Dry-jet-wet-spinning vs Wet-spinning vs Dry-spinning
Carbon fibre is hailed as the “king of new materials”, finding extensive applications in aerospace, automotive manufacturing, sports equipment and beyond. But did you know? While all carbon fibre shares the same name, its manufacturing processes differ vastly. Today, we comprehensively analyse the three key technologies for producing carbon fibre—dry-jet-wet-spinning, dry-spinning and wet-spinning—and examine how leading domestic and international enterprises select these techniques.
Dry-jet-wet-spinning (the mainstream choice for high-performance carbon fibres)
Definition
Dry-jet-wet-spinning, as the name suggests, combines the characteristics of both dry spinning and wet spinning processes. This technique is primarily employed in the production of high-performance PAN-based carbon fibre precursors.
Process Flow
(1) Preparation of Spinning Solution: Polyacrylonitrile (PAN) is dissolved in a specific solvent to form a viscous spinning solution.
(2) Dry Spinning Stage: The spinning solution is extruded through a spinneret plate and first passes through an air layer (typically several millimetres to several centimetres).
(3) Wet Spinning Stage: The fibre bundle subsequently enters a coagulation bath, where it rapidly solidifies and takes shape.
(4) Post-Processing: Through washing, stretching, oiling, drying and other procedures, the carbon fibre precursor is ultimately formed.
Technical Advantages
(1) More uniform fibre structure: stretching within the air layer enhances molecular chain orientation
(2) Smoother surface: reduces surface defects, improving the mechanical properties of the final carbon fibre
(3) Higher production efficiency: spinning speeds can reach 2-3 times that of wet spinning
(4) Suitable for producing high-performance fibres: such as T700, T800 and higher grades of carbon fibre
Wet Spinning (Traditional Mature Process)
Definition
Wet spinning represents the earliest industrialised method for producing carbon fibre precursors. While technically mature, it possesses certain limitations.
A polymer is dissolved in a suitable solvent to form a concentrated solution (spinning bath). This solution is then extruded through the micro-pores of a spinneret and directly ejected into a solidification bath containing a non-solvent. Within the bath, bidirectional diffusion occurs between the solvent in the spinning stream and the non-solvent in the bath. This causes the polymer to precipitate and solidify from the solution, forming the primary fibre.
Process Flow
(1) Spinning Solution Preparation: PAN dissolved in solvent (e.g., DMF, DMSO)
(2) Direct Solidification: Spinning solution extruded from spinneret directly into solidification bath
(3) Phase Separation Solidification: Solidification achieved through double diffusion process
(4) Post-treatment: Washing, stretching, drying, etc.
Technical Characteristics
(1) Cross-sectional shape limitations: Primarily circular or oval
(2) Relatively low spinning speeds: Typically 50–150 m/min
(3) Susceptibility to surface defects: Prone to surface voids and grooves
(4)Relatively simple equipment: Suitable for medium-to-low performance carbon fibre production
Dry Spinning (Speciality Carbon Fibre Selection)
Definition
Dry spinning constitutes another significant method for preparing carbon fibre precursors, particularly employed in the production of certain speciality carbon fibres.
Dry spinning involves extruding a polymer solution through spinnerets, where the solvent is directly volatilised by hot air to solidify into fibres (as in spandex production). However, within the carbon fibre sector, it is frequently misused as an abbreviation for ‘dry-spun wet-laid’.
Process Flow
(1) Solution Preparation: Dissolve the polymer in a volatile solvent
(2) Extrusion and Solvent Evaporation: The solution is extruded through a spinneret plate and enters a hot-air-filled spinning tunnel
(3) Solvent Recovery: The evaporated solvent is recovered for reuse
(4) Fibre Collection: Fully solidified fibres are collected by winding
Technical Characteristics
(1) Diverse fibre cross-sectional shapes: Capable of producing fibres with irregular cross-sections
(2) Complex solvent recovery system: Requires sophisticated solvent recovery apparatus
(3) Suitable for specific polymers: Such as certain modified polyacrylonitrile (PAN) or other carbon fibre precursor polymers
Comprehensive Comparison Table of Three Major Technologies
| Dry-jet wet spinning | Wet spinning | Dry spinning | |
| Process Flow | First air layer stretching, then solidification bath curing | Directly enter the solidification bath for curing | Curing by solvent evaporation in hot air |
| Spinning Speed | High(200-400m/min) | Low(50-150m/min) | Medium |
| Fibre Structure | Dense and uniform, with a smooth surface | Relatively loose, with surface imperfections | Unique structure, accommodating non-standard cross-sections |
| Product Performance | High performance(Above T700) | Medium to low performance | Special properties |
| Production Costs | Relatively high | Relatively low | High (requires solvent recovery) |
| Technical Barriers | High | Medium | High |
| Principal Applications | Aerospace, high-end sports equipment | Industrial sector, general civilian use | Specialised fields, specialised fibres |
Future Development Trends
(1) Optimisation of Dry-Jet Wet-Spinning Technology: Advancing towards higher spinning speeds and more stable quality to further reduce the cost of high-performance carbon fibres
(2) Upgrading Wet Spinning: Enhancing the performance of wet-spining fibres through process improvements to broaden application fields
(3) Process Integration Innovation: Developing novel composite spinning techniques by combining the advantages of different processes
(4) Green Manufacturing: Developing environmentally friendly solvent systems to reduce the environmental burden during production
The lightweight and resilient properties of carbon fibre stem from the meticulous craftsmanship of its manufacturing processes. From the traditional wet-layup method to specialised dry-layup applications, and the high-performance breakthrough of dry-jet-wet spinning, each technique represents the culmination of materials scientists’ ingenuity.
Understanding these technical distinctions not only explains the wide price variations among different carbon fibres but also sheds light on the arduous journey and remarkable achievements of China’s carbon fibre industry as it transitions from catching up to running alongside global leaders. On the path to becoming a materials powerhouse, every technological breakthrough deserves our attention and applause.