Looking beyond the word ‘acrylic’ in filter bag applications

Different fibre types may be suitable for different operating conditions and process requirements in industrial filtration applications. Each fibre type has its own characteristics in terms of temperature resistance, chemical resistance, moisture behaviour and mechanical performance.
For many cases, ‘fibre’ is often treated as a single material category for filter bag selection. In practice, however, this is not the case. Two different acrylic fibres (also referred to as ACN-containing fibres) may appear similar, be supplied with comparable commercial specifications and even demonstrate acceptable initial mechanical properties.
Nevertheless, their long-term performance can vary significantly due to one critical factor: acrylonitrile content, commonly referred to as ACN percentage.
This difference becomes particularly important in cement applications where moisture, acidic gas components, moderate temperatures and heavy dust loads are present simultaneously. Under such conditions, the difference between the high ACN content found in homopolymer acrylic fibres and the lower ACN content found in other acrylic fibres can directly influence service life, colour stability, hydrolysis resistance and ultimately the reliability of the filter media.

Acrylic fibre: Same family, different behaviour
In the filtration industry, the definition of acrylic fibre generally begins with its ACN content. A fibres with a composition close to pure polyacrylonitrile behaves differently from modified structures containing higher levels of comonomers or functional groups.
This is where the concept of homopolymer acrylic becomes important. In homopolymer acrylic fibres containing approximately 99–100 per cent ACN, molecular chains are packed more tightly and aligned more uniformly, creating a highly ordered and crystalline polymer structure.
This high ACN content provides the fibre with a more consistent chemical structure and fewer reactive side groups. Such chemical consistency is particularly valuable in hot gas filtration applications.

Thermal stability: Delayed reaction means greater confidence
One of the clearest ways to understand the difference between homopolymer acrylic fibres with high ACN content and acrylic fibres with lower ACN content is through thermal behaviour.
Homopolymer acrylic fibres with high ACN content generally exhibit a more stable thermal profile than fibres with lower ACN levels. They tend to react later when exposed to heat and demonstrate lower overall reactivity. This characteristic provides a significant advantage in filtration systems operating continuously at elevated temperatures by helping the fibre maintain its structural integrity.
To support this technical evaluation, a comparative DSC thermal analysis was carried out in AKSA laboratory according to ISO 11357. The purpose of this test was not to simulate full baghouse lifetime, but to check the thermal response and relative reactivity of homopolymer acrylic fibre under controlled laboratory conditions.
For filter media applications, where gas temperatures may fluctuate, this difference is important because higher thermal reactivity may increase the risk of structural changes when the fibre is exposed to heat, moisture and chemically aggressive gas components over time. Better thermal stability provides a wider operating safety margin for the filter media.
This DSC analysis should be interpreted as supporting evidence for thermal stability and reactivity differences.

Hydrolysis and acid gas resistance
Process gases in cement plants often contain moisture. In certain stages of production, these gases may also contain acidic components. When moisture and acidic gases are present simultaneously, hydrolyses weaken the fibre structure and may result in loss of mechanical strength, increased emissions, poor cleaning performance and premature filter bag failure.
Thanks to the high ACN content within its structure, homopolymer acrylic fibre offers a significant advantage over acrylic fibres that may be commercially considered equivalent alternatives but contain lower ACN levels. The lower presence of chemically reactive functional groups increases resistance to moisture-related degradation. As a result, homopolymer acrylic can provide improved hydrolysis resistance and maintain filtration performance for longer periods.

Mechanical performance: Initial strength is not the whole story
Fibres with lower ACN content may demonstrate acceptable initial mechanical properties and can often be processed efficiently into yarns or felts. However, if the polymer structure is more reactive, maintaining these properties under actual operating conditions becomes more challenging over time. Lower chemical and thermal resistance compared with homopolymer acrylic fibres may eventually lead to reduced filtration performance and negatively affect overall system reliability.
The primary advantage of homopolymer
acrylic fibre lies in the contribution of its high ACN content to maintaining structural stability in environments where hydrolysis and acidic gas exposure are concerns.

Conclusion
The DSC results also support this distinction: homopolymer acrylic fibre with ACN ≥99.5 per cent shows later thermal reaction and lower reactivity. This confirms that ACN content is not only a compositional detail, but a key factor influencing thermal stability and long-term filtration reliability.
By choosing Acryterna, you are selecting a genuine homopolymer acrylic fibre containing approximately 100 per cent ACN within its structure. This high ACN content provides important advantages in terms of thermal stability, hydrolysis resistance, acid gas resistance and long-term filtration performance.

Note: These DSC results reflect laboratory test conditions only and do not represent recommended operating temperatures or actual filter bag application conditions.

(Communication by the management of the company)