Special Resin Systems

Although polyimides are the largest class of high temperature resin systems, other resins have been developed that are used for specialist applications or, alternatively, were never developed commercially, perhaps due to cost considerations. 

Ashland Chemical Company (PBOX) are bisoxazoline phenolics and are thermosetting poly(amide ethers), prepared from phenolic resins and bisoxazolines. They can be cured with a catalyst at 175°C and post cured at 225°C. 

Bayer introduced the Blendur resins (EPIC) based on the catalyzed reaction of an epoxy resin with an isocyanate. 

Dow Chemical introduced benzocyclobutene (BCB), curing without the evolution of volatiles. The reaction proceeds by the four membered benzocyclobutene rings opening to give o-quinodimethane structures. 

Societe Nationale des Poudres et Explosifs (SNPE) have developed the polystyrylpyridine (PSP) resins, which do, however, evolve volatiles during the curing process. 

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This paper discusses our analyses of two such specialized resin systems and the development of models that will allow us to predict the time required to cure given a particular set of light intensity and temperature conditions. 

Four commercial epoxy resins were investigated, which are described in Table I. For research purposes, four special resin systems were used with well-defined, but different cross-linkings. The average chain length, 5, between two cross-links... 

Most of the resin systems used in commodity composites are slight modifications of the standard commercial mol ding grade material. Usually certain selected properties, such as purity or molecular weight range or distribution, are enhanced or carehiUy selected. In addition, special additives, such as flow controllers, thermal stabilizers, or antioxidants, are often added by the resin manufacturer prior to shipment. Many of the conventional or commodity-type resins used in thermoplastic composites are Hsted in Table 1 and the preparation of each of these is described. AH resins and blends described in the hterature are not Hsted, and the synthesis described is not the only procedure available, but is usually the most common commercial process. 

To maximize thermal stability at conventional running temperatures (350°F) EnBA-based systems are chosen [20]. This polymer is much more thermally stable than EVA. Open time is longer than EVA, so special resins are not required for this purpose, even in freezer-grade systems. 

Special resins consist of a two-phase system composed of a mix of a highly condensed, and no longer soluble, PF-resin with a standard type PF-resin [63]. Another two-phase resin is composed of a highly condensed PF-resin, still in an aqueous solution, and of a PF dispersion [64]. The purpose of such special resins is the gluing of wet wood, where the danger of overpenetration of the resin into the wood surface exists and would cause a starved glue line. 

Polyurethane mortar flooring systems based on somewhat similar technology to this special polyester system have also been used in chemical plants and have given excellent service. The basic urethane polymer is more elastomeric than either epoxy or polyester resins and, as such, is reported to have excellent thermal properties up... 

Suitable paints for use underwater include vinyl resin systems, coal tar paints over inorganic zinc-rich primers, and some coal-tar epoxy primers have also proved themselves Special paints are available for application under water, e.g. epoxy modifications with polyamides. 

Several other microanalytical methods in common use potentially have application on soil and sediments section samples. Laser-ablation inductively coupled plasma mass spectrometery (LA-ICP-MS) has been used on soil thin-sections from a controlled field experiment (21) but required special resins in the preparation. There is presently (May 2006) no reported use of this method on archaeological soil samples. Likewise, for extremely fine-resolution studies (i.e. <10 pm) with low minimum detection limits and despite difficult calibration, secondary ion microscopy (SIMS) has a potential role in examining archaeological soil thin sections. At even higher lateral resolutions ( 100 nm) Auger electron spectroscopy (AES) could also be considered for surface (<5 nm deep) analyses. At present however, the use of these methods in soil systems is limited. SIMS has been focused on biochemical applications (22), whereas AES... 

The lower-viscosity grades have an EEW of about 175 and are virtually pure diglycidyl ethers of bisphenol A. They are so pure, however, that they will crystallize on storage. The crystals melt on warming above 40°C, and heating can be used to restore a crystallized resin to its previous form. Special crystallization-free resins systems have been formed by blending low-viscosity DGEBA resins with more conventional bisphenol A-based epoxy resins. 

Some of the solvents that are commonly used in epoxy resins can present a flammability hazard and special health hazards. Contact with solvents will cause drying of the skin, which may result in an increased probability of skin irritation, especially when one comes in contact with curing agents. Solvents also have the ability to dissolve epoxy resin system components and carry them through the skin in liquid form or into the respiratory system in vapor form. The inhalation of solvent vapors or mist may cause respiratory irritation and... 

Although it may require special designs, pressure transfer does eliminate the problems that occur with gear pumping methods. Many resinous systems may be moved from their original drums by air pumps. Transfer distances should be short, and lines should be smooth and noncorrosive. In some instances, barrel warmers and heated lines may be required to reduce pressures required to transport materials. Under no circumstances should the same transfer equipment be used on different resins without complete and thorough cleaning. This will avoid the contamination of one resin system with the other. 

Specialized Light Curing Resin Systems for Fabrication of Inflatable Rigidizable Structures... 

In recent years, epoxy resin systems have been utilized for special applications on the exteriors of buildings. One of these systems involves the use of an epoxy plaster, which is troweled onto the surface of an exposed wall, into which are set stone aggregates. This surfacing resembles a pre-cast concrete panel with an exposed aggregate facing. This method is utilized, not only in new construction, but in re-surfacing deteriorated areas. 

Most high performance applications in aircraft use epoxy-based resin systems. Silicones, phenolics and polyimides are limited to special high temperature or electrical applications. Although thermosetting resins such as epoxy are commonly used in filament winding, there has been recent research into using thermoplastic matrix materials [9]. 

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