Bakelite Parts is made from a formulated thermal phenolic resin and is the first commercial plastic1. Phenolic resins are commercially important today because of their low cost, ease of manufacture, can be formulated for a wide range of applications, and exhibit excellent properties once cured. Durable in applications that require prolonged exposure to moisture, acids, cleaning solutions, lubricants and high temperatures. The market for phenolic resins includes: wood construction adhesives (plywood, oriented particle board, particle board); molding compounds for laminates, friction materials such as brake pads and clutch plates, abrasive products such as abrasive wheels, casting molds, and gears, pulleys and Rigid parts for rollers; paper and cloth impregnated for engine filters; adhesives for printing inks and tire manufacturing; even photoresist 1,2.
The simplest form of phenolic resin is the product of the reaction of phenol or substituted phenol with formaldehyde. Resins are divided into two basic categories, depending on the ratio of phenol to formaldehyde and process chemistry. The novolac is produced because the molar ratio of formaldehyde to phenol's acid-catalyzed condensation is less than 1: 1, so it is favorable for the reaction of formaldehyde with various phenols. The result is a non-crosslinked more or less linear oligomer of aromatic rings connected by methylene, as shown in Figure 13 (note that both ortho and para substitutions will occur on the phenol ring, but only the ortho Bits and neighbors occur). Show replacement). Due to the lack of formaldehyde relative to phenol, novolak resins have no residual reactive functional groups and do not cure to form a crosslinked material until additional formaldehyde is added and heated. Other formaldehyde is usually added in the form of hexamethylenetetramine or paraformaldehyde 4.