How Much Hardener Do I Need For Epoxy Resin?
How Much Hardener Do I Need For Epoxy Resin?
Mixing the resin and hardener for a two-part epoxy system in several ways. The most common method is to mix by volume, using a 2:1 ratio of resin to hardener. Measure out two parts resin to 1-part hardener and mix the two components together.
Another common method is to mix by weight, using a 100:35 ratio of resin to hardener. This can be done by weighing 100 grams of resin and 35 grams of hardener or using a pre-measured kit.
It is common in the resin industry to specify a mix ratio in terms of parts per hundred resin (phr). This term refers to the amount of amine added per 100 parts of resin by weight. In other words, 20 phr would be equivalent to adding 20 parts by weight of amine per 100 parts of resin.
This system is useful because it allows for quick and easy calculation of the amount of amine needed for a given resin. For example, if you have 1000 grams of resin, you would need 200 grams of amine to achieve a 20 phr ratio.
It is important to note that the phr system is only applicable when dealing with pure resins. In reality, most resins are mixtures of more than one hardener with up to 10 different amines available. A mix ratio of simple weight will be used for these resins instead.
It is also important to note that the phr system is not directly applicable when dealing with polyester resins. Instead, the resin must be measured by weight and used at a specific percentage of resin by weight.
The easiest way to determine the percentage of resin in a polyester resin mixture is to weigh 100 grams of polyester and calculate the amount needed for 25 phr (100% polyester).
How Much Vacuum Is Needed For Epoxy Resin?
The amount of vacuum required for various applications can vary greatly. In general, however, a vacuum of 29 inches of mercury (Hg) is sufficient for most purposes.
In some cases, such as high-volume production, a vacuum of only 2 mm may be sufficient. It is important to use a large container to allow the material to rise under a vacuum.
Always use a large enough container to allow the material to rise under the vacuum so the vacuum can be maintained and the material can be protected from damage. However, a smaller vessel is typically used to minimize the material used.
The container holding the resin must have enough headspace to accommodate three times the original volume of the resin. The vacuum is pulled to 29 inches of mercury.
The air is sucked out of the resin, causing the bubbles to rise and collapse. This process typically takes a couple of minutes. However, the vacuum must be pulled prior to mixing the resin and hardener.
Care should be taken when handling epoxy resin under a vacuum. Never leave the resin under a vacuum for more than 90 minutes.
Avoid touching the lid of the container to avoid contamination of the surface. Always mix clean solvents in a dry environment, such as a fume hood or glove box. It is also important to monitor storage temperature and exposure to light, which may reduce physical properties over time.
