: How stable are these two epoxies when exposed to UV light? Do they stay clear
: or change color? Do they degrade or erodesignificantly in, say, 5 years of
: direct exposure to sunlight? Do they have any built in UV blockers, or do
: they need any? Other epoxies are generally coated with a varnish having a
: UV filtering capability. Is this also the case with your products?

: PGJ

Hello Paul,
For clear resins and if it is going to be continually be exposed to direct sunlight exposure, yes, a top coat such as an aliphatic polyurethane or acrylic based resin will be necessary as primary line of defense against UV degradation. Please check out our MAX SEAL:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=270181516708

Almost all epoxy resin that is commercially sold belongs to the family of thermosetting plastic called "aromatics". This group of polymers offers excellent mechanical properties but require further modification to improve UV stability.

Aliphatic based resins on the other hand, are the elite polymers that are truly UV resistant and exhibit excellent outdoor weather resistant properties, polyurethanes of the same family group for example.

Unfortunately aliphatic “epoxy” resins (cycloaliphatic resin) are highly cost prohibitive and typically require heat curing, so the dichotomy of aromatic and aliphatic polymers continues…

We do utilize anti-oxidants, ozone protectors, UV stabilizers (Hindered Amine Light Stabilizers or HALS), and UV absorbers in all our epoxy resins to improved its resistance from direct sunlight exposure.

These additives called "sacrificial additives" will absorb/refract and compete for the damaging UV energy that sunlight emits in lieu of disrupting its host’s cross-linked structure, but just like the law of energy states: “matter exist in a constant state of flux” so it to will degrade over time.

Back to the MAX CLR-HP as point of reference; yes it contains all of the inhibitors and stabilizers that will make it a UV resistant resin system. One of the biggest factors that set it apart from other epoxy formulation is how we incorporate these additives into the formulation. Our proprietary blending method controls aspect that will noticeably improve its color stability and reduce loss of mechanical performance.

We batch our resins under controlled environment such as moisture and temperature during processing. Free radical contamination is also controlled as well as exclusion of silicone based surfactants that affect interlaminar adhesion and turbidity; finally the batch is vacuum degassed to remove any dissolve gasses.

Coupled with the low plasticizer content in our curing agent, I can say with great reliance that the MAX CLR-HP will rival if not out perform epoxy resin systems from our competitors.

The typical process we recommend for applications such as kayak building is to use the MAX CLR-HP as the primary resin system for fiberglassing and bonding; and then our MAX SEAL as the top coat. MAX SEAL is a hybridized acrylic/aliphatic polyurethane water-dispersed polymer that was formulated to replace solvent laden systems. The combination of these two products forms an excellent synergistic system suitable for kayak construction.

Well, I can go on and on about the physics, do’s and don’ts of epoxy resins and other polymers related to this application, but I think I may over explaining the topic. I am sure this group’s collective experience in building a kayak is far greater than what I will ever attain. I did however build one using the resins I mentioned above. I use it often enough here in Southern California’s raging waters from our man-made lakes and it still fairs well.

In any regard, thanks for the inquiry and I am always looking for a collaborative effort in building the next one…stealth technology perhaps...hmm.
Gerald L.