Polyimides polyimide

VDP Polyimides. Polyimide films have also been prepared by a kind of VDP (16). The poly(amic acid) layer is first formed by the coevaporation and condensation of two monomers, followed by copolymerization on the substrate. The imidization is carried out in a separate baking step (see POLYIMIDES). 

Polyimide. Polyimide is a biaxiaHy oriented high performance film that is tough, flexible, and temperature- and combustion-resistant. Its room temperature properties compare to poly(ethylene terephthalate), but it retains these good characteristics at temperatures above 400°C. Its electrical resistance is good and it is dimensionally stable. The principal detriment is fairly high moisture absorbance. The main uses are for electrical insulation, particularly where high temperatures are prevalent or ionizing radiation is a problem. The films may be coated to reduce water absorption and enhance... 

Figure 5.21. SEM micrographs of laser-etched PTFE doped with polyimide and neat polyimide. Polyimide concentration in samples are 0.5% (a), 1.0% (b), 5.0% (c) 100% (d), and 5.0% (at 45°) (e). Fluence was 12 J/cm2 at 308 nm (a-d from Egitto and Davis5 7 and e from Davis et al. 72). (Reduced 50% for reproduction).

To achieve a high fluorine content in polyimides, 6FDA and TFDB are selected for polyimide synthesis (Figure 15.1). 6FDA is a typical monomer for fluorine-containing polyimides. Polyimides synthesized from 6FDA have a high fluorine content and a flexible structure compared with other conventional... 

It is customary to apply these polymers as the poly(amic -acids) and to dehydrate the film, coating, fiber or molded forms by heating to produce the polyimides. Polyimides are insoluble in most solvents hut are attacked by alkalies, ammonia and amines. These heat resistant polymers are used without fillers and with a graphite filler. 

The semi-IPN concept has also been used in order to improve the high-temperature adhesive properties of a flexible polyimide. Polyimide prepared with isophthaloyldiphthalic anhydride and mefa-phenylenediamine presents good adhesive properties but is limited to 270 °C. By blending it with a bisnadimide... 

Polyimide surface modification by a wet chemical process is described. Poly(pyromellitic dianhydride-oxydianiline) (PMDA-ODA) and poly(bisphenyl dianhydride-para-phenylenediamine) (BPDA-PDA) polyimide film surfaces are initially modified with KOH aqueous solution. These modified surfaces are further treated with aqueous HC1 solution to protonate the ionic molecules. Modified surfaces are identified with X-ray photoelectron spectroscopy (XPS), external reflectance infrared (ER IR) spectroscopy, gravimetric analysis, contact angle and thickness measurement. Initial reaction with KOH transforms the polyimide surface to a potassium polyamate surface. The reaction of the polyamate surface with HC1 yields a polyamic acid surface. Upon curing the modified surface, the starting polyimide surface is produced. The depth of modification, which is measured by a method using an absorbance-thickness relationship established with ellipsometry and ER IR, is controlled by the KOH reaction temperature and the reaction time. Surface topography and film thickness can be maintained while a strong polyimide-polyimide adhesion is achieved. Relationship between surface structure and adhesion is discussed. 

Polyimide-Polyimide Adhesion. To study polyimide-polyimide adhesion (10). a thin layer (200 A) of gold was sputter-coated onto one side (20% of the total area) of the polyimide sample to initiate peel (polyimide has a poor adhesion to gold). The surface of the polyimide in the exposed area was modified to the polyamic acid surface. PMDA-ODA polyamic acid in NMP solvent was spin-coated to the surface-modified (to polyamic acid) polyimide film, and subsequently cured at 400 °C under nitrogen. Thickness of the adherate layer (peel layer) after curing is approximately 20 um and the width of the peel layers is 5 mm. The peel strengths were measured by 90° peel of the top polyimide layer. The failure occurs at the interface between... 

Many of the above described features are quite different to published and our own data for polyimide. Polyimide (PI) has a linear absorption coefficient at 308 nm similar to the designed polymers (around 95,000 cm-1). The first pronounced differences between the ablation characteristics between PI and our polymers are the higher threshold of ablation (three times), lower etch rates, and an effective absorption coefficient which is similar to the linear absorption coefficient. A comparison of the ablation quality between a designed polymer (TP) and the standard polymer (PI) is shown in Fig. 74. 

UP, Alkyd resins -PET, PBT -Polyimides -Polyimides -UP, Alkyd resins... 

In order to better understand miscibility in polyimide-based systems. Sun et al. (1991) prepared pairs of polyimide blends with different molecular structures by two ways, mixing of the polyamic acid precursors with subsequent imidization and direct solution mixing of the polyimides. Dynamic mechanical analysis (DMA) techniques showed that aU of the blends prepared in the two different ways were miscible, as evidenced by the existence of only one Tg for all of the blends. It was proposed that the miscibility of these polyimide/polyimide blends is a result of the strong intermolecular charge-transfer interaction between the chains of the blend components. 

Polyimides. Polyimides are the highest-temperature polymer in the general advanced composite with a long-term upper temperature hm-it of 232 to 316°C (450 to 600°F). Table 2.34 is a list of commercial polyimides being used in structural composites. 

Polyimides. Polyimide coatings have excellent long-term thermal stability, wear, mar and moisture resistance, as well as electrical properties. They are high in price. 

Another approach to soniconductor encapsulation is using polyimides. Polyimides are promising because of their higher glass transition temperature, low coefficient of... 

Special considerations trace metals such as Co, Cu, Ni radically reduce thermal stabihty some carbon fibers cause degradation due to the surface impurities some types of glass reduce stability of polyimide polyimide is used as modifier of PEEK/carbon fiber composite ... 

GLASS REINFORCED POLYIMIDE POLYIMIDE 8( POLY(AMIDE-IMIDE)... 

Polyimide Polyimide Excellent Fire-resistant Upjohn... 

Polyimides Polyimides are actually a subset of polyamides, but forms when both carboxylic acid groups in diacid monomer react with an amine. As shown, a benzene ring with two acid groups on adjacent carbons (in the ortho position) condenses with an amine to form a single bond. The result is an imide linkage. 

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