Polyacrylonitrile fibers: Performance analysis and application boundaries of synthetic wool 

Among the synthetic fibers, Polyacrylonitrile fibers (commonly known as acrylic in domestic products) are the third largest synthetic fiber variety after polyester fibers and polyamide fibers. It is not a simple imitation of natural wool, but an independent material system with unique physical and chemical properties. It has clear application coordinates in the fields of thermal insulation filling, outdoor textiles, and industrial uses. 

Material nature and performance baseline 

Polyacrylonitrile fibers are formed by the polymerization of acrylonitrile monomers. The highly polar cyano groups on the large molecular chains give them unique high resilience and excellent light resistance compared to other synthetic fibers. The density of standard polyacrylonitrile fibers is approximately 1.16 - 1.18 g/cm³, which is about 20% lighter than wool and 15% lighter than polyester. This makes it have a natural advantage in scenarios that require lightweight warmth. 

Its thermal conductivity is approximately 0.04 - 0.05 W/(m·K), which is at the same level as wool. This means that, under the same weight, the thermal insulation efficiency of Polyacrylonitrile fibers is comparable to that of natural wool, but the cost is significantly lower. The standard moisture regain of this fiber is about 1.0% - 2.5%, which is lower than that of cotton and wool, but it is at a medium level among synthetic fibers. The wearing comfort is better than that of completely hydrophobic polypropylene fibers. 

The practical value of differentiated varieties 

The core value of the modern polyacrylonitrile fiber industry lies in differentiation and functionality. By modifying the spinning process or the composition of the copolymer monomers, the properties of the fibers can be selectively adjusted: 

Fleece-like acrylic: Through curling processing, the fibers are endowed with the fluffy and cohesive properties of natural wool, and are widely used in coarse-woven fabrics and overcoats. These products have a full feel, moderate draping, and are not prone to moth damage, with lower maintenance costs than pure wool products. 

Anti-static and conductive acrylic fibers: By adding conductive carbon black or metal oxides, the surface resistance can be reduced to below 10⁷ Ω, effectively solving the static electricity problem when wearing in winter, and suitable for electronic industrial clean suits or protective work clothes in explosion-proof areas. 

Flame-retardant modified acrylic fiber: By introducing halogen-containing or phosphorus-containing flame-retardant monomers in a copolymerization process, the limit oxygen index (LOI) of the fiber is increased to 28%-32%. This material does not melt and drip when exposed to fire, and the smoke density during combustion is relatively low. It is widely used in fireproof curtains, mattress covers, and children's sleepwear fabrics. 

Direct dyeing acrylic fiber: Pigments are directly added to the spinning solution, resulting in uniform and durable fiber color, with a sunfastness level of 4-5 grades (Blue Standard). This process eliminates the subsequent dyeing process, significantly reducing the discharge of dyeing wastewater. 

Process Characteristics and Applicable Scenarios 

The glass transition temperature (Tg) of polyacrylonitrile fibers is approximately 80℃ - 100℃, which is an important reference indicator for processing and usage of these fibers. When the temperature is below Tg, the fibers exhibit rigidity; when the temperature is above Tg, the molecular chain segments move more vigorously, causing the fibers to become softer and possess stretchability. Therefore, these fibers should not be used for a long time in environments above 120℃, and the "synthetic fiber" setting should be selected when ironing. 

In outdoor applications, the photobleaching resistance of polyacrylonitrile fibers is outstanding - even after continuous exposure to ultraviolet rays for 700 hours, the strength retention rate remains above 90%, far superior to nylon and ordinary polyester. This characteristic makes it an ideal choice for sunshade tarpaulins, outdoor ropes and car interior textiles. 

In the field of civil engineering, high-strength and high-modulus polyacrylonitrile fibers are used as reinforcement materials for concrete. Their tensile strength can reach 600-900 MPa, and their adhesion to the cement-based material is better than that of polypropylene fibers, which can effectively control the early plastic shrinkage cracks of concrete. 

Selection Suggestions and Precautions 

When purchasing polyacrylonitrile fiber products, it is recommended to pay particular attention to the two indicators: fiber linear density deviation and tensile elongation at break. For use as insulation padding, hollow or irregularly shaped varieties have higher insulation efficiency; for use in structural reinforcement, products that have undergone surface treatment should be preferred to ensure the bonding force between the interface and the base material. 

It should be noted that the dimensional stability of polyacrylonitrile fibers in high-temperature and high-humidity environments is limited. The boiling water shrinkage rate of these fibers is typically between 1% and 3%. If the product requires extremely high dimensional accuracy, it is recommended to use the specifications that have undergone heat setting treatment. Additionally, when this material burns, it will produce smoke containing hydrogen cyanide. During fire handling, self-contained breathing apparatus must be worn - this is an inherent physical property of this material system and is not a quality defect. 

Overall, polyacrylonitrile fibers represent an effective material solution that strikes a balance between warmth retention, durability, and cost. They are not a "cheap substitute" for wool; instead, through precise modification, they surpass the functional boundaries of natural fibers in specific performance dimensions. For industrial and civilian applications that require lightweight warmth retention, high light resistance, or flame retardant protection, polyacrylonitrile fibers offer a proven engineering option. 

Shandong Huimin Taili Chemical Fiber Products Co., Ltd. is located in "the hometown of rope nets in China". It mainly deals in polypropylene high-strength yarn, polypropylene colored yarn, polypropylene fibers, polyester fibers, polyacrylonitrile fibers, polypropylene mesh fibers, safety ropes, safety nets, etc. Please feel free to send samples for testing and communicate about specific application scenarios.