What are novolac resins?
Novolac resins are amorphous (not crystalline) thermoplastics. As they are most typically used, they are solid at room temperature and will soften and flow between 150° and 220°F (65°C – 105°C). The number average molecular weight (Mn) of a standard phenol novolac resin is between 250 and 900.
What is the difference between resol and novolac?
Difference Between Novolac and Resole Novolac is produced using excess phenol and an acid or metal salt catalyst, whereas resole is produced using excess formaldehyde and a basic catalyst. Novolac is not self-curing; it requires an extra curing agent, whereas resole is selfcurable without an additional catalyst.
How epoxy novolac are made?
Epoxy novolacs are formed by reaction of the novolac with epichlorohydrin first to form the corresponding chlorohydrin ether intermediate followed by dehydrochlorination to the epoxy novolac itself.
How phenol formaldehyde resin is made?
phenol-formaldehyde resin, also called phenolic resin, any of a number of synthetic resins made by reacting phenol (an aromatic alcohol derived from benzene) with formaldehyde (a reactive gas derived from methane). The other method involves reacting formaldehyde with an excess of phenol, using an acid catalyst.
Where is melamine formaldehyde used?
A complex, interlinked polymer that cures to a clear, hard, chemically resistant resin, melamine formaldehyde is employed in plywood and particleboard adhesives, laminated countertops and tabletops, dishwasher-safe tableware, and automotive surface coatings.
Which type of polymer is novolac?
phenolic resin
Novolac is a phenolic resin type of polymer.
Is phenol-formaldehyde resin safe?
As a result of this screening assessment, the Government concluded that the 8 substances in the Phenol-formaldehyde Resins Group are not harmful to human health or to the environment at levels of exposure considered in the assessment.
Is phenol formaldehyde resin safe?
What are the uses of cresol novolac resins?
Cresol novolac high heat-resistance multifunctional epoxy resins. They are used for semiconductor encapsulants, electrical laminates, and solder resist. DIC can also customize these products in various ways. Contact us for details.
What’s the difference between novolac and randomly linked resins?
Novolac resins made with these catalysts tend to cure more rapidly than the standard randomly linked resins. Novolac resins are amorphous (not crystalline) thermoplastics. As they are most typically used, they are solid at room temperature and will soften and flow between 150° and 220°F (65°C – 105°C).
Which is the most common cross linking agent for novolac?
Because an additional agent is required to complete the resin’s cure, the industry commonly refers to novolac resins as “two-stage” or “two-step” products. The most common phenolic resin cross-linking agent is hexamethylenetetramine, also known as hexa, hexamine, or HMTA.
How is the molecular weight of cresol controlled?
A series of linear, controlled molecular weight, 2,6-dimethylphenol endcapped cresol novolac resins have been synthesized and characterized. The molecular weight control was achieved by adjusting the stoichiometric ratio of cresol to 2,6- dimethylphenol and using an excess of formaldehyde.