Poly Amide-imide Research Articles

Topological Polymer Networks-Enabled Mechanically Strong Polyamide-Imide Aerogel Fibers for Thermal Insulation in Harsh Environments.

Aerogel fibers have sparked substantial interest as attractive candidates for thermal insulation materials. Developing aerogel fibers with the desired porous structure, good knittability, flame retardancy, and high- and low-temperature resistance is of great significance for practical applications; however, that is very challenging, especially by using an efficient method. Herein, mechanically strong and flexible aerogel fibers with remarkable thermal insulation performance are reported, which are achieved by constructing stiff-soft topological polymer networks and a multilevel hollow porous structure. The combination of polyamide-imide (PAI) with stiff chains and polyurethane (PU) with soft chains is first found to be able to form a topological entanglement architecture. More importantly, multilevel hollow pores can be constructed synchronously through just a one-step and green wet-spinning process. The resultant PAI/PU@340 aerogel fibers show an ultrahigh breaking strength of 94.5 MPa and superelastic property with a breaking strain of 20%. Furthermore, they can be knitted into fabrics with a low thermal conductivity of 25 mW/(m·K) and exhibit attractive thermal insulation property under extremely high (300 °C) and low temperatures (-191 °C), implying them as promising candidates for next-generation thermal insulation materials.

Optimization of Electrospun TORLON® 4000 Polyamide-Imide (PAI) Nanofibers: Bridging the Gap to Industrial-Scale Production.

Polyamide-imide (PAI) is an exceptional polymer known for its outstanding mechanical, chemical, and thermal resistance. This makes it an ideal choice for applications that require excellent durability, such as those in the aerospace sector, bearings, gears, and the oil and gas industry. The current study explores the optimization of TORLON® 4000 T HV polyamide-imide nanofibers utilizing needleless electrospinning devices, ranging from laboratory-scale to industrial-scale production, for the first time. The PAI polymer has been dispersed in several solvent systems at varying concentrations. The diameter of the electrospun PAI nanofibers ranged from 65.8 nanometers to 1.52 μm. Their filtering efficiency was above 90% for particles with a size of 0.3 microns. The TGA results proved that PAI nanofibers have excellent resistance to high temperatures up to 450 °C. The PAI nanofibers are ideal for hot air intake filtration and fire-fighter personal protection equipment applications.

Hydrolytic Aging of Wire Enameled with Polyesterimide and Polyamide Imide Used in Electrical Machines

Hydrolytic Aging of Wire Enameled with Polyesterimide and Polyamide Imide Used in Electrical Machines

Room temperature 3D printing of high-temperature engineering polymer and its nanocomposites with porosity control for multifunctional structures

There is an increasing demand for the development of additive manufacturing techniques that support diverse materials with specific properties and performance characteristics. Engineering polymers are a type of high-performance material with lightweight, strong, and heat resistant. These properties enable replacing more dense materials, such as metals, and make them essential for application in various high-tech industries. Polyamide-imide (PAI) is an advanced engineering polymer with exceptional mechanical properties and thermal stability. However, due to the high glass transition temperature (Tg), the additive manufacturing of PAI 3D structures has not been realized through existing technologies. This study demonstrates room-temperature 3D printing for the PAI and PAI-based functional nanocomposite. Moreover, through a designed post-process drying procedure to control porosity, it is possible to enhance 3D structures' mechanical properties and functionality. The nanocomposite 3D systems exhibit a tensile strength of up to 105 MPa and Tg of 295 °C with aramid nanofibers, and an electrical conductivity of 200 S/m at 250 °C with carbon nanotubes. Given the high performance of printed nanocomposites with designed processes, we explore the potential and expended usage of more robust and lightweight polymer structures featuring diverse functionality for high-tech industries such as aerospace, air mobility, and semiconductor packaging.

Electro‐Conductive Ti3C2 MXene Multilayered Membranes: Dye Removal and Antifouling Performance

AbstractThis work describes the fabrication of a novel electroconductive membrane made of Ti3C2Tx (MXene) nanosheet coating through a one‐step pressure‐assisted technique. Ti3C2‐MXene is firmly attached over a polyamide–imide (PAI) microfilter by employing a binder composed of carboxymethyl cellulose (CMC)/glutaraldehyde (GA). Through coating a proper amount of multilayer Ti3C2‐MXene, the electrical conductivity of 174 ± 0.16 S m−1 is achieved. The rejection rates of reactive red 120 (RR120), reactive black (RB), and methyl orange (MO) by the pristine PAI membrane are 45.2%, 40.81%, and 33.65%, respectively. However, rejection rates significantly improve with the Ti3C2 MXene coating to over 99.71%, 97.95%, and 68.91% for RR120, RB, and MO. Applying a 4 V cathodic potential resulted in a flux recovery ratio (FRR) of 99.83% and a flux decline rate (FDR) of less than 1% during humic acid (HA) filtration. Without applying voltage, the MXene‐coated membrane shows an FRR and FDR of 92.51% and 45.56%, respectively. Surface energy analysis reveals strong repulsive interactions between foulants and the membrane surface. Moreover, the surface free energy indicates that foulants such as sodium alginate (SA) and bovine serum albumin (BSA) exhibit stronger adhesion to the membrane than HA, consistent with the fouling experiment results.

Atomic oxygen resistance and tribological performance of a self-stratifying Polydimethylsiloxane-polyamide-imide/molybdenum disulfide lubricating coating

Bonded lubricating coatings for spacecraft are subject to the combined effect of the low-earth orbit environment, ground environment and mechanical wear, making it difficult to meet long-life and high-reliability requirements. In this study, Polydimethylsiloxane (PDMS)-modified polyamide-imide (PAI) /molybdenum disulfide (MoS2) coatings were prepared using a self-stratifying strategy. The structural and tribological performance changes of coatings after atomic oxygen (AO) irradiation were investigated. The results showed that the PDMS segments improved the AO erosion resistance due to the inorganic layer produced on the surface of coating. The structural integrity of the binder and lubricant decreased the effect of AO erosion on the tribological performance of lubricating coatings. The PDMS-PAI/MoS2 coating have application prospects in the field of lubricating coating for spacecraft.

Colorless Polyamide–Imide films with tunable coefficient of thermal expansion and their application in flexible display devices

In a previous study, our group reported the fabrication of a series of colorless polyamide–imide (PAI) films (named TFDB-DABPO-TPC-6FDA) with good thermal stability. To further improve their properties, herein, the effect of adding blocks in molecules on the performance of polyimide (PI) films was studied. By changing the order and amount of the four reactants added each time, seven PAIs with different structures and block lengths were obtained. Their glass transition temperatures (Tg) ranged from 359 °C to 368 °C, and their transmittance at 430 nm (T430) was 82.7%–85.1 %. Importantly, the coefficient of thermal expansion (CTE) of these seven PAIs decreased almost linearly from 31.1 to 18.5 ppm/K, making it possible to fabricate PI films with a desired CTE value for specific applications. Furthermore, the PAI-6-T film, which had the longest polyamide block and the best overall performance (Tg = 362 °C, CTE = 18.5 ppm/K, T430 = 83.1 %, tensile strength = 179.4 MPa, dielectric constant (Dk) = 2.53, and dielectric loss (Df) = 0.0088 at 10 GHz) was used as a substrate to fabricate a flexible printed circuit board (FPCB) and an organic light-emitting diode (OLED). Mechanical–electrical test shows that Ag was firmly bonded with the PAI-6-T film, and the resistance of FPCB@PAI-6-T only increased by 14.8 % after 150,000 folding tests. The flexible OLED@PAI-6-T exhibited pure green emission, a turn-on voltage of 3.0 V, a luminance of 1000 cd/m2 at 6 V, a current efficiency of 1.31 cd/A, and an external quantum efficiency of 0.44 %.

Oriented BN/BNNT heterostructure constructed by interface engineering strategy for polyamide-imide composite film with advanced flexibility and thermally conductive properties

Thermal conductive polymeric materials have aroused increasing attention as thermal management materials in the field of intelligent electronic devices due to their intriguing advantages. However, the discontinuity of phonon transmission path construction represents the bottleneck for thermal conductivity enhancement of composite materials, which limits the practical application of composite materials. Herein, flexible polyamide-imide (PAI) thermally conductive composite films with hierarchical structure composed of synergistically assembled functionalized boron nitride nanosheets (FBN) and polydopamine (PDA)-modified boron nitride nanotubes (FBT) by layer-by-layer assembly strategy are constructed. Benefitting from the optimized interface engineering with the ordered oriented arrangement FBN/FBT filler structure, the obtained composite film with optimized hybrid filler contents exhibits the super high thermal conductivity of 71.1 W·m−1·K−1, prominent thermal conductivity enhancement as high as 3663 % and excellent mechanical flexibility. The introduction of FBT can further expand the thermal contact area attributed to its inherent high thermal conductivity and aspect ratio. Additionally, the consecutive dual-channel phono transmission paths can be constructed in PAI composites under the synergistic action of FBN and FBT, further improving the phonon transmission density and suppressing phonon scattering, which endows PAI composite films with excellent thermal conductivity under low load of filler. The resulting multifunctionalities make the PAI composite films promising for flexible intelligent wearable electronic devices as thermal management materials.

Research Progress in Special Engineering Plastic-Based Electrochromic Polymers.

SPECPs are electrochromic polymers that contain special engineering plastic structural characteristic groups (SPECPs). Due to their high thermal stability, mechanical properties, and weather resistance, they are also known as high-performance electrochromic polymer (HPEP or HPP). Meanwhile, due to the structural characteristics of their long polymer chains, these materials have natural advantages in the application of flexible electrochromic devices. According to the structure of special engineering plastic groups, SPECPs are divided into five categories: polyamide, polyimide, polyamide imide, polyarylsulfone, and polyarylketone. This article mainly introduces the latest research on SPECPs. The structural design, electrochromic properties, and applications of these materials are also introduced in this article, and the challenges and future development trends of SPECPs are prospected.

Electrospinning of High-Performance Nanofibres: State of the Art and Insights into the Path Forward

Nanofibrous membranes have gained interest for their small pore size, light weight, and excellent filtration. When produced from high-performance polymers, nanofibrous membranes also benefit from excellent mechanical properties, thermal resistance, and chemical resistance. Electrospinning is a common method of producing high-performance nanofibres. However, there are still major challenges with the dissolution and electrospinning of these polymers, as well as in the performance of the resulting nanofibres, which is often less than what would be expected from a conventional high-performance fibre. This review assesses the state of progress in the electrospinning of five high-performance fibres: meta-aramid (m-aramid), para-aramid (p-aramid), polyamide-imide (PAI), polybenzoxazole (PBO), and polybenzimidazole (PBI). Polymers that can be readily dissolved in organic solvents, such as m-aramid, PAI, and PBI, have been more widely researched for electrospinning compared to those that can only be spun from precursors or dissolved in non-volatile solvents. Major focuses within the literature include optimizing the electrospinning process and improving the mechanical performance of the nanofibres. This review demonstrates a clear need for more standardized characterization methods and consideration for the longevity of the nanofibrous membranes. Future research should also focus on scale-up methods of electrospinning so that the benefits of nanofibres made from high-performance polymers can be leveraged by the industry.

Polyamide-imides as novel high performance primary protective coatings of silica optical fibers: Influence of the structure and molecular weight

Polyimides are commonly used as primary protective optical fiber coatings for high-temperature applications. However, a number of significant drawbacks such as thermal and hydrolytic instability of polyamiс acid, its incomplete transformation into polyimide, several deposition cycles of the required thickness and insufficient adhesion of polyimide coatings to the surface complicate the manufacture of special optical fibers and their widespread use. In this study we showed the principal possibility of utilizing polyamide-imides (PAIs) as primary protective coatings of high operational reliability. Two series of high-molecular-weight (Mw = 84–365 kDa) and thermostable (T10% = 490–520 °C) PAIs were synthesized by low temperature polycondensation of terephthaloyl chloride and various tetracarboxylic acid dianhydrides with 9,9-bis(4-aminophenyl)fluorene or 2,2′-bis(trifluoromethyl)benzidine in NMP. Coatings of a thickness of 10–15 μm with good adhesion to the optical fiber were formed from the PAIs solutions in NMP with no any additives and in a single application cycle. Apart from the influence of solution viscosity and drawing parameters on the coating quality, a particular attention was paid to the dependency of the strength and mechanical reliability of the fibers with resulting coatings on the structure and molecular weight of the polymer. It was established that the fibers coated with PAIs prepared from 2,2′-bis(trifluoromethyl)benzidine (Mw = 190–200 kDa) can withstand 3 and 72 h annealing at 350 and 300°С, respectively, retaining >80% of the original strength. Thus, PAIs are considered as a promising candidate for further studies, i.e., for the creation of optical fiber sensors for large-scale applications.

Polyamide-imide copolymer-derived carbon molecular sieve membranes for efficient hydrogen/carbon dioxide separation

Carbon molecular sieve (CMS) membranes are emerging porous carbon membranes for chemical separation and purification. Polyamide-imide (PAI) copolymers have shown attractive separation performance for natural gas upgrading and organic solvent separations. However, PAIs are rarely used as precursors to derive CMS membranes. This work shows that CMS hollow fiber membranes made from a PAI (Torlon®) can provide highly competitive H2 permeability and H2/CO2 selectivity overcoming the 2008 Robeson upper bound under both single-gas and mixed-gas permeation. With imide and amide moieties, the PAI showed intermediate H2/CO2 separation performance between a polyimide (PI) and a polyaramid (PA). Interestingly, the trend was translated to the CMS membranes, i.e., the PAI-derived CMS membrane showed intermediate H2/CO2 separation performance between the PI-derived CMS membrane and PA-derived CMS membrane with an excellent balance of H2 permeability and H2/CO2 selectivity. Sorption studies indicate that the PAI-derived CMS membrane had intermediate H2 diffusivity and H2/CO2 diffusion selectivity, which was further attributed to its intermediate ultramicropore size. To our best knowledge, this was the first report of PAI-derived CMS hollow fiber membranes with competitive gas separation performance and the first investigation of the chemistry and pore structure of PAI-derived porous carbon. This study also underscores the role of precursor backbone chemistry in tailoring CMS membrane properties, further suggesting that CMS membranes derived from copolymers comprising mixed backbone chemistry can give simultaneously attractive permeability and selectivity.

Thermal Evaluation of Silica-Based Insulated Magnet Wires from the Sol-Gel Process.

The conventional enameling process used in the fabrication of magnet wires requires harmful processes and products. The target of the industry in the actual context of electrification is to increase the electrical machines' efficiency. Indeed, the electrical insulation systems (EIS) of an electrical machine undergo various environmental constraints that can shorten their lifespans. Consequently, aspects of the insulation need to be improved, such as its thermal resistance. One of the challenges is to implement sustainable technology without losing performance. This work consists of the thermal performance evaluation of new magnet wires insulated by three types of composites of silica-based solution from the Sol-gel process and amorphous polyamide-imide (PAI). These composite coats are overcoated by an extruded thermoplastic resin with and without fillers. Different types of insulation are tested and compared to determine the better configuration. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) analysis, scanning electron microscopy (SEM) analysis, curing characteristics by tangent delta curve, and thermal-aging tests at three temperatures were carried out on the different EIS systems. Dielectric measurements were made between thermal-aging cycles. Their basic mechanical, electrical, and thermal characteristics are promising: the cut-through temperature is situated above 430 °C, their breakdown voltage values are between 5 kV and 9 kV (grade 3), and a good adhesion (overcoming more than 140 turns on a peel test). The thermal-aging results have been consistent with the TGA analysis results. The thermal index following the IEC standards was estimated for the selected EIS, which would have the main basic characteristics of a magnet wire of 200 class; moreover, it would be a greener enameled wire compared to the conventional one.

Synthesis of highly thermoplastic polyamide-imides with high transparency and low coefficient of thermal expansion

With the applications of injection molding optical components, higher requirements are put forward for thermoplastic polyimides (TPIs) in terms of transparency and coefficient of thermal expansion (CTE). Two series of thermoplastic polyamide-imides (PAIs) derived from 2,2'-(2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diyl)bis(1,3-dioxoisoindoline-5-carbonyl chloride) (CT-TFDB) and rigid/flexible aromatic diamines with specific groups were prepared at room temperature, which both exhibited moderate glass transition temperatures (Tgs) in the range of 251–274 °C, excellent dimensional stability with CTE values of 17–34 ppm/K, high transmittance (T450nm ≥ 59%) and good thermoplasticity with -d logE'/dT values of 0.08–0.34. Among them, PAI-2a exhibited the best comprehensive performances, especially for the high thermoplasticity (-d logE'/dT = 0.34), low CTE (28 ppm/K), and high transmittance (T450nm = 84%), which provides a new strategy for the research on thermoplastic PAI materials in optical field.

Study on Flame Retardancy of Enamelled Wires Using a Cone Calorimeter

The flame-retardancy of enamelled wires was studied by using a cone calorimeter. The characteristic parameters including time to ignition, heat release rate, total smoke release and so on, were obtained. The effect of heat radiation flux on the flame retardancy was analyzed. The results show that the flame retardancy of enamelled wires is related to the content of different components in the composite insulation layer. Polyimide enamelled wires have good flame retardant performance, followed by corona resistant wire with filler, and ordinary polyamide imide composite polyester imide enamelled wire has poor flame retardant performance. In conclusion, the heat release rate measured by cone calorimeter can be used for evaluate the flame retardancy of enamelled wires and provide a reference for the development and application of flame retardant enamelled wires.

Mechanical Properties and Synergistic Interfacial Interactions of ZnO Nanorod-Reinforced Polyamide–Imide Composites

Metal oxide nanoparticle -reinforced polymers have received considerable attention due to their favorable mechanical properties compared to neat materials. However, the effect of nanoscale reinforcements of the interface on the composites' mechanical properties has not been investigated in-depth to reach their optimal performance in structural applications. Aiming at revealing the effect of synergistic interfacial interactions on the mechanical properties of polymer composites, using a nanoscale reinforcement, herein, a series of zinc oxide nanorod-reinforced polyamide-imide (PAI)/ZnO) composites were fabricated and their mechanical properties and viscoelastic responses were investigated. The composite prepared by reinforcing them with 5 wt % ZnO nanorods resulted in improved elastic modulus, stiffness, and hardness values by 32%, 14% and 35%, respectively, compared to neat polymer thin films. The viscoelastic dynamics of the composites revealed that there was an 11% increase in elastic wave speed in the composite, containing 5 wt % ZnO nanorods, indicating better response to high impacts. Delayed viscoelastic response decreased by 67% spatially and 51% temporally, with a corresponding decrease in the creep rate, for the 5 wt % ZnO nanorod- containing composite, evidencing its potential applicability in high strength lightweight structures. The improved mechanical properties with respect to the filler concentration evidence strong particle-polymer interfacial interactions, creating "chain-bound" clusters, providing clear reinforcement and polymer chain mobility retardation. However, hypervelocity impact testing revealed that all the composites' films were vulnerable to hypervelocity impact, but the spallation region of the composite films reinforced with 2.5 wt % and 5 wt % ZnO nanorods exhibited a cellular-like matrix with shock-induced voids compared to a rather hardened spallation region with cracks in the neat film.

High efficiency synthesis of temperature resistant polyamideimide resin with branched structure using microreactor

Polyamideimide (PAI) resins have a wide range of applications. It is significant to explore novel and efficient synthesis methods. This paper describes a method for the rapid synthesis of branched PAIs in a microreactor using 4,4-methylenediphenyl diisocyanate (MDI) and 1,2,4-benzoic acid anhydride (TMA) as substrates. The isocyanate group reacts with the amide bond to build the branched structure. A high molar ratio of substrate helps to form more branched structures. High molar ratios also lead to high molecular weight products with narrow distribution, where the number average molecular weight of PAI-1.35 is as high as 1828.14 kg/mol and the molecular weight distribution index is only 1.09. Some oligomers are present in the products obtained at low molar ratios, which affect the mechanical and thermal properties of the products. Curing with epoxy resin can form a bulk structure and eliminate the effect of oligomers. The PAI films obtained after curing have excellent mechanical and thermal properties.

Novel piezoelectric properties of electrospun polyamide-imide nanofiber membranes

Electrospun polyamide-imide (PAI) nanofiber membranes exhibit excellent piezoelectric properties under both ambient temperature and high-temperature conditions.

How moisture driven mechanochemistry stabilizes transfer film adhesion and cohesion in ultralow wear PTFE composite

Prior studies suggest mechanical interlocking, preferential adhesion of polar polymers, and PTFE tribochemistry all contribute to the wear reduction in polar polymer-filled PTFE composites; whereas their relations remain poorly understood. This study aims to decouple the relevant mechanisms by investigating wear and tribofilm environmental sensitivities of a 5 wt% polyamide-imide (PAI) filled PTFE composite. The results highlight (1) strong correlation between a carboxylate-salt-rich transfer film and ultralow wear, and (2) a tribochemical interface gradient that discourages transfer film removal. We proposed that PTFE tribochemistry induces ultralow wear by significantly increasing (1) transfer film adhesion through a virtuous cycle of tribochemical accumulation and wear reduction and (2) transfer film cohesion by promoting a surface energy interface gradient beneficial to low wear.

Colorless Polyamide–Imide Films with Enhanced Thermal and Dimensional Stability and Their Application in Flexible OLED Devices

In this study, we intend to solve the problem of the low glass transition temperature (Tg) and the high coefficient of thermal expansion (CTE) that colorless polyimide (PI) films always exhibit. First, we copolymerized 2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diamine (TFDB) with 4,4′-(hexafluoroisopropene) diphthalic anhydride (6FDA) and p-phthaloyl chloride (TPC) and obtained a series of transparent and colorless films (PAI-10). These PAI films showed a high Tg of 346–362 °C and a low CTE of 25.2–62.9 ppm/K, which were better than those of PI6FDA-TFDB. Subsequently, three rigid diamines, p-phenylenediamine (p-PDA), 5-amino-2-(4-aminophenyl)benzoxazole (DAPBO) and 5-amino-2-(4-aminophenyl)benzimidazole (DAPBI), were used to replace 10% of the TFDB (PAI-9P-5, PAI-9O-5, and PAI-9I-5, respectively) to investigate the effect of the rigid structure on the thermal and optical properties. The results showed that rigid structures can greatly improve the thermal properties but impair transparency to some extent. Among these, PAI-9O-5 possessed the best performance with T430 of 81.9%, Tg of 364 °C, and CTE of 19.8 ppm/K. Furthermore, we fabricated an organic light-emitting diode (OLED) with PAI-9O-5 as the substrate. The flexible and bendable OLED@PAI-9O-5 showed typical green emission at 520 nm, a turn-on voltage of 2.9 V, a luminance of 1000 cd/m2 at 5 V, a current efficiency (CE) of 2.53 cd/A, and an external quantum efficiency (EQE) of 0.81%, which were comparable to those of devices fabricated on conventional glass substrates.