Epoxy novolac resins

The most commonly used novolac epoxy resin has n 1.6. Novolac epoxy resins with functionalities of 2.5 to 6.0 are also available commercially [340, 341]. 

Synthesis Epoxy resins consisting ofglycidyl ether, ester and amines are generally prepared by the condensation reaction between diol, dibasic acid or amine and epichlorohydrin in the presence of sodium hydroxide with the elimination of hydrochloric acid. The commercially available epoxy resins are, however, made by the reaction of epichlorohydrin and bisphenol-A. Cashew nut shell liquid (CNSL)-based novolac epoxy resins have also been reported [342]. 

Novolac resins are condensation products of phenol and formaldehyde made in the presence of an acid catalyst such as hydrochloric acid, sulfuric acid or oxalic acid. For novolac resins, mole ratios of phenol to formaldehyde vary from 1 0.5 

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Fig. 1. Structures of commercial epoxy resins (a) phenolic novolac epoxy resin, (b) glycidated polybasic acid, (c) glycidated polyamine (A,A,A, A -tetraglycidyl-4,4 -diaminodiphenylmethane [28768-32-3] (TGMDA)), and (d) glycidated bisphenol A.

When novolac epoxy resin, for instance, was blended with nearly symmetric poly(methyl acrylate-co-glycidylmclhacrylalc)-b-polyisoprcnc and cured with MDA, a significantly different phase behaviour was found [201] (Fig. 67). 

Fig. 67 Schematic of phase behaviour for blend of novolac epoxy resin with nearly symmetric poly(methyl acrylate-co-glycidylmelhacrylate)-0-polyisoprene. Ordered L can be swollen with up to about 30% of resin before macroscopic phase separation occurs, producing heterogeneous morphologies containing various amounts of L, C, worm-like micelles and pristine epoxy. At lower concentrations, disordered worm-like micelles transform into vesicles in dilute limit. According to [201]. Copyright 2003 Wiley...

DSC and DMA scans of, 18 778 Novolac epoxy resins, 10 349 Novolac resins, 15 163. See also Novolacs in coatings, 18 782 in fiber bonding, 18 792 from phenolic resin polymerization,... 

Novolac epoxy resins are produced by reaction of novolac, a phenolformaldehyde resin, with epichlorohyrin and a base. ... 

Novolac epoxy flexibilizers Improve low and high temperature characteristics of novolac epoxy resins for inhibition of composite rocket propellants [164]. 

Epoxidized soyabean or linseed oils Plasticizers for novolac epoxy resins. Also prevent auto-catalytic decomposition of NG during storage... 

Similar to composite propellants, flexibilized epoxy or novolac epoxy resins reinforced with fillers or fibers are used for inhibition of fuel-rich propellants. 

A collapsible mandrel is prepared by applying a very thin coat of silicone grease on it followed by application of aluminum foil of suitable thickness. This prepared mandrel is then held in the lathe machine. A thin uniform coat of resin (novolac epoxy resin plus hardener) is applied to the prepared collapsible mandrel revolving at a speed of 40 rpm and is allowed to cure partially. Then the dried rayon thread on a spool is passed through the resin formulation and is wound on to the mandrel... 

The inhibition of composite propellants is somewhat easier than that of DB propellants. The binders used for composite propellants (with or without fillers) have been reported for inhibition of composite propellants. Such inhibition systems possess stronger bonds with composite propellants and prove to be more compatible coupled with better shelf-life of the inhibited propellants. However, epoxy or novolac epoxy resin with or without inert fillers is generally preferred for the inhibition of composite propellants due to a combination of properties possessed by them. The inhibition is usually done by casting technique and inhibition thickness is usually required on higher side in order to make the missions successful. In India, thread winding technique or inhibitor sleeve technique is preferred where 2.5-3.0mm inhibition thickness is sufficient as against 3.5-4.0 mm in case of inhibition by casting technique . 

Considering thermodynamics of adhesion, epoxy/novolac epoxy resins play a vital role for bonding applications especially for inhibition of composite propellants. In view of this fact, it is considered worthwhile to discuss the chemistry of epoxy/novolac epoxy resins in this section before we discuss other systems for this purpose. 

An outline of the general method of synthesis of epoxy resin and novolac epoxy resin are shown in Schemes 4.9 and 4.10 respectively. 

Agrawal, J.P., Dev, S.S., Gholap, D.H., Satpute, R.S., Tapaswi, M.A., and Nigde, B.N. (1986) Improvement of Low and High Temperatures Characteristics of Novolac Epoxy Resin Used for Inhibition of HTPB Based Composite Propellants. ERDL Report No. 8/86. 

Ho et al (1996) examined polyol or polysiloxane thermoplastic polyurethanes (TPUs) as modifiers in cresol-formaldehye novolac epoxy resins cured with phenolic novolac resin for computer-chip encapsulation. A stable sea-island dispersion of TPU particles was achieved by the epoxy ring-opening with isocyanate groups of the urethane prepolymer to form an oxazolidone. The flexural modulus was reduced by addition of TPU and also the Tg was increased due to the rigid oxazolidone structure. Mayadunne et al (1999) extended this work to a series of phenol- and naphthol-based aralkyl epoxy resins. 

EPN 1139 Low molar mass novolac epoxy resin ETT Effective time theory... 

A typical commercial novolac epoxy resin (VI) produced by epoxidation of phenolic hydroxyl groups of novolac (see the section on phenolformaldehyde resins) by treatment with epichlorohydrin has an... 

Because of higher functionality, the novolac epoxy resins give, on curing, more hightly cross-linked... 

Solid epoxy resins based on bisphenol A can be categorized as effectively non-toxic they are not irritating and scarcely sensitizing. The same is true for the novolac epoxy resins although their liquid forms can have a sensitizing effect. 

Chem. Deserp. One-part, water-based epoxy resin with conosion inhibitors Bisphenol /Vepichlorohydrin epoxy (< 10%), bisphenol A novolac epoxy resin (< 10%), ethanol (2-10%), propylene glycol (5-15%), carbo) zircoaluminate sol n. (< 5%), etc. 

Epoxy cresol novolac epoxy resin, food-contact coatings Epoxy cresol novolac epoxy resin, high performance aircraft bodies/components p,p, p"-Tri (2,3-epoxypropoxy) triphenylmethane epoxy resin, high-temp, adhesives Epoxy cresol novolac epoxy resin, laminating prods. 

Chemical Resistance Ratings for Novolac Epoxy Resins... 

Later work by the same team compared ODOPB and bis(3-dihydroxyphenyl) phenyl phosphate (BHPP) as reactive flame retardants in o-ciesol formaldehyde novolac epoxy resin. Since the ODOPB has a rigid, cyclic side chain sfructure, the resultant phosphorus-containing epoxy resin had a higher Tg, better flame retardancy properties, a higher modulus, and increased thermal... 

Methylimidazole (EMI) n. An epoxy-resin curing agent with a heterocyclic structure. EMI is used with epoxies formed from epichlorohydrin and bisphenol A or -F, and for novolac epoxy resins. It provides ease of compounding, long pot life, low viscosity, and non-staining characteristics. 

Novolac epoxy resins, phenolic or cresol novolacs, are reacted with epichlorohydrin to produce these novolac epoxy resins which cure more rapidly than the epi-bis epoxies and have higher exotherms. These cured novolacs have higher heat-deflection temperatures than the epi-bis resins as shown in Table 2.8. The novolacs also have excellent resistance to solvents and chemicals when compared with that of an epi-bis resin as seen in Table 2.9. 

Figure 3.11 Conversion versus temperature transformation diagram showing conditions under which gelation, vitrification and chemical degradation take place, as well as restriction arising from topological limitations for novolac epoxy resin cured with DDS. Reprinted with permission from RA. Oyanguren and R.J.J. Williams,/owmia/ of Applied Polymer Science, 1993, 47,1361 1993,...

Yoshida, T. Hozumi, T. Aral, M. Baba, T. Novolac epoxy resin-based adhesive film for electronic packaging. Jpn. Kokai Tokkyo Koho JP 2004273809, 2004 Chem. Abstr. 2004,141, 296985. 

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