Property of Polyester Resin
Property of Polyester Resin
(OP)
My question concerns that very useful property that unwaxed polyester resin has of not curing in air so you can get a good chemical bond. Is it just a coincidence of it's chemical composition or is it engineered in?
If it is manufactured that way on purpose why can't it be made to cure in air? (without adding wax to it)
Thanks for any information.
If it is manufactured that way on purpose why can't it be made to cure in air? (without adding wax to it)
Thanks for any information.





RE: Property of Polyester Resin
RE: Property of Polyester Resin
The air inhibition is an unfortunate side effect of the peroxide curing mechanism.
The discovery that wax could be added to the uncured resin and would separate during the cure and seal the surface, was a step forward in improving the handling qualities of the resin.
B.E.
RE: Property of Polyester Resin
Berkshire -- I noticed you called it an 'unfortunate side effect'. I would of thought it was an advantage. Having seen the effects of delamination many times and I am sure you have too, don't you think the better chemical adhesion is an advantage with polyester.
(Of course I do not know for sure what caused the delam. but I suspect it was the poor mechanical bond of polyester and/or difficulty in cleaning wax off.)
Any thoughts.
RE: Property of Polyester Resin
If you are working in a controlled environment it can be an advantage. In that the uncured resin will cure when sealed over with new resin with active peroxide in it. It is often used on large part layups to allow an exothermic reaction to subside before adding more resin and reinforcements.
The basis of my remark comes from old history of working on fiberglass boats in the 70s (Bass Boats). They were typically built from orthophalic resin, air inhibited cure applied with a chopper gun. Secondary bonding was very often done weeks after the initial layup by wiping the area to be bonded with a little acetone on a rag and gluing in the part.
Testing on bond lines later revealed this to be hit or miss at best. We evolved a policy, that if the part was cured more than one week you sanded the bond line after rinsing it off with acetone, before gluing on a part.
Relying on a mechanical bond more so than a chemical one.
B.E.
RE: Property of Polyester Resin
RE: Property of Polyester Resin