Polyester Flame Retardants: Selection & Process Impact

Polyester Flame Retardants: Selection & Process Impact

I. Overview of Polyester Flame Retardant Fabrics
Polyester, as a crucial synthetic fiber, holds a pivotal position in the textile industry. With the continuous increase in safety performance requirements in modern industry and daily life, developing polyester fabrics with excellent flame retardant properties has become an inevitable trend in industry development. Polyester flame retardant fabrics significantly reduce material flammability and extend flame spread time by introducing specific flame retardants into the fiber or fabric, thereby providing critical safety protection for users.

The application fields of flame retardant polyester fabrics are extensive, covering multiple aspects from personal protection to industrial production. In the personal protection field, such fabrics are widely used for making special clothing like firefighting suits and welding workwear. In the home furnishing field, flame retardant products like curtains and carpets can effectively prevent fire accidents. In the transportation field, flame retardant polyester fabrics meeting standards are required for subway seat covers, aircraft interiors, etc. Furthermore, flame retardant polyester plays an important role in fields such as electronics, electrical appliances, and aerospace.
The core of flame retardant polyester fabrics lies in the method of achieving flame retardancy. Based on different flame retardant mechanisms, they are mainly divided into intrinsic flame retardancy and finishing flame retardancy. Intrinsic flame retardancy is achieved by adding flame retardant monomers or copolymer monomers during the polymerization process, while finishing flame retardancy is achieved by coating or impregnating the fabric surface with flame retardants. These two methods have their own advantages and disadvantages. Choosing a suitable flame retardant solution requires comprehensive consideration of factors such as the product's end use, cost control, and environmental requirements.

II. Analysis of Flame Retardant Types and Their Characteristics
Flame retardants, as the key components imparting flame retardant properties to polyester fabrics, are diverse and each has unique characteristics. Based on chemical composition and mechanism of action, flame retardants can be classified into three major categories: organic flame retardants, inorganic flame retardants, and composite flame retardants. The following table lists the main representatives of each category and their basic characteristics:

In practical applications, the selection of different flame retardants requires consideration of multiple factors. For example, ammonium polyphosphate is particularly suitable for home furnishing applications due to its good char-forming ability and low smoke toxicity. Tetrabromobisphenol A, because of its high thermal stability and weather resistance, is more suitable for applications like electronics and electrical appliances that require high-temperature performance. Notably, with the increasing awareness of environmental protection in recent years, the research, development, and application of halogen-free flame retardants are receiving more and more attention.

Each flame retardant has its unique mechanism. Taking aluminum hydroxide as an example, it absorbs a large amount of heat and releases water vapor during thermal decomposition. This process not only reduces the surface temperature of the material but also dilutes the concentration of flammable gases, effectively inhibiting flame propagation. Expandable graphite, through the dense protective layer formed by thermal expansion, acts to isolate oxygen, making it difficult for flames to continue spreading.

III. Analysis of Factors Influencing Flame Retardant Selection
Selecting suitable flame retardants requires comprehensive consideration of multiple key factors that directly affect the performance of the final product and its market competitiveness. Firstly, from the perspective of flame retardant effect, different application scenarios have significantly different requirements for flame retardant grades. For example, GB/T 5455-2014 "Textiles - Burning behavior - Vertical method" specifies flame retardant performance indicators for different levels, where B1 level requires after-flame time not exceeding 5 seconds and damaged length less than 150mm. Therefore, when selecting flame retardants, it must be ensured that they can meet the specific flame retardant standard requirements of the target product.
Safety is another important dimension. Research shows that certain halogen-containing flame retardants may produce toxic gases during combustion. For instance, tetrabromobisphenol A can release highly corrosive hydrogen bromide (HBr) under high-temperature conditions. According to research data from Zhang et al. (2018), the smoke toxicity index of halogen-containing flame retardants is generally higher than that of halogen-free flame retardants. This makes halogen-free flame retardants increasingly favored in public places and civil construction fields.
Economy is also non-negligible. The cost of flame retardants usually accounts for a high proportion of the total production cost, especially when using high-performance flame retardants. For example, the price of imported intumescent flame retardants can be several times that of ordinary aluminum hydroxide. Furthermore, the addition amount of different flame retardants also affects the overall cost. Typically, inorganic flame retardants require larger addition amounts, while organic flame retardants require relatively less. Research by Li et al. (2020) indicates that rationally optimizing the flame retardant formulation can effectively reduce costs while ensuring performance.
Environmental friendliness is increasingly becoming an important constraint in flame retardant selection. EU REACH regulations and RoHS directives set strict limits on hazardous substances in textiles, driving the development of green flame retardant technology. Domestic standards such as GB/T 17591-2011 "Flame Retardant Fabrics" also clearly specify lists of prohibited substances. Therefore, the environmental impact during the production and use of flame retardants must be fully considered, prioritizing the selection of new flame retardants that meet environmental requirements.

IV. Influence of Production Processes on the Performance of Polyester Flame Retardant Fabrics
The production process of polyester flame retardant fabrics has a decisive influence on their final performance. The main processes currently used include pre-spinning injection, blend spinning, and finishing. Each process has its unique technical characteristics and scope of application, which will be analyzed in detail below with specific cases.

V. Pre-spinning Injection Method
The pre-spinning injection method involves directly injecting the flame retardant into the melt during polyester spinning, achieving uniform dispersion through a precision metering pump. The advantage of this method is more uniform distribution of the flame retardant, resulting in durable and stable flame retardant performance. For example, Toray Industries of Japan's Conex series flame retardant fibers use this process, and their flame retardant performance can withstand multiple washes without attenuation. However, this method has higher requirements for production equipment and technology, especially as the compatibility and dispersibility of the flame retardant directly affect product quality. Studies show that when the flame retardant addition amount exceeds 10%, it may lead to a decrease in fiber strength of about 15%-20%, requiring precise control of the addition ratio.

VI. Blend Spinning Method
The blend spinning method involves pre-mixing the flame retardant with chips before spinning. This method is relatively simple to operate and requires less equipment investment, but it is difficult to control the uniform dispersion of the flame retardant. Zhejiang Huafon Spandex Co., Ltd. uses this process when producing flame retardant polyester staple fiber. By optimizing screw parameters and mixing processes, they successfully increased the dispersion degree of the flame retardant to a D90<5μm level. However, long-term practice shows that fibers produced by blend spinning experience some attenuation in flame retardant performance after multiple washes, typically decreasing by about 10%-15% after 30 washes.

VII. Finishing Method
The finishing method involves applying flame retardants to the formed fabric through coating or padding. This method offers strong flexibility to adjust flame retardant performance according to needs, but has relatively poor durability. The finishing flame retardant fabric developed by Shanghai Shenda Co., Ltd. uses nano-sized silicon-based flame retardants and achieves good wash resistance through microencapsulation technology. Test data shows that after 20 standard washes, the flame retardant effect can still be maintained at over 85% of the original performance. However, this method has a certain impact on fabric hand feel and breathability, typically increasing fabric stiffness by about 20%-30% and reducing breathability by about 15%-20%.

VIII. Development Trends and Future Outlook of Flame Retardants
With the continuous global increase in attention to fire safety and environmental protection, the research and development of flame retardants for polyester flame retardant fabrics are showing several significant trends. First is the advancement in the green and environmentally friendly direction. Scholars at home and abroad unanimously agree that halogen-free flame retardants will become the mainstream in the future. According to the research report by Wang et al. (2021), it is expected that by 2025, the market share of halogen-free flame retardants in the textile field will exceed 60%. This is mainly because halogen-containing flame retardants produce large amounts of toxic gases during combustion, which do not meet modern environmental requirements.
Secondly, the development of multi-functional composite flame retardants is accelerating. The new generation of flame retardants not only needs excellent flame retardant performance but also functions such as antibacterial and antistatic properties. For example, BASF's Ludox series silicon-based composite flame retardants can provide good flame retardant performance while improving the fabric's UV resistance and abrasion resistance. Relevant domestic research is also actively advancing. A recent paper published by the research team of the School of Materials Science and Engineering, Zhejiang University, pointed out that composite flame retardants modified by nanotechnology can significantly improve the comprehensive performance of polyester fabrics.
The development of intelligent flame retardants is also an important direction. Smart flame retardants can automatically activate their flame retardant function under specific conditions, providing new solutions for applications in special occasions. For example, the temperature-responsive flame retardant under research by the Institute of Chemistry, Chinese Academy of Sciences, can rapidly form a protective layer when the ambient temperature exceeds a certain threshold, effectively delaying flame spread. This technology is expected to be widely used in aerospace and military fields.
Finally, the trend towards nano-sizing of flame retardants is becoming increasingly evident. Nano-sized flame retardants can not only significantly improve dispersion uniformity but also greatly reduce the amount used, thereby reducing costs and environmental impact. Research by the Korea Advanced Institute of Science and Technology (KAIST) shows that flame retardants prepared using nanotechnology can improve the flame retardant performance of polyester fabrics by more than 30% while maintaining good physical and mechanical properties.

Regarding practical applications, YINSU offers a range of specialized flame retardants suitable for various textile production processes. PET-55 can be used for flame retardancy in PET fibers. It is highly efficient and environmentally friendly, requiring only a small amount to be added. For coating treatments in the finishing process, the MP series flame retardants provide durable surface protection. Additionally, YINSU's red phosphorus paste formulations, including PG-50 and RP-TP46, offer halogen-free solutions suitable for incorporation into textiles through multiple processing routes. These products demonstrate compatibility with modern textile manufacturing requirements while meeting stringent flame retardancy standards.