In the non-woven fabric industry, the spunbond method accounts for over 35% of global non-woven fabric production due to its efficient process characteristics of “melt direct spinning, high-speed stretching, and direct web formation”. In the selection of main materials for spunbond method, polyester (polyethylene terephthalate, PET) has become the “preferred solution” in various fields such as geotechnical building materials and medical protection due to its high adaptability to processes, balanced performance, and industry maturity. This article will analyze the core logic behind polyester becoming the optimal main material for spunbond production from three aspects: process adaptation, performance matching, and industry support. By comparing it with other materials, the comprehensive considerations behind “optimal” will be clarified.
Characteristics of spunbond process: bottom layer constraints for main material selection
The core process of spunbond method is “polymer melt → spinneret extrusion → high-speed airflow stretching → fiber networking → thermal bonding/needle punching reinforcement”. Its process characteristics put forward three rigid requirements for the main material: good melt stability, excellent fiber stretching properties, and fast curing and shaping. These three requirements constitute the “entry threshold” for the selection of main materials, and polyester perfectly fits these process constraints.
1. Melt flowability: the foundation of spunbond high-speed spinning
The spinning speed of spunbond method usually reaches 2000-4000m/min, far exceeding the traditional spinning speed of 300-800m/min. It requires the polymer melt to have stable flowability and resistance to degradation at high temperatures. The melt flow rate (MFR) of polyester is usually controlled at 25-35g/10min (280 ℃, 2.16kg), which can ensure uniform flow of the melt in the nozzle holes without causing “melt fracture” (roughness and breakage during spinning) due to excessive fluidity.
By comparison, although the MFR of polypropylene (PP) can be adjusted to a similar range, it is prone to thermal oxidative degradation at high temperatures (>230 ℃), resulting in a viscosity fluctuation of ± 5% or more in the melt. In contrast, the viscosity fluctuation of polyester at processing temperatures of 280-300 ℃ can be controlled within ± 2%, making it more suitable for continuous high-speed production of spunbond method. The production practice of a certain enterprise shows that under the same equipment, the breakage rate of polyester spunbond fabric (0.3 times/ton) is only 1/5 of PP, directly improving production efficiency.
2. Stretching into fibers: the key to high-strength fibers
The spunbond method stretches the melt stream through high-speed airflow, aligning the molecular chains along the fiber axis to obtain high-strength fibers. There is a wide stretchable range between the glass transition temperature (70-80 ℃) and melting point (255-265 ℃) of polyester. At a stretching temperature of 100-150 ℃, the molecular chains can achieve full orientation without fracture.
Experimental data shows that the stretching ratio of polyester spunbond fibers can reach 5-8 times, and the fracture strength of the fibers after stretching can reach 4.5-5.5cN/dtex, which is much higher than the 3.0-3.5cN/dtex of PP spunbond fibers. This high stretchability allows polyester to improve the softness and breathability of products through “fine denier” (reducing fiber fineness to below 1.0dtex), while maintaining sufficient mechanical strength – this is also the core reason why polyester spunbond fabrics can balance “lightness” and “toughness”.
3. Curing and shaping: guarantee of network stability
The time from stretching to forming a web for spunbond fibers is only 0.5-1 second, requiring rapid cooling and solidification of the polymer to avoid fiber adhesion before forming the web. The crystallization rate of polyester is moderate (with a half crystallization time of about 10-15 seconds), and under airflow cooling conditions (wind temperature of 20-25 ℃), it can complete preliminary curing within 0.8 seconds, forming fibers with stable morphology.
On the other hand, nylon 6 (PA6) has a very fast crystallization rate (half crystallization time<5 seconds), and the fine flow of the melt is prone to premature crystallization during the stretching process, leading to fiber brittleness and fracture; However, the crystallization rate of polylactic acid (PLA) is too slow (half crystallization time>30 seconds), and the fibers still maintain a certain viscosity after cooling, which is prone to “merging” and poor uniformity of the network. The “moderate” crystallization characteristics of polyester perfectly match the curing rhythm of spunbond method.
Performance balance: Polyester becomes the “optimal” core competitiveness
The “optimum” of spunbond main materials is not the ultimate single performance, but a comprehensive balance of mechanical strength, weather resistance, chemical stability, and functional modifiability. The balanced performance of polyester in these key performance dimensions enables it to adapt to diverse application scenarios of spunbond technology.
1. Mechanical performance: Full scene coverage from load-bearing to protection
The longitudinal and transverse strength ratio of polyester spunbond fabric is usually 2.5-3.5:1, with a fracture elongation of 15-25%, which combines high strength and a certain degree of elasticity, and can meet the mechanical requirements of different scenarios:
Geotechnical field: When used for geotextiles, the CBR bursting strength of polyester spunbond fabric can reach 3.5-4.5kN, the static water pressure resistance is greater than 100kPa, it can withstand the long-term load of the roadbed without breaking, and the service life is over 50 years, far higher than the 20-30 years of PP geotextiles;
Medical field: When used for the outer layer of surgical gowns, the tear resistance of polyester spunbond fabric is greater than 20N, which can resist friction and pulling during the surgical process while maintaining good breathability;
Packaging field: When used for heavy-duty packaging bags, the sewing strength of polyester spunbond fabric is greater than 60N/3cm, and it can carry heavy objects of over 50kg, replacing traditional canvas and woven bags.
2. Weather resistance and chemical stability: reliability in extreme environments
The chemical structure of polyester does not contain active groups other than easily degradable ester bonds, and has excellent acid resistance, alkali resistance, and UV aging resistance:
Chemical resistance: In acidic and alkaline environments with pH values of 2-12, the strength retention rate of polyester is greater than 90%, while PP will degrade in environments with pH<4 or pH>10, resulting in a strength loss of over 30%;
Aging resistance: After adding antioxidants and UV stabilizers, the strength retention rate of polyester spunbond fabric still reaches 70% after 5 years of outdoor exposure, while that of PP spunbond fabric is only 30-40%.
This stability makes polyester spunbond fabric widely used in extreme environments such as mine dust prevention, marine engineering, and agricultural coverage, while other materials are difficult to replace.
3. Functional modifiability: Expansion potential for adapting to high-end applications
The molecular structure of polyester is modifiable, and functionalization can be achieved through copolymerization, blending, post finishing, and other methods to meet the high-end requirements of spunbond technology
Hydrophilic modification: By adding polyethylene glycol (PEG) copolymer component to polyester melt, the contact angle of spunbond fabric can be reduced from 90 ° to below 30 °, and the moisture absorption rate can be increased by three times. It is used for medical wiping cloth and hygiene products;
Anti static modification: After adding carbon nanotubes or anti-static agents, the surface resistance of polyester spunbond fabric can be reduced from 10 ¹⁴ Ω to below 10 ⁸ Ω, which is used for electronic component packaging to prevent static damage;
Flame retardant modification: After adding bromine or halogen-free flame retardants, the limit oxygen index (LOI) of polyester spunbond fabric can be increased from 21% to over 30%, meeting the GB 8410-2019 flame retardant standard, and used for automotive interiors and fire protection clothing.
In contrast, the modification difficulty of PP is relatively high (such as the attenuation of hydrophilic modification effect), and the cost of PA6 is too high, while the modification technology of polyester is mature and the cost is controllable, making it the preferred choice for high-end spunbond products.
Industrial support: the practical basis for the “optimal position” of polyester
The selection of main materials is not only determined by the process and performance, but also deeply influenced by the supply of raw materials, production costs, and the supporting industrial chain. The dominant position of polyester in the spunbond process is largely attributed to its well-developed industrial ecosystem.
1. Raw material supply: Adequate and stable industrial chain guarantee
The raw materials for polyester (PTA and EG) come from the mature petrochemical industry chain, with a global annual production capacity of over 100 million tons, sufficient supply, and stable prices. In 2024, the fluctuation range of domestic PTA spot prices is 5000-6000 yuan/ton, far lower than the 12000-15000 yuan/ton of PA6, and the supply fluctuation is small (annual fluctuation rate<10%).
On the other hand, bio based materials such as PLA rely heavily on crops such as corn for their raw material (lactic acid), which is greatly affected by climate and food prices. In 2024, the fluctuation rate of PLA raw material prices will reach over 30%, making it difficult to meet the demand for large-scale continuous production by spunbond method.
2. Production cost: the absolute advantage of cost-effectiveness
In the production cost structure of polyester spunbond fabric, raw materials account for about 60-70%. Due to the low cost of raw materials and high production efficiency (the annual output of high-speed spunbond lines can reach more than 10000 tons), its unit cost is only 50-60% of PA6 spunbond fabric and 40-50% of PLA spunbond fabric.
Taking 1.5m wide and 20g/m ² spunbond fabric as an example, the production cost of polyester products is about 1.2-1.5 yuan/meter, while PP products are about 1.0-1.2 yuan/meter (slightly lower), but the selling price of polyester products can reach 1.8-2.2 yuan/meter (due to better performance), with a gross profit margin of 30-40%, higher than 20-25% of PP spunbond fabric. The characteristics of “moderate cost and strong premium ability” make polyester the preferred choice for enterprises to balance profit and market competitiveness.
3. Equipment and Technology: Mature Industry Supporting System
Global spunbond equipment giants such as Germany’s Leifenhauser and Italy’s STP have developed dedicated production lines for polyester, from screw extruders (using barrier type screws to improve melt mixing uniformity) to spinnerets (using irregular hole designs to achieve fine denier), and finally to thermal bonding devices (using infrared heating to avoid local overheating), forming a complete technical support.
Domestic equipment companies such as Jiangsu Jinweier and Shandong Tongjia have also achieved localization of polyester spunbond equipment, with equipment investment costs 30-40% lower than imported equipment and fast after-sales service response. This mature equipment matching reduces the entry threshold for enterprises and further consolidates the mainstream position of polyester.
Comparison and Reflection: The Applicable Boundaries and Alternative Possibilities of ‘Optimal’
The “optimum” of polyester in spunbond process is not absolute, and in specific scenarios, other materials can achieve local substitution with a single performance advantage. Through comparative analysis, the core competitiveness boundary of polyester can be more clearly defined.
1. Comparison with Polypropylene (PP): Balancing Cost and Performance
PP is the most direct competitor to polyester, with the advantage of lower raw material costs (PP price is about 7000-8000 yuan/ton in 2024, lower than PET’s 8000-9000 yuan/ton) and lower density (0.90g/cm ³ vs 1.38g/cm ³), making it suitable for producing low-cost, disposable products such as shopping bags and disposable mask outer layers.
But the shortcomings of PP are also very obvious: poor heat resistance (softening point of 80-90 ℃, unable to withstand disinfection treatment above 100 ℃), weak aging resistance, and poor impact resistance. Therefore, in scenarios that require long-term use, high temperature resistance, or weather resistance (such as geotextiles, car interiors), polyester is still an irreplaceable choice.
2. Comparison with Nylon (PA6/PA66): Cost Compromise for High End Performance
The fracture strength (5.5-6.5cN/dtex) and wear resistance of PA6/PA66 are superior to polyester, making it suitable for producing high-end filter materials (such as air purifier filters) and wear-resistant products (such as conveyor belts). However, the raw material cost of PA6 is 1.5-2 times that of polyester, and it has strong moisture absorption (4-5% at 23 ℃ and 65% RH), which leads to poor product size stability and limits its large-scale application.
PA6 will only replace polyester in fields that require extreme performance and are insensitive to cost, such as aerospace filter materials.
3. Comparison with Bio based Materials (PLA/PBAT): Challenges and Opportunities under Environmental Trends
Under the promotion of the “dual carbon” policy, bio based biodegradable materials such as PLA and PBAT have become new research hotspots. PLA spunbond fabric can be completely degraded in natural environments, but there are three major shortcomings: high cost (raw material price is 2-3 times that of polyester), high brittleness (elongation at break is only 5-10%), and poor heat resistance (softening point 55-60 ℃).
At present, PLA only replaces polyester in niche scenarios such as disposable tableware packaging and agricultural covering films, and needs to be blended with PBAT to improve performance. In the short term, the dominant position of polyester in spunbond technology will not be shaken by bio based materials, but in the long run, with the breakthrough of PLA modification technology and cost reduction, it may achieve partial substitution in environmentally sensitive fields.
Conclusion: “Optimal” is the inevitable result of comprehensive weighing
The reason why polyester has become the optimal main material for spunbond process is the result of the synergistic effect of process adaptability, performance balance, and industrial economy:
From a process perspective, its melt stability, stretchability, and solidification characteristics perfectly match the high-speed production requirements of spunbond method;
From a performance perspective, its balanced performance of strength, weather resistance, and chemical stability covers a diverse range of application scenarios from low-end to high-end;
From an industrial perspective, sufficient raw material supply, mature equipment support, and controllable costs provide a realistic foundation for its large-scale application.
This “optimum” is not the ultimate in a single dimension, but a multidimensional balance – it may not be the lowest cost or the most extreme performance, but it is the material that finds the best balance between “meeting process requirements, adapting application needs, and controlling production costs”.
In the future, with the upgrading of spunbond technology towards “fine denier, functionalization, and greenization”, polyester will consolidate its dominant position through further modification (such as bio based polyester and biodegradable polyester), while complementing other materials to jointly promote the high-quality development of the spunbond nonwoven industry.
Have you ever encountered confusion in the selection of main materials in the production or use of spunbond products? Welcome to share your experience in the comment section and explore the ways to choose materials together!
Dongguan Liansheng Non woven Technology Co., Ltd. was established in May 2020. It is a large-scale non-woven fabric production enterprise integrating research and development, production, and sales. It can produce various colors of PP spunbond non-woven fabrics with a width of less than 3.2 meters from 9 grams to 300 grams.
Post time: Sep-03-2025