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•BPPA can improve the mechanical properties of PA6 composites through the alloying effect.•Similarity compatibility structures of imide and amide can improve the mechanical properties ...of PA composites.•ADP and BPPA can provide excellent charring properties and gas-phase flame retardancy effect on PA6.
A novel flame retardant − bismaleimide polyalkyl phosphinate aluminium (BPPA), containing both imide and phosphinate structures, was designed and synthesized to investigate the intramolecular synergistic flame retardant effect between imide and phosphinate structures and alloying effect of the imide structure with PA6. Based on the flame retardant and mechanical properties of BPPA/PA6 composites, the alloying flame retardant effect of BPPA on PA6 was systematically investigated. The PA6 material had almost no char after burning; however, BPPA can produce a large amount of residue and form a dense char layer during combustion of PA6 matrix, effectively reducing the heat release, while BPPA also improved the mechanical properties of PA6 composites through the alloying effect. The peak heat release rate (pk-HRR) decreased by 55.8 %, and the residue yield increased by 9.2 wt% for 20BPPA/PA6, compared with the PA6. After compounding aluminum diethylphosphinate (ADP) and BPPA, the flame retardancy of the composites can be further improved. The LOI value of the 8ADP/6BPPA/PA6 was increased to 29.8 % and passed the test of UL94 V-0 level. Its pk-HRR and residue yield were similar to that of the 14BPPA/PA6, which indicated that the compounding system of ADP and BPPA can provide excellent charring properties and gas-phase flame retardancy of PA6. Meanwhile, the alloying BPPA with PA6 not only reduced the effect on the tensile strength of ADP on PA6, but also improved the breaking elongation of the composite. In conclusion, it provides a new direction for developing high-performance halogen-free flame retardant polyamides.
In this study, a water-based aminoethylpiperazine-polyamide (AEPPA) is synthesized and its water-based sizing agent is prepared to improve the interfacial properties of carbon fiber reinforced ...polyamide 6 (CF/PA6) composites. The results show that the AEPPA sizing layer enhances the wettability of CF surface, thereby promoting the sufficient impregnation of PA6 resin on the fiber surface. Meanwhile, a strong interface is formed due to the interdiffusion and hydrogen bond formation between AEPPA and PA6 molecular chains. Accordingly, the interfacial shear strength increases by 29.3% and 20.2% from 41.9 MPa for as-received and 45.1 MPa for desized CF/PA6 composites to 54.2 MPa for 4 wt% AEPPA sizing agent treated CF/PA6 composites. In addition, to clarify the applicability of the resultant sizing agent, unidirectional CF/PA6 prepregs are prepared, and the mechanical properties of CF/PA6 composites are evaluated in detail. The average interlaminar shear strength, tensile strength and flexural strength increase by 14.2%, 10.5% and 20.0% from 73.8, 2198.1 and 1393.6 MPa for desized CF/PA6 composites to 84.3, 2638.7 and 1539.9 MPa for those treated with AEPPA sizing agent due to the effective stress transfer across the interface, respectively. Moreover, the cross-section morphologies and fracture behavior are analyzed to verify the improvement of mechanical properties. Furthermore, the strengthening mechanism of interfacial properties is intensively discussed.
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•Polyamide 6 (PA6) coating with high thermal resistance was synthesized on the carbon fiber (CF) surface by in-situ polymerization. It is suitable for high-temperature molding of ...CF/polyamide composites.•This method is cost-effective and environmentally friendly, and the amount of PA6 coating on the CF surface can be easily controlled.•The introduction of PA6 coating made up for the defect on the CF surface and improved the tensile strength of CF.•After CF was modified with PA6 coating, the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of CF/PA6 composites were significantly increased by 49.92% and 31.94%, respectively.•The main mechanism of interfacial properties improvement is that the PA6 coating was tightly bonded with the polyamide matrix due to its similar molecular structure, and the mechanical meshing between PA6 and CF surface grooves was formed, which ensures that the resin matrix can effectively transfer the stress to CF.
Commercial carbon fiber (CF) sizing agent is generally characterized by poor temperature resistance and incompatibility with polyamide resin, which adversely affects the interfacial properties of CF/polyamide composites. In this paper, we utilize the feature that anionic ring-opening polymerization of caprolactam (CPL) can synthesize polyamide 6 (PA6) in situ, introduce CPL precursor on the CF surface, and initiate polymerization to generate PA6 coating to modify CF. By changing the concentration of precursor solution, the amount of PA6 on the CF surface was effectively regulated, and the modified CF coated completely and uniformly can be obtained. The results show that PCF-20 (CF treated with 20 wt% precursor solution) reinforced polyamide composites have the best interfacial properties. Compared with the desized CF/PA6 composites, the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of PCF-20/PA6 composites increased by 49.92% and 31.94%, respectively. The interface image illustrated that the high interfacial wettability of PA6 coating on CF surface results in mechanical mesh between fiber and resin, which is the main reason for the enhancement of composite interfacial properties. Therefore, the in-situ synthesis of PA6 coating to modify CF is an effective method to improve the interface properties of CF/polyamide composites.
Nanoparticles are used to compatibilize immiscible polymer blends. The key to success is to localize nanoparticles at polymer-polymer interfaces. This work aims to use silica nanoparticles (SiO2) to ...compatibilize polyamide 6 (PA6)/polycarbonate (PC) blends. The strategy to ensure the interfacial localization of the SiO2 in the blends is to graft a methacrylic monomer onto the SiO2 and then copolymerize this methacrylic monomer with styrene (St) and 3-isopropenyl-α,α′-dimethylbenzyl isocyanate (TMI). When PA6 and PC are blended in the melt in the presence of the above surface modified SiO2 (denoted as SiO2-PST), PA6 chains are grafted onto the SiO2-PST to form PA6-SiO2-PST through a coupling reaction between the terminal amine group of the PA6 and the isocyanate moieties of the PST grafts which are partially miscible with the PC. It is shown that an optimum TMI content allows for the SiO2-PST to be preferentially localized at the interfaces between the PA6 and PC. This leads to a significant decrease in the PC domain diameter from 1.6 μm to 0.6 μm without and with the SiO2-PST, respectively. The presence of the SiO2-PST (0.5 wt% with an optimum TMI content) increases the tensile strength of the PA6/PC (70/30 by weight) from 64.1 to 79.6 MPa, the elongation at break from 84.7 to 284.7%, and the notched Charpy impact strength from 10.3 to 29.4 kJ/m2.
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•Nano silica with reactive group (SiO2-PST) is prepared for compatibilizing PA6/PC blends.•Localization at the PA6/PC interfaces is ensured by the formation of PA6 and PS grafts on the SiO2.•Interfacially localized nanoparticles reduces the PC domain diameter.•The addition of SiO2-PST increases the mechanical properties of PA6/PC blends.
•Phytic acid and taurine are derived from different crops.•Phytate taurine salt (PTS) is successfully synthesized by ion reaction.•PTS coating displays high flame retardant efficiency and ...anti-dripping ability on PA6 fabric.•PTS coating mainly works in condense- and gas-phase.•PTS coating offers an effective and cleaner strategy to minimize fire hazards of PA6 textiles.
Eco-friendly and sustainable flame retardant (FR) approaches derived from natural products for polyamide 6 (PA6) fabrics are of interest. Therefore, a novel biomass phytate taurine salt (PTS) was synthesized using phytic acid and taurine, and then it was coated onto PA6 fabric. The chemical structure of PTS, and the flame retardant performance and mechanism, the washing durability and physical properties of coated PA6 fabrics were explored. The damaged length of coated PA6 fabrics reduced to 12.0 cm without droplets during the vertical burning test, achieving a UL94 V-0 level. The LOI increased from 23.0% to 31.8% after PTS coating. The results of cone calorimetry showed that the pHRR of PA6-PTS sample decreased by about 11.0% with a char residue of 12.0%. The investigations on violates and char residues confirmed that PTS coating improved the flame retardancy of PA6 fabric through a combined gas-phase and condensed-phase action. In addition, the coated PA6 fabrics could still maintain V-0 level after 15 washing cycles. The tensile strength of PA6 fabrics was also slightly improved after PTS coating. In general, this work developed a durable and sustainable PTS coating with excellent flame retardancy for PA6 fabric.
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Functionalized polyamide 6 (PA 6) filament fabric with excellent thermal stability and UV resistance was copolymerized with methyl methacrylate (MMA) via in-situ grafting initiated by immobilized ...ascorbic acid and hydrogen peroxide. Grafting modification process was determined at 30 % of H2O2, at 70 °C for 60 min of duration, and the grafting degree could be tuned by adjusting the amount of MMA. Microscopic investigations confirmed the granular MMA was immobilized on the surface of PA 6 fibers. A strong peak at 1729 cm−1, assigning to CO stretching of ester bond of MMA, demonstrated MMA was successful grafted. The decomposition temperature of grafted PA 6 occurring at 444.6 °C, was 40 °C higher than that of pristine PA 6 (403.4 °C). Additionally, the introduction of MMA also improved the UV resistance of PA, more than 80 % decrease in transmittance of UVA band and UVB band with only 0.34 % grafting degree. Therefore, it can be concluded that in-situ grafting of MMA can endow PA 6 with excellent thermal stability and UV resistance. We believe that in-situ grafting of MMA would have important guiding significance for the fabrication of PA 6 based textiles with excellent thermal stability and UV resistance.
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•Functionalized PA6 was copolymerized with MMA via in-situ grafting initiated by immobilized H2A and H2O2 in aqueous solution.•The grafting degree can be tuned by the amount of MMA and the process parameters of in-situ grafting.•Thermal stability of grafted PA6 was promoted greatly with the Td 40 °C higher than that of pristine PA 6.•UUV resistance of grafted PA 6 was enhanced dramatically.
Information on the interactions of microplastics (MPs) with dissolved organic matter (DOM) is essential for understanding their environmental impacts. This study selected fulvic acid (FA) as a ...typical DOM to investigate the influence of contact time, temperature, dosage, solution pH, salinity, and coexisting metal ions on the adsorption of FA onto polyamide 6 (PA6) MPs. The adsorption kinetic and isotherm can be successfully described by mixed-order (MO) and Freundlich models. The adsorption site energy distribution based on the Freundlich equation was applied to analyze the interaction between FA and PA6-MPs and the adsorption site heterogeneity. Thermodynamic analysis demonstrated that the values of parameters (ΔGads°, ΔSads°, ΔHads°) were significantly affected by initial solution concentrations and the adsorption process was spontaneous, endothermic, and randomness-increased. Fourier transform-infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed the importance of amide functional groups of PA6-MPs in controlling FA adsorption. Hydrogen bonds, hydrophobic, electrostatic, and n-π electron donor-acceptor (n-π EDA) interactions played different roles on adsorption of FA under different conditions of solution chemistry. These findings are beneficial to provide new insights involving the adsorption behavior and interaction mechanisms of FA onto PA6-MPs for the environmental risk assessment of MPs.
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•FA adsorption was mainly controlled by the step of adsorption on active sites.•FA adsorption was affected by pH, salinity, temperature and coexisting metal ions.•Solution chemistry led to different contributions of four interaction mechanisms.•This study provides new insights for the environmental risk assessment of MPs.
Preparing flame-retardant polyamide 6 (PA6) composites with low addition of flame retardant remained one of the biggest concerns nowadays. In this work, a novel aromatic Schiff base-containing ...branched polysiloxane (PCNSi) with high thermal stability and great capacity of charring was first synthesized as a self-crosslinking flame retardant, and then PA6/PCNSi composites were prepared through melt blending with different contents of PCNSi. Inspiringly, a sharp reduction of about 48.9% in peak heat release rate (PHRR) was found for PA6 composite with only 6 wt% of PCNSi in contrast with PA6, and serious melt-dipping behavior of PA6 was suppressed totally as 4 wt% of PCNSi was added into PA6. The formation of a self-extinguished layer was considered as the essential factor for reinforcing the flame retardancy of PA6. This layer was generated under the synergistic effects of the cross-linking reaction of Schiff base structure and thermo-oxidative degradation of polysiloxane units in PCNSi. These composites also presented similar mechanical properties to PA6 due to the low addition of PCNSi and good interfacial interactions between PCNSi and PA6.
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•An aromatic Schiff base-containing branched polysiloxane (PCNSi) was prepared as a self-crosslinking flame retardant.•A sharp reduction of 48.9% in peak heat release rate (PHRR) was achieved for PA6 when 6 wt% of PCNSi was added.•The serious melt-dipping behavior of PA6 was suppressed totally only with 4 wt% of PCNSi.•PA6/PCNSi composites still retained the close mechanical properties to PA6.
•An inherently FR-PA6 with commercial DDP and synthesized polydiphenylsiloxane (PDPS) was prepared using a facile method.•FR-PA6 containing 5 wt% DDP and 5 wt% PDPS (FR-PA6-5-5) exhibited a UL94 V-0 ...rating with no melt droplets.•FR-PA6-5-5 showed a 31.0% reduction in HRR and a 18.8% reduction in THR compared to PA6 in the cone calorimetric tests.•FR-PA6-5-5 filaments with a tensile strength of approximately 2.27 cN/dtex were successful prepared.
The absence of inherently flame-retardant polyamide 6 (FR-PA6) with enhanced anti-dripping and melt spinnability has significantly limited its further application in textiles. In this work, a binary reactive flame retardant composed of commercial 9,10-dihydro-10-2,3-di(hydroxycarbonyl)propyl-10-phosphaphenanthrene-10-oxide (DDP) and synthesized polydiphenylsiloxane (PDPS) was employed to fabricate FR-PA6 through a facile synthetic route. The prepared FR-PA6 containing 5 wt% DDP and 5 wt% PDPS (FR-PA6-5-5) exhibited a UL94 V-0 rating with no melt-droplets during combustion, a 31.0% reduction in heat release rate and a 18.8% decrease in total heat release compared to pure PA6 in cone calorimetric tests. The improved fire safety of FR-PA6-5-5 was contributed to the gas-phase quenching and dilution effect and the condensed-phase barrier effect, which was enhanced by the synergistic charring effect achieved through the formation of P(=O)-O-Si. Additionally, FR-PA6-5-5 exhibited excellent melt spinnability as demonstrated by the successful preparation of filaments with a tensile strength of approximately 2.27 cN/dtex.
An integrally skinned organic solvent-resistant membrane with asymmetric structure for organic solvent nanofiltration (OSN) application was developed via thermally induced phase separation (TIPS) of ...nanocomposite polyamide 6. The nanocomposite polyamide 6 contains intercalated silicate sheets, which could improve the mechanical properties of the resultant membrane, as well as mitigate swelling after exposure in solvent. The influence of nanocomposite polyamide 6 composition of the hollow fiber membrane and the subsequent thermal annealing was investigated in this study. Crystallinity data revealed that polyamide 6 crystal formed during the TIPS process was primarily α-phase type, but the use of nanocomposite polymer initiated the formation of γ-type crystalline structure. Thermal annealing at 120 °C was also found to even promote a higher overall crystallinity of the membranes. The membranes were subjected for OSN operation with methanol (MeOH) as solvent and cyanocobalamin (vitamin B12) as the solute. The intercalated silicate sheets in the nanocomposite polyamide 6 brought about the dense outer surface and sublayer formation, resulting in higher mechanical properties and stability in MeOH; however, the membranes formed with purely nanocomposite polyamide 6 suffered from very low permeance, primarily due to the dense outer surface and sublayer. The membrane whose composition is 50% nanocomposite polyamide 6 exhibited MeOH permeance of 0.1 L m−2 h−1 bar−1 and vitamin B12 rejection of over 99.0%. This work was able to provide how polymeric material, thermal annealing, and the resultant crystallinity could affect the membrane’s mechanical properties and filtration performance with solvent resistance.
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•Nanocomposite polyamide 6 hollow fiber membranes were prepared for OSN application.•The influence of thermal annealing on crystallinity and performance was evaluated.•Pure nanocomposite polyamide 6 membrane showed dense outer surface and sublayer.•Thermal annealing resulted in higher membrane crystallinity and mechanical property.•Dense outer surface and sublayer resulted in enhanced strength and rejection.
