Pre-oxidized acrylic blended woven fabric for protective clothing in the chemical and petrochemical industries

Preoxidized polyacrylonitrile fiber, formally known as preoxidized polyacrylonitrile fiber, is an intermediate product formed by thermally stabilizing polyacrylonitrile fiber in an air atmosphere at 200–300°C. It typically appears black, with a partially cyclized chemical structure that confers high thermal stability, making it a precursor for carbon fiber production; it can also be used as a standalone specialty fiber. Acrylic fiber, or polyacrylonitrile fiber, is an important category of synthetic fibers and serves as the direct raw material for producing preoxidized polyacrylonitrile fiber. Although the two are chemically related, the preoxidation process imparts a qualitative leap in heat resistance and flame retardancy to the preoxidized fiber.

Blending pre-oxidized silk with acrylic fiber represents a technical solution that balances performance optimization with cost considerations. This blend leverages the exceptional high-temperature resistance and flame-retardant properties of pre-oxidized silk, while benefiting from the relatively good spinnability, elasticity, and cost advantages of acrylic fibers. The woven manufacturing process further imparts to the fabric stable structure, dimensional stability, and high tensile strength. With a basis weight of 300 g/m², the fabric falls into the medium-thickness category: it provides a more robust physical barrier and thermal insulation than lightweight fabrics, yet remains softer and more flexible than heavier fabrics weighing over 400 g/m²—making it well suited for applications that demand both protective performance and a degree of wearing comfort and mobility.

Characteristics of pre-oxidized acrylic blended woven fabric:

1. Excellent flame retardancy and high-temperature resistance

High Limiting Oxygen Index: The limiting oxygen index is a key parameter for assessing a material’s flame retardancy, defined as the minimum oxygen concentration in a nitrogen–oxygen mixture required to sustain combustion. Pre-oxidized filaments exhibit an exceptionally high limiting oxygen index, typically exceeding 45% and sometimes reaching 55%–62%, classifying them as noncombustible materials. This means they are extremely difficult to ignite in ordinary ambient air (with an oxygen content of about 21%) and will self-extinguish rapidly even when removed from an open flame.

Outstanding thermal stability: Pre-oxidized filaments exhibit excellent stability at high temperatures. Their decomposition temperature is no lower than 640°C, and they can maintain stable performance over long-term use at temperatures between 250°C and 300°C. They demonstrate stable performance even in a 300°C environment and, after brief exposure to 500°C, still retain most of their strength. Unlike many synthetic fibers that melt upon contact with fire, pre-oxidized filaments do not melt, soften, or shrink in flames; they do not produce molten droplets, but instead undergo surface carbonization to form a dense char layer. This characteristic is critically important, as molten droplets can carry high heat and cause severe secondary burns, whereas the “droplet-free” nature of pre-oxidized filaments provides a higher level of safety.

Effective thermal insulation: The fabric itself has a low thermal conductivity, and combined with a fabric thickness of 300 grams, it can form an effective thermal barrier between high-temperature sources and the human body or equipment, thereby slowing down heat transfer.

2. Composite Mechanical and Physical Properties

Pure pre-oxidized silk fibers suffer from low tensile strength, brittleness, and poor fiber cohesion, resulting in poor spinnability. The introduction of acrylic fibers is precisely aimed at addressing these shortcomings.

Enhancing Spinnability and Yarn Strength: Acrylic fibers typically exhibit excellent crimp and elasticity; when blended with pre-oxidized yarns, they significantly improve the processability of the blended yarns and reduce breakage rates during spinning and weaving. The resulting blended yarns demonstrate superior overall strength and tenacity compared with pure pre-oxidized yarns, thereby imparting greater mechanical durability to the final woven fabrics.

Enhanced wearing performance: Compared with pure pre-oxidized silk fabrics, the incorporation of acrylic fibers imparts a relatively softer hand, reduces stiffness, and improves both comfort and adaptability. Moreover, acrylic fibers exhibit superior dyeability compared with black pre-oxidized silk, thereby expanding the range of color options available for the fabric.

3. Stable Chemical and Environmental Resistance

Pre-oxidized silk fibers exhibit excellent chemical resistance, demonstrating strong resilience to common acidic and alkaline environments as well as good radiation resistance. This makes blended fabrics suitable for complex industrial settings in sectors such as chemicals and metallurgy, where corrosive media are present. Moreover, their performance is stable and they are resistant to aging and degradation caused by environmental factors.

4. Safety and Environmental Protection Attributes

During combustion or high-temperature decomposition, pre-oxidized silk does not release toxic and harmful halogenated hydrogen gases, unlike certain halogen-based flame-retardant materials; thus, it is a relatively clean flame-retardant material. Its protective performance relies on the intrinsic structural characteristics of the fiber itself, rather than on post-finishing additives, resulting in durable performance and excellent wash resistance.

Applications of pre-oxidized acrylic blended woven fabrics:

1. Specialized Industrial Protective Clothing Sector

This is a typical and direct application area for this fabric. Its balanced combination of protective performance and flexibility makes it ideally suited for manufacturing workwear designed for routine, non-extreme environments where workers are exposed to high temperatures and sparks.

Welding protective clothing: Designed for electric welding, gas welding, and other similar trades, it safeguards against flying arc sparks and molten metal spatter. Weighing 300 grams, it provides adequate protection without imposing an excessive burden during frequent movement.

High-temperature furnace-front workwear: Provides thermal insulation and protection for workers in industries such as steelmaking, foundry operations, and glass manufacturing who work near hot furnaces or handle high-temperature semi-finished materials.

Protective clothing for the chemical and petrochemical industries: designed for workstations where there is a potential flame hazard and where contact with chemicals is required, providing flame resistance and basic chemical protection.

Power industry maintenance uniforms: provide protection for power maintenance personnel who may come into contact with high-temperature equipment or are at risk of electric arcs.

2. High-Temperature Industrial and Equipment-Integrated Materials field

High-temperature thermal insulation curtains and protective shields: used to partition high-temperature work areas and to cover the doors and windows of high-temperature equipment (such as heat-treatment furnaces and ovens) to prevent heat loss and accidental contact by personnel, or as fire barriers in welding areas.

Fire blankets and escape blankets: Equipped in gas stations, laboratories, factory workshops, and other facilities for extinguishing initial fires or wrapping around the body for emergency escape.

Heat-resistant conveyor belt liner: Used as a cushioning or thermal-insulating layer for conveyor belts on production lines that handle high-temperature components.

3. Flame-retardant decoration and vehicle interior applications

With the enhancement of public safety standards, this fabric is also being used in decorative applications that require flame retardancy.

Interior trim for special vehicles: seat fabrics, interior linings, or partitions used in mining vehicles, construction machinery, and other specialized vehicles, designed to meet their flame-retardant safety requirements.

Basic flame-retardant padding material: can be used as a flame-retardant and thermally insulating interlayer within the seating of aircraft, high-speed trains, coaches, and other modes of transportation (not as the direct upholstery fabric), or as an insulation and soundproofing layer for cabin walls.

Flame-retardant products for public spaces: such as stage curtains and backdrop decorative fabrics in theaters and hotels that must meet specific fire-resistance ratings.

4. Other Specialized Protective Equipment

Fire-resistant gloves: protective gloves designed for medium- to high-temperature applications that require dexterity.

Fire-resistant webbing and escape ropes: safety rescue equipment components manufactured using their high-temperature resistance.

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