Question about resin and blushing

you got it right in your first post Declan, epoxy is sensitive to uv and is more expensive and not as tolerant of adverse application and work practices.
Polyester is the predominate resin used in the Mariner industry and for many others for many good reasons.
Many inexperienced applicators waste time and money sanding,grinding and doing work that is not necessary and just contributes to contamination of the work surface.
Sanding and cleaning a work surface that is already smooth and clean may make you feel good that you are doing a good job but does not contribute to a lasting all round finish.

 

Thanks. I knew my question was a loaded question.
Here's another
Is the majority of these unrefined epoxies used as is in non-marine industries or is the majority specialty formulated?

 

Thanks. On the labels I've seen flexible and non-blushing advertised and different working times advertised: fast, normal, and slow hardeners. Other than that it's hard to differentiate one formulation from another for me. What other major properties are formulated to create marine resins?

 

The bottom line is, Why use a blushing epoxy at all when non blushing epoxies are available? that's like using a typewriter when you can use a wordprocessor/computer.

 

PAR is right. I don't have the chemistry background to know. Cost is the only thing I can think of. Unless there are a hundred trade-offs in each formulation and there is some advantage that's more important for something. I did a contract last month and the agent used a typewriter to do a carbon form. Must be some legal requirement technicality - there was a computer sitting on their desk with a printer too and he didn't enjoy typing out the form. I wish the formulators posted practical explanations of what their epoxy is engineered for and what the trade-offs are for each one.

 

Solar, if you saw the technical differences of the various formulations (there's hundreds of them), they'd seem either insignificant or possibly you'd focus on one thing being more important than it really is. Simply put, it's a pretty complex subject, but for the most part the major players do suggest what their formulations are aimed at, without baffling you with a bunch of stuff you wouldn't understand anyway.

At first glance you'd think, well how about some general comparisons, such as viscosity, blush, hardness, elongation, etc., but this information might just make you think you need three different formulations, to cover all your needs, when one will do, unless you're building some really high end stuff, where weight, stiffness, application and physical properties are absolutely critical.

As a rule, the unrefined epoxies can cost less, but most of these outfits are pricing with the other guys and taking advantage of the margin, so there's no advantage, cost wise. Also most formulators do offer physical properties data for their products.

 

some of the reasons for forumulated epoxies

1 - to make more money for the vendor (the curing agents are the $$ part, the more part A and less part B - the more money for the vendor) - ditto with adding lots of nonyl phenol to part a and or b (like watering down the whisky).

2 - to adjust for blushing vs UV issues, viscosity, working/cure time, etc (fast - slow cures etc), brittleness

3 - to get the mix ratios into whole numbers

note that are dozens of different curing agents and even more additives - formulators use a carefully crafted blend. - things can also go into the part A