Fabrics or textile structures made of glass filament products can be impregnated with various chemicals to impart the characteristics required by the end application, for example, alkali, acid- or high-temperature resistance or compatibility with bituminous sheet.
When the fabrics are used as reinforcement, such as in laminate for printed wiring boards, the textile structure can't be used directly because the textile sizes are not compatible with synthetic resins.
Therefore, additional operations are required:
- Desizing in order to remove all organic materials applied to the glass filaments during the previous processing stages.
- Impregnation by a coupling agent system (silanes), which are substances that promote a strong bond at the interface of the matrix resin and the glass filament surface.
Special textile plastic sizes are available for fabric formation. Glass fabrics made with these sizes don't require processing through a desizing operation.
Description of the process
Glass fabrics can be impregnated with a continuous processing line for industrial textiles, taking into account the specificity of glass products, i.e., the low elongation as well as the sensitivity to abrasion. For the reinforcement of resin, desizing is performed by heat cleaning.
Modern weaving technologies allow the production of large glass fabric rolls. The quantity of organic materials is high and the heat cleaning process generally necessitates two steps:
- FIRST STEP:
The glass fabric runs at a high temperature for a very short time in a continuous oven and is wound on a metallic mandrel. Most of the organic materials are removed. The operation is often called coronizing or caramelizing because the fabric color during the operation becomes brown.
- SECOND STEP:
The metallic mandrels, on which the glass cloth has been wound, are put in a large static oven. The batch heat cleaning operation can take three days and the temperature can reach about 400°C (752°F). After this operation, the glass fabric is white again and the LOI is below 0.1%.
Finally, the finish (coupling agent system) is applied on the heat-cleaned fabric with a finishing line that is generally equipped with modern automatic inspection systems to check the fabric surface.