Other Resin Systems

PTFE is outstanding in this group. In thin films it provides the lowest coefficient of friction (0.03—0.1) of any polymer, is effective from —200 to 250°C, and is generally unreactive chemically. The low friction is attributed to the smooth molecular profile of PTFE chains which allows easy sliding (57). Typical apphcations include chemical and food processing equipment, electrical components, and as a component to provide improved friction and wear in other resin systems. 

Synthetic resins, such as phenoHc and cresyUc resins (see Phenolic resins), are the most commonly used friction material binders, and are usually modified with drying oils, elastomer, cardanol [37330-39-5] an epoxy, phosphoms- or boron-based compounds, or even combinations of two. They ate prepared by the addition of the appropriate phenol and formaldehyde [50-00-0] in the presence of an acidic or basic catalyst. Polymerization takes place at elevated temperatures. Other resin systems are based on elastomers (see Elastomers, synthetic), drying oils, or combinations of the above or other polymers. 

Bismaleimides - Bismaleimides resins were first introduced into the market in the early 1970 s. As with other resin systems, there are many variations of bismaleimides. The Kermid and Kinel bismaleimide products as marketed in the U. S. by Rhodia are representative examples. Bismaleimide chemistry is represented in Eq. 3 where curing can be accomplished thermally through the unsaturation in the maleimide or by way of the Michael Reaction where an appropriate curing agent such as aromatic diamine adds across the activated double bond. In most instances, a combination of curing thermally through the double bond and via an aromatic diamine is used in actual practice. Bismaleimides are frequently formulated... 

The only remaining use of any importance is the manufacture of a number of specialty phthalate plasticizers for PVC and other resin systems. Plasticizers account for about 8 percent of demand and the remaining 10 percent involve a variety of miscellaneous applications. 

While the initial concern for formaldehyde emissions in the hardwood plywood industry was in the wall paneling sector there is a strong and decided movement by many manufacturers to apply new low emitting adhesive technology to other hardwood plywood products. Low emitting UF products are nearing the emission characteristics of certain other resin systems assumed to be likely substitutes. 

Jet Fil . [Luzenac R.T. Vanderbilt] Talc filler for PP and other resin systems. 

Table 3.2 also includes data for the advanced thermoplastic resins (PEEK) and for a thermosetting resin, an end-capped bismaleimide (BMI) called PMR-15. Moisture contents tend to be lower for these advanced materials [12,13]. One way to overcome the environmental sensitivity of epoxide resins is to employ these advanced resins, as demonstrated in Table 3.2. However, changing to other resin systems brings with it other concerns. For example, PEEK relies on crystallinity for its higher temperature performance. Its glass transition temperature is only 143°C and a change in modulus can be observed at that temperature. In addition, higher process temperatures are required both for high performance thermosets and thermoplastics. The consequent higher residual thermal stresses can off-set some of the advantages of a higher service temperature, in comparison with advanced epoxy resins.

Uses Basic polymer or properties enhancer for adhesives and coatings Features Contains functional hydroxyl groups which can be reacted with melamines, isocyanates, and other resin systems Properties Off-wh. solid soften, pt. 69-72 C Adura 50 [Air Prods.]... 

Epoxies are preferable to other resin systems in that they can be formulated to bond to moist hardened concrete and yet be able to cure within the wet environment of the fresh concrete. Polyesters do not generally bond reliably under wet conditions. The system must also be selected with due regard to the temperature of application. Resins claimed to have good bonding performance at 20 C may give rather poor bond strengths at the lower cure temperatures prevalent on UK construction sites during much of the year. 

Conversion. The cure of many oxidative thermosetting coatings is accelerated by heating. In other resin systems, such as thermosetting acrylics and alkyd melamines, the reactions do not occur below tern-... 

Free resonance analyzers normally are limited to rod or rectangular samples or materials that can be impregnated onto a braid. This last approach is how the curing studies on epoxy and other resin systems were done in torsion and gives these instruments the name of torsional braid analyzers (TEA). 

A typical blade of large wind turbines consists of outer skins supported by a main spar and stiffeners. The blades are generally constructed using fibre/ polymeric matrix composites and may have a sandwich construction with low density polymer foam or balsa wood cores. The epoxy-based eomposites are of greatest interest to wind turbine manufacturers beeause they dehver a combination of environmental, production and cost advantages over other resin systems. Epoxies also improve wind turbine composite blade manufacture by allowing a shorter cure cycle, increased durability and improved surface finish. The utilisation of epoxy infusion or prepreg manufacture (see Sections... 

Comprehensive Index Phenolic - Laminating Other Resin Systems... 

Prepreg Manufacture (See also under other resin systems.)... 

Series—Silane sized fibers for improved bonding between the inorganic glass and the organic resin. Sizings are available for polyesters, epoxies, phenolics, polyurethanes, polyvinyl chloride and other resin systems. 

PEEK and epoxy have similar properties in flexural fatigue and it is from a consideration of other properties such as high temperature capability, processability or cost that specific advantages might accrue to one or other resin system. 

In terms of their thermal behavior, phenolic resins are superior to other resin systems. As a result they are used as brake and coupling linings or in abrasive disks, where temperature peaks up to 400 °C may occur phenolic resins also exhibit reiatively high flame resistance. 

Aqueous polyurethane dispersions are not new they have been available since the early 1970s. However, environmental concerns and impending legislation are in favour of non-solvent containing materials and reduction of VOCs making these systems commercially available nowadays. Performance of new aqueous dispersions has reached the point that they exceed the performance of some solvent-based systems [16]. These urethane dispersions can also often be processed with the same or similar equipment as solvent systems. They may be used as the sole resin or blended with other resin systems, such as acrylics. 

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