Journeykc;3216450; said:
We will be adhereing the thermo sheet to the plywood, sealing the corners with silicone, then using the fiberglass to completely seal the corners, making it a plastic lined plywood box......we hope
There are several different polymer blends sold as thermoplastic sheeting but in general their extreme chemical resistance means they don't work well with many adhesives.
Do you have a specific product name?
Regardless, my concern is not whether or not you'll be able to bond the thermoplastic to the plywood, my concern is the integrity of the joints.
Silicone does not form a strong bond with many thermoplastic materials. Likewise the polyester resin you plan to use won't adhere to the exposed silicone. I'm not sure how well the polyester will bond to the thermoplastic.
I would test various silicones on the thermplastic and I would use epoxy resin rather than polyester to fiberglass the corners. Epoxy should have better adhesion and also be more flexible and less likely to crack.
I like the idea of using a durable plastic sheeting on the tank walls. There are hundreds of types of plastic sheet material and I would check and see if the exact one you have will work with the adhesives you plan to use.
And whether you use polyester or epoxy resin to wet out the fiberglass in the corners I'm not sure that doing so over silicone is a good idea.
Maybe epoxy/fiberglass the corners, assuming it will bond, and the make a large fillet of silicone over that. Silicone will stick to cured epoxy but epoxy won't bond to cured silicone.
