Pure Polyamide Research Articles

Improvement of the flame retardancy of polyamide 6 by the incorporation of UiO-66 and UiO-66/melamine

The flame retardancy of polyamide 6 (PA6) has been investigated through the incorporation of the metal–organic framework (MOF) UiO-66 and a composite of UiO-66/melamine during the extrusion process. The prepared materials have been characterised by various techniques: XRD, XPS, FTIR, TGA, DSC, SEM, EDX and mechanical properties. Moreover, to examine the efficiency of the flame retardants, the composites have been tested using the UL-94 vertical and, horizontal burning test, as well as the limiting oxygen index (LOI). The UL-94 V-2 standard has been achieved with only a 4 wt% load of either UiO-66 or UiO-66/melamine, compared to pure polyamide, which is not classified. The best results have been achieved with the UiO-66/melamine sample at 7 wt%, which prevents the agglomeration of UiO-66 alone. The highest LOI value was also obtained with this sample, achieving a value of 35.5 %, compared to pure PA6 and with UiO-66, which reached values of 22.4 % and 23.2 %, respectively. A flame suppression mechanism of the UiO-66/melamine composite is proposed, based on the formation of zirconium oxide, gas adsorption by the MOF and release of NH3.

Highly enhanced toughness and thermal oxygen aging resistance of PA 6 via novel designed macromolecular antioxidants

Polyamide 6 (PA6) is widely utilized, yet it confronts challenges such as susceptibility to thermal oxidative aging and high sensitivity to notch impact during usage. In addressing these issues, two novel toughening macromolecular antioxidants, 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid 2-acrylamidoethyl ester styrene copolymer (PAS) and 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid 2-acrylamidoethyl-N-phenylmaleimide copolymer (PAN), were synthesized via free radical copolymerization. Upon incorporation into PA6, their effects on PA6 performance were investigated. Relative to pure PA6, PA6/PAN and PA6/PAS exhibited significant improvements in fracture elongation, with increases of 136.91 % and 313.83 % respectively, along with notch impact strength enhancements of 18.55 % and 24.89 % respectively. This enhancement can be attributed to PAN and PAS reducing the hydrogen bond density between PA6 molecular chains. Subsequent long-term accelerated thermal aging tests conducted at 150 °C, as well as performance testing of samples before and after aging, revealed that the aging of PA6/PAN and PA6/PAS could be delayed by 4–12 days. The exceptional anti-thermal oxidative aging ability and toughening effect of these two macromolecular antioxidants in PA6 showcase promising prospects for its expanded applications.

Analisis Gugus Fungsi dan Sifat Termal Limbah Jaring Ikan Untuk Produk Otomotif

Plastic has been used in daily life due to its durability. Fishing net waste is a type of plastic waste that is dangerous. Fishing net waste can also damage marine biota, such as coral reefs and marine animals. One type of polyamide that is widely used is nylon. Fishing net waste containing nylon has the potential to be recycled. In this research, fishing net waste is used for automotive product applications using a twin-screw extruder. There are five variations: pure polyamide (PA), recycled polyamide (rPA), PA-rPA 50:50, PA-rPA 75:25, and PA-rPA 25:75. To be able to determine the characteristics of the mixed product, several tests were carried out, including testing the thermal properties of the final product with DSC and FTIR testing to identify functional groups. Based on the research results, it was found that all variations contained polyamide polymers, which were characterized by a melting temperature of 218.8–224.4 °C and obtained carbonyl functional groups (C=O) and secondary amine functional groups (N–H) in the FTIR test results, which indicated the presence of amide bonds in the samples.

Towards the Reuse of Fire Retarded Polyamide 12 for Laser Sintering.

The control of powder aging during Selective Laser Sintering (SLS) processing is one of the challenges to be overcome for the implementation of this technique in serial production. Aging phenomena, because of the elevated temperatures and long processing times, need to be considered when a fraction of the polymer powders present in the build chamber and not used to manufacture the parts are reused at various times. The aim of this study was to investigate the influence of successive reuse of blends of pure Polyamide 12 and its blends with two types of flame retardants (FR): ammonium polyphosphate (APP) and zinc borate (ZB). The composition of the blends was 70/30 (wt/wt) PA 12/FR. Four successive processing stages have been carried out by collecting the remaining powder blend each time. The powders were re-used using the same processing parameters after sieving. DSC measurements showed that the incorporation of FRs entailed a reduction in the processing window up to 4 °C; nevertheless, no further reduction was noted after aging. The TGA curves of aged blends of powders were also similar for pure PA 12 and PA 12 with FR. In addition, initial and reused powders presented a higher degree of crystallinity than the specimens processed from the powders. The heterogeneous character of the PA 12 after LS processing or reprocessing was shown through Pyrolysis Combustion Flow Calorimetry (PCFC) and cone calorimeter (CC) tests. FTIR analysis also showed that post-condensation reactions have occurred. The mode of action of the flame retardants was clearly seen on HRR curves at both tests. The first reuses of PA 12 powders entailed a significant reduction in time to ignition at the cone calorimeter (150 for the initial material to around 90 s for the reused material), indicating the formation of short polymer chains. Only in the case of zinc borate was it noticed that re-used powder was detrimental to the fire performance because of a strong increase in the value of pHRR (between 163 and 220 kW/m2 for reused material instead of 125 kW/m2 for the initial one).

Molecular Dynamics Simulation of Hydrogen Barrier Performance of Modified Polyamide 6 Lining of IV Hydrogen Storage Tank with Graphene.

The polymer liner of the hydrogen storage cylinder was studied to investigate better hydrogen storage capacity in Type-IV cylinders. Molecular dynamics methods were used to simulate the adsorption and diffusion processes of hydrogen in a graphene-filled polyamide 6 (PA6) system. The solubility and diffusion characteristics of hydrogen in PA6 systems filled with different filler ratios (3 wt%, 4 wt%, 5 wt%, 6 wt%, and 7 wt%) were studied under working pressures (0.1 MPa, 35 MPa, 52 MPa, and 70 MPa). The effects of filler ratio, temperature, and pressure on hydrogen diffusion were analyzed. The results show that at atmospheric pressure when the graphene content reaches 5 wt%, its permeability coefficient is as low as 2.44 × 10-13 cm3·cm/(cm2·s·Pa), which is a 54.6% reduction compared to PA6. At 358 K and 70 MPa, the diffusion coefficient of the 5 wt% graphene/PA6 composite system is 138% higher than that at 298 K and 70 MPa. With increasing pressure, the diffusion coefficients of all materials generally decrease linearly. Among them, pure PA6 has the largest diffusion coefficient, while the 4 wt% graphene/PA6 composite system has the smallest diffusion coefficient. Additionally, the impact of FFV (free volume fraction) on the barrier properties of the material was studied, and the movement trajectory of H2 in the composite system was analyzed.

Biomimetic interlayer brought unexpected enhancement in permeability and rejection of polyamide nanofiltration membrane

Construction of interlayer between porous substrate and polyamide (PA) layer has been proved to be an effective way in improving membrane separation performance by the regulation of membrane structure and chemical properties. In present study, biomimetic material—1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) lipid bilayer was selected to serve as the interlayer prepared by suction filtration due to its unique advantages such as smooth, continuous, uniform and hydrophilic surface. The results showed that DOPE interlayer effectively lowered the diffusion rate of piperazine (PIP) from membrane surface to organic phase and thus contributing to the thinner and smoother PA layer. The permeability of the interlayer-based PA membrane reached 35.9 L/m2·h·bar, which was 190 % higher than pure PA NF membranes. More important, the interlayer-based PA membrane exhibited excellent Na2SO4 rejection about 99.8 % accompanied by a good separation selectivity between univalent and bivalent ions. Besides, the interlayer-based PA membrane possessed good stability to the changes of operating pressure, concentration and pH of feed solution, and the long-term NF test. Meanwhile, it performed well in removing NTU, TOC, Mg2+ and SO42− in the treatment of surface water and showed its potential in the practical application. In all, the present work brought new interlayer material in fabricating high-performance NF membrane.

Molecular Dynamics Simulations of Gas Transport Properties in Cross-Linked Polyamide Membranes: Tracing the Morphology and Addition of Silicate Nanotubes.

This study employs molecular dynamics (MD) simulations to fundamentally provide insight into the role of cross-link density in the CO2 separation properties of interfacially polymerized polyamide (PA) membranes. For this purpose, two atomistic models of pure polyamide membranes with different cross-link densities are constructed by MD simulations to conceptually determine how the fractional free volume of polyamide affects the gas separation performance of the membrane. The PA membrane with a lower cross-link density (LCPA) shows a higher gas diffusion coefficient, a lower gas solubility coefficient, and a higher gas permeability than the PA membrane with a higher cross-link density (HCPA). Moreover, the pristine and modified silicate nanotubes (SNTs) as the fast gas transport channels are incorporated into the polyamide membranes to assess the effect of the SNT/PA interface chemistry on the CO2 separation properties of the membranes. SNTs are systematically modified by three modifying agents with different CO2-philic groups and different interfacial interaction energies with the polyamide matrix. The results of MD simulations demonstrate that the incorporation of silicate nanotubes into the PA matrix increases the gas diffusivity and permeability and decreases the CO2/gas selectivity. Moreover, the membranes containing modified SNTs possessing high CO2-philicity and high SNTs/PA interfacial interactions show a high CO2 separation performance.

A macromolecular flame retardant for polyamide 6 and its filaments with enhanced fire safety, tensile and UV-blocking performance

In the pursuit of enhancing the fire safety of polyamide 6 (PA6), the addition of flame retardants generally leads to hydrogen bond dissociation, which results in detrimental effects on the mechanical properties of PA6 composites and impedes processing and application in the textile field. In this study, a macromolecular flame retardant, PPB, designed with hydrogen bond donor-acceptor spacing aligned with PA6, was synthesized to increase the number of hydrogen bonds. The addition of 10 wt% PPB to the PA6 matrix (PA6/PPB10) endowed the composite with the limiting oxygen index (LOI) increased to 31.6 % and V-0 rating in the vertical burning (UL-94) test. PA6/PPB10 also exhibited significant enhancement in tensile strength by 12.6 % compared to pure PA6 and demonstrated a superior ultraviolet protection factor (UPF) value of 573, greatly exceeding the value of 3 for PA6. The quenching effect, diluting effect in the gas phase, and hydrogen bond interactions between PPB and PA6 backbones imparted PA6/PPB composites with satisfactory flame retardancy and mechanical properties. As a representative example, PA6/PPB10 was melt-spun into filaments with a pleasing tenacity of 3.6 cN/dtex and self-extinguishing capability within 5 s after ignition, confirming the sustained comprehensive properties after spinning and drawing into filaments.

Preparation and mechanism of fly ash based composite fillers with different morphologies and its application in filling polyamide 6

In order to realize the high value-added utilization of coal-based solid waste fly ash (FA) and enhance the performance of polyamide 6 (PA6), three kinds of core-shell structure FA-based composite fillers with different shell morphologies (nano-flake, spherical and rod-like particles) were prepared using FA as raw material, MgSO4, MgCl2, Mg(NO3)2 and NaOH as coating agents, which were noted as composite powder 1 (CP1), composite powder 2 (CP2) and composite powder 3 (CP3). The specific surface areas were enhanced to 97.41, 58.59 and 20.21 m2 g−1 from 1.71 m2 g−1 (FA), while the corresponding pore volumes were increased from 0 to 0.31, 0.22 and 0.06 cm3 g−1. Si-O-C-O-Mg and Si-O-Mg-OH bonds were formed between Si-O-Si, Si-O bonds on the surface of FA and hydrated MgCO3 (MCH), Mg(OH)2 (MH). Three types of CPs were filled into PA6, respectively. After filling, CP2 caused silver grain effect when the material was damaged, which had better toughening effect on the matrix. Compared with pure PA6, the limiting oxygen index of pure MH, FA, CP1, CP2, and CP3 increased by 0.60, 0.70, 1.30, 2.30 and 4.10%, respectively. The thermal deformation temperature was increased by 29.10, 46.20, 53.70, 31.90 and 42.00°C respectively. The melting index decreased by 1.05, 0.70, 0.49, 0.17 and 0.47 g/min, respectively.

Polymer-type flame retardants based on a DOPO derivative for improving the flame retardancy of polyamide 6: Preparation, properties and flame retardancy mode of action

A polymer-type flame retardant (PFR) based on a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivative was synthesised here to improve the flame retardancy of polyamide 6 (PA6). The chemical structure and thermal property of the PFR were characterised by Fourier-transform infrared (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The PFR and PA6 were melt-blended to obtain a flame-retardant polyamide 6 (FRPA6). Its thermal property, mechanical property and flame retardancy were characterised via TGA, DSC and tensile, impact, vertical burning and limiting oxygen index (LOI) tests. Its flame-retardant mode of action was analysed by scanning electron microscopy, FTIR spectroscopy, cone calorimetry and pyrolysis-gas chromatography-mass spectrometry. The FRPA6 with a phosphorus content of 3000 ppm passed the UL-94 V-0 rating, and the LOI of the FRPA6 with a phosphorous content of 5000 ppm reached 28.8 %. Compared with pure PA6, the peak heat release rate, total heat release and effective heat of FRPA6–5000 were reduced by 35.4 %, 21.9 % and 26.5 %, respectively. These results indicate that the flame-retardant mode of action of PFR mainly involved the quenching effect of phosphorus-containing radicals in the gas phase.

Improve the thermal properties of oil‐loaded polysulfone microcapsules by optimizing copper layer for self‐lubricating polyamide

AbstractThis work reports polymer/metal double‐shell microcapsules with polysulfone (PSF) and copper as walls for application in self‐lubricating polymer. First, polyalphaolefin 40 (PAO40) was selected as lubricant oil, and PAO@PSF single shell microcapsules were prepared. A critical issue for the formation of copper layer is the sensitization of PSF shell, which can affect not only the adhesion between PSF shell and copper layer, but also the density of copper layer. The sensitization conditions were discussed in detail, and the corresponding effect on the formation of copper layer was evaluated. PAO@PSF/Cu microcapsules obtained under optimal sensitization condition were characterized by scanning electron microscopy (SEM), thermogravimetric analyzer (TGA), x‐ray energy dispersive spectrometer (EDS) and fourier transform infrared spectroscopy (FTIR). A uniform and compact copper layer improved the thermal properties of microcapsules. PSF/Cu microcapsules maintained relatively complete spherical shape when were heated to 300°C, while the PSF microcapsule softened and deformed at 200°C. The self‐lubricating polyamide 6(PA6) composites containing PAO@PSF/Cu microcapsules were fabricated at 230°C, microcapsules maintained complete structure and uniform distributed in the polymer matrix. Coefficient of friction (COF) and wear rate of PA6 composites were tested under different friction conditions. Compared with pure PA6, 15 wt.% PAO@PSF/Cu microcapsules could reduce the COF by 79.5%, and the wear rate was decreased by 98.3% under 300 rpm sliding speed and 50 N friction load.Highlights PSF/Cu double‐shell oil‐loaded microcapsules were designed and prepared. The copper layer effectively improved the thermal properties of microcapsules. The self‐lubricating PA6 composite exhibited excellent tribological properties.

Bicomponent melt-spinning of filaments for material extrusion 3D printing

In material extrusion (MEX) 3D printing, the layer-by-layer structure often presents challenges such as poor adhesion, void formation and rough surfaces, which can compromise the mechanical properties of printed parts and limit their applications. This study investigates whether 3D printing from bicomponent core-sheath filaments instead of printing from conventional monofilaments provides a potential solution to some of the described issues. Based on different material selections, various bicomponent filaments, comprising a rigid core and a soft sheath, were produced through co-extrusion and overcoating extrusion techniques. Tensile properties of 3D-printed specimens with different raster angles (0° vs 45°) from bicomponent filaments are compared to the properties of reference specimens printed from conventional monofilaments. While similar mechanical properties were observed for some 3D-printed specimens from bicomponent filaments (e.g., polylactic acid (PLA)-based), as compared to reference specimens, some core-sheath combinations of polyamide (PA) demonstrated a noticeable improvement of the mechanical properties of 3D-printed specimens, particularly for 45° raster angles. In particular, bicomponent filaments comprising a carbon fiber reinforced PA (PACF) core and a pure PA sheath exhibited improved processability and enhanced structural strength. Moreover, two overcoated filaments consisting of polyethylene terephthalate (PET) and polyphenylene sulfide (PPS) monofilament cores with a copolyester (CoPES) sheath were prepared for 3D printing. 3D-printed parts made from PET/CoPES overcoated filaments exhibited good compatibility and satisfactory results when printed at temperatures above the melting point of PET. These findings demonstrate the potential of bicomponent filaments to enhance both printability and mechanical performance of 3D-printed parts, offering new avenues for material selection and design optimization in various 3D printing applications.

Fabrication of robust polyamide 6 with local cross‐linked structure via dynamic vulcanization

AbstractPolyamide 6 (PA6) is a widely used thermoplastic engineering polymer, and the toughening modification for PA6 is always a main research topic. Meanwhile, the rigidity and heat resistance of PA6 usually deteriorate. To address this conflict, an epoxy compound (EGDE‐GA) was designed and synthesized and used to modify PA6 by dynamic vulcanization in twin‐screw extruder. EGDE‐GA is a linear molecule with a flexible molecular structure, which is favorable to toughening of PA6, and epoxy groups of EGDE‐GA can form local cross‐linked structure to improve the rigidity and retain the heat resistance of PA6. At the loading of 20 wt% of EGDE‐GA, the modified PA6 (PA6/EGDE‐GA 20) exhibited very high elongation at break and notched impact strength, which were increased by 413% and 520%, respectively, compared to those of PA6. The tensile strength was 61.4 MPa, which was higher than that of PA6. The heat deflection temperature remained almost unchanged. The results showed that the modified polymers may possess the high toughness without sacrificing the original rigidity by building the local crosslinked structure using dynamic vulcanization. The findings provide a feasible method for reusing and upcycling PA6 and other polymers with higher value and wider use in the industry.Highlights The polyamide 6 (PA6) is toughened via dynamic vulcanization. The toughness of modified PA6 is increased by 520% compared with pure PA6. The toughened PA6 exhibits higher tensile strength than that of pure PA6. The toughened PA6 maintains its rigidity and heat resistance.

A new strategy for preparing high oil content PAO40@HMCs microcapsules for improving tribological properties of PA6 composites

Enhancing the tribological characteristics of polyamide 6 (PA6) represents an effective strategy for extending the service life of self-lubricating PA6 composites. In this investigation, hollow mesoporous carbon spheres (HMCs) with an average diameter of 10 μm were synthesized using the template method, and the crucial factors influencing HMCs preparation were thoroughly examined. Successful synthesis of polyalphaolefin oil-containing microcapsules (PAO40@HMCs) was achieved, utilizing HMCs as microcontainers and PAO40 lubricant as the core material. The self-lubricating PAO40@HMCs microcapsules exhibited a notable oil content of 76.0 wt%. The tribological properties of the prepared self-lubricating PA6 composites were significantly better than those of pure PA6. When the content of PAO40@HMCs microcapsules in the composite reached 7 wt%, the coefficient of friction (COF) for the PA6 composite decreased by 87.9% (from 0.420 to 0.051), and the wear loss was reduced by 80% (from 0.115 to 0.023 g/0.5h). Through an analysis of the morphology and transfer film of the wear surface and friction pair, it was evident that microcapsules played a pivotal role in enhancing the self-lubricating properties of PA6 composites.

Enhanced Water Flux of Aromatic Polyamide Membranes by Grafting Imidazolium‐Type Ionic Liquids Containing Silsesquioxane Frameworks

AbstractAn imidazolium‐type room‐temperature ionic liquid containing silsesquioxane frameworks is successfully prepared. The polar ionic liquid products are grafted onto the surface of prepared aromatic polyamide (PA) membranes to improve water flux of PA membranes. Membranes grafted with an ionic liquid exhibit a water flux of 1.89 L m−2 h−1 bar−1), 48% higher than that of pure PA membranes while the salt rejection still remains at 96%. This improvement can be attributed to the enhanced hydrophilicity of the membrane surface, as evidenced by the reduced water contact angle.

Fabrication of a novel nanofiltration membrane using an Mg-Fe layered double hydroxide for dye/salt separation.

Mg-Fe layered hydroxide (LDH) was synthesized by the double titration method and added to trimesoyl chloride (TMC) to prepare an Mg-Fe LDH-modified polyamide nanofiltration (NF) membrane by interfacial polymerization (IP). Compared to the pure polyamide NF membrane, the Mg-Fe LDH-modified membrane presented a wrinkled structure and a comparatively smooth surface. Additionally, the permeation flux and rejection rate of the modified NF membrane for 1000 mg L-1 Na2SO4 solution were 61.7 L m-2 h-1 and 95.9%, respectively. When the Mg-Fe LDH modified NF membrane was used to separate dye/NaCl mixed solutions, the rejection of NaCl was less than 17% and the rejection rate of Coomassie Brilliant Blue (CBB) molecules was close to 100%. At the same time, the concentration of CBB increased from 500 mg L-1 to 1151 mg L-1 which means that the LDH modified NF membrane could separate CBB/NaCl effectively and could concentrate CBB at the same time.

The antioxidant mechanism of hindered phenolic antioxidants bonded with para bridge groups in PA6

The correlations between the antioxidant activity and hindered phenolic antioxidants bonded with para bridge structures in polyamide 6 (PA6) were studied by comparing the antioxidant properties of three hindered phenolic antioxidants bonded with different bridging groups. The antioxidant properties of the pure PA6 and stabilized PA6 were investigated in terms of mechanical properties, rheological properties, crystallization properties, chemical structure, and the migration resistance of antioxidants. The radical scavenging activity and capacity of hindered phenolic antioxidants were also compared. The results showed that the hindered phenolic bonded with the aromatic ring exhibits the best activity and capacity in scavenging radical and the best migration resistance in PA6. Therefore, the tensile strength of PA6/HPAP remains at 117 % of the unaged sample after 12 days of thermal oxygen aging at 150 °C, and the notch impact strength of PA6/HPAP remains at 68 % of the unaged sample. The mechanical properties of PA6/HPAP are comparable to PA6/1098 (a commonly used commercial antioxidant in PA) after 12 days of thermal oxygen aging. The mechanism of the hindered phenolic antioxidants bonded with para bridge structure in scavenging PA6 free radicals and inhibiting the aging of PA6 macromolecular chains was explored in this article.

Effects of Hybrid POSS Nanoparticles on the Properties of Thermoplastic Elastomer-Toughened Polyamide 6.

In this study, polyamide 6 (PA6)/thermoplastic elastomer (TPE) blends were prepared to decrease the notch sensitivity of PA6 for automotive applications, and the morphological, rheological, mechanical, and thermal properties of PA6/TPE blends, which are partially miscible or immiscible depending on the TPE ratio, were significantly improved in the existence of polyhedral oligomeric silsesquioxane (POSS) nanoparticles with multiple reactive epoxy groups as compatibilizers. An unstable phase morphology was obtained with the addition of TPE into PA6 without POSS nanoparticles, whereas interfacial interactions between phases in the presence of POSS were enhanced as a result of a significant decrease in the average particle size from 1.39 to 0.41 μm. The complex viscosity value of the 70PA6/30TPE blend, which was 20 kPa/s-1 at 0.1 rad/s angular frequency, reached 380 kPa/s-1 with the addition of POSS due to the formation of long chains by the generation of graft and/or block copolymers, which resulted in a 65% increase in Young's modulus value. Most notably, the Izod impact strength of pure PA6, which was 10 kJ/m2, increased by 290% with the incorporation of POSS. It was confirmed by FTIR analysis that the reactive multiple epoxy groups of MultEpPOSS and EPPOSS nanoparticles react with the proper groups of PA6 and/or TPE, and also, a partial hydrogen bonding interaction occurs between PA6-TPE from the shifting of N-H and carbonyl peaks. In conclusion, it can be suggested that POSS nanoparticles can serve as highly effective compatibilizers for PA6/TPE blends and have potential commercial applications, especially in the automotive sector.

A novel phosphorus-nitrogen-based hyperbranched polysiloxane for improving the fire safety of PA6 with suppressed melt droplets and good mechanical properties

The combustible defects of polyamide 6 (PA6), especially the flammable melt-dripping behavior, have greatly limited its application in some particular fields. In this work, a halogen-free hyperbranched polysiloxane (PBDSi) containing DOPO and Schiff base was designed via Michael's addition reaction and dehydration-condensation reaction. Results showed that the char yield (Yc) of PBDSi attained 37.9 wt%, confirming the satisfactory charring behavior of PBDSi for preparing flame-retardant PA6. Just by adding 3 wt% of PBDSi, the serious melt droplets of PA6 were suppressed effectively. The prepared PA6/PBDSi-3 with 5 wt% of PBDSi could achieve the highest value of limited oxygen index (LOI) of 27.2 %, while that of PA6 is 21.0 %. Meanwhile, PA6/PBDSi-3 obtained an apparent reduction in the peak heat release rate (PHRR) value of 31.1 % compared with pure PA6. The cooperated effect of DOPO, Schiff base, and polysiloxane that contributed to generating a silicon-phosphorous-rich char layer and releasing incombustible volatiles that were determined to be the essential factor for the improved fire safety of PA6/PBDSi were explored intensively. Inspiringly, PA6/PBDSi composites exhibited a slight mechanical loss concerning PA6, overcoming the great challenge of developing additive flame-retardant materials to balance mechanical properties and fire safety.

The Effect of AZ61 Content on Mechanical Strength and Surface Hardness of PA6-AZ61 Magnesium Alloy

In this study, a Polyamide 6 (PA6)-AZ61 magnesium alloy composite and pure PA6 were fabricated using a compression molding instrument. Both the matrix and reinforcement were prepared in powder form. A planetary ball milling machine was employed to mix the PA6 and AZ61 micro powders. The effects of AZ61 content at different percentage on the final properties of the composite were investigated. X-ray diffraction (XRD) analysis and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) were employed to verify the uniformity of the mixing process and to confirm the composition of both the raw materials and the composite. The result, relative to pristine PA6, the ultimate tensile strength (UTS) demonstrated a substantial increment of 48.3%, reaching 58 MPa. Whereas the yield strength (YS) exhibited a notable surge to 49.38 MPa, constituting a 52.9% enhancement. Additionally, the PA6-5AZ61 composition achieved the highest microhardness value at 21.162 HV, signifying a remarkable 66.3% augmentation compared to the unalloyed PA6 material. This result suggests that AZ61 has the potential to improve the properties of the matrix material.