What does PF stand for?

[FORMULA NOT REPRODUCIBLE IN ASCII] CONCLUSIONS The used molar ratio of phenol/formaldehyde (P/F) gives resins with a very low content of monomers and a similar ratio of hydroxymethyl/methylene groups.

Random pre-polymers of phenol/formaldehyde are prepared by reacting phenol on the ortho and para positions in the boxing ring with bifunctional formaldehyde, where the bases catalyzed reaction produce a mixture of methylol phenols where the composition of the mixture can be varied by altering the phenol to formaldehyde ratio Inorganic catalysts such as copper halides are known to catalyze phenol polymerization in the presence of molecular oxygen [17].

It has been shown that phenol/formaldehyde resins are important binder resins especially useful for positive g and i-line sensitive resists (2).

Since the resol type phenol-formaldehyde resin used in this study was procured from a commercial source, the actual phenol/formaldehyde ratio is not known.

Free phenol/formaldehyde levels are low, both in the resin as supplied and in the mixed sand.

Since the resol type phenol-formaldehyde resin used in this study was procured from a commercial source, the actual phenol/formaldehyde ratio is not disclosed.