Types of bonds in boat work.

[Ross]

The bonds that we are most concened with are cohesive and adhesive. There are several other types of bonds.
Cohesion happens when a material sticks to itself. Epoxy will stick to epoxy while uncured and when cured willl form a solid mass that shows no joints.
Oil and water are not cohesive.
Adhesion happens when epoxy sticks to another material such as wood or existing fiberglass.
A mechanical bond happens when a nail, screw, or bolt is used to join to items. The hinge to the door for example. A dovetail joint is also a mechanical bond.
A fusion bond happens when two like materials are joined by partially melting and mixing the joint area. This is also called welding.
A metallurgical bond happens when two metals are joined by soldering with a third metal of lower melting temperature than either of the first two. Example using silver solder to join stainless steel to copper.

 

[Maine Sail]

The bonds that we are most concened with are cohesive and adhesive. There are several other types of bonds.
Cohesion happens when a material sticks to itself. Epoxy will stick to epoxy while uncured and when cured willl form a solid mass that shows no joints.
Oil and water are not cohesive.
Adhesion happens when epoxy sticks to another material such as wood or existing fiberglass.
A mechanical bond happens when a nail, screw, or bolt is used to join to items. The hinge to the door for example. A dovetail joint is also a mechanical bond.
A fusion bond happens when two like materials are joined by partially melting and mixing the joint area. This is also called welding.
A metallurgical bond happens when two metals are joined by soldering with a third metal of lower melting temperature than either of the first two. Example using silver solder to join stainless steel to copper.

Ross,

In the marine industry they are commonly referred to as a primary bond, eg: chemical cross linking of the resins to form one contiguous mass, and secondary bonds. Hot coating a barrier coat is a form of primary bond where the resins cross link in a cure window. Miss the hot coat/cure window and you need to wash the blush, sand and be satisfied with a secondary bond. I usually always try for a primary bond when laminating epoxy, v-ester or p-ester.

A secondary bond is basically a glue type bond in that it does not chemically cross link to the old substrate but rather glues to it, adhesive. Different resins have different strengths when used in a secondary adhesive bond situation.

Primary bonds, when you can do them, are the preferred method but just not always feasible.

This description comes from West Systems:

Primary/Secondary Bonding

Primary bonding relies on the chemical linking of adhesive layers such as the wet lay-up of fiberglass laminate in a mold. All the layers of adhesive cure together in a single fused layer. Epoxy applied over partially cured epoxy will chemically link with it and is a primary bond. The ability to chemically link diminishes as the epoxy cures and it becomes a secondary bond.


Secondary bonding relies on the mechanical linking of an adhesive to a material or cured epoxy surface. The adhesive must "key" into pores or scratches in the surface-a microscopic version of a dovetail joint. Proper surface preparation provides a texture that will help lock the cured epoxy to the surface.

 

[Ross]

Yup! that primary bond is cohesive. In a large area with enough hands you can work quite continously moving from fresh to gelled to almost hard and then back.

 

[Billbeard]

Sanding dissimilar materials can help with adhesion problems. In finishing sanding is sometimes referred to as giving surface teeth. But some products cannot be over coated with another such as lacquer over enamel or polyesters over epoxies. While the reverse is true as long as you give the substrate teeth.

 

[Ross]

You can't use lacquer over paint because the solvents loosen the paint. Polyester simply won't bond with epoxy and epoxy won't bond with PVC but polyester will bond to PVC so you can prime with polyester and then lay up epoxy and glass on the primed surface. Poly urethane varnish doesn't get on well with shellac but alkyd varnish will serve as a primer over shellac for urethane finishes.

 

[Billbeard]

Almost always there is a barrier coat you can apply to over come two different and non compatible materials in finishing a alcohol based product like shellac will over come over coating enamel with lacquer.

 

[Ross]

Almost always there is a barrier coat you can apply to over come two different and non compatible materials in finishing a alcohol based product like shellac will over come over coating enamel with lacquer.

that's one I didn't know about.

 

[zeehag]

now ye really have me scratching my head--lol.....yipes what did they make leaky teakies out of??