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.
Glass fiber (GF) can be deemed as a double-edged sword, which improves the strength of polymers but impairs the flame retardant efficiency and toughness. Herein, a novel phosphorus-containing ...polymeric compatibilizer (PPC) with multiple anhydride reaction sites was synthesized from radical copolymerization. PPC was directly compounded with 3-aminopropyltriethoxysilane modified GF, polyamide 6 (PA6) to prepare fire retarded glass fiber reinforced polyamide 6 (GFPA6) containing aluminium diethlyphosphinate. The multiple anhydride groups on PPC chain can react simultaneously with the amino groups on modified GF and the terminal amino groups on PA6 chain during processing. The modified GF and PA6 matrix are linked in this way, thereby enhancing the interface adhesion between GF and PA6 matrix. The addition of PPC can effectively heighten the tensile, flexural and Izod notched impact strength of GFPA6 composites. When GFPA6 burns, the addition of PPC leads to more continuous and dense carbonaceous char on GF surface, which weakens the “wick effect” and improves the flame retardant efficiency. This work also opens the door for new generations of inorganic reinforced polyamide, polyester and polyurethane.
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•A novel phosphorus-containing polymeric compatibilizer (PPC) with multiple anhydride reaction sites was synthesized.•Both PA6 and silane-coated GF can be grafted onto the PPC backbone simultaneously during processing.•Adding PPC can simplify the preparation process and improve the mechanical properties and flame-retarded efficiency of GFPA6.
•PF6− endow the PEO solid electrolyte an excellent flame-retardant performance.•Ionic liquids act as flame retardants and also facilitate to form robust SEI.•COMSOL Multiphysics is used to simulate ...lithium-ion deposition.•The combustion process of SSE was analyzed by genetic algorithm and experiment.•A new instrument is used to evaluate battery combustion performance.
The safety problems of lithium-ion batteries (LIBs) have aroused great concern on account of their extensive use. It is believed that the replacement of flammable liquid electrolytes with solid electrolytes (SSE) will solve this problem and provide an unmatched energy density for lithium-based batteries. Here, Lithium hexafluorophosphate (LiPF6) and ionic liquid serve as flame retardants for Poly (ethylene oxide) (PEO) solid electrolytes with Polyamide 6 (PA6) membrane as the skeleton. PA membrane can not only decrease the crystallinity of PEO to facilitate lithium-ion migration, but also inhibit the growth of lithium dendrites, which is attributed to its lithium-philic properties, adequate mechanical properties and flexibility. In addition, the increase of ionic liquid, on the one hand, can provide hexafluorophosphoric acid ions, which endow the SSE with excellent flame-retardant performance. The electrolyte exhibits self-extinguishing properties after ignition. On the other hand, the ionic liquid can protect the lithium anode and develop a robust SEI, thus giving the battery smooth long-cycle performance (Capacity retention rate at 1800th cycle: 89.06%). The innovative design idea of developing high-powered LIBs by introducing low-cost PA6 membranes into all solid compounds is appealing, and it can also be expanded to a combination of assorted polymers to encounter the requirements of a variety of batteries.
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•New DOPO-NH-functionalized caprolactam comonomer was synthesized.•New FR PA6 with pendant DOPO-NH– group was produced.•DOPO-NH– group increased thermo-oxidative residue of PA6 at ...500 °C by 35%.•FR PA6 was successfully melt spun into multi-filaments of 65 µm in diameter.•Melt spun filaments were self-extinguishing in 1 s by vertical flame spread test.
This work presents a unique approach for the preparation of a flame retardant (FR) polyamide 6 (PA6) polymer with chemically bonded 9,10-dihydro-9,10-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as a pendant group bridged to the polymer via an –NH- group. A novel phosphonamidate co-monomer (DOPO-A-CLM) was synthesized from DOPO and α-amino-ε-caprolactam (A-CLM). This co-monomer was subsequently used in the hydrolytic polymerization with ε-caprolactam (CLM) in different weight ratios to prepare DOPO-NH-functionalized PA6 (PA6-xDC, x = 7, 10, and 15 wt% DOPO-A-CLM). Chemical incorporation of DOPO-A-CLM into the PA6 backbone decreased the molecular weight of the polymer from 15387 for neat PA6 to 12375, 10516 and 9316 for PA6-7DC, PA6-10DC and PA6-15DC, respectively. The DOPO-NH– pendant group accelerated start of the PA6 thermal decomposition and increased the char residues at 500 °C from 1% for PA6 to 4.6, 4.9, and 5.0% for the PA6-7DC, PA6-10DC, and PA6-15DC samples, respectively, indicating crosslinking reactions in the condensed phase. The evolved phosphorus-active species in the gas phase inhibited the PA6 depolymerization, resulting in increased thermo-oxidative stability and about a fourfold higher residue at 500 °C in the case of PA6-15DC compared to PA6. The intrinsically flame retardant PA6 filament yarns with chemically bound FR pendant group were successfully melt spun from PA6-10DC, drawn and wound on bobbin. The DOPO-NH– pendant group decreased filament flammability and inhibited flame propagation, resulting in immediate self-extinguishment after flame removal. Incorporation of DOPO-A-CLM decreased the filament tensile properties compared to the neat PA6, which correlates with the decreased polymer molecular weight.
Bringing biobased nanomaterials into polymer manufacturing is essential to enhance polymers' properties and address the challenges posed by plastic waste. Using polymers such as polyamide 6 (PA6) in ...advanced industries, e.g., automotive sector, has been impeded as a direct consequence of their inability to meet the required mechanical properties. Herein, we utilize bio-based cellulose nanofibers (CNFs) to enhance the properties of PA6 by green processing, with no footprint on the environment. We address the issue of the dispersion of the nanofillers in polymeric matrices and demonstrate direct milling (cryo-milling and planetary ball milling) to facilitate a thorough integration of the components. Nanocomposites incorporating 1.0 wt% CNF, processed by pre-milling followed by compression molding, are shown to possess a storage modulus of 3.8 ± 0.2 GPa, Young's modulus of 2.9 ± 0.2 GPa, and ultimate tensile strength of 63 ± 3 MPa (all measured at room temperature). To show the superiority of direct milling in achieving these properties, other frequent approaches used to disperse CNF in polymers, such as solvent casting and hand mixing, are meticulously investigated and compared for the performance of their resulting specimens. The ball-milling method is demonstrated to provide PA6-CNF nanocomposites with excellent performance, better than solvent casting, with no associated environmental concerns.
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Using star‐branched polyamide 6 (SPA6) with hexafunctional cyclotriphosphazene core as a matrix resin and glass fiber (GF) as a reinforcing material, star‐branched polyamide 6/glass fiber (SPA6/GF) ...composites with different GF content were prepared by melt‐compounding method. The star‐branched structure of SPA6 and GF content have great effects on the properties of SPA6/GF composites. Compared with linear polyamide 6 (LPA6), SPA6 with star‐branched structure has low viscosity, high melt flowability and good impregnation and adhesion to GF, which endow SPA6/GF composites outstanding processability, good surface qualities and excellent mechanical properties even when the content of GF reaches 60 wt%. The use of SPA6 resin with star‐branched structure fundamentally solves the industry problem of traditional LPA6 resin in high‐filled modification. Such high‐performance SPA6/GF composites will provide great promise for large‐scale applications.
A novel organic‐inorganic flame retardant (SP‐APP) was first designed by coating ammonium polyphosphate (APP) with Schiff base‐containing branched polysiloxane via ion exchange reaction and ...dehydration‐condensation. High water resistance and charring capacity of the SP‐APP greatly overcame the poor water resistance of APP and endowed polyamide 6 (PA6) with excellent flame retardancy and anti‐dripping. The prepared PA6/SP‐APP composite with 12 wt% of SP‐APP reached the highest limited oxygen index (LOI) of 32.5% and passed V‐0 rating of UL‐94 test with non‐dripping, while PA6 and PA6/APP with 12 wt% of APP failed to pass the UL‐94 test. A sharp reduction of 50.9% in peak heat release rate (PHRR) and 29.4% in total heat release (THR) was found for PA6/SP‐APP in contrast with PA6. The working mechanism of SP‐APP in enhancing the flame retardancy of PA6 was also explored intensively and the synergistic effects of catalytic degradation of APP, self‐crosslinking behavior of Schiff base structure and thermo‐oxidative degradation of branched polysiloxane contributed to the improvement of flame retardancy of PA6/SP‐APP.
To expand the scientific base for the usage of the fused layer modelling (FLM) process for the production of polyamide 6 (PA 6) parts, in this work the influence of processing (injection moulding, ...compression moulding and FLM) and molecular weight on the end-use properties of PA 6 is elucidated. Besides its viscosity, the molecular weight of PA 6 also influences crystallinity and crystallization temperature. The mechanical properties of the fabricated specimens were studied in detail, also in the fatigue range, and analysed focusing on the fusion of interfaces in compression moulding and fused layer modelling. The analysis reveals, that the molecular mobility in the melt (i.e. viscosity and diffusion coefficient) as well as the amount and orientation of interfaces (as determined by the processing procedure) strongly influences the end-use properties. In the case of FLM printed parts, mechanical failure due to quasistatic and fatigue loading essentially depends on the quality of fusion of adjacent layers, which is strongly determined by molecular weight and processing temperature. Generally, a lower viscosity of PA 6 favours fusion of adjacent layers.
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•Analysis of influence of processing and molecular weight on properties of PA 6 parts.•Low melt viscosity promotes fusion of adjacent layers in fused layer modelling.•The amount of weld lines influences the mechanical properties under tensile loading.•Injection moulded specimens attain highest stiffness and resistance to fatigue.
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Endowing wound dressings with drug delivery capability is a suitable strategy to transfer medicinal compounds locally to damaged skin layers. These dressings are especially useful for ...accelerating the healing rate in the cases of long-term treatment, and adding more functionalities to the platform. In this study, a wound dressing composed of polyamide 6, hyaluronic acid, and curcumin-loaded halloysite nanotubes (PA6/HA/HNT@Cur) was designed and fabricated for wound healing applications. The physicochemical properties of this platform were investigated through Fourier-transform infrared spectroscopy and field-emission scanning electron microscopy. Moreover, wettability, tensile strength, swelling, and in vitro degradation were assessed. The HNT@Cur was incorporated in the fibers in three concentrations and 1 wt% was found as the optimum concentration yielding desirable structural and mechanical properties. The loading efficiency of Cur on HNT was calculated to be 43 ± 1.8%, and the release profiles and kinetics of nanocomposite were investigated at physiological and acidic pH. In vitro antibacterial and antioxidation studies showed that the PA6/HA/HNT@Cur mat had strong antibacterial and antioxidation activities against gram-positive and -negative pathogens and reactive oxygen species, respectively. Desirable cell compatibility of the mat was found through MTT assay against L292 cells up to 72 h. Finally, the efficacy of the designed wound dressing was evaluated in vivo; after 14 days, the results indicated that the wound size treated with the nanocomposite mat significantly decreased compared to the control sample. This study proposed a swift and straightforward method for developing materials that might be utilized as wound dressings in clinical settings.
The low-viscosity
ε
-caprolactam resin exhibits rapid infiltration in thermoplastic resin transfer molding (T-RTM), causing an unstable flow front at a macroscopic level and uneven impregnation ...between inter-/intra-tows. Uneven impregnation arises when there is a substantial difference between external and capillary pressures, resulting in the formation of micro-/macrovoids in the fiber preform. To address this issue, we propose to minimize total void content by regulating key parameters (contact angle between resin and carbon fiber, surface tension, viscosity, and resin infiltration viscosity) related to capillary pressure. Unlike previous studies focused on optimizing impregnation velocity through external pressure control, our approach employs polyamide 6 oligomers to enhance the compatibility between
ε
-caprolactam resin and carbon fiber, reducing the contact angle and minimizing void content by managing capillary pressure.
