Properties Of Polyamide Research Articles

Polydopamine-modified polysulfone/silica double-walled heat-resistant microcapsules efficiently improve the tribological properties of polyamides

The tribological properties of nylon 6 (PA6) play an important role in regulating the energy consumption, component integrity, and reliability of construction machinery. In order to improve the tribological properties of polyamide, by using high temperature resistant green lubricant ionic liquid (IL) lubricant as core material and polysulfone (PSF) and SiO2 hybrid system as wall materials, double-walled IL@PSF/SiO2 self-lubricating microcapsules with high core content has been prepared. By exploring different emulsifiers and different agitation rates, the degree of encapsulation of an ionic liquid (IL) has been improved and the optimal synthesis conditions for microcapsules have been determined. And the core content was as high as 68 wt% The introduction of SiO2 in the wall material increased the thermal softening temperature of the microcapsules up to 400 °C. The friction coefficient and specific wear loss of a PA6 composite containing 10 wt% IL-loaded microcapsules were reduced by 82% and 87.9% comparing with pure PA6, respectively. The self-lubrication mechanism has been investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and atomic force microscope (AFM), and the results showed the formation of a uniform, continuous, and thin boundary lubricating film on the wear surface to be the main reason for the improved tribological performance.

Adsorption and dyeing properties of acid dye on bio-based polyamide 11 fibers

The dyeing mechanism of bio-based polyamide 11 fibers with acid dyes was explored in order to provide a theoretical foundation for the dyeing properties of polyamide 11 fibers. The surface morphology and diameters of polyamide 11 fibers and polyamide 6 fibers were compared. Both polyamide 11 fibers and polyamide 6 fibers were dyed with acid dye Isolan blue NHF-S, and the effects of the initial dye concentration, pH values, dyeing temperature and time on the dyeing properties were investigated. The effects of the dyeing kinetics and thermodynamic model of Isolan blue NHF-S on polyamide 11 fibers were analyzed, and the corresponding parameters were calculated. It was found that the dyeing properties of polyamide 11 fibers were not comparable to those of polyamide 6 fibers, while the washing and rubbing fastness were more or less the same. The dyeing mechanism of Isolan blue NHF-S on polyamide 11 was a combination of localized and non-localized adsorption, which conformed to the pseudo-second-order kinetic model and the Redlich–Peterson thermodynamic model. Increasing dyeing temperature could shorten the half-dyeing time and improve the average diffusion coefficient and affinity between the dye and polyamide 11 fibers.

Long-term ageing effect on mechanical properties of polyamide 12 printed by Multi-Jet-Fusion

Multi-Jet-Fusion (MJF) is a relatively new powder-based face-sintering additive manufacturing technique that exhibits great potential in high-volume manufacturing due to its rapid printing speed. Extensive research has been conducted on the mechanical properties of MJF-printed polyamide 12 (MJF PA12) by investigating the powder characteristics and build orientations. However, no work has been conducted to study the effect of humidity and physical ageing on the mechanical performance of MJF PA12 specimens. Here, the physical and mechanical properties of MJF PA12 specimens that were printed in different build orientations and stored under ambient and dryer conditions for 474 days were investigated. It was found that specimens stored under ambient conditions exhibited a drop in glass transition temperature due to moisture absorption followed by an increase, which could indicate that ageing of the specimens occurred. The moisture absorption was also found to have an insignificant effect on the crystallinity and crystallite size of the specimens. The change in mechanical properties, such as the tensile modulus and ultimate tensile strength, was more significant for specimens stored in ambient conditions than those in dryer conditions. It was also found that the build orientation does not have a significant impact on the moisture absorption rate, glass transition temperature, and the change in the trend of mechanical properties. In addition, an artificial neural network was adopted to predict the mechanical properties of the MJF PA12 specimens under the influence of physical ageing, humidity, and build orientations. The neural network adopted in this work can predict the change in the mechanical properties of differently-orientated MJF PA12 with different moisture content over time. The neural network prediction could be useful in providing guidance on the structure and risk assessment of the parts before print.

Effect of injection molding conditions on the properties of polyamide 6/calcium carbonate nanocomposite

AbstractThe application range of polyamide 6 in lightweight part applications can be significantly increased by using appropriate processing parameters and by incorporating additives. Therefore, specimens were manufactured at varying mold temperatures and injection velocities to study the effect of injection molding parameters on the properties of polyamide 6 and its nanocomposite with nano‐calcium carbonate. Mechanical properties, degree of crystallinity, density, heat deflection temperature, and melt flow index were measured to assess the effect of injection molding conditions on material properties. Mold temperature was the process factor that most affected polyamide 6 and polyamide 6/nano‐calcium carbonate properties. Increasing this parameter increased density, impact strength, flexural strength, flexural modulus, and heat deflection temperature. The nanocomposite's degree of crystallinity, tensile modulus, and melt flow index also increased. High injection velocity reduced only the impact strength of the nanocomposite. The findings indicate that by modifying injection parameters, it is possible to improve mechanical properties and processing efficiency of polyamide 6 and its nanocomposites, bringing them closer to their maximum potential. Incorporating the nanofiller increased almost all properties except for impact strength and elongation at break. Nano‐calcium carbonate provided considerable advantages to polyamide 6 mechanical performance and processability while increasing sample weight by only 1.5%.

Structural Hierarchy of PA6 Macromolecules after Hydrostatic Extrusion.

This article presents the influence of severe plastic deformation by hydrostatic extrusion (HE) on the thermal and structural properties of polyamide 6 (PA6). During the hydrostatic extrusion process, a fibrous structure oriented along the extrusion direction is formed, which was visualized during microscopic observations. The degree of crystallinity was analyzed by differential scanning calorimetry (DSC). Wide-angle X-ray scattering diffraction (WAXS) analysis was used to partially characterize the PA6 structure after the HE process. The contents of various forms of the crystalline phase in PA6 samples before and after the HE process were analyzed in fragments of spectroscopy in infrared (FTIR). The favorable properties of PA6 after the HE process were obtained after deformation under conditions generating an adiabatic temperature higher than the glass transition temperature and lower than the temperature of the onset of melting of the crystalline phase. Thermal analysis using DSC allowed us to conclude that in the PA6 after the HE process generating deformations in the range of 0.68-1.56, the proportion of the crystalline phase α increases in PA6. As the deformation increases in the HE process, the crystalline phase proportion increases by 12% compared to the initial material (before HE). The glass transition temperature of PA6 is ca. 50.6 °C, reduced for the sample after the HE process at a small deformation of 0.68 (PA6_0.68) to ca. 44.2 °C. For other samples, Tg is ca. 53.2-53.5 °C. As a result of the analysis of WAXS diffractograms of PA6 samples after various deformations in the HE process, the presence of typical peaks of phases α1 and α2 and γ was observed. The results of the FTIR spectroscopic analysis confirm these observations that as the deformation increases, the proportion of the crystalline phase α increases.

Surfactant-induced intervention in interfacial polymerization to develop highly-selective thin-film composite membrane for forward osmosis process

Thin-film composite (TFC) membrane capable of superior permeability contributes to the industrial implementation of forward osmosis (FO) technology, but it is plagued with some bottlenecks including the unsatisfactory selectivity. Herein, the surfactant-induced intervention in interfacial polymerization was performed by incorporating hexadecyltrimethylammonium toluene-p-sulphonate (CTAT) into the amine aqueous solution for developing the highly-permeable TFC membrane with exceptional selectivity. The effect of CTAT incorporation on the physicochemical properties of polyamide (PA) layer was systemically investigated by conventional characterizations, so as to unravel the mechanism for the improved performance of resultant TFC-FO membrane. Besides, three typical surfactants of Tween 80, sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium chloride (CTAC) were also introduced and studied contrastively for comparison. Amongst the fabricated membranes, the optimized TFC-CTAT membrane achieves the improved water fluxes (JV) of 31.8 and 21.7 L.m-2.h−1 accompanied with the reduced specific reverse salt fluxes (JS/JV) of 0.05 and 0.04 g·L−1 in active layer facing the draw solution (AL-DS) and active layer facing the feed solution (AL-FS) orientations respectively, using 1 M NaCl solution and deionized water as draw and feed solutions. Therefore, this work provides a new perspective for constructing TFC-FO membrane with high perm-selectivity by employing suitable surfactant at the relatively low concentrations.

Improving flame retardancy and mechanical properties of polyamide 6 induced by multiple reactions among flame retardants and matrix

A bio-based flame retardant TFD was synthesized using tyrosine (Tyr), furfural and 9,10-Dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) which was used in polyamide 6 (PA6) to modify its flame retardancy. A bio-based chain extender EDPDO which was obtained by epoxidation of the reaction product between phenylphosphonic dichloride and magnolol, was used to regulate the mechanical properties of PA6. TFD endows PA6 with a UL-94 V0 rating at the content of 12 wt%. If TFD and EDPDO were premixed and incorporated into PA6, 8 wt% TFD and 1 wt% EDPDO are needed for PA6 to display a UL-94 V0 rating. Moreover, the mechanical properties were improved. The tensile strength of PA6 containing 8 wt% TFD and 2 wt% EDPDO is 97 MPa which is 21 MPa higher than that of PA6. The TFD reduces the molecular weight of PA6, while the chain extension reactions increase the molecular weight to a certain extent. In addition, the adhesion among the char particles is so poor that some small char particles volatilize into the gas phase to form smoke. The improved flame retardancy in UL-94 test is mainly caused by the melting-away effect.

Characterisation of the mechanical properties of polyamide 12 powder when using titanium dioxide as antimicrobial additive

AbstractAntimicrobial properties of plastic components are an important part of polymer engineering. One commonly used additive with an antibacterial effect is titanium dioxide. The aim of this study is to investigate the influences on the mechanical properties resulting from the addition of titanium dioxide as an antimicrobial additive and the processing of the compounds with selective laser sintering. Compounds with 5 %, 10 % and 15 % titanium dioxide and polyamide 12 as matrix material are fabricated. Tensile test specimen are produced from the compounds, examined and the results compared with virgin polyamide 12. The investigations show a general loss in the ultimate tensile strength compared to the virgin polyamide 12. Comparing the different titanium dioxide contents with each other, an increasing tensile strength with increasing titanium dioxide content of the compound can be examined. A decreasing elongation at break and thus a decreasing ductility can also be observed. Furthermore, the results of the tensile test show a stiffening effect, i. e. an increase in the elastic modulus due to the addition of titanium dioxide.

Polyamide 11 Composites Reinforced with Diatomite Biofiller—Mechanical, Rheological and Crystallization Properties

Amorphic diatomaceous earth is derived from natural sources, and polyamide 11 (PA11) is produced from materials of natural origin. Both of these materials show a low harmfulness to the environment and a reduced carbon footprint. This is why the combination of these two constituents is beneficial not only to improve the physicochemical and mechanical properties of polyamide 11 but also to produce a biocomposite. For the purpose of this paper, the test biocomposite was produced by combining polyamide 11, as well as basic and pre-fractionated diatomaceous earth, which had been subjected to silanization. The produced composites were used to carry out rheological (melt flow rate-MFR), mechanical (tensile strength, bending strength, impact strength), crystallographic (X-ray Diffraction-XRD), thermal and thermo-mechanical (differential scanning calorimetry-DSC, dynamic mechanical thermal analysis-DMTA) analyses, as well as a study of hydrophobic-hydrophilic properties of the material surface (wetting angle) and imaging of the surface of the composites and the fractured specimens. The tests showed that the additive 3-aminopropyltriethoxysilane (APTES) acted as an agent that improved the elasticity of composites and the melt flow rate. In addition, the produced composites showed a hydrophilic surface profile compared to pure polylactide and polyamide 11.

Effect of infusion strategy on vacuum bagging process and properties of polyamide 6 composites

Effect of infusion strategy on vacuum bagging process and properties of polyamide 6 composites

Evaluation of Cross-Linked Polyamide 6 Micro-Indentation Properties: TAIC Concentration and Electron Radiation Intensity

Nowadays, technical practice puts emphasis on improving selected material properties of polymers which could lead to new applications. Material properties can be modified in numerous ways, among which is radiation treatment. This study looks into the influence of beta radiation on several properties of polyamide 6, e.g., indentation hardness, modulus and creep. Main changeable parameters were the concentration of triallyl isocyanurate (TAIC), which promotes cross-linking, and intensity of radiation. The concentration was in the range from 2 to 6 wt.%, while the radiation dose was 0, 66, 99 and 132 kGy. The treated materials were measured for indentation hardness, modulus and creep. Degree of cross-linking was verified by thermo-mechanical analysis (TMA), while degradation processes was investigated by Fourier-transform infrared spectroscopy (FTIR). The results indicate that electron radiation positively affects the tested material properties. The best results were seen in polyamide with 6 wt.% of TAIC, which demonstrated a 38% improvement in mechanical properties after exposure to 132 kGy. This improvement in properties affects the final parts and their application (e.g., in the automotive industry-engine parts; in electrical engineering-insulation of wires and cables; and in industry-pipes for underfloor heating, etc.).

Effect of matrix composition on properties of polyamide 66/polyamide 6I-6T composites with high content of continuous glass fiber for optimizing surface performance

Abstract To optimize the surface performance of the composites of polyamide 66 and continuous glass fiber (50/50, weight ratio), poly(hexamethylene isoftalamide-co-terephthalamide) (PA6I-6T) was introduced. The composites were prepared by a twin-screw extruder, and the effect of PA6I-6T on the thermal and mechanical properties, as well as surface appearance was investigated. The results showed that the crystallization temperature and the melting point of the composites decreased with increasing the amount of PA6I-6T. The Jeziorny method proved that the presence of PA6I-6T did not change the nucleation mode and the crystal growth of PA66 in the hybrid matrix, and the Mo method revealed that the crystallization rate of PA66 decreased first and then increased with the increase of the PA6I-6T content. The reduction in the “floating fiber” on the surface of the composites was attributed to the decrease of the crystallization rate of PA66 in the presence of PA6I-6T. It was shown that the composites with smooth surface had a large melt flow index. Moreover, the composites with high content of PA6I-6T had low heat deformation temperatures. The mechanical properties of the composites did not change significantly with the increase of the PA6I-6T content. Scanning electron microscope (SEM) images revealed that glass fiber was evenly distributed in the matrix and strongly oriented parallel to the injection direction.

Tribological Properties of Glass Bead-Filled Polyamide 12 Composite Manufactured by Selective Laser Sintering.

To enhance the properties of polyamide 12 (PA12/Nylon 12) manufactured by the selective laser sintering (SLS) process, micron-sized glass beads are used as a filler, and the resulting composite is known as glass bead-filled PA12 (PA 3200 GF). Despite PA 3200 GF basically being a tribological-grade powder, very little has been reported on the tribological properties of laser-sintered objects based on this powder. As the properties of SLS objects are orientation-dependent, this study is devoted to investigating the friction and wear characteristics of the PA 3200 GF composite sliding against the steel disc in the dry-sliding mode. The test specimens were aligned in the SLS build chamber along five different orientations (X-axis, Y-axis, Z-axis, XY-plane, and YZ-plane). Additionally, the interface temperature and the friction-induced noise were measured. The pin-shaped specimens were examined using a pin-on-disc tribo-tester for 45 min to investigate the steady-state tribological characteristics of the composite material. The results revealed that the orientation of build layers relative to the sliding plane was a ruling parameter that determined the dominant wear pattern and the wear rate. Accordingly, where build layers were parallel or inclined to the sliding plane, abrasive wear predominated, and wear rate became 48% higher than that of specimens with perpendicular build layers, for which adhesive wear predominated. Interestingly, a noticeable synchronous variation of adhesion and friction-induced noise was observed. Taken together, the results from this study can efficiently serve the goals of fabricating SLS-functional parts with customized tribological properties.

INVESTIGATION OF DRILLING PERFORMANCE OF REINFORCED POLYAMIDE 6 POLYMER COMPOSITE

Polyamides are preferred polymer materials for manufacturing industrial products due to their lightness, resistance to corrosion, ease of processing, and recyclability. In this study, the machinability properties of Polyamide 6 (PA6) polymer composite plates reinforced with chopped carbon fiber (CF) and multi-walled carbon nanotube (MWCNT) in different proportions were investigated by the drilling method using different cutting tools and cutting parameters. The experiments were carried out according to the L16 orthogonal array. Drilling experiments were carried out in a dry environment. The deformations occurring on the inlet and outlet surfaces of the drilled samples were calculated, and the surface roughness (Ra) of the hole walls was measured. According to the results obtained, the particle addition made to the PA6 polymer reduced the Ra. It has been observed that high cutting speed and low feed rate are ideal parameters to achieve low Ra and low inlet-outlet deformations.

Organo-modified nanoclays induce changes in the physical properties of polyamide 66

Organo-modified nanoclays induce changes in the physical properties of polyamide 66

Polypyrrole-modified multi-functional coatings for improved electro-conductive, hydrophilic and flame-retardant properties of polyamide 66 textiles

Polypyrrole-modified multi-functional coatings for improved electro-conductive, hydrophilic and flame-retardant properties of polyamide 66 textiles

Boosted Mechanical Properties of Polyamide 11 Tube Originated from the Hierarchical Architecture Manipulation by Helical Flow Field

Polyamide 11 (PA11) is a biobased polymer originated from the renewable plant-based resources and thus holds promising potential in reducing the consumption of limited fossil resources and protecting the environment. Compared to the commonly investigated polyolefin, the flow manipulation strategy for improving the mechanical properties of PA11 still remained a huge challenge because the strong intermolecular interactions elevated the difficulty of stretching the polar polymer chains. Herein, a helical flow was introduced in the PA11 tube extrusion by superposing a hoop flow from mandrel rotation onto an axial flow. Then, the helical flow-induced hierarchical architecture was investigated to reveal the effect of intermolecular interactions on the orientation and crystalline structure. Limited by strong hydrogen bonds between the amide groups, the PA11 chains were not stretched sufficiently to form anisotropic shish-kebab crystals but assembled into a helically aligned configuration in amorphous regions, similar to that in natural materials, endowing the as-prepared tube with enhanced hoop kink resistance and axial compression properties which were favorable to the practical application of the thin-wall tube. This study not only can provide a feasible way to tailor the mechanical properties of the PA11 tube by constructing a special multidimensional flow but also is beneficial to the fundamental understanding on the flow-induced crystallization mechanism of polar polymers with strong intermolecular interactions.

Mechanical and Tribological Performances of Thermoplastic Polymers Reinforced with Glass Fibres at Variable Fibre Volume Fractions.

High wear rates and frictional coefficients have always been the primary reasons for limiting the service life of critical elements such as pumps, couplings, bushings, bearings and gears. The premature and erratic failures are costing the industries extensive amounts of money every year. Additionally, under severe service conditions, the wear resistance requirements are higher, which greatly hinders the application of neat thermoplastics in different sectors. Hence, it is vital to enhance the tribological characteristics of thermoplastics. The mechanical and tribological properties of Polyamide 6, Thermoplastic Polyurethane, and glass fibre reinforced (GFR) Polyadmide 6 Composites of variable fibre volume fractions were investigated. Pin specimens of Polyamide 6 reinforced with (25%, 33%, and 50%) by volume of fibres were fabricated by an injection moulding process. The specimens were tested for tensile, compression, hardness, and wear under dry abrasive conditions using a pin-on-disc setup. Furthermore, the samples were scanned using micro-computed tomography (micro-CT), and the worn-out samples were analysed using field emission scanning electron microscopy. The experimental results showed that the fibre volume fraction was inversely proportional to the wear resistance of the prepared composite materials. This research will enable the industry partners to supply cutting-edge technologies to the global oil and gas industry that not only minimizes the well running cost but also improves the well resilience.

Effect of different fillers on thermal conductivity, tribological properties of Polyamide 6

An influence of different filler types and filler content on the thermal and abrasive wear properties of polyamide-6 is investigated. Al2O3, MgO, two glass powders with different SiO2 contents, and natural zeolite powder were selected as fillers. The fillers individually were added to the polymer matrix in proportions of 50 and 70% by weight. A hybrid filler-containing composite was created by mixing PA6/70 wt% MgO and PA6/80 wt% zeolite. The results show that the thermal conductive enhancement factor is highest for PA6/70 wt% Al2O3 (145%) and PA6/hybrid fillers 75 wt% (92%). The Lewis-Nielsen and Reciprocity models agreed with the measured data with less than 26% deviation, except for the MgO-loaded composites. In the case of a hybrid composite, the additive model proves to be a good approximation. The abrasive effect of the different fillers was characterised by the volume loss of the steel pin using the pin-on-disc method. A new parameter is developed that considers the thermal conductivity enhancing effect of the fillers and their abrasive effect. In addition to ceramic fillers, aluminium-hydro-silicate, e.g. natural zeolite, and their mixtures offer new opportunities for the development of thermally conductive composites, as they are more economical to use in manufacturing processes.

Preparation and properties of flame retardant biobased polyamide elastomer with shape memory

AbstractNylon is the general name of high molecular polymers with amide bonds repeat structure in the main chain. Because of its good wear resistance, excellent chemical resistance and outstanding impact resistance, it is widely used in various fields of national life, such as automobile parts, oil pipelines, electronic parts, gears, connectors, coating materials and medical applications. Using isocyanate terminated polyamide prepolymer as hard segment, polypropylene glycol as soft segment and triethanolamine as crosslinking agent, polyamide elastomer was flame retardant modified by adding reactive P flame retardant and P/N synergistic flame retardant mechanism. The sample was named IAHDP‐x, in which IAHD is the synthetic hexamethylene diamine polyaitaconic acid, and x is the mass of the added flame retardant DDP. Its tensile properties, fatigue resistance, self‐recovery and tear resistance were investigated. The results revealed that the synthesized phosphorus flame retardant (9,10‐dihydro‐9‐oxa‐10‐[N,N‐bis‐(2‐hydroxyethylamino methylene)]‐10‐phenanthroline‐10‐oxide (DDP)) could not only enhance the flame retardancy, but also strengthen the mechanical properties of polyamide. Among them, the LOI and UL‐94 of IAHDP‐1.2 were 27.6% and V‐0, respectively, indicating that it could be used as flame retardant material; Cyclic tensile test demonstrated that it had good fatigue resistance and self‐recovery; Besides, the tear resistance of IAHDP‐1.2 could reach 35.24 kJ/m2. Interestingly, IAHDP‐1.2 also displayed shape memory characteristics, and the sample could be restored to its original state at 60°C. The synthetic IAHDP‐x also had excellent flame retardancy, high mechanical properties, fatigue resistance, tear resistance, shape memory, so the material can be used in satellite wings, solar panels, electronic and electrical equipment, and smart materials.