Polyesters are "Alcohol + Acid". Polyamides are "Amine + Acid". Phenol-Formaldehyde resins (like Novolac and Bakelite) use formaldehyde as the linking agent, creating ether or methylene bridges.
To determine which among the options is not a polyester, we need to understand what polyester is and evaluate each option in context:
Polyester: Polyesters are polymers that have ester functional groups in their main chain. Generally, they are formed through a polycondensation reaction between diols and dicarboxylic acids.
Glyptal: Glyptal is a polyester resulting from the reaction of glycerol (a triol) and phthalic anhydride. Thus, it is a type of polyester.
Novolac: Novolac is a phenolic polymer formed by the polymerization of phenol with formaldehyde in the presence of an acid catalyst. Novolac does not contain ester linkages; rather, it has phenolic characteristics. Therefore, it is not a polyester.
Dacron: Dacron is a type of polyester known chemically as polyethylene terephthalate (PET). It is made from terephthalic acid and ethylene glycol. Hence, it is a polyester.
PHBV (Polyhydroxybutyrate-co-valerate): PHBV is a biodegradable polyester formed from hydroxybutyrate and hydroxyvalerate. Thus, it is indeed a polyester.
To conclude, Novolac is the option that is not classified as a polyester since it does not contain any ester linkages, distinguishing it from the rest of the options.
