Thermosetting epoxy compounds

Curing of One-Package, Thermosetting Epoxy Compounds. The thermo-setting epoxy resin mixture was cured at 160°C for 2 hours. 

Thermosetting-encapsulation compounds, based on epoxy resins (qv) or, in some niche appHcations, organosiHcon polymers, are widely used to encase electronic devices. Polyurethanes, polyimides, and polyesters are used to encase modules and hybrids intended for use under low temperature, low humidity conditions. Modified polyimides have the advantages of thermal and moisture stabiHty, low coefficients of thermal expansion, and high material purity. Thermoplastics are rarely used for PEMs, because they are low in purity, requHe unacceptably high temperature and pressure processing conditions. 

This paper reports the results of a molecular-level investigation of the effects of flame retardant additives on the thermal dedompositlon of thermoset molding compounds used for encapsulation of IC devices, and their implications to the reliability of devices in molded plastic packages. In particular, semiconductor grade novolac epoxy and silicone-epoxy based resins and an electrical grade novolac epoxy formulation are compared. This work is an extension of a previous study of an epoxy encapsulant to flame retarded and non-flame retarded sample pairs of novolac epoxy and silicone-epoxy compounds. The results of this work are correlated with separate studies on device aglng2>3, where appropriate. 

The most common and widely used thermoset molding compounds are classified as follows (a) alkyd, (b) allylic (diallyl phthalate), (c) amino (melamine and urea), (d) epoxy, (e) phenolic, (f) polyester, and (g) silicone. There may be other specialty thermoset resin materials used on specific applications. 

Thermoset molding compounds, when contained within a hardened steel mold, require heat and pressure to be polymerized into a solid mass. Molds may be heated by steam, electricity, or hot oil to temperatures of 280° to 425°F, depending entirely on the type of material and method of molding. Molding pressures may vary from a low of 50 p.s.i. to 15,000 p.s.i. Epoxy materials will mold at 50 p.s.i. whereas, phenolic fabric-filled material may require excessive pressures. Again, the method of molding dictates molding pressures. 

The claimed compound of the invention is produced by the reaction of epichloro-hydrin and bisphenol A and was well known in the art and was also known to be useful in the preparation of thermosetting epoxy resins. The claim preamble As a manufacture..., is equivalent to saying As a product of manufacture..., which in turn means that these two claims are compound claims. Although the compound was well known in the literature, it was reported in the context where it made up to 70% to 90% of a complex liquid mixture. According to the applicant s patent application specification, no method had been described that would allow the production of pure 2,2-bis-[(4)-2,3-epoxypropoxyphenyl]propane directly from a reaction mixture. Prior attempts to recover the product of the reaction resulted in, at best, a viscous liquid that adversely affected the usefulness of the product. In contrast to the prior art, applicant s methods resulted in material of sufficient purity that the compound was isolated as a free-flowing, crystalline powder. This material could be easily handled and allegedly could be used to prepare epoxy resins equal or superior to the liquid material prepared previously. 

Adherent Technologies Inc. [8] has developed a process for the reclamation of carbon fibers from carbon/epoxy composites. It has studied the depolymerization of thermoset carbon fiber reinforced epoxy matrix composites using a low temperature (20 min at 325°Q catalytic tertiary recycling reclamation process and has been able to obtain a product with 99.8% carbon and 0.2% residual resin, with only a loss of about 8.6% in fiber tensile strength. The process can be economically viable, provided sufficient scrap feedstock is available. Possible applications for the recovered fiber include thermoplastic and thermoset molding compounds. 

Epoxy compounds were discovered by Prileschaiev in 1909, but its importance was realized only during WW2. In 1956, glass fiber reinforcements were introduced. The thermoset polyesters (TS) were developed by Ellis in 1933-1934. The first use of glass-reinforced TS dates from 1938. 

Phenol-formaldehyde was reported as the first commercially synthetic polymer (1899) which was introduced as BakeliteT by Baekeland in 1909. This was the period which marked the dawn for the production of commercial synthetic thermosetting polymers. Other advances in the field included the discovery of urea-formaldehyde resins in 1884 and the beginning of their commercialization as Beetle moldable resin in 1928, followed by thiourea-formaldehyde (1920), aniline-formaldehyde (Cibatine by Ciba, 1935) and melamine-formaldehyde (1937) moulding powders. The year 1909 marked the discovery of epoxy compounds by Prileschaiev, which were not used until World War 2. The first thermoset polyesters, invented by Ellis, date back to 1934 and in 1938 was reported their first use in the forms of glass-reinforced materials [1]. 

As thermosetting binder, an epoxy resin is used (49). Such an epoxy compound can be conventionally cured with a carboxylic acid. The epoxy binder is produced by the radical polymerization of glycidyl methacrylate and methyl methacrylate. As initiator ferf-butylperoxy-2-ethyIhexanoate is used. 

Epoxy resins are thermoset polymers prepared by the reaction of an epoxy compound, typically a low molecular weight diepoxide, with a curing agent. These two parts are combined and a chemical reaction causes the cure. They are often called two-part epoxies. They come in two tubes for home use. There are many variants of epoxy compounds and curing agents but diglycidyl ethers of bisphenols cured with diamines are common. The diglycidyl ethers are readily prepared from epichlorohydrin. The reaction is... 

Xylox Resin n Trade name for a family of heat-resistant thermosetting resins made by the condensation of aralkyl ethers and phenols, resulting in hydroxyphenylene-p-xylene prepolymers that can be cured to hard, intractable resins by reaction with hexamethylenetetramine or epoxy compounds. These thermosetting resins have the good qualities of phenolics and epoxies, with superior mechanical and electrical properties at elevated temperatures. 

Spiral flow (test and mold). There are two types of spiral flow molds—one for the very soft flow encapsulation compound generally associated with the encapsulation grades of the epoxy family of compounds, and a spiral flow mold, which is used when testing the high-pressine phenolic, DAP, melamine, urea, epoxy, and thermoset polyester compounds. 

Another approach for obtaining carboxyl-functionalized PBDs by a postpolymerization technique from PBD is the reaction of olefinic double bonds with thioglycolic acid. Addition of the thiol functionality to the double bonds results in a carboxylic PBD, which reacts with epoxy compounds to form thermoset resins [193]. 

This class of compounds is one of the most important adhesive groups with applications ranging from consumer to aerospace markets. Epoxies are thermosets and are cross-linked during the cure cycle. The chemical stmcmre for a simple epoxy (ethylene oxide) in its unhardened state is shown in Figure 5.2. All epoxy compounds contain two or more of these groups. Epoxy resins form adducts with vinyl, acrylic, and polyester resins producing compounds such as phenol novolac, cresol novolac, bis-[4(2,3-epoxy propyoxy) phenyl] methane, and phenol hydrocarbon novalac [53]. 

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. 

Commonly accepted practice restricts the term to plastics that serve engineering purposes and can be processed and reprocessed by injection and extmsion methods. This excludes the so-called specialty plastics, eg, fluorocarbon polymers and infusible film products such as Kapton and Updex polyimide film, and thermosets including phenoHcs, epoxies, urea—formaldehydes, and sdicones, some of which have been termed engineering plastics by other authors (4) (see Elastol rs, synthetic-fluorocarbon elastol rs Eluorine compounds, organic-tdtrafluoroethylenecopolyt rs with ethylene Phenolic resins Epoxy resins Amino resins and plastics). 

Consist of a range of chemicals which promote cross-linking can initiate cure by catalysing ( catalysts , hardeners, initiators), speed up and control cure (activators, promoters) or perform the opposite function (inhibitors) producing thermosetting compounds and specialised thermoplastics (e.g. peroxides in polyesters, or amines in epoxy formulations). The right choice of a cure system is dependent on process, process temperature, application and type of resin. 

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