River Tables Epoxy Casting Systems

Epoxy to Cast River Tables.

We have many types of resins and hardeners. All formulated in South Africa. 

LR113 is the mos economic, as it contains a small % of cyclo - aliphatic epox resin.

LR114 is the second most economic, followed by LR115. LR311 is 100% cyclo - alipatic resin.

All these resins also contain UV protection additives. However, no epoxy can widthstand continous outdoor exposure. They will all become yellow over time.

We are currently conducting a long term UV testing propram, to compare the UV effects in a QUV machine against the UV effects of the sun. We hope to be able to correlate these two methods. Obvioulsy the UV machine will age the samples faster, and we need to determine what one month of exposure to the UV lamp equantes to how many months of continous outdoor exposure.

We can also measure the initial clarity of each resin system, and how it is reduced by the effects of UV. 

Comparing different types of resins, and their costs vs the benefits, in a scientific manner is the goal.

All the resins and hardeners have very low viscosity, to prevent air bubbles from forming. Normally it is not necessary to use any blow torches to remove air bubbles. Also the use of these heat guns, will raise the temperatute, which may lead to shrinkage. A 10 degree rise in temperaure, in a short space of time, may create a feedback system, which causes the reaction to accelerate. Casting in winter where the temperature is 15 C and casting in summner at 30 C, will make a huge difference.

Resin viscosities are about 600 cP and hardener about 60 cP.

It is very important to seal the wood with a faster epoxy system, for instance using EH48 hardener. The humidity, and oils in the wood, may interfere with the liquid resins, if they are not sealed. Some people have used water based sealers, with drastic consequences. 

We have many combinations of hardeners. EH49 is one of the slowest. Followed by EH59. EH48 is the fastest. Blending EH59 with EH49 or EH48 gives different setting times, and therefore different casting thickness, without shrinkage.

EH5949.3 has been used to cast 100 mm blocks.

EH5948.07  is the nex slowest. casting about 40 to 60 mm

EH5948.4 is a medium hardener, castings from 20 to 50 mm.

EH5948.2 is faster for castings from 10 to 30 mm.

All these combinations should be tested, by casting in a Tuppeware box, to verify the reaction, setting time, air bubbles etc. 

Every time a table is cast, the customer should always cast a disk about 10 to 20 mm thick as a control. The batch numbers, date and ambient temperature should be written on the sample.

All resins and hardeners should be weighed accurately into one clean container,mixed for 2 minutes, then the entire contents transferred toa second clean container. The sides and bottom of the first bucket, must be scrapped well. Then mixed again in the second container. 

Mixing and casting will introduce air bubbles, but these should all escape witout any blowguns. 

 

 

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