Effect Of Polyimide Research Articles

Effects of polyimide on corrosion and wear resistance of PEO composite coating on AZ91 Mg alloy

The accelerated deterioration resulting from microscopic defects in Mg alloy PEO coatings is a notable issue. This study introduced a PEO/PI composite coating on the surface of AZ91 Mg alloy PEO coating through coating method, aiming to enhance its corrosion resistance and wear resistance. The findings indicated that as the coating time increases, the surface micropores sealed and filled by the PI coating. This led to a positive shift in the corrosion potential of the composite coating, a significant decrease in corrosion current density by three orders of magnitude, and a marked improvement in corrosion resistance. The strong adhesion of the PI coating to the PEO surface acted as a lubricant, making the composite coating self-lubricating. Additionally, PI's excellent high temperature resistance ensured that surface wear was not induced by elevated temperatures resulting from localized friction.

Study on Development of Composite PAM/PI Gel Abrasive Tools and Finishing Performance on the Sapphire Substrates

A sol-gel method was proposed to prepare the abrasive tool to solve the problem of abrasive agglomeration in the traditional hot-pressing abrasive tool. In this paper, the effect of AM acrylamide (AM) monomer concentration on the polyacrylamide (PAM) gel performance and the effect of abrasive mass fraction on viscosity were investigated. Experiments about the effect of polyimide (PI) resin mass fraction on the mechanical properties, surface morphologies and friction wear performance of the abrasive tool were conducted. The polishing experiments were conducted to compare the machining effect of the gel abrasive tool, hot-pressing abrasive tool and the polyurethane polishing pad. Results show that the PAM gel has the best uniformity when the concentration of AM monomer reaches 7 wt%, when the mass fraction of PI resin in the abrasive tool reaches 12 wt%, the mechanical properties is the best. When the mass fraction of PI resin is 8 wt%, the gel abrasive tool has the most stable friction coefficient. The average surface roughness reaches 2.706 nm, and the flatness reaches 0.631 μm when the sapphire was processed by the gel abrasive tool. After Chemical mechanical polishing (CMP), a scratch-free surface was obtained and the average surface roughness reached 0.724 nm.

Thermal and Mechanical Characterization of Epoxy/Polyimide Blends via Postcuring Process

In this study, the effects of polyimide (PI) content and postcuring on thermal and mechanical properties in PI and epoxy (EP) blending systems were investigated. EP/PI (EPI) blending reduced the crosslinking density and improved the flexural and impact strength due to ductility. On the other hand, in the postcuring of EPI, the thermal resistance improved due to the increased crosslinking density and the flexural strength increased by up to 57.89% due to the enhanced stiffness, but the impact strength decreased by up to 59.54%. EPI blending induced the improvement in the mechanical properties of EP, and the postcuring process of EPI was shown to be an effective method to improve heat resistance. It was confirmed that EPI blending induces improvement in the mechanical properties of EP, and the postcuring process of EPI is an effective method for improving heat resistance.

Effects of polyimide curing on image sticking behaviors of flexible displays

Flexible displays on a polyimide (PI) substrate are widely regarded as a promising next-generation display technology due to their versatility in various applications. Among other bendable materials used as display panel substrates, PI is especially suitable for flexible displays for its high glass transition temperature and low coefficient of thermal expansion. PI cured under various temperatures (260 °C, 360 °C, and 460 °C) was implemented in metal–insulator–metal (MIM) capacitors, amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFT), and actual display panels to analyze device stability and panel product characteristics. Through electrical analysis of the MIM capacitor, it was confirmed that the charging effect in the PI substrates intensified as the PI curing temperature increased. The threshold voltage shift (ΔVth) of the samples was found to increase with rising curing temperature under negative bias temperature stress (NBTS) due to the charging effect. Our analyses also show that increasing ΔVth exacerbates the image sticking phenomenon observed in display panels. These findings ultimately present a direct correlation between the curing temperature of polyimide substrates and the panel image sticking phenomenon, which could provide an insight into the improvement of future PI-substrate-based displays.

Green Fabrication of Polyimide Fibers with Phosphate Monoester Network to Reinforce Carbon Nanotube Polymer Composites: Simultaneously improving the Mechanical Properties and Flame Retardancy

To further enhance the reinforcing effect of polyimide (PI) fibers on carbon nanotube polymer composites, in this work, networks of long chains of phosphate monoester (PMOEs) were grown on the surface of PI fibers, and silanized multiwalled carbon nanotubes (Si-MWCNTs) were dispersed into the phenolic resin (PR) matrix. Subsequently, these two interpenetrating networks were entangled tightly at the PI-PMOEs fiber paper/PR matrix by vacuum-assisted wet papermaking technology and impregnation and vacuum curing technology. A novel type of PI-PMOEs fiber-reinforced carbon nanotube polymer composite was prepared. Structural observation and analysis revealed that the fiber surface activity and roughness were improved, resulting in enhanced interfacial adhesion. The Si-MWCNTs at the interface play an anchoring role, which leads to a strong mechanical interlock between the PI-PMOEs fibers and the matrix. Therefore, the generation and propagation of cracks encountered greater resistance, and the mechanical properties of the composites were improved. Compared with the Si-MWCNTs/PR composite with tensile strength of 20.29 MPa and elongation at break of 0.1%, the tensile strength and elongation at break of 80PI-PMOEs/Si-MWCNTs/PR (the basis weight of paper is 40 wt.%) composite are increased to 91.22 MPa and 2.0%, respectively. In addition, a tightly connected fiber "large skeleton" was provided by the PI-PMOEs fiber paper with a uniform pore size distribution. The Si-MWCNTs network and the thermally degraded carbides of the matrix formed a "small skeleton" based on the "large skeleton", resulting in a complete and dense protective barrier layer. The volatilization of pyrolysis products (CO, small-molecule hydrocarbons, aromatic compounds, etc.) was restricted, and heat and mass transfer were suppressed. Finally, the composites exhibited excellent flame retardancy.

Effects of polyimide/silica and polyimide/pores fillers on the morphology, thermal, mechanical, and tribological properties of polytetrafluoroethylene composites

The effects of polyimide with silica (SiO2‐PI) and pores (porous PI) on the morphology, thermal, mechanical, and tribological properties of polytetrafluoroethylene (PTFE) composites were investigated. SiO2‐PI and porous PI fillers decrease the compactness of PTFE matrices within PTFE/SiO2‐PI composites and PTFE/porous‐PI composites. In addition, SiO2‐PI fillers improve the interfacial bonding between PI fillers and PTFE matrices, which is opposite to the detrimental effect of porous PI fillers. Thermal and mechanical properties of PTFE composites were deteriorated apparently. The friction coefficients of PTFE/SiO2‐PI and PTFE/porous‐PI composites are 9.5% and 8.5% lower than that of PTFE/PI, respectively. The wear resistance of PTFE/SiO2‐PI and PTFE/porous‐PI composites is enhanced by 77.8% and 70.1%, respectively. Scanning electron microscopy (SEM) of worn surface indicates that SiO2‐PI and porous PI fillers protect PTFE matrices from counterpart ball, which inhibits the plastic flow of PTFE matrices effectively. In addition, the uneven worn surface decreases the contact area between PTFE composites and counterpart ball. Compared with SiO2‐PI fillers, the extension of porous PI fillers in friction process increases the contact area between PTFE composites and counterpart, which induces the relatively poor tribological performance of PTFE/porous‐PI. Furthermore, SiO2‐PI and porous PI fillers contribute to the formation of smooth and uniform transfer films, which improve the tribological performance of PTFE composites effectively. In addition, compared with adding SiO2‐PI into PTFE, the addition of SiO2 nanoparticles into PTFE/PI induces the rough and uniform transfer films, which is bad for tribological performance of PTFE/PI/SiO2 composites. POLYM. COMPOS., 40:3438–3452, 2019. © 2019 Society of Plastics Engineers

Remarkable improvement of the wear resistance of poly(vinylidene difluoride) by incorporating polyimide powder and carbon nanofibers

Poly(vinylidene difluoride) (PVDF) composites reinforced via adding different fillers have attracted wide attention in the field of dielectric materials, but few have been reported in the tribological area. In this paper, the effect of polyimide (PI) powder and carbon nanofibers (CF) as reinforcement phases on the friction and wear performance of PVDF composites has been investigated. It was found that PI powder enhances the mechanical and tribological properties of PVDF and especially as the content of the PI powder reaches 5 wt%. In addition, CF and PI exhibited synergistic effect on the tribological properties of PVDF. With PVDF containing 5 wt% PI powder and 20 wt% CF, the friction and wear behavior of the PVDF composite showed the best performance. PVDF, PI powder and CF can form a consistent network structure, which prevents the polymer molecular chains from moving or deformation, decreasing the wear loss of PVDF composites.

Pervaporative studies using polyimide‐filled PDMS membrane

AbstractThe application of pervaporation (PV) to the removal of volatile organic from aqueous solutions has become very interesting in the last few years. It is caused by the increasing level of compounds, such as petrochemical solvents (benzene, toluene, and xylenes) or chlorinated solvents (trichloroethylene or tetrachloroethylene), which are polluting the natural environment. In this work, effects of polyimide (PI) (prepared by direct polycondensation of dianhydride and diamine followed by thermal cyclization of polyamic acid) filler on PV properties of poly(dimethyl siloxane) (PDMS) have been studied. PDMS membrane filled with PI was used for the separation of benzene (Bz) and toluene (Tol) from the diluted aqueous solution and the results were compared with the neat PDMS membrane of similar thickness. The PDMS‐PI membrane showed normalized flux (J′) upto 1.2 kg μm/m2h for Bz and 1.48 kg μm/m2h for Tol and selectivity of organics varies from 7.3 to 3.2 for Bz and 8.9 to 2.8 for Tol with increasing concentration of organics. Concentration of PI filler in PDMS varied 5–25% w/w. PI filler increases thermal as well as mechanical stability of filled PDMS membranes. PDMS membrane filled with 25% PI was chosen for the pervaporation studies. The membranes were characterized by FTIR, thermogravimetric analyser and scanning electron microscopy. The mechanical strength of PDMS filled with 25% w/w PI (SPI‐25) membrane was found to be 2.7 MPa. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010