Frequently question and solution of pultrusion resin products


Common problems and solutions of tension and compression molding process

In the process of pultrusion, problems such as surface peeling and cracking of bubbles often occur. There have always been 7 major problems and corresponding solutions.

1. Peeling

When artificial surfaces have love from the mold, this phenomenon is called flaking or missing particles.


• Increase feed end temperature on artist's early models.

• Reduced line speed to allow agencies to advertise earlier.

• Stop line to clean up (30 to 60 seconds).

• Increase the concentration of cryogenic reagents.

2. Foaming

When blistering occurs on the surface of the component.


• Raise the temperature of the plug-in end for exemplary performance in public service

• Decrease line speed, same effect as above

• Improved foaming levels, sustained increase from low emissivity.

3. Surface wilderness

The surface is caused by overdose.


• Increase mold temperature to mold speed

• Decrease line speed, same effect as above

• Increased loading or fiber content increases the amount of machine pressure, thereby reducing shrinkage and pressure

• Add surfaces or faces to parts

•Add low temperature adhesive or use current temperature adhesive.

4. Internal cracks

Internal cracks are usually associated with an excessively thick section, and cracks may appear in the center of the laminate or at the surface.


• Increase feed end temperature for earlier resin cure

• Lower the mold temperature at the end of the mold to act as a heat sink to reduce exothermic peaks

• If the mold temperature cannot be changed, increase the line speed to reduce the temperature of the outer contour of the part as well as the exothermic peak, thereby reducing any thermal stress.

• Reduce initiator levels, especially high temperature initiators. This is the best permanent solution, but needs some experimentation to help.

• Replace the high temperature initiator with a low exothermic but better cure initiator.

5. Chromatic aberration

Hot spots can cause uneven shrinkage, resulting in chromatic aberration (aka color transfer)


• Check the heater to make sure it is in place so that there is no uneven temperature across the die

• Check the resin mix to ensure that fillers and/or pigments do not settle or separate (color difference)

6. Low barcol hardness

Low barcol hardness; due to incomplete curing.


• Reduce line speed to accelerate resin curing

• Increase mold temperature to increase cure rate and degree of cure in the mold

• Check for mixture formulations that lead to excessive plasticization

• Check for other contaminants such as water or pigments that can affect the cure rate

Note: Barcol hardness readings should only be used to compare cures with the same resin. They cannot be used to compare cures with different resins, as different resins are produced with their own specific glycols and have different depths of crosslinking.

7. Bubbles or pores

Bubbles or pores may appear on the surface.


• Check to see if excess moisture and solvent are caused during mixing or due to improper heating. Water and solvents boil and evaporate during the exothermic process, causing bubbles or pores on the surface.

• Decrease line speed, and/or increase mold temperature, to better overcome this problem by increasing surface resin hardness.

• Use a surface mask or surface felt. This will strengthen the surface resin and help eliminate air bubbles or pores.



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