There is a kind of glass fiber classification called non-twisted roving, also called alkali-free glass fiber, and alkali-free glass fiber is also called E glass fiber, which refers to glass fiber with low alkali metal oxide content. There are many methods for glass fiber molding. Specifically, let's understand the twistless roving for jetting, the twistless roving for winding, and the twistless roving for pultrusion.
Untwisted roving is made up of parallel strands or parallel monofilaments. According to the glass composition, the twistless roving can be divided into: non-alkali glass, glass non-twisted roving and medium alkali glass non-twisted roving. The diameter of glass fiber used in the production of glass roving ranges from 12 to 23 μm. The number of untwisted roving ranges from 150 to 9600 (tex). Untwisted roving can be directly used in some composite material forming methods, such as winding and pultrusion. Because of its uniform tension, it can also be woven into untwisted roving fabric. In some applications, the untwisted roving is further chopped. .
1. Twistless roving for jetting: The roving that is suitable for FRP jet molding must have the following properties:
①Good cutting performance, less static electricity during continuous high-speed cutting;
②The efficiency of dispersing the untwisted roving into raw silk after cutting is high, that is, the splitting rate is high, usually more than 90%;
③The chopped strands have excellent mold covering properties and can cover all corners of the mold;
④The resin soaks quickly, is easy to be flattened by the roller and easy to drive out bubbles;
⑤The original yarn tube has good retreat performance and uniform coarse yarn density, suitable for various spray guns and fiber conveying systems. The non-twisted roving for jetting is made from multiple strands of raw silk, each containing 200 glass fiber monofilaments.
2. Untwisted roving for winding: The winding method is used to manufacture FRP pipes and storage tanks of various calibers. The number of untwisted rovings used for winding ranges from 1200 to 9600, and the winding large pipes and storage tanks tend to be direct untwisted rovings, such as 4800tex direct untwisted rovings. The requirements for untwisted roving for winding are as follows: ①Good ribbon formation and flat ribbon shape; ②The untwisted roving has good decoupling properties, and does not fall off the loop when unwinding from the bobbin, and does not form a "bird's nest"-like mess; ③ Uniform tension and no overhanging phenomenon; ④ Uniform linear density, generally less than ±7%; ⑤ The untwisted roving has good permeability and is easy to wet and penetrate the resin when passing through the resin tank.
3. Non-twisted roving for pultrusion: pultrusion is used to manufacture various profiles with the same cross-section. It is characterized by high glass fiber content and high unidirectional strength. The untwisted roving for pultrusion can be a combination of multiple strands of raw filaments or a direct untwisted roving, and its linear density ranges from 1100 to 4400. Various performance requirements are roughly the same as those of winding untwisted roving.