查找使用阿拉丁产品的科研文献

Discarded Polyimide Film-Derived Hierarchical Porous Carbon Boosting the Energy Density of Supercapacitors in Na2SO4 and Spiro-(1,1′)-bipyrrolidinium Tetrafluoroborate Electrolytes

Yuzhe Liu,Qingjuan Ren,Shuo Liang,Lin Li,Shaohui Wang,Zhiqiang Shi,Zonglin Pan,Tonghua Wang

Na2SO4 and spiro-(1,1′)-bipyrrolidinium tetrafluoroborate (SBPBF4) are very promising electrolytes with low cost and high conductivity. For matching with two electrolytes to boost the energy density of the supercapacitor, a suitable electrode needs to be fabricated. Herein, porous carbon derived from discarded polyimide films is fabricated via H3PO4-assisted KOH activation. The hierarchical pore framework of porous carbon, which consists of micro–mesopores concentrated at 0.7–1 nm and >2 nm along with abundant cracks in the cross section, increases the effective energy storage sites and facilitates the ion diffusion rate of electrolytes. The high synergy between electrolytes and the architecture of electrodes endows the symmetrical capacitors (SCs) with outstanding performance. The SC in the Na2SO4 electrolyte delivers the operating voltages of 1.8 V and an energy density of 23.2 Wh kg–1 at a power density of 450 W kg–1. In the SBPBF4 electrolyte, the SC exhibits a high withstand voltage of 3.2 V and a conspicuous energy density of 70.2 Wh kg–1 at a power supply of 320 W kg–1. This work constructs a cooperative system of porous carbon electrodes and electrolytes boosting the energy density of supercapacitors and a sustainable strategy for resource utilization of discarded polyimide films.

Fabrication of polyimide foams with superior mechanical and flame resistance properties utilizing the graft copolymerization between red phosphorus and graphene oxide

Hongtao Liu,Yi Guo,Huafeng Tian,Yuanyuan Yao,Qian Liu,Aimin Xiang,Hongfu Zhou

In this work, red phosphorus (RP) grafted graphene oxide (GO) was generated inside polyimide foam (PIFs) matrices using a novel method. Definite chemical interaction between RP and GO was confirmed. The RP grafted GO (GO-RP) as a beneficial additive greatly improved the mechanical, thermal and flame resistance properties of the PIFs. Scanning electron microscopy (SEM) revealed the cell size of PIFs/GO-RP minished and homogenized when compared to the pristine PIF. The mean cell diameter decreased to 0.29 mm from 0.38 mm and the open cell content was reduced by 4%. The specific strength increased greatly after adding GO-RP, from 2.14 × 10 3  N·m/kg to 2.48 × 103 N·m/kg. Besides, the pyrolysis temperature of PIFs/GO-RP shifted to a higher value and the carbon residue increased at 800 °C, indicating excellent thermal properties. The flame resistance property of foams significantly enhanced while the peak heat release rate (PHRR) was reduced by 66% compared to that of the pristine foams. The craft of PIFs/GO-RP presented here has greatly provided an potential value in the design of materials.

Effects of ionic liquid types on the tribological, mechanical, and thermal properties of ionic liquid modified graphene/polyimide shape memory composites

Yuting Ouyang,Qiu Zhang,Xiukun Liu,Ruan Hong,Xu Xu,Shaorong Lu,Yuqi Li

Different ionic liquid modified graphene nanosheets (IG) were induced into polyimide (PI) to improve the tribological, thermal, and mechanical properties of shape memory IG/PI composites. The results demonstrated that when using 1-aminoethyl-3-methylimidazole bromide to modify graphene nanosheets (IG-1), the laser-driven shape recovery rate of IG-1/PI composites (IGPI-1) reached 73.02%, which was 49.36% higher than that of pure PI. In addition, the IGPI-1 composite materials reached the maximum shape recovery rate within 15 s. Additionally, under dry sliding, the addition of IG can significantly improve the tribological properties of composite materials. IGPI-1 exhibited the best self-lubricating properties. Compared with pure PI, the friction coefficient (0.19) and wear rate (2.62 × 10–5) mm3/Nm) were reduced by 44.1% and 24.2%, respectively, and the T10% of IGPI-1 increased by 32.2°C. The Tg of IGPI-1 reached 256.5°C, which was 8.4°C higher than that of pure PI. In addition, the tensile strength and modulus of IGPI-1 reached 82.3 MPa and 1.18 GPa, which were significantly increased by 33.6% and 29.8%, respectively, compared with pure PI. We hope that this work will be helpful for the preparation of shape memory materials with excellent tribological, thermal, and mechanical properties.

Synergistic effect of polyimide charring agent and hexaphenoxycyclotriphosphazene on improving fire safety of polycarbonate: High graphitization to strengthen the char layer

Haisheng Feng,Lijun Qian,Lingang Lu

To meet the increasingly stringent requirements for the excellent fire safety, low addition, low cost, and good mechanical properties for polycarbonate (PC), a novel aromatic polyimide (API) charring agent was synthesized and used synergistically with hexaphenoxycyclotriphosphazene (HPCTP) to flame-retardant (FR) PC. The incorporated API and HPCTP improved FR performance and the fracture toughness of the PC, simultaneously. The 4H-2A passed the UL94 V-0 rating with a limited oxygen index of 32.5%. Moreover, the heat release rate of the PC was also suppressed significantly by the dense and strengthening carbon layer. The mechanism of synergistic charring effect of API and HPCTP were analyzed: In the initial and developing stages of combustion (below 450°C), the quenching effect and dilution effect of HPCTP played a major role in flame retardancy; and due to the barrier function of the highly graphitized char layer, the combustion process rapidly enters weakening stages (above 450°C) and finally extinguishes. Moreover, it was founded that API improved the antiimpact performance of PC matrix, which offsets the negative effect of HPCTP on the impact performance of PC matrix.

The impact of the flexibility of photosensitive polyimide backbone on the properties of liquid-crystal alignment under non-polarised ultraviolet light

Fei Wang,Gang Zhu,Xinjian Gong,Pengfei Geng,Zhenwei Gao,Yinghan Wang

Bioinspired construction of BN@polydopamine@Al2O3 fillers for preparation of a polyimide dielectric composite with enhanced thermal conductivity and breakdown strength

Duan Guangyu,Cao Yutong,Quan Jiayou,Hu Zuming,Wang Yan,Yu Junrong,Zhu Jing

This paper reports that a novel polyimide dielectric composite with three-dimensional (3D) thermally conductive networks and enhanced breakdown strength was firstly fabricated by filling with core-double-shell structured F-BA fillers. The F-BA particles were composed of nano-sized boron nitride (nBN) and polydopamine-coated spherical alumina (PDA@Al 2 O 3 ). Moreover, to ameliorate interfacial compatibility between F-BA fillers and PI matrix as well as restrain phonons scattering during propagation, 1,6-Diisocyanatohexane (HDI) was innovatively used as “bridge agent” to connect and functionalize nBN and PDA@Al 2 O 3 particles to generate core-double-shell structure. The results revealed that breakdown strength of PI dielectric composite with 25 wt % F-BA fillers was increased to 146.3 MV·m −1 , showing an increment of 68.5% in comparison with that of pure PI. Furthermore, the thermal conductivity of F-BA/PI composite with 25 wt % F-BA fillers increases to 6.41 W/m·K of in-plane direction and 1.01 W/m·K of through-plane direction, respectively, which shows 36 and 6 times higher than polyimide of 0.18 W/m·K. For dielectric properties of F-BA/PI composite, the dielectric constant and loss are less than 3.5 and 0.02, respectively. Considering these properties, the prepared PI dielectric composite shows potential application in high-performance electronic devices.

Fabrication of flame-retardant and smoke-suppressant isocyanate-based polyimide foam modified by silica aerogel thermal insulation and flame protection layers

Gaohui Sun,Tianjiao Duan,Cheng Liu,Liu Zhang,Rongrong Chen,Jun Wang,Shihui Han

Because of containing urea groups, flame resistance and smoke releasing behaviors of isocyanate-based polyimide foam (IBPIF) produced using free foaming technology require further improvement. In this work, silica aerogel layers were incorporated into cells of IBPIF through an in situ growth process of silica sol (SS). Compared with silica aerogel particles directly mixed into the foaming slurry, the silica aerogel layers that firmly attached to the pores and surfaces of cells not only provided exceptional thermal insulation and flame protection, but also kept original cellular structure. With increase in ratio of SS mass to IBPIF volume, silica aerogel incorporation dosage was gradually increased. Accompanied by flame resistance was obviously improved and smoke releasing behavior was effectively suppressed. Those were indicated by the improved limiting oxygen index (LOI), decreased heat release rate (HRR), peak of HRR, and specific optical density of smoke (Ds) in trials with pilot flames. Compared with pure IBPIF, when the ratio reached to 5/15 g/cm 3 , it resulted in LOI increasing from 22.0% to 33.0%, peak of HRR, total smoke production (TSP), and maximum value of Ds decreasing from 174 to 72 kW/m 2 , 1.11 to 0.37 m 2 /m 2 , 45.90 to 17.45, respectively.

Enhancing the Toughness of Free-Standing Polyimide Films for Advanced Electronics Applications: A Study on the Impact of Film-Forming Processes

Ruoqing Zhao,Hao Wu,Xuan Dong,Manzhang Xu,Zhenhua Wang,Xuewen Wang

High-quality and free-standing polyimide (PI) film with desirable mechanical properties and uniformity is in high demand due to its widespread applications in highly precise flexible and chip-integrated sensors. In this study, a free-standing PI film with high toughness was successfully prepared using a diamine monomer with ether linkages. The prepared PI films exhibited significantly superior mechanical properties compared to PI films of the same molecular structure, which can be attributed to the systematic exploration of the film-forming process. The exploration of the film-forming process includes the curing procedures, film-forming substrates, and annealing treatments. Additionally, the thickness uniformity and surface homogeneity of free-standing films were crucial for toughness. Increasing the crystallinity of the PI films by eliminating residual stress also contributed to their high strength. The results demonstrate that by adjusting the above-mentioned factors, the prepared PI films possess excellent mechanical properties, with tensile strength and elongation at break of 194.71 MPa and 130.13%, respectively.

Formation of Macrovoid-Free PMDA-MDA Polyimide Membranes Using a Gelation/Non-Solvent-Induced Phase Separation Method for Organic Solvent Nanofiltration

Yuan Li,Jingjing Xue,Xu Zhang,Bing Cao,Pei Li

For the first time, we demonstrated that the gelation/nonsolvent induced phase separation (Gel-NIPs) method could be applied to fabricate macrovoid-free flat-sheet nanofiltration membranes based on organo-insoluble polyimide (pyromellitic dianhydride–4,4′-diaminodiphenylmethane; PMDA-MDA). Specifically, the PMDA-MDA polyamic acid (PAA)/N-methyl pyrrolidone (NMP) dope was cast on a polyester-based nonwoven, gelatinized in a fridge, and immersed in water. Gelation greatly inhibited the growth of macrovoids and resulted in an asymmetric membrane with high permeability but low rejection. After adding 4 wt % TiO2 sol into the dope, the gelation process was accelerated, and the PMDA-MDA/TiO2 membrane had a dense skin layer with a macrovoid-free cross-sectional structure. Its permeability and rejection to Rose Bengal (RB, Mw = 1017 Da) were 8.3–9.2 L·m–2·h–1·bar–1 and 89.5–95.7%, respectively, in solvents including DMF, THF, and DMSO. The separation performance was stable at a feed pressure of 25 bar, indicating a great potential for organic solvent nanofiltration (OSN).

Preparation of tetraethoxysilane-based silica aerogels with polyimide cross-linking from 3, 3′, 4, 4′-biphenyltetracarboxylic dianhydride and 4, 4′-oxydianiline

Fei Zhifang,Yang Zichun,Chen Guobing,Li Kunfeng

Abstract Polyimide cross-linked silica aerogels with different weight percentages of polyimide were prepared through sol–gel technology and supercritical CO 2 fluid drying technology. Tetraethoxysilane (TEOS) was used as a silica source precursor, 3-aminopropyltriethoxysilane (APTES) end-capped polyimide was used as a cross-linking agent, derived from 3, 3′, 4, 4′-biphenyltetracarboxylic dianhydride (BPDA) and 4, 4′-oxydianiline (ODA). The acid produced during the imidization process catalyzed the hydrolysis reaction without additional catalyst. After condensation reaction catalyzed by ammonium hydroxide solution, the polyimide cross-linked silica gels were obtained and then dried in supercritical CO 2 . The polyimide cross-linked silica aerogels have low density (0.132~0.187 g/cm 3 ), high specific surface area (623–741 m 2 /g), low thermal conductivity (0.0306~0.0347 W/m K at room temperature), relatively high compressive strength (1.03~3.82 MPa) and high thermal decomposition temperature (360 °C). This research provided a simple and efficient method that used the polyimide as a strengthening phase to improve the mechanical properties of TEOS-based silica aerogels.

Enhanced thermal and electrical insulation properties of polyimide films determined via a two-dimensional layered double hydroxide–potassium perfluorooctane sulfonate material

Lili Ma,Qingquan Lei

Polyimide (PI) films used in aerospace and rail applications are degraded by thermal, chemical, and electric power under the effect of insulation aging. To prevent these types of degradation, we prepared nanocomposite films of PI and layered double hydroxide (LDH) modified with the potassium perfluorooctane sulfonate (FS) by an in situ method. On the whole, the glass-transition temperature, dielectric constant (ɛ′), and corona-resistance lifetime of the nanocomposite films increased over those of the pure PI film, but the temperature at 10 wt % weight loss, breakdown strength, and volume resistance decreased correspondingly as a whole. The PI matrix was protected by the inorganic material of LDH–FS with a high ɛ′ from corona corrosion. Furthermore, the heat and chemical interactions of the composite films improved the corona-resistance lifetime, despite the decrease in the breakdown strength; this should result in promising applications for insulation parts of variable-frequency motors. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135 , 46528.

Constructing high-toughness polyimide binder with robust polarity and ion-conductive mechanisms ensuring long-term operational stability of silicon-based anodes

Yongjun Kang,Nanxi Dong,Fangzhou Liu,Daolei Lin,Bingxue Liu,Guofeng Tian,Shengli Qi,Dezhen Wu

Silicon-based materials have demonstrated remarkable potential in high-energy–density batteries owing to their high theoretical capacity. However, the significant volume expansion of silicon seriously hinders its utilization as a lithium-ion anode. Herein, a functionalized high-toughness polyimide (PDMI) is synthesized by copolymerizing the 4,4′-Oxydiphthalic anhydride (ODPA) with 4,4′-oxydianiline (ODA), 2,3-diaminobenzoic acid (DABA), and 1,3-bis(3-aminopropyl)-tetramethyl disiloxane (DMS). The combination of rigid benzene rings and flexible oxygen groups (-O-) in the PDMI molecular chain via a rigidness/softness coupling mechanism contributes to high toughness. The plentiful polar carboxyl (–COOH) groups establish robust bonding strength. Rapid ionic transport is achieved by incorporating the flexible siloxane segment (Si-O-Si), which imparts high molecular chain motility and augments free volume holes to facilitate lithium-ion transport (9.8 × 10 − 10  cm 2  s −1 vs. 16 × 10 − 10  cm 2  s −1 ). As expected, the SiO x @PDMI-1.5 electrode delivers brilliant long-term cycle performance with a remarkable capacity retention of 85% over 500 cycles at 1.3 A g −1 . The well-designed functionalized polyimide also significantly enhances the electrochemical properties of Si nanoparticles electrode. Meanwhile, the assembled SiO x @PDMI-1.5/NCM811 full cell delivers a high retention of 80% after 100 cycles. The perspective of the binder design strategy based on polyimide modification delivers a novel path toward high-capacity electrodes for high-energy–density batteries.