Ester Resins

The trimerization reaction of the polyfunctional cyanates is catalyzed by zinc or manganese octoate, copper carboxylates, and acetylacetonate metal chelates with a synergistic effect when the catalyst is mixed with 4-nonylphenol [21]. The final cure or postcure temperature depends on the glass transition temperature of the tridimensional network. This means that the semi-solid biscyanate 88 is cured at 180-195 C (Tg 192°C) while the biscyanate 85 is cured at 250-300°C (Tg 290°C). However, the maximum cure temperature can be reduced to 120°C in the former example by adding 6-10% of 4-nonylphenol. When compared to epoxies, cyanate esters have higher glass transition temperatures, better thermal stability, and improved dielectric properties. Cyanate esters have been primarily developed 

Two silver-filled adhesives, Johnson Matfliey JM 7000 and JM 7800, have respective elastic modulus of 10 and 5.8 GPa, 7g 250 and 210°C, thermal conductivity 1.1 and 1.6Wm K , volume resistivity 2x10 and 5 X 10 n cm. According to the manufacturer, the thermal stresses, determined by measuring the radius of curvature of silicon chips, are far from the level of stress where the risk of cracking and delamination increases considerably. In 1994 Johnson Matthey proposed a low-stress cyanate adhesive (JM 2500) exhibiting a modulus of elasticity of only 0.4 GPa. The low stress properties of this material were demonstrated by the large radius of curvature (Im)ofa 15x 15 mm die bonded to a 0.15 mm thick leadframe. This value remained constant after KKX) thermal cycles from — 65 to 150°C. 

In electronics, polyimides are now extensively used in the form of self-standing films for flexible circuitry, deposited films for interlayer dielectrics, passivation and buffer coatings, moulding thermoplastic powders for PCBs, and adhesive pastes or tapes. The basic polyimide chemistry has been adapted to fulfill the specific requirements of these applications. A series of books provides complete information not only on the chemistry of polyimides but also on their utilization in electronics [4,23,24]. The following figures summarize the chemical formulae of the most important categories of polyimide precursors or precyclized polymers that are commonly used in electronics. 

A marginal production is based on the acetylene-terminated oligoimides presented in another chapter (see Volume 2, Chapter 7 Heat-Resistant Adhesives), and a proprietary composition has been used at National 

Semiconductors [25]. In this later example, the die attach material is prepared from a PMDA-ODA polyamic acid solution in NMP (Du Pont PI 2561) mixed with 7-aminopropyltriethoxysilane and loaded with silver flakes. The adhesive composition is used to bond semiconductor dice in ceramic packages with a first 

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Vinylene shift Vinyl ester Vinyl ester resins... 

Rosin ester resins are used extensively in pressure-sensitive adhesives as tackifiers. The adhesive is formulated by blending the resin with a polymer in solution or as aqueous emulsions. Typical compositions may contain about 50% resin. The glycerol or pentaerythritol esters of stabilized rosins are often used because they are stable on aging. 

Rosin ester resins are used as modifiers in the formulation of chewing gum. The rosin derivative modifies the physical properties of the polymer used, providing the desired masticatory properties. The glycerol ester of hydrogenated rosin is the predominant choice, because stabilized materials have improved aging resistance, which extends the shelf life of the gum. 

Vinyl ester resins generally offer mechanical properties superior to those of polyester matrices but at an increased cost. Vinyl esters are chemically similar to epoxy resins but are manufactured via a cold-curing process similar to that used in the manufacture of polyester resins. Vinyl esters offer superior resistance to water and chemical attack and are used in such appHcations as underground pipes, tank liners, and storage tanks (see Vinyl polymers). 

Note X=in-plane 0°, Y=in-plane 90°, 2 = through thickness, V,=fibev volume fraction, M=Tnat VGCF, H=hybrid VGCF, S=short staple VGCF, P=P-55 fiber, E=cpoxy, CER=cyanate ester resin. 

Note UTS=ullimate tensile strength, vokimc fraction, M=mat VGCF, H= CER-cyanate ester resin. 

This provides excellent adhesion to the metal. The PVB will crosslink in the presence of the acid with phenolic resin, and epoxy or epoxy ester resin... 

A further type of ester resin is the unsaturated polyester where the unsaturation is built into the backbone by the use of maleic anhydride ... 

Novolac hydroxyl groups reacted with cyanogen bromide under basic conditions to produce cyanate ester resins (Fig. 7.41).105,106 Cyanate esters can thermally crosslink to form void-free networks, wherein at least some triazine rings form. The resultant networks possess high s, high char yields at 900°C, and high decomposition temperatures.105... 

Novolac resins containing cardanol moieties have also been converted to cyanate ester resins.107 The thermal stability and char yields, however, were reduced when cardanol was incorporated into the networks. 

High-temperature cement formulations are basically polymer concrete. Mainly unsaturated polyesters or vinyl ester resins with allylphthalate as vinyl monomer are in use [927]. Cming is achieved with peroxides, which decompose sufficiently fast at temperamres between 120° and 200° C. Polymer concrete requires additional materials, which compensate shrinkage. 

Raynolds, S., "The Dependence of Physical Properties on the Constitution of Alkyl Polymethacrylate-ester Resins", Thesis, Master of Science, University of Pittsburgh, 1954. 

Reghunadhan Nair, C. R, Mathew, D. and Ninan, K N. Cyanate Ester Resins, Recent Developments. Vol. 155, pp. 1-99. 

Rink, H. (1987) Solid-phase synthesis of protected peptide fragments using a trialkoxy-diphenyl-methyl-ester resin. Tetrahedron Lett. 28, 3787-3790. 

The fluorine content, density, critical surface energy, glass transitions, thermal expansion coefficient above and below the glass transition, and 300°C isothermal thermogravimetric stabilities of the fluoromethylene cyanate ester resin system with n = 3, 4, 6, 8, 10 are summarized Table 2.2. Also included for the purpose of comparison are the corresponding data for the aromatic cyanate ester resin based on the dicyanate of 6F bisphenol A (AroCy F, Ciba Geigy). 

The fluorine content for the fluoromethylene cyanate ester resin system is clearly significantly greater than that for AroCy F and also significantly less than that for PTFE (76.0%). Correspondingly, the density reflects the fluorine content. As a homologous series, the contribution of incremental CF2 units can be quantified. From the density data, the volume equivalent of 41. 0 A1 /CF, structural unit in an amorphous thermoset matrix has been determined.8... 

The surface properties are of particular interest for composites and coatings. The n = 6 monomer will wet Teflon, and PTFE filled composites can be prepared. The critical surface tension of wetting for the fluoromethylene cyanate ester resin series has been determined from contact-angle measurements on cured resin surfaces. As indicated in Table 2.2, it parallels the fluorine composition and begins to approach the PTFE value of 18 dyn/cm. 

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