Hello friends,

I intend to make a medium-sized piece (1.35mx 0.30m) with polyester resin, but I saw that it corrodes the potential risk of shrinkage during resin curing.

- The resin has the gel time of: 30 minutes and the manufacturing process would be by Hand Layup + vacuum bag or Resin nfusion.

The doubts are as follows:

"What do I have to do to stop this from slowing down?"
Because I can not have dimensional changes due to the product accessories.

Desmoulding after 4 hours of lamination cause me problems?

We have a small production line and we need to be quick in our process.

Thanks,
Dezer

no, I am talking about the first hour of curing. polyester reaches this "jelly stage" in wich it is no longer liquid, and cannot flow infinitely under shear stresses (the definition of a liquid). from this point on, the resin still shrinks massively, but cannot flow anymore, to compensate the shrinkage.
and I not talking about my experiences, this is state of the art university knowledge. you can find this information in "konstruieren mit faser-kunstoff-verbunden" written by Helmut schürmann, professor at TU Darmstadt. one of the best (mostly theoretical) books about composites in my opinion.

I forgot a good countermeasure against warping and shrinking:
use woven cloth instead of chopped strand mat. and use a symmetrical layup. for example layer a, then layer b, then b and finally a again.
with woven cloths you can achieve higher fibre contents, and the symmetrical layup cancels the warping forces out against each other.

+x

 

oekmont - 2/19/2018 7:30:03 AM

no, I am talking about the first hour of curing. polyester reaches this "jelly stage" in wich it is no longer liquid, and cannot flow infinitely under shear stresses (the definition of a liquid). from this point on, the resin still shrinks massively, but cannot flow anymore, to compensate the shrinkage.
and I not talking about my experiences, this is state of the art university knowledge. you can find this information in "konstruieren mit faser-kunstoff-verbunden" written by Helmut schürmann, professor at TU Darmstadt. one of the best (mostly theoretical) books about composites in my opinion.

I forgot a good countermeasure against warping and shrinking:
use woven cloth instead of chopped strand mat. and use a symmetrical layup. for example layer a, then layer b, then b and finally a again.
with woven cloths you can achieve higher fibre contents, and the symmetrical layup cancels the warping forces out against each other.

Hi my friend 
Please help me
I apply gel coat as first layer . After 2 hrs I apply second layer " mixed polyester resin  around 35% and 5 % pigment and silica powder 30 % and carbonate calcium 30 % as filler around 60 %
I demold after 1 hrs but back side of mold comes out very good but top side is not come out easily .
Please help me what is my problem ?
Also I add cobalt 0.05 % and peroxide 1.8 %
How can i remove my part easily  ?
My part thickness is 1.2 mm

Tanks so much in advance