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Novolac and high temperature epoxies are a small niche of epoxies in general. It's hard to find information about these two subgroups other than what can be discerned from the product discriptions of these kind of products, hence the creation of this page, which can be assumed to be a work in progress.
Progressive Epoxy Polymers, Inc. www.epoxyproducts.com
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Novolac Epoxies
Novolac epoxies are formulated with Bis F or novolac epoxy resins (as compared to 'ordinary' Bis A epoxy resins).
Novolac epoxies provide an increase in chemical resistance over regular epoxies. This increase is about 30%. Epoxy
chemical resistance to sulfuric acid, as example, increases from about immersion service at 70% concentration to
immersion service at 98% concentration. Resistance to heat also increases.
Progressive Epoxy Polymers, Inc. sells NOVOLAC 555, a
general purpose novolac epoxy paint. Find in the epoxy paint section of our online catalogs.
High Temperature Epoxies
temperature ranges of epoxies:
Generally regular epoxies (Bis A epoxies) can handle constant or repeated temperatures of about 160 -170 degrees F in dry conditions and about 140 - 160 degrees F in wet conditons. They can handle 300 degrees F on a non regular basis. This is called service temperature.
Generally 'high temperature epoxies' can handle constant or repeated temperatures of about 300 - 350 degrees F
in dry conditions and about 250 - 300 degrees F in wet conditons. To achieve this they need a few hours of additional
curing at temperatures of about 130 - 150 degrees F to complete their curing process which began (and get the epoxy
hard) at room temperature. This is called a post cure.
Most high temperature epoxies are made from high quality, Novolac (part A) resins with hazmat shipping restrictioned
curing agents (part B) or regular Bis A epoxy resin (part A) with a special hazmat, high temperature curing agents
(part B). There are other 'blends' and something called Bis F epoxies that are also sometimes used to formulate
high temperature epoxies. Note that the non-hazmat shipping based curing agents do not have temperature resistance.
You can have high temperature resistance or chemical resistance but not both. As you raise the temperature chemicals become much more reactive and the even the most chemical resistant epoxy will fail chemically at elevated temperatures.
Epoxy data sheets list either a 'heat distortion temperature' or a 'T sub g' temperature. They are similar but not same. Basically both give an indication of the point where the epoxy begins to soften (it will harden up when the epoxy cools down). The temperature varies some from epoxy to epoxy but generally for a regular (bis A) epoxy the temperature is about 140 degrees F. For high temperature epoxies the initial value is about 125 degrees F but after a post cure of several hours at about 150 degrees F, the new heat distortion temperature is about 160 degrees F. Consider these temperatures as the point where the epoxy will begin to soften when under a load. This is different from the maximum 'service' temperature of these epoxies.
We only sell one novolac epoxy - NOVOLAC 555 -
FOR MORE INFORMATION AND DETAILS VISIT OUR CHEMISTRY OF EPOXIES
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Presented by Paul Oman/Progressive Epoxy Polymers, Inc.
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