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The synthetic resins, originally viewed assubstitutes for copal, dammar, and elemi naturalresins, have a large place of their own in industryand commerce. Phenol-formaldehyde, phenolurea,and phenol-melamine resins have beenimportant commercially for a long time. Anyunplasticized organic polymer is considered aresin, thus nearly any of the common plasticsmay be viewed as a synthetic resin. Water-solubleresins are marketed chiefly as substitutesfor vegetable gums and in their own right forhighly specialized applications. Carboxymethylcellulose,hydroxyalkylated cellulose derivatives,modified starches, polyvinyl alcohol,polyvinylpyrrolindone, and polyacrylamidesare used as thickening agents for foods, paints,and drilling muds, as fiber sizings, in variouskinds of protective coatings, and as encapsulatingsubstances.
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