How much internal mold release should I mix into the resin for testing?
The amount of internal mold release added is measured in terms of parts per 100 resin, by weight (phr). This is based on the unfilled (neat) resin. For example, adding 1.0 phr of internal mold release means that 1 part of internal mold release is added to 100 parts of the neat resin.
The amount of internal mold release will vary depending on the resin formulation. The type of resin, concentration of fillers and pigments, and die geometry can all affect the necessary amount of internal mold release required.
Generally, a typical polyester pultruded stock may use 0.25–2.0 phr of internal mold release whereas an epoxy pultruded stock may use 1.0–3.0 phr of internal mold release. It is generally recommended to start at a higher level for testing and reduce to lower levels to optimize while in production.
Chem-Trend has performed extensive testing in its labs, and has established starting points and relevant ranges for each of its internal mold releases. See the product datasheet for suggested loading levels of each Chemlease® product.