Binder thermosetting system

Binders. Thermosetting and thermoplastic binders are listed, together with their abbreviations, in Table 3.6. A broad range of raw materials is now available and it has become difficult to systematically classify binder properties. Outstanding properties are obtained with suitably selected systems and have contributed to increased... 

The binder system of a plastic encapsulant consists of an epoxy resin, a hardener or curing agent, and an accelerating catalyst system. The conversion of epoxies from the Hquid (thermoplastic) state to tough, hard, thermoset soHds is accompHshed by the addition of chemically active compounds known as curing agents. Flame retardants (qv), usually in the form of halogens, are added to the epoxy resin backbone because epoxy resins are inherently flammable. 

Thermoset polyurethane as a binder material for gravel systems is also under development. Applications could include roofing systems that require a high degree of uv light and abrasion resistance. 

As a binder system polymers are utilized. If the binders contain energy or gas-producing molecular groups (-N02, -N3), one classifies the binders as Active Binders (e.g. polynitropolyphenylene, glycidyl azide polymer, polyvinyl nitrate and nitrocellulose). If these substances are not present, then the binders are classified as inert binders. Depending on available processing methods, binder types such as thermoset material, thermoplast or gelatinizers can be used. They can then be formed and cured by chemical or physical means. 

The production of LOVA powders is dependant on the chosen binder type. When thermoset materials are used, the system of energy carrier/binders/curing agents is kneaded together. The same is true when gelatines are used, however in this case, gelatinizing solvents (usually alcohol and ether) are added. 

Table 3.4 summarizes the consumption of thermosetting binders used in various regions. The epoxy-polyester systems predominate over polyester-trisglycidyl iso-cyanurate and epoxy systems. The consumption of thermoplastic coating powders, particularly those used in the fluidized-bed and flocking processes, is substantially lower than that of thermosetting powders (Table 3.5). Their production does not show a comparably significant growth rate.

The thermosetting binders are the most important. Their properties are summarized in Table 3.7. The quantitatively predominant EP, EP-SP, and SP-TGIC types cure by polyaddition without release of split-off products. SP-PUR and AY-PUR systems are cured by polycondensation and release some caprolactam. SP-HAA systems are also cured by polycondensation and release water as a product. 

The so-called solvent-based binder systems contain polymers which solvate or swell in a solvent (e.g. water, alcohol). Typical polymers used in extrusion are PEG, PVA, agar agar and cellulose. Thermoplastic materials are polymers which when heated, soften, melt or become more pliable, and harden during cooling in a reversible physical process. Materials in this class which are used quite often for ceramic processing are PE, PP, EVA, POM and PMMA. Thermosetting materials are polymers which can be melted only once and which, after melting, harden as more heat is added. Thermoset plastics which are used in the ceramic industry are phenolic resins and different silicon resins like polysiloxane. 

Various binder systems have been used in ceramic injection molding, which can be classified into five types (i) thermoplastic compounds, (ii) thermosetting compounds, (iii) water-based systems, (iv) gelation systems, and (v) inorganics. Among these, thermoplastic compounds are the most widely used and understood, which are mainly commercial polymers. The ratio of powder to binder is a key parameter. 

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