Here are 15 common problems and solutions in pultruding fiberglass-reinforced plastic

Problems Encountered in the Production Process of FRP Pultruded Profiles-1

1. Causes of surface droplets:Incomplete curing, low fiber content, and large shrinkage. Also, a large gap between the product surface and the mold wall, and migration of uncured resin.

Solution:Increase the temperature or reduce the drawing speed. This ensures full curing, which is crucial for thick-walled products. Increase the fiber content or add low-shrinkage agents and fillers.

2. Causes of surface peeling and cracking:

An excessive resin-rich layer on the surface. Crawling and creeping at the exit point. A large difference between gel time and curing time. The exit point being too far ahead of the curing point.

Solution:Boost the fiber content to raise the mold’s internal pressure. Also, tweak the initiation system and modify the temperature.

3. White powder causes poor demolding, mold adhesion, and scratches on the product. It also raises the inner mold wall’s roughness due to wear or rust.

Solution:Use a good demolding agent. Clean, repair, or replace a qualified mold. Stop the machine for a moment, then restart it. Pull out the adhered fragments to clean them.

4.Causes of an obvious parting line and wear at the parting line include:

• Low accuracy in the mold’s dimensions.

• Large positioning errors of each module when closing the mold.

• Mold adhesion at the parting line, leading to white lines.

Solution:Repair the mold. Then, disassemble and reassemble it. Finally, stop and restart the machine.

5. Fiber exposure and fuzzing causes:This defect usually occurs in products made only with fiber yarns, like rods. Possible reasons are too high a fiber content or resin debris sticking to the mold’s inner wall.

Solution:Reduce the fiber content, stop the machine, and restart.

Q&A—2

6. Poor aging resistance and fading happen due to a lack of light and heat stabilizers. Also, the pigment has low lightfastness.

Solution: Add anti-aging agents and use high-quality color pastes.

7. Poor insulation causes poor insulation of the resin and fiber. Also, poor bonding at the interface.

Solution: Improve raw material selection. Use coupling agents to boost interfacial performance.

8. Insufficient strength and poor properties cause low raw material strength and low curing.

Solution: Use high-quality raw materials, like strong fibers and resins. Control process parameters to ensure proper curing. Perform post-curing treatment.

9. Dense pores cause poor quality of raw materials and unreasonable temperature control.

Solution: Use good raw materials and control the temperature to not be too high.

10. Color spots, uneven color, and color change causes: Uneven mixing of pigments in the resin and poor heat resistance of the pigments.

Solution: Stir more to mix the resin slurry evenly. Also, switch the pigment type.

11. Causes of contamination and foreign matter mixing: Foreign matter in the resin slurry, a contaminated glass mat surface, and foreign matter in the mold.

Solution: Check carefully to avoid mixing in foreign matter during molding. Also, replace any contaminated raw materials.

12.Rough and dull surfaces occur due to several reasons:

• High mold roughness

• A poor demolding agent.

• Low resin on the product’s surface.

• Insufficient mold pressure during molding.

These factors can lead to an undesirable texture.

Solution: Use a mold with a low surface roughness. Use a good demolding agent. Use a surface mat or pass a continuous mat and knitted mat through the impregnation bath. Increase the fiber content or add fillers.

Q&A—3

13. Causes of surface indentation: low fiber content or mold adhesion. This leads to fragment buildup that scratches the product’s surface.

Solution: Increase the fiber content. Clean the mold. Stop and restart the machine. Use a good demolding agent.

14. Incomplete glass mat wrapping causes a narrow mat width and a faulty positioning device. The mat deviates during molding.

Solution: When designing the mat width, consider a certain overlap length. Also, there must be a precise mat guide seam on the mold before the mat enters it. Add a limit card at the mold entrance if necessary.

15. Causes of surface wrinkles: The glass fiber mat is too hard. It folds when entering the mold. The polyester surface mat (or non-woven fabric) is too soft and has a certain slope when entering the mold. During the pull molding of curved products, wrinkles occur due to the pulling force.

Solution: Use a softer glass surface mat. When using a polyester surface mat or non-woven fabric, operate carefully. If necessary, set up a fixture at the mold opening for precise positioning.