If yes.
(2) Do one need to recover them after UPR production or they become part of the UPR compositions?
It is understandable that one need to apply them for curing of UPR during composite production (with addition of filler). I will like to know if one still need to apply them for just UPR production without getting to the composite production stage.
Thank you so much.
The use of both initiator & promoter would be decided by the temperature, process.
If it is high temperature operation, you are required to use only initiator.
But for ambient temperature operations, you may have to use both. Sometimes, the resin is pre-promoted by the manufacturer & in such cases, you hav eto use only initiator.
Unsaturated polyester resins (UPR) are usually the condensation products of unsaturated acids or anhydrides with diols examples of which is the UPR obtained by reacting maleic anhydride or maleic acid with propylene glycol. Later on, such resins are compounded with various fillers, reinforcements and then cured by using free radical initiators to yield thermoset articles.
The unsaturation present in these polyesters provides a site for subsequent cross-linking which is a major aim.
Therefore, there is no need to use an initiator or a promoter in the initial production of the polyesters & only heat is required.
The nature of the final composite would have been affected by the type & amount of initiator/promoter used in curing and the advice of polymer experts is to use a small amount of them.
Yes Nizar, you are right. No promoter & initiator are needed for the manufacture of Ortho (phthalic anhydride based) UP resins. For Isophthalic acid & terephthalic acid based UP Rresins you need to have esterification catalyst.
@Joshi Sir, Could you kindly inform which catalyst is used for Iso & PTA based esterification reaction process
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