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Phenol-formaldehyde resin

Phenol-formaldehyde resin

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Phenol-formaldehyde resin

chemical compound

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External Websites
  • University Federico II of Naples, Italy – What is Chemistry? – Phenol-formaldehyde resin

Alternative Title: phenolic resin

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

). Phenol-formaldehyde resins were the first completely synthetic

polymers

to be commercialized. In the first decades of the 20th century,

Bakelite

, a trademarked phenolic

plastic

, revolutionized the market for molded and laminated parts for use in electrical equipment. Phenolics are still very important

industrial polymers

, though their most common use today is in adhesives for the bonding of plywood and other structural wood products. The chemical

composition

of phenol and formaldehyde and their combination into networks of permanently interlinked large molecules are explained briefly in the article

aldehyde condensation polymer

.

In industrial practice, there are two basic methods for making the polymer into useful resins. In one method, an excess of formaldehyde is reacted with phenol in the presence of a

base

catalyst

in water

solution

to yield a low-molecular-weight prepolymer called a resole. The resole, frequently in

liquid

form or solution, can be cured to a

solid

thermosetting network polymer by, for instance, sandwiching it between layers of wood veneer and then heating the assembly under pressure to form a plywood.

The other method involves reacting formaldehyde with an excess of phenol, using an

acid

catalyst. This process produces a solid prepolymer called a novolac (or novolak), which resembles the final polymer except that it is of much lower

molecular weight

and is still thermoplastic (that is, it can be softened by reheating without undergoing chemical decomposition). Curing can be accomplished by grinding the novolac to a powder, mixing it with fillers such as wood flour, minerals, or glass fibres, and then heating the mixture in a pressurized mold. In order to be cured to a thermosetting

resin

, novolacs require the addition of more formaldehyde or, more commonly, of

compounds

that decompose into formaldehyde upon heating.

Phenol-formaldehyde resins make excellent wood adhesives for plywood and particleboard because they form chemical bonds with the phenol-like

lignin

component of wood. They are especially desirable for exterior plywood, owing to their good moisture resistance. Phenolic resins, invariably reinforced with fibres or flakes, are also molded into insulating and heat-resistant objects such as appliance handles, distributor caps, and brake linings.

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Learn More in these related Britannica articles:

  • Figure 1: The linear form of polyethylene, known as high-density polyethylene (HDPE).
    major industrial polymers: Phenol formaldehyde
    Also known as phenolic resins, phenol-formaldehyde polymers were the first completely synthetic polymers to be commercialized. Although molded products no longer represent their most important application, through their use as adhesives they still represent almost half of the total production of thermosetting polymers.…

  • phenol-formaldehyde resin
    phenol: Formation of phenol-formaldehyde resins
    Phenolic resins account for a large portion of phenol production. Under the trade name Bakelite, a phenol-formaldehyde resin was one of the earliest plastics, invented by American industrial chemist Leo Baekeland and patented in 1909. Phenol-formaldehyde resins are inexpensive, heat-resistant, and waterproof, though somewhat…

  • phenol-formaldehyde resin
    aldehyde condensation polymer
    The resultant polymers—known as phenol-formaldehyde resin, urea-formaldehyde resin, and melamine-formaldehyde resin—are widely used as adhesives in plywood and other structural wood products. In the first half of the 20th century they were made into very important plastics such as Bakelite and Beetleware.…

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