Properties Of Polyimide Foams Research Articles

Effect of Dibutyltin Dilaurate and Triethanolamine Catalysts on Structure and Properties of Polyimide Foams

A series of rigid polyimide (PI) foams were prepared by the prepolymer method with pyromellitic dianhydride and polyaryl polymethylene isocyanate as the starting materials and dibutyltin dilaurate (DBTDL), and triethanolamine (TEOA) as catalysts. The effect of the two kinds of catalysts on the structure and properties such as molecular structure, cell morphology, density, mechanical properties, thermal properties, and flame retardancy of the resulting foams were characterized in detail. The experimental results showed that the PI foams prepared in this work possessed low density, good mechanical properties, outstanding thermal stability, and excellent flame retardancy. The thermal stability and flame retardancy were improved obviously with the increase of DBTDL content. While with the increase of the content of TEOA, the mechanical strength and apparent density of PI foams increased significantly. Therefore, different structure and performance of PI foams can be prepared by adjusting the content of these two catalysts. J. VINYL ADDIT. TECHNOL., 25:385–395, 2019. © 2019 Society of Plastics Engineers

Improved mechanical, thermal and flame resistant properties of flexible isocyanate-based polyimide foams by graphite incorporation

In order to improve the mechanical, thermal and flame-resistant properties of polyimide foams (PIFs), in the present study, flexible polyimide (PI)/graphite composite foams were prepared with dianhydride and isocyanate as the starting materials and graphite as the filler. The experimental results showed that most cells of PIFs possessed an open cell structure, and the open cell content decreased by graphite incorporation. While with the increase in graphite, the distribution of cellular size became uneven and the size distribution became broad. The compressive strength increased initially and then decreased and reached the maximum value of 26.4 kPa when the graphite content was 1.98 wt%, but all the composite foams exhibited higher strength than the neat PIF. In addition, the limiting oxygen index increased from 31% to 34.8% with the increase in graphite from 0 wt% to 3.25 wt%. The peak heat release rate of composite foams was 2.3% to 24.7% lower than the neat PIF and reached a minimum value of 42.36 kW m−2 with the graphite content of 1.98 wt%. Considering the above analysis, it is feasible to improve mechanical properties, thermal stability and flame-resistant properties of PIFs by graphite addition.

Synthesis and properties of polyimide foams containing benzimidazole units

A series of novel polyimide foams containing benzimidazole units were prepared from polyester ammonium salt (PEAS) precursor powders, which were synthesized by co-polymerization of BTDA with two diamines, BIA and ODA, in various molar ratios.

The compressive behaviour and constitutive equation of polyimide foam in wide strain rate and temperature

These days, polymer foams, such as polyurethane foam and polystyrene foam, are used in various situations as a thermal insulator or shock absorber. In general, however, their strength is insufficient in high temperature environments because of their low glass transition temperature. Polyimide is a polymer which has a higher glass transition temperature and high strength. Its mechanical properties do not vary greatly, even in low temperature environments. Therefore, polyimide foam is expected to be used in the aerospace industry. Thus, the constitutive equation of polyimide foam that can be applied across a wide range of strain rates and ambient temperature is very useful. In this study, a series of compression tests at various strain rates, from 10 −3 to 10 3 s −1 were carried out in order to examine the effect of strain rate on the compressive properties of polyimide foam. The flow stress of polyimide foam increased rapidly at dynamic strain rates. The effect of ambient temperature on the properties of polyimide foam was also investigated at temperature from − 190 ° C to 270° ∘ C. The flow stress decreased with increasing temperature.

Effect of Carbon Black on the Properties of Polyimide Foams

Polyimide foams (PIF) contained carbon black were prepared from polyimide precursors by inflation process. The structure, compressive strength and heat-resistance of the PIF were studied. The FT-IR results confirmed the successful synthesis of PIF.Tgvalue of PIF with different content carbon black was over 255°C.With the increasing of carbon black content,Tgof PIF decreased. PIF decomposition temperature (Td5%) was higher than 540°C,while the compression strength of PIF about 0.12MPa with low content carbon black.

Preparation and performance of a novel polyimide foam

AbstractA new type of polyimide foam (PIF) was prepared and characterized based on a one‐pot process by the reaction of a first solution with different ratios of a second solution. The first solution was comprised of pyromellitic dianhydride (PMDA), N, N‐dimethyl formamide (DMF), methanol, water, surfactant, and catalysts, while the second solution contained polyaryl polymethylene isocyanate (PAPI). In the present study, the relationships among compositions, structures, and properties of PIFs were investigated. The results indicated that with the increase in the weight ratio of PAPI/(first solution), the foaming degrees of PIFs increased from 10.14 to 10.52 times and the apparent densities before postcure decreased from 15.96 to 14.51 kg/m3. The open cell contents, average sound absorption coefficients, and average cellular diameters of PIFs after postcure increased with increase in the weight ratio of PAPI/(first solution). The glass transition temperatures (Tg) of PIFs after postcure first increased from 287 to 299°C, then decreased to 292°C, and the 5% weight loss temperatures and 10% weight loss temperatures presented the same trend as well. The compressive and flatwise tensile properties scaled very well with the relative densities of the foams after postcure, with the highest compressive strength of 0.03 MPa and the highest flatwise tensile strength of 0.15 MPa. Copyright © 2011 John Wiley & Sons, Ltd.

Polyimide foams with ultralow dielectric constants

AbstractTo explore ultralow dielectric constant polyimide, the crosslinked polyimide foams (PIFs) were prepared from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA), 4,4′‐oxydianiline (ODA), and 2,4,6‐triaminopyrimidine (TAP) via a poly(ester–amine salt) (PEAS) process. FTIR measurements indicated that TAP did not yield a negative effect on imidization of PEAS precursors. SEM measurement revealed the homogeneous cell structure. Through using TAP as a crosslinking monomer, the mechanical properties of PIFs could be improved in comparison with uncrosslinked BTDA/ODA based PIF. The crosslinked PIFs still exhibited excellent thermal stability with 5% weight loss temperatures higher than 520°C. In the field with frequency higher than 100 Hz, the dielectric constants of the obtained PIFs ranged from 1.77 to 2.4, and the dielectric losses were smaller than 3 × 10−2 at 25–150°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1734–1740, 2006