Coating

Various chemical substances can coat either glass filament yarns
or fabrics. Major applications are:

• PVC coated yarns for sun and insect screening
• PTFE coated fabrics for high-end printed wiring boards (low dielectric constant/low losses), architectural and roofing membranes
• Specific properties of PTFE fabrics – such as non-stick and smooth surface, resistance to chemicals, compliance with food regulation, temperature resistance and high tensile strength – benefit a wide range of applications, including food processing, conveyor belts, release sheets, thermal insulation, sealing and more

Description of the process

PVC coated yarns

Single yarns pulled from a creel are drawn through a PVC jet or bath and a die to form the desired round section shape. Then the coated yarn is dried and thermally cured in a continuous oven and wound onto a paper tube to make products suitable for additional textile operations like beaming and weaving. Required properties of single yarns are high twist to promote round section, high tensile strength and compatibility with PVC so that all of the yarn is coated evenly.

PTFE coated fabrics

Glass fabrics are impregnated on a finishing line with PTFE dispersion. The coating layer build-up occurs in three steps: elimination of water, removal of dispersion surfactants to
250°–280°C (482°–536°F) and sintering to 450°C (842°F). The impregnation process can be repeated up to eight times in order to reach the required PTFE thickness. Other chemicals can be added to impart specific properties. Additional partial heat cleaning is also sometimes processed in order to suit the required color of fabric.