Silanes for fiberglass and composite application

Fiberglass description:

For their high specific modulus, high specific strength, fiberglass and its reinforced polyester composites application field: 

Aerospace, auto bodies, chemical and automation industries.

Why?

Fiberglass and the resin matrix are hardly to achieve satisfactory bond strength at the interface as the surface of fiberglass is very smooth. 

Fiberglass consists mainly of silica, alumina, magnesia and other metal oxide, so the fiber is very hydrophilic and easily attracts water to the interface and has a very bad effect on the bond between the fiber and the resin. 

Therefore, it is necessary to conduct a surface treatment on glass fiber to improve its compatibility, infiltration and reactivity with the resin, and forming a good composite with optimum properties.

When organic polymers are reinforced with glass fibers or minerals, the interface, or interphase region, between the polymer and the inorganic substrate is involved in a complex interplay of physical and chemical factors. These factors are related to adhesion, physical strength, coefficient of expansion, concentration gradients and retention of product properties.

A very destructive force affecting adhesion is migration of water to the hydrophilic surface of the inorganic reinforcement. Water attacks the interface, destroying the bond between the polymer and reinforcement, but a “true” coupling agent creates a water-resistant bond at the interface between the inorganic and organic materials.

Advantages of Using Silane coupling agents:

It has the unique chemical and physical properties not only to enhance bond strength but also, more importantly, to prevent de-bonding at the interface during composite aging and use.

Silane coupling agents are silicon-based chemicals that contain two types of Reactive functional groups, inorganic and organic, in the same molecule. A typical general structure is Y-R-SiX3

Where Y is an organofunctional group, such as epoxy, methacryloxy or amino, and X is a hydrolyzable group, such as ethoxy, methoxy, acetoxy, etc.

The silane coupling agents have the unique chemical and physical properties and will act at interface between glass and organic polymer to bond, or couple, these two dissimilar materials, plays a role in improving the mechanical properties of composites and, more importantly, to prevent de-bonding at the interface during composite aging and use.

Silane coupling agents also increase the bond strength of coatings and adhesives as well as their resistance to humidity and other adverse environmental conditions.

The silane bond to the fiberglass inorganic substrate can be summarized as the following four points：

-alkoxy groups on silicon hydrolyze to silanols；

-silanols react with other silanols to form a siloxane bond；

-with the evaporation of water, intramolecular Hydrogen Bond Formation；

-after drying, the hydroxyl group of silane coupling agent condenses with the hydroxyl group on the fiberglass and form ether bond.

Other benefits silane coupling agents can provide include:

-Better wetting of inorganic substrates

-Lower viscosities during compounding

-Smoother surfaces of composites

-Less catalyst inhibition of thermoset composites

-Clearer reinforced plastics

Recommended SIWIN CODE：

Siwin-A110 ; Siwin-E560 ; Siwin-M31