A single thread is not a thread

There is a saying is "a single thread is not a line", meaning the individual strength is weak, encourage people to unite; The idea is that a single filament cannot be turned into yarn. Carbon fiber products are no exception - carbon fiber tow, carbon fiber rope are composed of multiple wires.

We know that the pore size of the activated carbon is very small, but the number of pores is large, which makes the activated carbon have special properties. Carbon fiber is the same, quantitative change causes qualitative change.

（See also: What is Activated Carbon? What is hard carbon?）

The thickness of carbon fiber wire is 5-7μm (note: 1μm=0.001mm), such a thin single wire is not suitable for large-scale production and application. In practical applications, this high-performance material is generally not in the form of a single filament, but is made into carbon fiber filament yarn, non-continuous fiber yarn, woven fabric, woven fabric, knitted fabric, felt and other products.

Carbon fiber tow and carbon fiber rope are different from elongated products made of multiple carbon fiber wires.

左：一筒碳纤维丝束，右：一把碳纤维绳

What is carbon fiber tow?

The head carbon fiber enterprises at home and abroad are also constantly breaking through the carbon fiber preparation technology of high strength, high modulus and large tow. At present, the most advanced carbon fiber technology is still in the hands of a few companies in a few developed countries such as the United States and Japan.

Whoever can be the first to achieve efficient and low-cost production of high-performance carbon fiber tow will be able to seize a position in high-end applications, and the price of carbon fiber in high-end applications is much higher than the price of ordinary carbon fiber.

Taking the global carbon fiber market demand in 2022 as an example, the price of carbon fiber applied to aerospace military industry is $79.2 / kg, and the price of carbon fiber applied to wind power blades is $18.5 / kg.

In addition to being used in aerospace, fan blades, transportation and other fields, carbon fiber tow is also used in the production of some graphite hard composite felt, which plays a role in shaping and improving the mechanical properties of products.

What is carbon rope?

Carbon rope is also known as "carbon fiber rope". Because of its excellent mechanical properties, high temperature resistance, and soft for processing, carbon fiber tow is also suitable for making ropes.

There are three main ways to process carbon fiber ropes:

1. Twist method. The principle is the process of twisting back the single yarn, network cable, or rope. Starting from life experience, many tug-of-war ropes are made by twisting. We can see that the tug-of-war rope is made by twisting several thinner strands of rope, and each strand is made by twisting several yarn, and then the subdivision of these yarn is made by twisting fibers.

According to the manufacturing order, it is more standardized to say that twisting can make fibers into yarn, yarn into rope strands, and rope strands into ropes. If the aforementioned carbon fiber tow is used to make a rope, the tow is originally a number of parallel continuous fiber filaments, which are yarns and can be directly twisted into rope strands. The twisting of carbon fiber tow can enhance the adhesion and strength of the single fibers.

2. Rope knitting. There are many ways to weave, one of which makes the carbon fiber rope look like a braid - three strands of carbon fiber strands are braided into a "braid", and then three such "braids" are braided into carbon fiber rope in the same way.

3. Three-dimensional weaving method. Three-dimensional braiding is carried out on a special three-dimensional braiding machine, which can be divided into two steps, four steps, rotating braiding and so on. In the four-step braiding process, the yarn moves alternately in four directions in rows and columns, moving four times for a braiding cycle.

Although you can see the shadow of other common rope forming from the processing of carbon fiber rope, carbon fiber rope has its particularity after all, and "good steel is used on the blade". Carbon fiber rope can be used in some special fields, such as Marine cables, reinforced concrete, mountaineering ropes and so on.

Carbon fiber rope is also used as a bridge cable, a total length of 377 meters of Qingdao Haikou Road across the wind River Bridge on the 12 suspension rods are all "carbon fiber bars", the shape of steel, but the weight is much lower than steel.

Due to its high temperature resistance and other characteristics, carbon rope is also used in thermal fields.