Untwisted roving

Twistless roving is composed of parallel strands or parallel monofilaments bundled together. Twistless roving can be divided into: alkali free glass untwisted roving and medium alkali glass untwisted roving based on glass composition. The diameter of glass fibers used in the production of glass roving ranges from 12 to 23 μ M. The count of untwisted roving ranges from 150 to 9600 (tex). Untwisted roving can be directly used in certain composite material forming methods, such as winding and pultrusion processes. Due to its uniform tension, it can also be woven into untwisted roving fabrics, and in some applications, untwisted roving can be further shortened.

(1) Twistless roving for spraying is suitable for fiberglass spray forming. Twistless roving for spraying should have the following properties: ① good cutting performance, low static electricity generated during continuous high-speed cutting; ② The efficiency of dispersing untwisted roving into raw yarn after cutting is higher, which means a high splitting rate, usually requiring over 90%; ③ The short cut raw silk has excellent moldability and can cover all corners of the mold; ④ Resin is quickly soaked, easy to be flattened by rollers, and easy to drive away bubbles; ⑤ The raw yarn barrel has good unwinding performance, uniform roving linear density, and is suitable for various spray guns and fiber conveying systems. Jet spun roving is made from multiple strands of raw silk, each strand containing 200 fiberglass monofilaments.

(2) SMC uses untwisted roving SMC, also known as sheet molded plastic, mainly used for pressing automotive components, bathtubs, water tank boards, purification tanks, various seats, etc. When manufacturing SMC sheets, untwisted roving for SMC needs to be cut into a length of lin (25mm) and dispersed in resin paste. Therefore, the requirements for untwisted roving for SMC are good short cut, less yarn, excellent anti-static performance, and the short cut yarn will not adhere to the cutting roller during cutting. For colored SMC, untwisted roving needs to be soaked in resin paste with high pigment content. Usually, SMC untwisted roving is 2400 tex, and in a few cases, 4800 tex is also used.

(3) The winding method of untwisted roving is used to manufacture various caliber fiberglass pipes, storage tanks, etc. The number of untwisted roving used for winding ranges from 1200 to 9600. Large pipelines and storage tanks tend to be wrapped with direct untwisted roving, such as 4800 tex. The requirements for untwisted roving used for winding are as follows: ① good tape formation and flat strip shape; ② The untwisted roving has good unwinding performance, and does not detach from the loop when unwinding from the bobbin, without forming a "bird's nest" like tangled yarn; ③ The tension is uniform and there is no overhanging phenomenon; ④ The linear density is uniform, generally less than ± 7%; ⑤ Twistless roving has good permeability and is easily wetted and soaked by resin when passing through resin grooves.

(4) Twistless roving for pultrusion is used to manufacture various profiles with consistent cross-sections, characterized by high glass fiber content and high unidirectional strength. Twistless roving for pultrusion can be a combination of multiple strands of raw silk or a direct roving, with a linear density range of 1100 to 4400. The various performance requirements are generally the same as those for wrapped roving.

(5) An important use of untwisted roving for weaving is to weave various thicknesses of checkered or unidirectional untwisted roving fabrics, which are mostly used in hand layup fiberglass forming processes. There are the following requirements for non twisted roving used in strong manufacturing: ① good wear resistance; ② Good zonality; ③ Twistless roving for weaving needs to be forced dried before weaving; ④ The tension of untwisted roving should be uniform, and the drape should meet a certain standard; ⑤ The untwisted roving has good unwinding performance; ⑥ Twistless roving has good permeability.

(6) The preform is made of untwisted roving. In the preform process, the untwisted roving is cut short and sprayed onto a predetermined shaped mesh, while a small amount of resin is sprayed to fix the fiber mesh into shape. The formed fiber mesh is then moved into a metal mold and injected with resin for hot pressing to obtain the product. The performance requirements for this process of untwisted roving are basically the same as those for jet spun roving.

Twistless roving fabric

Checker cloth is a plain weave fabric made of untwisted roving, and is an important substrate for hand laid fiberglass. The strength of checkered fabric mainly lies in the warp and weft directions of the fabric. For situations where high warp or weft strength is required, unidirectional checkered fabric can also be woven. It can arrange more untwisted roving in the warp or weft directions.

The quality requirements for the fabric are as follows: ① The fabric is uniform, the edges are straight, the fabric surface is flat and in a mat shape, without stains, fuzzing, creases, wrinkles, etc.; ② The density of warp and weft, area weight, fabric width, and roll length all meet the standards; ③ Wrap it neatly on a sturdy paper core; ④ Rapid and good resin permeability; ⑤ The dry and wet mechanical strength of laminated materials made of fabrics should meet the requirements.

Composite materials formed by laying checkered cloth are characterized by low interlayer shear strength, poor compressive and fatigue strength.