Property evolution and molecular mechanisms of aluminized colorless transparent polyimide under space ultraviolet irradiation

Polyimide (PI) with ultra-high thermal resistance and stability is essential for application as a flexible substrate in electronic devices. Here, the Upilex-type polyimides, which contained flexibly “twisted” 4,4′-oxydianiline (ODA), have achieved various performance improvements via copolymerization with a diamine containing benzimidazole structure. With the rigid benzimidazole-based diamine bearing conjugated heterocyclic moieties and hydrogen bond donors fused into the PI backbone, the benzimidazole-containing PI showed outstanding thermal, mechanical, and dielectric performance. Specifically, the PI containing 50% bis-benzimidazole diamine achieved a 5% decomposition temperature at 554 °C, an excellent high glass transition temperature of 448 °C, and a coefficient of thermal expansion lowered to 16.1 ppm/K. Meanwhile, the tensile strength and modulus of the PI films containing 50% mono-benzimidazole diamine increased to 148.6 MPa and 4.1 GPa, respectively. Due to the synergistic effect of rigid benzimidazole and hinged, flexible ODA, all PI films exhibited an elongation at break above 4.3%. The electrical insulation of the PI films was also improved with a dielectric constant lowered to 1.29. In summary, with appropriate mixing of rigid and flexible moieties in the PI backbone, all the PI films showed superior thermal stability, excellent flexibility, and acceptable electrical insulation.

Section: Resultssupporting

confidence: 94%

The Pivotal Role of Benzimidazole in Improving the Thermal and Dielectric Performance of Upilex-Type Polyimide

Lian

Zhao

et al. 2023

“…Feng et al considered some of the most used polyimides for space applications and investigated their performance in a simulated vacuum ultraviolet (VUV) environment [ 43 ]. The purpose of their work was to add detailed information about the behavior of these PI-based materials under space-like conditions.…”

Section: Thermal Stability Of Polyimide-based Materials For Space App...mentioning

confidence: 99%

“…Considering the CPI-L/Al sample, a decomposition region was observed, and the maximum degradation rate was near 461 °C ( Figure 3 b). In the case of the CPI-T/Al film, two decomposition regions could be identified ( Figure 3 d), where the second one (near 250 °C) can be ascribed to the emission of small molecules [ 43 , 44 ]. The DMA measurements showed that the T g of the CPI-L/Al and CPI-T/Al films before irradiation was 329 °C and 280 °C, respectively.…”

Section: Thermal Stability Of Polyimide-based Materials For Space App...mentioning

confidence: 99%

A Comprehensive Review on the Thermal Stability Assessment of Polymers and Composites for Aeronautics and Space Applications

Barra,

Guadagno,

Raimondo

et al. 2023

This review article provides an exhaustive survey on experimental investigations regarding the thermal stability assessment of polymers and polymer-based composites intended for applications in the aeronautical and space fields. This review aims to: (1) come up with a systematic and critical overview of the state-of-the-art knowledge and research on the thermal stability of various polymers and composites, such as polyimides, epoxy composites, and carbon-filled composites; (2) identify the key factors, mechanisms, methods, and challenges that affect the thermal stability of polymers and composites, such as the temperature, radiation, oxygen, and degradation; (3) highlight the current and potential applications, benefits, limitations, and opportunities of polymers and composites with high thermal stability, such as thermal control, structural reinforcement, protection, and energy conversion; (4) give a glimpse of future research directions by providing indications for improving the thermal stability of polymers and composites, such as novel materials, hybrid composites, smart materials, and advanced processing methods. In this context, thermal analysis plays a crucial role in the development of polyimide-based materials for the radiation shielding of space solar cells or spacecraft components. The main strategies that have been explored to improve the processability, optical transparency, and radiation resistance of polyimide-based materials without compromising their thermal stability are highlighted. The combination of different types of polyimides, such as linear and hyperbranched, as well as the incorporation of bulky pendant groups, are reported as routes for improving the mechanical behavior and optical transparency while retaining the thermal stability and radiation shielding properties. Furthermore, the thermal stability of polymer/carbon nanocomposites is discussed with particular reference to the role of the filler in radiation monitoring systems and electromagnetic interference shielding in the space environment. Finally, the thermal stability of epoxy-based composites and how it is influenced by the type and content of epoxy resin, curing agent, degree of cross-linking, and the addition of fillers or modifiers are critically reviewed. Some studies have reported that incorporating mesoporous silica micro-filler or microencapsulated phase change materials (MPCM) into epoxy resin can enhance its thermal stability and mechanical properties. The mesoporous silica composite exhibited the highest glass transition temperature and activation energy for thermal degradation among all the epoxy-silica nano/micro-composites. Indeed, an average activation energy value of 148.86 kJ/mol was recorded for the thermal degradation of unfilled epoxy resin. The maximum activation energy range was instead recorded for composites loaded with mesoporous microsilica. The EMC-5p50 sample showed the highest mean value of 217.6 kJ/mol. This remarkable enhancement was ascribed to the polymer invading the silica pores and forging formidable interfacial bonds.

“…In recent times, colorless polyimides (CPIs) have been widely studied for applications in prospective flexible substrates of electronic and micro-optical devices [ 1 , 2 , 3 ]. They can be used in fields where glass is usually used such as in displays [ 4 , 5 ], memory [ 6 ], lighting, solar cells [ 7 ], etc.…”

Section: Introductionmentioning

confidence: 99%

High-Transparency and Colorless Polyimide Film Prepared by Inhibiting the Formation of Chromophores

Liu

Yue

et al. 2022

Colorless polyimides (CPIs) with outstanding mechanical properties are essential materials in the production of flexible display panels, foldable windows, and even spacecraft cockpits. This paper specifically elaborates that the Morkit unit, and azo and nitro chromophores are important factors contributing to yellow PI, together with the well-known charge transfer complex (CTC) theory. Three diamine monomers, two anhydrides monomers, and three blockers were used to inhibit chromophores formation and, thus, obtain CPI films. The cut-off wavelength was blue-shifts to 334 nm and the transmittance is improved to 98.9% in the UV–vis range. Mechanical and thermal properties of the CPI films are not reduced through coupling effects of the blockers. Therefore, the inhibition method of the Morkit units and chromophore groups is a promising process for preparing CPIs to be used as flexible display materials.