Epoxies novolak

The (9-cresol novolaks of commercial significance possess degrees of polymerization, n, of 1.7—4.4 and the epoxide functionaUty of the resultant glycidylated resins varies from 2.7 to 5.4. Softening points (Durran s) of the products are 35—99°C. The glycidylated phenol and o-cresol—novolak resins are soluble in ketones, 2-ethoxyethyl acetate, and toluene solvents. The commercial epoxy novolak products possess a residual hydrolyzable chlorine content of <0.15 wt% and a total chlorine content of ca 0.6 wt % (Table 2). 

Subsequent epoxidation with epichl orohydrin yields the highly functional epoxy novolak. The product can range from a high viscosity Hquid of n = 0.2 to a soHd of n value greater than 3. 

The multiepoxy functionality of the epoxy novolaks (2.2 to >5 epoxy groups per molecule) (3) produce more tightly cross-linked cured systems having improved elevated temperature performance and chemical resistance than the difunctional bisphenol A-based resins. 

The thermal stabiUty of epoxy phenol—novolak resins is useful in adhesives, stmctural and electrical laminates, coatings, castings, and encapsulations for elevated temperature service (Table 3). Filament-wound pipe and storage tanks, liners for pumps and other chemical process equipment, and corrosion-resistant coatings are typical appHcations using the chemically resistant properties of epoxy novolak resins. 

The products of the chemical degradation of PETP with triethylene tetramine and triethaneolamine can be used as epoxy resin hardeners, it is demonstrated. Products of PETP aminolysis with triethylene tetramine and aminoglycolysis with triethanolamine, were characterised using NMR and rheometric measurements. Characteristics of the crosslinking process for the system epoxy resin/ PETP/amine degradation product, and epoxy resin/TETA for comparison were investigated by DSC. Three classes of liquid epoxy resins based on bisphenol A, bisphenol F and epoxy novolak resins were used in the experiments. 16 refs. 

Resin type Orthophthalic, isophthalic, low profile, halogenated Epoxy Novolak, methacrylate esters of bisphenol epoxy resins Epichlorohydrin/ bisphenol-A... 

Curing agents lhai give the optimum in elevated temperature properties for epoxy novolaks arc (hose with good high icmperaiure performance such as aromatic amines, catalytic curing agents, phenolics. and some anhydrides... 

Cross-linking systems employed are hexamethylenetetramine or paraformaldehyde. The OH function can also be used by reaction with epichlorohydrin to form epoxy novolaks. 

A foam was prepared firom polymeric isocyanate (134 pbw) 3,3, 4,4 -benzophenonetetracarboxylic dianhydride (45 pbw) epoxy novolak resin (20 pbw) wetting agent (1 pbw) methanol (2.5 pbw) N,N, N -tris(dimethylaminopropyl)-s-hexahydrotriazine (2.5 pbw) triethylenediamine (2.5 pbw) and l-phenyl-3-methyl-2-phospholene 1-oxide (2.5 pbw). 

Another type is made from polyolefins oxidized with peracetic acid. These have more epoxide groups, within the molecule as well as in terminal positions, and can be cured with anhydrides, but require high temperatures. Many modifications of both types are made commercially. Halogenated bisphenols can be used to add flame-retardant properties. See epoxy novolak. 

As previously mentioned, several commercial hybrid thermosets are known to be co-reacting thermosets, i.e. when the mixture of two different thermosetting monomers or prepolymers is cured, there is a simultaneous graft or co-reaction between the components along with the crosslinking reactions. These systems may therefore be considered as co-polymerizing thermosets and not as true blends. Examples of such systems are phenolic novolak/epoxy resin (or epoxy novolaks) ... 

Figure 9.8 Photograph showing an epoxy novolak vinyl ester resin tank which has required no maintenance while holding 15-30% HCI at 40°C since 1971. It is now being replaced (1998)...

Chem. Descrip. Epoxy novolak aciylate/SR 351 (trimethylol propane triaciylate) blend... 

The base resin in epoxy adhesive products can be readily identified by IR and NMR spectrometry. The most commonly employed resin in these products (both one-part and two-part) is that based on the diglycidyl ether of bisphenol A (bisphenol A epoxy resin). Other resins of importance include the cycloaliphatic epoxies and phenolic epoxy novolaks. 

The durability of the bonded joints was greatly influenced by the nature of the adhesive the best performers in all climates were epoxy-novolak and nitrile-phenolic formulations. A tropical, hot-wet climate was the most damaging to bonded stmctures and the combination of high humidity and applied stress was particularly deleterious. During exposure to natural environments, the failure mode of aluminium joints was found to change gradually from wholly cohesive, within the adhesive, to include increasing amounts of interfacial failure (see Stress distribution mode of failure). 

Packaging of the chip portion of the chip/lead combined unit into a plastic or ceramic container is a semi-automated process involving the use of epoxy resins, usually epoxy novolak resin formations [15]. These should be fully cured prior to use, but unreacted monomers may be present, which can sensitise, as may other diluent and flame retardant materials, such as halogenated derivatives of bisphenol A, which are added to the resin prior to use. The completed devices are then laser marked in an enclosed system and tested, again in an automated process, prior to delivery for sale. 

Atlac 583 (Formerly 580/15) A flexible vinyl ester urethane resin having a tensile elongation of 15%. Atlac 590 A epoxy novolak resin. 

A high reactivity, low viscosity vinyl ester (epoxy-novolak base) offering extraordinary good chemical resistance and high dimensional stability at elevated temperature. Particularly resident to combinations of acids, halogenated organics, sodium hydroxide and solvents, b. 65.5% c. 340 - 510... 

Hydrocarbon epoxy novolak resin with aromatic amine curing agent... 

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