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Impact Of Internal Release Agents On Pultruded Profiles

Today, let’s talk about the impact of internal release agents on Pultruded Profiles.

Internal release agents play a key role in the pultrusion process of Pultruded Profiles. They are added to the resin and are compatible with the liquid resin but incompatible with the cured resin. At the appropriate processing temperature, they exude from the resin, forming a separation film to facilitate demolding. This additive helps maintain the surface quality of the product and the integrity of the mold, without affecting the curing characteristics of the resin or the physical and mechanical properties of the product. However, several issues need to be noted when using internal release agents: pigments sensitive to acid may change color; alkaline fillers may increase the viscosity of the mixture; aluminum hydroxide fillers may cause bubbles or cracks; the amount of internal release agent must be adjusted appropriately, as excessive amounts may delay curing; in pultrusion production, if the resistance is too high, it may be necessary to increase the amount of release agent.

We know that release agents with strong hydrophilicity can affect the strength of the pultruded products as they introduce more moisture into the pultrusion process. Meanwhile, during the resin mixing process, the water entering the resin will contain a lot of air. On the other hand, because water has strong hydrophilic surface activity, it can easily emulsify into very small droplets and disperse evenly in the resin mixture. During the pultrusion process, the water enters the interface between resin and fiber, affecting the interface strength and subsequently reducing it. The water content in the matrix also affects the strength of the cured matrix. The more water in the resin, the greater the impact.

In the pultrusion process, the release agent does not completely exude from the product; some remain inside. Hydrophilic release agents have strong hydrophilicity and become a pathway for water molecules to flow out. Water molecules use these pathways to accelerate the erosion and damage of the product. There is a type of release agent on the market that claims to be neutral and dissolves well in water. Due to its strong hydrophilicity, it is expected that this type of release agent will have a certain impact on the strength of the product.

The pultrusion process may seem simple, but it is actually a very complex technology. It involves a variety of raw materials, each type differing from the others. Various process issues may also arise. When we identify these issues, we must first find the causes in order to solve them.

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