Novalac resins

The/flc-ClRe(CO)3(4,7-Ph2-phen) complex has been demonstrated to be a useful spectroscopic probe in the curing of photosensitive epoxy-based materials [100], Emission spectra obtained from a 0.05-mm thickness film of a mixed epoxy system of bisphenol-A/novalac resin (Interz, SU8) and diglycidyl ether of bisphenol-A (DGEBA) containing cation-generating triarylsulfonium hexafluo-roantimonate salts as photoinitiators (Union Carbide, Cryacure UVI-6974) and... 

In another study, Nayak et al. (26) prepared CNSL-novalac resins by condensing cardanyl acrylate with p-aminobenzoic acid and formaldehyde in the presence of an acid catalyst. Thermogravimetric analysis and degradation studies on these resins have been carried out. It was observed that this resin decomposed with the removal... 

FIGURE 26.13 The second-charge discharge curves of novalac resin heat-treated at 1273 K. (Reprinted with permission from J.R. Dahn, T. Zheng, Y. Liu, and J.S. Xue, Mechanisms for hthium insertion in carhonaceous materials, Science, 270, 590 1995. Copyright 1995 AAAS.)... 

The effect of heat treatment on the dissolution rate of spin coated P(MMA) film on silicon has been studied by Greeneich (7 8). The results he obtained showed very strong dependence of the dissolution rate of P(MMA) on the prebake (hot plate) temperature and time as shown in (figure 1). This result has been interpreted (7 8) as mostly due to a reduction in the solvent content (drying) during heat treatment. More recent study on the effect of prebaking on the dissolution rate of a photo resist (a Novalac resin sensitized with 20 weight % diazo compound) showed a non monotonic decrease in the dissolution rate (S)... 

These adhesives are usually made by blending a nitrile rubber with a phenolic novalac resin, along with other compounding ingredients. Usage in... 

The formaldehyde curing of a melt spun novalac resin yields an infusible fiber, which when heat treated in an inert atmosphere, gives a 58% 5ueld of a carbon fiber at 700°C, with a carbon content of 94.5% and a strength of 0.69 GPa. Heat treatment to 1800°C increases the carbon content to 99.96% but decreases the strength to 0.47 GPa [294,295]. The product was not commercially successful. 

The second type of phenolics are the novalac resins formed by using a molar excess of phenol and an acid catalyst. The simplest form of a novalac resin is Bisphenol F ... 

Novalac resins cannot condense without the addition of a hardening agent, such as hexamine (hexamethylenetetramine), which will form HCHO ... 

A novalac resin is prepared by reacting a phenol with HCHO ... 

Epoxy novalac resins are prepared by reacting ECH with a novalac resin ... 

Novalac resins can be produced from alkyl phenols, aryl phenols and polyhydroxy phenols to obtain special properties and Table 13.5 lists resins derived from o-cresolformaldehyde and ECH. 

Tactix 556, marketed by Ciba Specialty Chemicals is a hydrocarbon epoxy novalac resin having a dicyclopentadiene backbone with ability to retain properties under conditions of moisture and elevated temperature. Tactix 556 can be cured for 3 h at 177°C using 27.6 phr of DDS and then postcured for 2 h at 232° C giving a of 210°C. 

Novalac resins made from p-cresol condensation with formaldehyde were characterized on a 50°C C,g column (A = 280nm) using a complex 55-min 0/50/50 50/50/0 THF/methanol/water gradient. Samples were made up as... 

Early resin materials used in mold compound formulations were sihcones, phenolic resins, and bisphenol-A or bisphenol-F epoxies. Because of shortcomings in performance, these materials have been displaced by epoxy phenol or cresol novalac resins (ECN resins) and by the biphenyl- and tris(triphenylmethane)-type epoxies (70) (Fig. 20). The high cross-link density of ECN-based materials results in low moisture absorption rate and higher thermal stabihty than... 

Vinyl ester epoxy novalac resins, only available unaccelerated and non-thixotropic, but in standard and low monomer versions. For chemical tanks, small and large diameter pipe, fume handling equipment and for example in the protection of equipment for use in desulphurisation plant. Upper temperature range in liquids 102 C and 107 C in vapours. 

Wei et al. (2002) have dip coated phenol-formaldehyde novolak resin containing a small amount of hexamethylene tetramine onto the surface of green tubular supports of fine phenol-formaldehyde novalac resin particles. During pyrolysis, the hexamethylamine has mobility that reduces the creation of large pores in the surface during pyrolysis. Because the selective layer and support have similar composition, there is also less stress during pyrolysis from shrinkage. The supported membranes were pyrolyzed at 900°C. The concentration of the solution used for the selective layer and the thickness had a considerable effect on the separation performance. 

---