is highly dependent on the numerical model and the time spent in data processing. In this paper, the effect of the extrapolation techniques on the creep curves trend is investigated using the SSM data of Polyamide test. Three extrapolation functions are used to offset the delay of the stress history: polynomial, power and exponential functions. Furthermore, a numerical routine is developed during the last step of the SSM, where the shift factors are computed taking into account the rescaling and the dwell times of each level of stresses. The processing of the SSM raw data has revealed that the rescaling parameters are the most determining factors to reach an accurate long-term creep curves. The rescaling process has shown an appropriate time, whether achieved by the exponential or power functions. Larger shift factors for exponential functions are assessed and therefore a long period of creep master curve was obtained. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced plastics (CFRP) bear a high potential in terms of electrical conductivity and its potential applications. A locally resolved electrical measurement method for these anisotropic materials is a key prerequisite for understanding the structural and manufacturing process-related interrelationships. The aim of this paper is to develop a measurement method that allows this to be achieved and also to investigate areas of overmolded metal contact pins in detail. CFRP samples with polyamide 6 and polycarbonate matrices were used, which were produced by using a custom-designed injection mold. In order to evaluate the measurement results and to correlate them to process related structural properties, reflected light microscopy and X-ray microtomography were used. Typical areas with significant fiber structures of assembly injection molded samples were electrically and structurally characterized to identify correlations. Among further results, the correlation of equipotential lines, acquired from the electrical analysis, with specific fiber orientations within the injection molded samples was demonstrated, fiber-poor areas were identified, and a beneficial influence of weld lines on contact resistances was determined. [ABSTRACT FROM AUTHOR]

The interest in composite materials has increased in the last decades since they have the advantages of combining intrinsic properties of each component and offer better performance with respect to the base constituents. In particular, these kinds of materials can have different electrical characteristics by varying the filling percentage and, therefore, they can be used in diverse applications. Thus, a detailed study of the microwave response of these composite systems is of great practical importance. In fact, the dielectric constant and loss tangent are key factors in the design of microwave components. In this frame, the outstanding properties of graphene-like fillers may be exploited to develop new very interesting materials to study and characterize. In this paper, microwave characterization of compounds, based on nylon 6 containing different percentages of graphene nanoplatelets, is carried out taking the neat matrix sample processed under the same conditions as benchmark. The measurements were carried out using two microwave systems, operating at two different frequency bands, appropriate to characterize solid and compact material samples. The achieved results, in line with limited data from the literature and from material data sheets, highlight the possibility to use the present polymers as an excellent electromagnetic interference shielding, as confirmed by full wave electromagnetic numerical simulations that were conducted with a numerical electromagnetic software. [ABSTRACT FROM AUTHOR]

Short-fiber reinforced composites are widely used for the mass production of high-resistance products with complex shapes. Efficient structural design requires consideration of plasticity and anisotropy. This paper presents a method for the calibration of a general material model for stress–strain curve prediction for short-fiber reinforced composites with different fiber mass fractions. A Mori–Tanaka homogenization scheme and the J2 plasticity model with layered defined fiber orientation were used. The hardening laws: power, exponential, and exponential and linear were compared. The models were calibrated using experimental results for melt front, orientation tensor analysis, fiber length, and diameter and tension according to ISO 527-2, for samples of PA6 which were either non-reinforced, or reinforced with 10%, 15%, 20%, and 30% carbon fiber mass fractions. The novelty of this study lies in the transition from the strain–stress space to the strain–stress–fiber fraction space in the approximation of the material model parameters. We found it necessary to significantly reduce the fiber aspect ratio for the correct prediction of the mechanical characteristics of a composite using the Mori–Tanaka scheme. This deviation was caused by the ideal solution of ellipsoidal inclusion in this homogenization scheme. The calculated strength limits using Tsai–Hill failure criteria, based on strain, could be used as a first approximation for failure prediction. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of 3D amplitude and functional parameters for worn surfaces of composites with polyamide 6 as matrix and different glass bead concentrations (0%, 2.5%, 5%, 10%, 20%, 30% and 50%wt). The worn surfaces after dry sliding of a steel pin on a disk, for 10 km, at constant velocity (0.5 m/s, 1 m/s and 1.5 m/s) and under an average pressure of 1 MPa. There were done two tests under the same conditions. On each worn track, there were investigated three surfaces of 500 μm x 500 μm with a contact profilometer. The number of points on the scan line was 200 points and the step between lines was 5μm. The following amplitude parameters were measured and calculated for assessed surfaces: the arithmetic mean deviation, Sa, the root mean square deviation, Sq, the maximum height of surface prominence, Sp, the maximum surface depth, Sv, the maximum height, St, the skewness factor, Ssk and the kurtosis, Sku. The discussed functional parameters are the reduced peak height, Spk, the height of the core of the surface, Sk and the depth of the valley zone, Svk. The comparison of their values makes posible to evaluate if the worn surface could function in a new running or the replacement of the component is recommended. Considering that machine components have intermittent operation, these worn surfaces becoming initial surfaces for the following cycle of contact operation. Based on the average values of amplitude and functional parameters, it was found that a relatively good surface quality is preserved for concentrations of 10...30%wt glass beads, for v=0.5...1 m/s (Sa and Sq having similar trend); for lower concentrations and for 50% glass beads, the parameter values increase but without identifying a distinct relationship with the working regime, especially for 2.5 and 5% glass beads. [ABSTRACT FROM AUTHOR]

The present paper aims to compare study the effect of porosity and degree of crystallinity on both quasi-static and fatigue behaviours of PA6 and PA12 specimens obtained by the fused filament fabrication (FFF). The glass transition and melting temperatures were measured complementary to understand better the process. Fatigue analysis is here described in visco-elastic domain of material. The results highlight that the mechanical and fatigue properties of PA 12 are better than those of PA6, in spite of almost amorphous state of PA12. Besides, porosity did not reveal the expected influence on these properties. The obtained results are also compared with conventional techniques given by the literature review. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced plastic (CFRP) has the advantages of being light weight, high strength, and corrosion resistant. At present, it is widely used in the lightweight design of automobile parts. The manufacturing of lightweight parts inevitably involves the connection between CFRP and the polymer material. The connection strength between CFRP and the polymer material significantly affects the service life of the composite parts. Taking CFRP and polyamide 6 (PA6) injection-molded composite parts as an example, this paper proposed a technological method to enhance the connection strength between CFRP and PA6. The proposed method was to fabricate micro-groove structures on the CFRP surface by compression molding. These micro-groove structures effectively increased the injection-molding area of the composite parts, thus enhancing the connection strength between CFRP and PA6. This paper presented a detailed study on the compression-molding process of micro-grooves on the CFRP surface, and successfully obtained the appropriate parameters. Finally, PA6 was used for injection molding on the CFRP with micro-grooves at an injection pressure of 8 MPa, an injection temperature of 240 °C, a holding pressure of 5 MPa, and a holding time of 2.5 s. The experimental results show that the micro-groove array structures on the CFRP surface could effectively improve the tensile strength of the connection interface in the composite parts. Compared with the composite part without micro-grooves, the tensile strength of the composite part with micro-grooves was increased by 80.93%. The composite parts prepared in this paper are mainly used in automobile interiors and the research results of this paper meet the actual needs of the enterprise. [ABSTRACT FROM AUTHOR]

Fiber-reinforced plastics (FRP) are widely used in the automotive industry due to their lightweight construction potential. Especially, injection-molded components are very popular because of their short cycle times. Unfortunately, this manufacturing process results in some disadvantages for delayed adhesive bonding. On the one hand, such thermoplastics have a very low surface energy (Polyamide 6 (PA6) 36 mJ/m), on the other hand residues of release agents on the surface hinder adhesion between product and adhesive. These disadvantages have to be overcome by the right surface pre-treatment process. Currently, a solvent-containing process is usually used for this purpose. If necessary, the use of primer is common. In the presented paper, the pre-treatment process of an injection-molded component made of polyamide 6 reinforced with glass short-fibers is presented. First, material-specific properties are measured. The influence of laser pre-treatment at 355 nm and 1064 nm wavelength is investigated. Measurements of surface free energy and surface roughness are conducted. The bonding strength is validated by peel test and tensile shear tests. The shear strength was doubled by laser pre-treatment at a medium energy level, partially cohesive failure of the adhesive was achieved. Both investigated wavelengths led to a great improvement of bonding strength at suitable parameters. [ABSTRACT FROM AUTHOR]

Cellulose Nanocrystal (CNC) films are from emerging nanoparticles recently known for photonic properties. The CNC films show nonuniform photonic domains resulting from structural irregularities in their typical self-assembled arrangements. This paper presents a drop-casting approach from Polyamide 6 to form a coating layer on the CNC films. This coating approach led to polycrystalline growth patterns known as spherulites on the CNC film. For the resulting coated CNC film, the spherulites yielded a unique set of enhanced physical properties including optical, mechanical and thermal as well as a new morphological appearance from their micro-scale average spherical shape; the ordering effect of their local radial symmetry and orientation positively influenced the effects of structural irregularities of the typical CNC films. Under polarized light, the optical transmission bands of the CNC film were perceived through radial symmetry of banded spherulites which were responsible for the formation of circular extinction patterns for the coated CNC film. The intermolecular interactions and interlamellar entanglement of spherulites provided enhanced flexibility and tensile strength for the coated CNC film. This protecting design allows for the future development of a variety of portable functional assemblies requiring enhanced performance in optical, mechanical and thermal properties of CNC films. [ABSTRACT FROM AUTHOR]

[Display omitted] • Linear polyamide 6 was synthesized through the simplest self-initiated anionic polymerization. • The polymerization products exhibit highly consistent properties comparable to commercial spinning grade polyamide 6. • In this paper a novel fiber forming method is proposed called reactive melt spinning. • The polyamide 6 micro-nano fiber materials were directly fabricated from ε-caprolactam monomer in one step. Polyamide 6 (PA6), as a well-established engineering thermoplastic, plays a crucial role in modern society. However, the traditional production mode of PA6 has many drawbacks such as complex processes, huge energy consumption and serious pollution, and it is often separated from the processing technology. Here we report a simple and efficient method for synthesizing linear PA6 polymers, i.e., self-initiated anionic polymerization of ε-caprolactam. It was found that a high conversion rate of over 94 % was achieved at 240 °C for 15 min using sodium hydride as a catalyst only. The polymerization products thus obtained exhibited characteristics consistent with those of commercial spinning grade PA6. Furthermore, we successfully prepared PA6 micro-nano fiber materials by seamlessly integrating the two processes of linear polyamide 6 synthesis and melt spinning. This innovative reactive melt spinning technology is expected to create a new situation in the preparation and application of high-performance fibers. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shenzhen University Science & Engineering is the property of Editorial Department of Journal of Shenzhen University Science & Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, glass fiber reinforced polyamide 6 (PA6/GF) composites were prepared through anionic polymerization of caprolactam and vacuum-bag press molding (VBPM). The effects of parameters such as curing temperature and impregnation method on the monomer conversion, crystallinity, and mechanical properties of the composites were investigated using continuous fiber-reinforced polyamide 6 reactive injection as a self-built VBPM experimental platform. The results indicated that the composites fabricated by isothermal impregnation had a high degree crystallinity and good internal homogeneity. Compared to the isothermal impregnation, the non-isothermal impregnation promoted higher overall reaction conversion and better mechanical performance for the fabricated composites. Through the non-isothermal impregnation, the composites obtained at the outlet achieved an increase in bending and shear strength by 10%~13% and 11%~16% than that at the inlet, respectively. The bending strength of the composites obtained at the outlet reached a maximum value of 273.65 MPa at 150 °C, and their maximum shear strength reached 47.32 MPa at 170 °C. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we studied the modifying effect of montmorillonite modified with polyfluorinated telomeric alcohols and of antimony(III) polyfluoroalkoxide on the structure and properties of polymer composites based on polyamide 6. The nature of the effect of the modifier on the state of amorphous and crystalline phases in the supramolecular structure of this heterochain polymer was determined by X-ray diffraction analysis and microscopy. The effect of reducing combustibility due to the introduction of a fluorine-containing modifier is considered. [ABSTRACT FROM AUTHOR]

• Extended S-N curve for a wet laboratory scale polyamide 6 sub-rope reaching 105 cycles. • Investigation of the damage mechanisms using X-ray tomography analysis and SEM images. • Use of a heat build-up measurement protocol for a rapid evaluation of the fatigue properties of ropes. Polyamide 6 fibre ropes are of interest for floating offshore wind turbine mooring lines but their fatigue durability represents a key aspect to characterize and validate on the new constructions and coatings developed for this long term application. This paper presents a fatigue study on laboratory scale polyamide 6 sub-ropes which were wetted before testing. A T-N curve describing ranges of [2%, 70%] of MBL and [102,105] cycles is obtained. An investigation of the damage mechanisms, using X-ray tomography analysis and SEM images, is performed and highlights the complexity of the mechanical response of twisted ropes, due to their hierarchical multi-scale construction. Cyclic loading changes significantly the sub-rope aspect and architecture. Finally, this study describes the use of a heat build-up measurement protocol, for a rapid evaluation of the fatigue properties of ropes. The cyclic dissipated energy was determined from temperature measurements by an infrared camera. A first prediction using this method is proposed and shows that it could provide a powerful solution, to overcome the very long testing times required for fatigue studies on synthetic sub-ropes. [ABSTRACT FROM AUTHOR]

At present, electrospinning technology is a versatile and simple method for generating nano-scale membranes, and it provides attractive solutions in solving environmental problems and many energy problems. However, such films generally have low mechanical properties which limit their use in industry. Nanocellulose with excellent mechanical properties, high specific surface area, and renewable nature is an ideal green reinforcing material. In this paper, the cellulose nanocrystals (CNC) coatings on electrospun polyamide 6 (PA6) were prepared via coating method and explored as potential high-performance reinforced materials. The extraction of CNC and the performance of the composite membranes were studied by calculating the yield, scanning electron microscopy, 3D imaging, mechanical testing, and thermogravimetric analysis. Results show that the yield of CNC is impacted by various factors among which acid concentration is the most important. The CNC/PA6 composite film shows lower porosity and higher surface roughness than the pure PA6 membrane. With the increase of CNC concentration, lower porosity and higher surface roughness are obtained. With CNC coatings, tensile strength and Young s modulus of PA6 increase dramatically, while the tensile strain decreases obviously. The Young s modulus of the composite film has been increased by 250%. The composite membranes reveal high mechanical strength and low porosity, which can be applied infiltration and packaging. [ABSTRACT FROM AUTHOR]

To quantify the influence of absorbed water in PA6 on the pre-treatment and bonding process, an unfilled and unreinforced PA6 material is investigated in a dried and saturated state. The material is pre-treated by atmospheric pressure plasma jet (APPJ) with varying jet distances. The surfaces are investigated by contact angle measurements, DSC and FTIR to detect molecular and morphological changes in the surface. To evaluate the bonding strength, samples are bonded with a two-component polyurethane adhesive and a two-component acrylate adhesive and tested in a lap shear and a tensile configuration. The results show that water content has a significant influence on the effectivity of the pre-treatment process and the resulting bonding strength and failure mechanism. The adhesion is majorly affected, however these effects do not influence the macroscopic wetting behavior and cannot be measured in contact angles. FTIR spectra and DSC scans do not show significant changes in molecular groups or crystallinity that would explain the observed adhesion improvement in dried samples. High bonding strength is only achieved with adherents at low water content. [ABSTRACT FROM AUTHOR]

In order to mitigate the release of toxic phosphine from aluminum hypophosphite in twin-screw processing, montmorillonite–melamine cyanurate was prepared by three methods: (1) mechanical intercalation, (2) water intercalation and (3) in situ intercalation. The sheet spacing of montmorillonite was increased from 1.140 nm to 1.141 nm, 1.208 nm and 1.217 nm for these three methods, respectively, and scanning electron microscope (SEM) and transmission electron microscopy (TEM) proved that melamine cyanurate was successfully inserted into the montmorillonite sheets. The montmorillonite–melamine cyanurate from in situ intercalation can best inhibit the release of PH3 from aluminum hypophosphite, and the peaks of phosphine, mean values of phosphine and integral of phosphine were reduced by 81.9%, 72.1% and 72.2%, respectively. The mode of action of montmorillonite–melamine cyanuric inhibition of the emission of phosphine from aluminum hypophosphite can be attributed to the physical absorption of montmorillonite and the chemical bonding of melamine cyanurate. In addition, in situ intercalation can slightly improve flame retardancy, attributed to incomplete exfoliation of montmorillonite sheets. [ABSTRACT FROM AUTHOR]

This study focuses on polyamide 6/organo-modified montmorillonite (PA6/OMMT) nanocomposites as potential liner materials, given the growing interest in enhancing the performance of type IV composite overwrapped hydrogen storage pressure vessels. The mechanical properties of PA6/OMMT composites with varying filler concentrations were investigated across a temperature range relevant to hydrogen storage conditions (−40 °C to +85 °C). Liner collapse, a critical issue caused by rapid gas discharge, was analyzed using an Ishikawa diagram to identify external and internal factors. Mechanical testing revealed that higher OMMT content generally increased stiffness, especially at elevated temperatures. The Young's modulus and first yield strength exhibited non-linear temperature dependencies, with 1 wt. per cent OMMT content enhancing yield strength at all tested temperatures. Dynamic mechanical analysis (DMA) indicated that OMMT improves the storage modulus, suggesting effective filler dispersion, but it also reduces the toughness and heat resistance, as evidenced by lower glass transition temperatures. This study underscores the importance of optimizing OMMT content to balance mechanical performance and thermal stability for the practical application of PA6/OMMT nanocomposites in hydrogen storage pressure vessels. [ABSTRACT FROM AUTHOR]

Kraft lignin coming from a paper industry was purified and the modified fraction by formic acid (FKL) was isolated to be used as an inhibitor of UV-photodegradation in polyamide 6 (PA6) films. Samples containing up to 1.00% of FKL in mass were prepared by casting using formic acid as solvent. The effects of UV light irradiation on these films (Hg lamp, 96 h) were studied by SEM, FTIR and XRD. It was observed that the variation of the carbonyl group content, crystallinity and morphology of the PA6 films were reduced by the FKL incorporation. Samples that were less susceptible to UV light were those that contained between 0.50 and 1.00% of LKF. This phenomenon is observed in both, difratometric and spectroscopic analyses, since it showed lower variation in results with relation to the same non-irradiated films. [ABSTRACT FROM AUTHOR]

Copyright of Science of Sintering is the property of National Library of Serbia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Polyamide 6 fiber ropes are of interest for floating offshore wind turbine mooring lines but could exhibit complex mechanical behavior during loading at sea, such as creep, relaxation, variable dynamic stiffness or visco-plasticity. There is a need for a model that could be introduced into finite element analyses to predict this complex response; it should also describe the effect of the loading history. This paper presents a visco-elasto-plastic behavior model based on four dashpot-ratchet-spring elements that allow a precise description of polyamide 6 rope behavior. An identification method, using a multi-relaxation test, is described. It has been implemented in a finite element analysis software and validations are made by comparing the model results to the experimental data. The present work is the result of an extensive effort initiated by the collaborative research project POLYAMOOR and continued by the MONAMOOR project, both led by France Energies Marines. • An elasto-visco-plastic behavior model that allows a precise description of polyamide 6 rope behavior. • A complete characterization of the mechanical behavior of synthetic ropes. • Proposition of a complete identification method using a multi-relaxation test. • First identification and validation on a reduced laboratory scale polyamide 6 sub-rope. [ABSTRACT FROM AUTHOR]

Copyright of BHM Berg- und Hüttenmännische Monatshefte is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the influence of four different process parameters on hot gas welding of CF/epoxy fiber composites functionalized with a PA6 thermoplastic film is investigated. Additional experiments are carried out on specimens adorned with triangular beads of coupling material that are printed onto the plates, ensuring extra material within the joining zone. This approach offers a great advantage for compensating geometric tolerances. The parameters considered are common process parameters for regular two-step processes: Heating element temperature (THE), heating time (HT), welding force (F) and welding time (HTF). The design of experiments (DoE) is planned according to the Taguchi method. An orthogonal array is used to set up the experimental plan. Three factor levels of each welding parameter are considered. The test series are carried out with two sample variants. In the second sample variant, additional thermoplastic material is placed in the joining zone. The strength of the welded joints is investigated by tensile shear tests according to DIN EN 1465. The results show that the welding force has the greatest influence on the welding strength. Heating times of 20 s were found to be optimal. Within the first sample variant, a saturation behavior of the welding force can be observed at 500 N. Higher heating element temperatures (500 °C) and welding forces (1165 N) are advantageous using additional material. High welding temperatures result in a negative effect on the interdiffusivity of the polymer chains. [ABSTRACT FROM AUTHOR]

Polymeric liners, one of the main components of hydrogen tanks, have attracted significant research interest because of their lightweight and high-impact strength. Despite their advantages, high gas permeability limits their applications. Thus, numerous studies have been conducted to improve the gas barrier properties of polymer-based composites. In this study, we used a polyamide 6 (PA6)/ethylene vinyl alcohol (EVOH) blend as a matrix for high hydrogen gas barrier properties and ethylene propylene diene monomer (EPDM) rubber as reinforcement for injection moldability. The ternary polymer blends were successfully injection molded, and their morphology, mechanical properties, and gas permeability were measured. In addition, we performed a rheological investigation to analyze the processability of the ternary polymer blends. As a result, the developed material system showed a 28% reduction in hydrogen permeability and a 11% improvement in tensile strength compared to a commercial material. This study will be a valuable resource for the research of polymeric liners with efficient and reliable performance. [ABSTRACT FROM AUTHOR]

In this paper, thermoplastic phenol formaldehyde (PF) grafted cyclic neopentyl phosphate (PFCP) was synthesized by using PF and 2,2-dimethyl-1,3-propanediol phosphoryl chloride. It was characterized by Fourier transform infrared spectroscopy (FTIR), 1H and 31P nuclear magnetic resonance (NMR). Compared to PF, PFCP shows improved thermal and thermoxidative stability and allows itself to be used in polyamide 6 (PA6). A micro-intumescent flame retardant system was constructed by using cyclic neopentyl phosphate as acid source, PF as charring agent and PA6 whose decomposition products work as blowing agent. The results showed that PA6/PFCP composite is classified the UL-94 V-0 rating and get a LOI value of 35.5% at 25% loading of PFCP. SEM results showed that the outside of char residues is continuous and dense, but the inside is micro-intumescent and porous. XPS analysis of char revealed that most of phosphorus remained in the char layer. All the results suggest that the mode of flame retardant's action for PA6/PFCP composites is shifted from melting away to charring protection with the content of PFCP increasing. The coherent char generated by the decomposition of PFCP contributes most to flame retardancy of PA6. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Copyright of China Textile Leader is the property of China Textile Information Center and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Textile Leader is the property of China Textile Information Center and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a fast and efficient computational method to predict the mechanical behaviour of plastic cylindrical gears made of fibre reinforced polyamide 6. Based on this method, an investigation on the relation between the fibre orientation and the gear behaviour is done. The numerical method uses a viscoelastic model accounting for the temperature, humidity and rotational speed dependence of the gear. This model is developed under the assumption that the material is stressed in its linear domain. The method is performed in three steps: the first one consists of defining the fibre orientation from simulation and experimental results. The second step characterises the viscoelastic behaviour of the material. The third step consists in calculating the load sharing with local meshing, which integrates the viscoelastic model over the entire surface of the tooth. This model permits computation of the load sharing between instantaneously engaged teeth and provides results such as contact pressure, tooth root stress and transmission error. Three fibre orientation models with an increasing complexity are compared. Simulation results show a limited influence of the fibre orientation on the contact pressure and tooth root stress, nevertheless difference up to 10 % are observed on the transmission error amplitude. [ABSTRACT FROM AUTHOR]

As the liner material of type IV hydrogen storage tank, polymer is restricted in commercial application due to its high hydrogen permeability. In this paper, for the first time, the suitability of polyamide 6 (PA6) filled with lamellar inorganic components (LIC) as the hydrogen storage tank liner is comprehensively investigated, including thermal and mechanical properties, morphology and structure, rheology, and the hydrogen permeability under various temperature (−10 °C, 25 °C, 85 °C) and pressure (25 MPa, 35 MPa, 50 MPa) conditions. The results show that comparing with PA6, the thermal and processing properties of LIC/PA6 have been improved, the tensile strength, bending strength and bending modulus of LIC/PA6 are increased by 36%, 17% and 12%, respectively. Especially, the hydrogen permeability of LIC/PA6 is decreased by 3–5 times which meets the requirements specified by the hydrogen tank standard. The research work provides a theoretical basis and reference for the preparation and selection of high barrier liner materials in the future. • Lamellar inorganic components/PA6 composite material for hydrogen tank is prepared. • LIC/PA6 exhibits better thermal, mechanical and rheological properties than PA6. • Hydrogen permeability coefficient of LIC/PA6 is decreased by 3–5 times than PA6. [ABSTRACT FROM AUTHOR]

Biaxially oriented polyamide 6 (BOPA6) films were prepared by extrusion casting and biaxial stretching with polyamide 6. The effects of different biaxially oriented on the macroscopic properties of BOPA6 were investigated by characterizing the rheological, crystallization, optical, barrier and mechanical properties. The results show that the increase of stretching temperature leads to the diffusion and regular stacking rate of BOPA6 chain segments towards crystal nuclei increases, the relative crystallinity increases, reaching 27.87% at 180 °C, and the mechanical strength and optical performance decrease. Heat-induced crystallization promotes the transformation of β-crystals to α-crystals in BOPA6, resulting in a more perfect crystalline structure and enhancing oxygen barrier properties. BOPA6 chains are oriented, and strain-induced crystallization (SIC) occurs during the biaxial stretching. Further increasing the stretch ratio, the relative crystallinity increased to 30.34%. The machine direction (MD) and transverse direction (TD) tensile strength of BOPA6 (B-33) are nearly two times higher than the unstretched film, reaching 134.33 MPa and 155.28 MPa, respectively. In addition, the permeation decreases to 57.61 cc·mil/(m2 day), and the oxygen barrier performance has improved by nearly 30% compared to the sample B-22. BOPA6 has a high storage modulus at a high stretching rate (300%/s). Rapid chain relaxation would promote the molecular chain disorientation, destroy the entangled network of the molecular chain, and lead to a decrease in tensile strength, reducing to about 110 MPa. [ABSTRACT FROM AUTHOR]

This study investigated the impact of stabilization time on pretreated polyamide 6 (PA6) fibers using various analytical techniques, including thermal analysis (TGA and DSC), infrared (IR) spectroscopy, X-ray diffraction (XRD), tensile testing, and density measurements. The two-step atmospheric air-based stabilization process for pretreated PA6 multifilament bundles involved initial thermal stabilization at 170 °C in an air atmosphere after ferric chloride impregnation, followed by a second step of thermal stabilization at 245 °C. Ferric chloride impregnation followed by thermal stabilization in an air atmosphere resulted in crucial structural transformations. The density values of the samples increased following thermal stabilization, accompanied by a decrease in tensile values. Ferric chloride pretreated and thermally stabilized PA6 fibers were found to be fully stabilized after 120 min of stabilization before the carbonization stage. The findings obtained from the DSC, XRD, and IR spectroscopy methods indicated the occurrence of disordering phases due to the scission of hydrogen bonds. The TGA findings showed significant increases in carbon yield percentages at 500 °C and 850 °C, reaching 71.4% and 63.5%, respectively, for the sample heat treated at 245 °C for 120 min. The addition of ferric chloride is expected to potentially reduce processing costs for final carbon fiber production by decreasing the time required for the thermal stabilization of PA6. [ABSTRACT FROM AUTHOR]

Polyamide 6 (PA6) is a widely-used polymer that could find applications in various sectors, including home textiles, transportation or construction. However, due to its organic nature, PA6 is flammable, and flame-retardant formulations have to be developed to comply with fire safety standards. Recently, it was proposed to use ammonium sulfamate as an effective flame retardant for PA6, even at low loading content. However, processing issues could occur with this additive considering large-scale production. This paper thus studies the use of another sulfamate salt--guanidine sulfamate (GAS)--and evidences its high efficiency when combined with melamine polyphosphate (MPP) as a flame retardant for PA6. A decrease of the peak of the heat release rate by 30% compared to pure PA6 was obtained using only 5 wt% of a GAS/MPP mixture in a microscale calorimeter. Moreover, PA6 containing the mixture GAS/MPP exhibits a Limiting Oxygen Index (LOI) of 37 vol% and is rated V0 for the UL 94 test (Vertical Burning Test; ASTM D 3801). The mechanisms of degradation were investigated analyzing the gas phase and solid phase when the material degrades. It was proposed that MPP and GAS modify the degradation pathway of PA6, leading to the formation of nitrile end-group-containing molecules. Moreover, the formation of a polyaromatic structure by the reaction of MPP and PA6 was also shown. [ABSTRACT FROM AUTHOR]

The creep test illustrates the tendency of materials to deform under constant loading; however, this test requires a very long testing time. The use of the time-stress superposition principle (TSSP) allows the prediction of the material performance very beyond the testing time by the construction of the creep master curve. Recently, a new accelerated creep testing method, called the stepped isostress method (SSM) was proposed. This technique requires specific handling of the test data in the construction of the master curve. Initially the method was used on technical yarns. This paper focuses on the effectiveness of this method for specimens having a large thickness. The considered material is a polyamide 6. A smooth creep master curve has been obtained. The obtained master curves by the SSM technique and the classical TSSP method are consistent. This result proofs the robustness of the SSM technique in the construction of the master curve. [ABSTRACT FROM AUTHOR]