Selection of glass fiber sizing
This article briefly introduces the types of commonly used glass fiber sizing agents and their applicable scenarios, helping users make more scientific decisions based on the project's process and resin system.
1.Sizing Properties
What is a sizing? A sizing is a functional coating applied to the surface of glass fiber. It is primarily used to strengthen the bond between the fiber and the resin matrix, improving the fiber's flexibility, wear resistance, and dispersion during processing. In the manufacture of FRP (fiberglass reinforced plastic) products, the properties of the sizing have a significant impact on the mechanical properties, interfacial bond strength, and service life of the final composite material.
2.Main Types of Sizing Agents and Applicable Systems
Sizing Agent Types | Matching Resin Systems | Applicable Processes | Features |
Silane Sizing | Polyester Resin, Epoxy Resin | Pultrusion, Winding, Molding | Strong adhesion, good chemical stability, and high versatility |
Polyurethane Sizing | Polyurethane, PVC | Spraying, hand lay-up, hot pressing | Excellent flexibility, suitable for soft composite materials |
Polyester Sizing | Unsaturated Polyester Resin | Hand lay-up, RTM, Winding | Stable performance, low cost, commonly used in the building materials industry |
Epoxy Sizing | Epoxy Resin | Pultrusion, Winding, Injection Molding | High bond strength, suitable for high-performance composite structures |
Specialty Surface Treatment Agents | Phenolic, Thermoplastic Resins, etc. | High-temperature or Specialty Molding Processes | High heat resistance, suitable for high-temperature/high-corrosion environments |
3.How to Choose a Sizing
Processes
Pultrusion and Winding: Silane or epoxy sizings are recommended for better adhesion.
For spraying and hand lay-up, polyester or polyurethane sizings are suitable, as they offer excellent workability.
Resin System Compatibility
If you are using unsaturated polyester resin, a polyester sizing will meet most general requirements.
If you are using epoxy resin, you should use a dedicated epoxy sizing to avoid interfacial failure.
Performance Requirements
For structural parts requiring high tensile strength, epoxy sizings are recommended.
For products requiring high flexibility and impact resistance, polyurethane sizings are recommended.
For projects requiring high corrosion resistance and durability, silane sizings are preferred.
Considering Cost and Supply Stability
Standard sizings can be used for general products to reduce costs.
For high-end projects, customized solutions can be provided based on specific requirements.
4.FAQ
Can different sizings be mixed?
Generally, mixing is not recommended. Each sizing has different chemical properties, and mixing them may lead to bond failure or interfacial instability.
If the resin type is changed for a project, is it necessary to change the sizing?
Yes. The sizing and resin system are compatible with each other. When changing resins, the type of sizing used for the glass fiber should be re-evaluated.
How can you determine if the glass fiber sizing you're using is appropriate?
This can be assessed by testing indicators such as tensile strength and interlaminar shear strength. Poor surface bonding, delamination, and whitening are all signs of mismatch.
5. Summary
Although the sizing accounts for less than 2% of the glass fiber's weight, it has a decisive impact on the overall performance of FRP composites. Choosing the right sizing not only improves the product's structural strength and service life but also increases efficiency during processing, reducing problems such as breakage and mold sticking. For export projects, it is crucial to ensure stable performance under varying climate, humidity, and transportation conditions.