Hybrids epoxy-silicone

Polyurethane sealant formulations use TDI or MDI prepolymers made from polyether polyols. The sealants contain 30—50% of the prepolymer the remainder consists of pigments, fillers, plasticizers, adhesion promoters, and other additives. The curing of the sealant is conducted with atmospheric moisture. One-component windshield sealants utilize diethyl malonate-blocked MDI prepolymers (46). Several polyurethane hybrid systems, containing epoxies, silicones, or polysulfide, are also used. 

Epoxy-silicone hybrid resins (Fig. 7.4) have generally been developed for use in the molding of microelectronic packages. These resins have moderate strength but exhibit a degree of elongation of about 60 percent at break. 

FIGURE 7.4 Chemical structure of epoxy-silicone hybrid resin.26... 

Silicones and epoxy-silicone (9) hybrids have also been used. The silicones are naturally flame retardant, have excellent electrical characteristics, good purity and good thermal stability. But they have poor mechanical strength and poor adhesion to the lead-frames. The poor strength has resulted in an excessive amount of... 

An epoxy-silicone hybrid resin with epoxy-silicone oligomers incorporated into the matrix at the nanometer level by sol-gel reaction has been prepared (Takahashi et al., 2005). This epoxy-silicone hybrid resin has shown excellent mechanical properties at high temperatures. Besides the thermal expansion coefficient mentioned above, the glass transition temperature was two-thirds of the conventional value. 

Takahashi A, Satsu Y, Nagai A, Umino M and Nakamura Y (2005), Heat-resistant epoxy-silicon hybrid materials for printed wiring boards , IEEE Trans Electron Packag Manuf 28, 163-167. doi 10.1109/TEPM.2005.846831. 

Polymers can be filled with hybrid particles or with a combination of fillers in order to better control their thermophysical behavior (Lee et al. 2006 Choi and Kim 2013). However, there are relatively few reports of polymers containing mixed fillers for heat conduction purposes. To improve thermal conductivity of an epoxy, silicon... 

Abstract In this chapter, classification of adhesive and sealant materials is presented. For this purpose, various categories are considered depending on the polymer base (i.e., natural or synthetic), functionality in the polymer backbone (i.e., thermoplastic or thermoset), physical forms (i.e., one or multiple components, films), chemical families (i.e., epoxy, silicon), functional types (i.e., structural, hot melt, pressure sensitive, water-base, ultraviolet/ electron beam cured, conductive, etc.), and methods of application. The classification covers high-temperature adhesives, sealants, conductive adhesives, nanocomposite adhesives, primers, solvent-activated adhesives, water-activated adhesives, and hybrid adhesives. 

Michael, K. W., Antonen, R. G., "The Properties of Silicone/Epoxy Electronic Grade Molding Compound", Proceedings of the Soc. of Hybrid and Microelectronics Conf, P. 253, Anaheim, Calif., 1978. 

The silicon substrate is removed while the temporary substrate provides mechanical support. Next, the substrate is bonded to a final carrier substrate 54 with a layer 52 of epoxy adhesive. The bonding layer 48 is removed, which also removes the temporary carrier substrate 50. The final carrier substrate is chosen according to the same criteria as described in the first embodiment. Processing continues by forming indium interconnects 34b for later hybridization of the read-out integrated circuit assembly with a detector array. 

Figure 8.5 depicts representative ranges of bond strength and elongations for typical structural adhesives such as epoxies, methacrylate, polyurethanes, and silicones. The silyl-epoxy hybrids conveniently fill the gap between the silicones and polyurethanes. 

In this book I have confined discussion to those polymeric materials which are cured by chemical reaction and which have found widespread application in the construction industry. As such, the book covers materials based on epoxies, polyurethanes, silicones, polysulphides, alkyds and polyesters. In addition, there is a chapter on hybrid polymer systems and one on acrylics. It is true that acrylic emulsions are not strictly thermosetting polymer systems, but their widespread use and importance made their exclusion difficult. These materials find use as coatings, sealants, adhesives, grouts, flooring compounds, repair compounds and waterproofing agents. 

Among the countless number of applications of polymers, the construction industry is one which utilises several polymeric materials. In this book I cover those polymeric materials which are single or bicomponent systems and are cured at ambient temperature either with the aid of curing agents or atmospheric moisture. The various polymers used in manufacturing such products include epoxies, polyurethanes, acrylics, silicones, polysulphides, alkyds and polyesters. As a result of innovation, new technologies exist which utilise more than one polymer in a single product. Such systems are discussed in Chapter 10, on hybrid polymers. 

The R groups can bear a polymerizable function such as methacrylate or epoxy acting as network formers. If the R-M bond is not cleaved, then R can also be considered a network modifier. Most of the works in this area are centered on silicon-based hybrids for protective coatings. 

This investigation of silicone-modified hybrid composites demonstrates that compatibilized, segmented liquid rubbers can be tailored to promote the formation of colloidal rubber dispersions, which enhance the toughness of the epoxy matrix. Furthermore, such segmented liquid rubbers can in situ-modify filler surfaces to form core-shell particles with a hard filler core and a thin... 

Reliability of the electrical properties of silicone-based isotropic adhesives has been the major difficulty to overcome and has essentially prevented commercialization. Another problem associated with silicones is that the addition polymerization reaction of silicones must be carefully controlled to prevent cure inhibition from various common chemical contaminants such as amines and sulfides. Other concerns include low-molecular-weight silicone polymer migration onto wirebond pads and very high GTE. There has been some activity in the development of hybrid resins that contain silicone blocks as comonomer with epoxies such that the epoxy processing can be maintained with the added stress reduction property of the silicones [52]. 

Nanofillers have actually been around for decades (the oldest for over a century) carbon blacks, pigments, precipitated silicic acid (Ultrasil, Degussa-Hiils), pyrogenic silicic acids (Aerosile, Degussa-Hiils), phyllosilicates, nucleation agents, reactive silicone nanoparticles for epoxy resins, ceramic materials and inorganic-organic hybrid particles from sol-gel transformations, for example synthetic, dispersible aluminate (boehmite) powder. 

Loctite 3564/ Loctite Fast flowing, liquid epoxy underfill 1 Silicon, ceramics, laminates Dispense, capillary imderfill Flip-chip underfill in bare-chip protection (memory cards, chip carriers, hybrids and MCMs)... 

A. Christou, Reliability Aspects of Moisture and Ionic Contamination Diffusion Through Hybrid Encapsulants, in Proceedings of the Technical Program—International Microelectronics Conference (1978) p. 237, Industrial Scientific Conference Management, Inc., New York. Electric insulators and dielectrics Silicone/epoxy-polyurethane interpenetrating networks, moisture, and ion diffusion through potting compounds. 

The primary chemical classes from which adhesives are made include epoxies, acrylics, phenolics, urethanes, natural and synthetic elastomers, amino resins, silicones, polyesters, polyamides, aromatic polyheterocyclics, and the various natural products such as carbohydrates and their derivatives as well as plant- and animal-based proteins. Chemical class was once a relatively clean differentiator of adhesives, but so many adhesives now are hybrids, designed to take advantage of specific attributes of more than one chemical class or type of material. Hybridization can be accomplished by incorporating into an adhesive a nonreactive resin of a different chemical class adding another type of reactive monomer, oligomer,... 

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